Biogas production from lignocellulosic feedstock

Abstract

A process for producing upgraded biogas, wherein lignocellulosic feedstock is fed to an anaerobic digestion that produces biogas and digestate, wherein at least some of the biogas is provided for biogas processing that produces upgraded biogas, wherein at least some of the digestate is subjected to processing including one or more thermochemical processes. The processing of the digestate produces carbon-containing material (e.g., carbon dioxide) provided for carbon capture and storage and produces one or more co-products (i.e., at least energy product). The export of energy product from the process is avoided such that a greenhouse gas removal resulting from the carbon capture and storage is associated with the upgraded biogas and is not shared with the co-product.

Description

BIOGAS PRODUCTION FROM LIGNOCELLULOSIC FEEDSTOCKTECHNICAL FIELD

[0001] The present disclosure relates generally to processes and / or systems wherein lignocellulosic feedstock is converted to biogas and digestate and wherein at least some of the digestate is converted to energy product (e.g., heat and / or power).BACKGROUND

[0002] Biogas is a renewable source of energy typically produced by the anaerobic digestion of organic matter. Biogas collected from an anaerobic digestion is a gas mixture that contains methane, the primary compound in natural gas, and carbon dioxide. While biogas collected from an anaerobic digestion can be combusted directly, it can be advantageous to upgrade the biogas (e.g., remove at least some of the carbon dioxide) so that it is substantially interchangeable with conventional natural gas. Such upgraded biogas, which is often referred to as renewable natural gas (RNG), typically can be distributed using natural gas pipelines and / or can be used in any application in which conventional natural gas is used (e.g., transportation, household heating, or industrial processes).

[0003] Presently, a relatively small but growing share of the biogas produced worldwide is upgraded to RNG. One barrier to producing RNG is the cost. For example, since the cost of biogas upgrading is significant, biogas upgrading is often only provided for relatively large- scale biogas productions (e.g., where the feedstock is manure from large livestock farms). Accordingly, there is a limited supply of RNG.

[0004] Using agricultural crop residue, such as straw, as feedstock for biogas production has the potential to significantly increase the global supply of RNG (e.g., since agricultural crop residue is generally abundant). Unfortunately, agricultural crop residue has various characteristics that have limited its use as feedstock for biogas production. For example, most agricultural crop residue is composed mainly of cellulose, hemicellulose, and lignin (i.e., is lignocellulosic). These components and / or their structural relationship can make agricultural crop residue resistant to microbial degradation. Moreover, agricultural crop residue typically has a high carbon to nitrogen ratio (C / N) (e.g., relative to manure). Both the recalcitrantstructure and the high C / N of agricultural residues have been linked to low biogas yields. Strategies to encourage the use of agricultural crop residue as feedstock for anaerobic digestion have generally focused on enhancing the anaerobic digestion performance (e.g., focusing on overcoming the recalcitrant structure and / or high C / N of agricultural crop residue). Improving the performance of anaerobic digestion can allow the anaerobic digestion to proceed close to completion within a relatively short time frame. Incomplete anaerobic digestion is generally viewed as a shortcoming for biogas production. For example, incomplete anaerobic digestion is generally associated with a relatively low biogas yield, and / or with producing digestate that is of poor quality (e.g., having a high residual biogas potential).

[0005] A high biogas yield is generally believed to be advantageous as it can increase revenues from the sale of products (e.g., RNG and / or electricity). Indeed, the lack of profit associated with low biogas yield has been reported as a primary reason that biogas plants cease operation. In addition, a high biogas yield and the production of digestate with minimal residual biogas potential (RBP) has been reported as essential in terms of economy, sustainability, and minimization of greenhouse gas (GHG) emissions. A high biogas yield is also believed to be important for large-scale biogas production (e.g., commercial-scale biogas production). For example, a high biogas yield and a reduction in amount of digestate produced have been identified as key factors in moving to large-scale operations.

[0006] Digestate, which can refer to the liquid and / or solid residue remaining after anaerobic digestion, typically contains significant amounts of organic matter and / or nutrients (e.g., nitrogen (N), phosphorus (P), potassium (K), etc.). As a result, the main use of digestate is often as a soil conditioner and / or fertilizer. In some cases, digestate may have to meet relevant quality standards before being land applied (e.g., as a soil conditioner and / or fertilizer).

[0007] Producing digestate with a relatively low RBP and / or with a reduced amount of volatile solids (VS) is generally viewed as advantageous because the digestate can release GHGs (e.g., methane) to the atmosphere if fed to an open lagoon and / or applied to land (e.g., as a soil conditioner and / or fertilizer), and / or because it may allow the digestate to meet therelevant quality standards for land application (e.g., stability standards). For example, in the United Kingdom (UK), digestate may need to have a RBP that is equal to or lower than 0.45 L biogas / g VS (28 day incubation) for land application.

[0008] Producing a relatively small amount of digestate has been generally viewed as advantageous because there is less material (e.g., waste) to process and / or dispose of. With respect to the former, digestate can require processing prior to land application (e.g., even when it has an RBP at or below 0.45 L biogas / g VS) and / or being provided as co-product. For example, in addition to having a specific nutrient content (e.g., a nitrogen-phosphorous- potassium ratio or NPK within a specific range), there may be regulations that require the digestate to be treated (e.g., pasteurized or sterilized) to reduce the number of pathogenic bacteria, viruses, or other harmful organisms (e.g., particularly if the feedstock includes manure) before being land applied.

[0009] The processing of digestate to produce co-product (e.g., energy product, fertilizer product, and / or fiber product) is generally viewed as having the potential to improve economic sustainability of biogas production and / or offset operating costs. Unfortunately, large-scale biogas productions can produce large quantities of digestate and managing and / or processing such large quantities of digestate can be challenging. For example, the amount of digestate that can be land applied over a given area over a given time period can be limited (e.g., to avoid over fertilizing, to avoid the build-up of nutrients and / or potentially toxic compounds in the soil, and / or to prevent contamination of ground water and / or surface water). Accordingly, if a large amount of digestate is produced, the process can require trucking at least some of the digestate long distances and / or landfilling at least some of the digestate. This increases the cost and operating expenses, has environmental consequences, and / or complicates the process (e.g., requires infrastructure to accommodate an increasing number of vehicles and / or causes logistical problems).SUMMARY

[0010] The present disclosure describes one or more processes and / or systems designed to address some of the challenges of biogas production from agricultural crop residue and / or other lignocellulosic feedstock, including, for example, challenges related to cost and / orscaling-up. The present disclosure also describes one or more processes and / or systems for producing at least one target product (e.g., upgraded biogas, or other product derived from the biogas) having relatively low life cycle GHG emissions.

[0011] In accordance with one aspect of the instant invention there is provided a process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) processing at least some of the digestate, the processing comprising one or more thermochemical processes and producing energy product, the processing further producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide; e) providing the energy product for the process so as to avoid export of the energy product from the process and such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

[0012] In accordance with one aspect of the instant invention there is provided a process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least a portion of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) generating energy product, the energy product derived from the lignocellulosic feedstock provided in a), the generating comprising subjecting at least some of the digestate to processing, the processing comprising one or more thermochemical processes, the processing further producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide; and e) providing the energy product for the process so as to avoid export of the energy product from the process and such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

[0013] In accordance with one aspect of the instant invention there is provided a method of reducing a carbon intensity of upgraded biogas, product derived from the upgraded biogas, or a combination thereof, wherein the upgraded biogas is produced from a process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; and c) subjecting at least some of the biogas to biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; and wherein the method comprises: (i) processing at least some of the digestate, the processing comprising one or more thermochemical processes, the processing producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide, the processing further producing energy product derived from the digestate, the co-product comprising energy product; and (ii) providing the energy product for the process so as to avoid export of the energy product from the process such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

[0014] In accordance with one aspect of the instant invention there is provided a process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) processing at least some of the digestate, the processing comprising one or more thermochemical processes, the processing producing carbon-containing material provided for carbon capture and storage, the carbon- containing material comprising carbon dioxide, the processing further producing co-product derived from the digestate, the co-product comprising energy product; and e) avoiding export of the co-product from the process such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported co-product.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further features and advantages of the present disclosure will become apparent from the following detailed description, taken in combination with the appended drawings, in which like features are identified by like reference numerals, and in which:

[0016] FIG. la is a block diagram of an embodiment of a process of producing product derived from biogas;

[0017] FIG. lb is a block diagram of an embodiment of a process of producing product derived from biogas, wherein the digestate processing includes a solids-liquid separation and thermochemical processing of at least some of the solids;

[0018] FIG. 1c is a block diagram of an embodiment of a process of producing product derived from biogas, wherein the digestate processing includes a solids-liquid separation, drying of at least some of the solids, and thermochemical processing of at least some of the dried solids;

[0019] FIG. Id is a block diagram of an embodiment of a process of producing product derived from biogas, wherein the digestate processing includes a solids-liquid separation, drying of at least some of the solids, and combustion of at least some of the dried solids;

[0020] FIG. le is a block diagram of an embodiment of a process of producing product derived from biogas, wherein the digestate processing includes a solids-liquid separation, drying of at least some of the solids, gasification of at least some of the dried solids, and the processing (e.g., combustion) of at least some of the syngas produced by the gasification;

[0021] FIG. If is a block diagram of an embodiment of a process of producing product derived from biogas, wherein the digestate processing includes a solids-liquid separation, drying of at least some of the solids, pyrolysis of at least some of the dried solids, and the processing (e.g., combustion) of at least some of the product (e.g., syngas, bio-oil, bio-char) produced by the pyrolysis;

[0022] FIG. 1g is a block diagram of an embodiment of a process of producing hydrogen; and

[0023] FIG. l is a schematic diagram of an embodiment wherein at least some of the solid digestate is combusted and carbon dioxide from the flue gas is captured and stored.DETAILED DESCRIPTION

[0024] It has now been recognized that biogas production can be improved and / or readily scaled up when the digestate is processed, including thermochemical processing, to produce carbon-containing material (e.g., carbon dioxide) provided for carbon capture and storage (CCS) and to generate energy product (e.g., heat and / or power) that is used within the process. More specifically, it can be advantageous when most or all of the energy product is provided for the process and is not exported from the process.

[0025] Minimizing or preventing the export of energy product from the process, can decrease the carbon intensity of the upgraded biogas, or target product derived from upgraded biogas. For example, avoiding export of energy product derived from the digestate can result in any GHG removals associated with the carbon-containing material being provided for CCS (e.g., carbon dioxide that is sequestered) being allocated only to the biogas, or target product derived from the biogas (e.g., the GHG removal is not allocated to exported energy product).

[0026] In addition, in minimizing or preventing the export of energy product from the process, any excess energy product (e.g., energy not required for basic operation and / or energy produced above a certain baseline level) can be used to improve the process. For example, excess energy product can be used for feedstock handling (e.g., to reduce the particle size of at least some of the feedstock), pretreatment (e.g., higher temperatures), anaerobic digestion (e.g., to increase temperature and / or mixing), biogas processing (e.g., compression), and / or digestate processing (e.g., drying and / or mechanical treatment of the digestate). Such embodiments can improve biogas production and / or improve efficiency of at least part of the process. In some embodiments, at least some of the excess energy product (e.g., electricity) is used to dry and / or mechanically treat (e.g., densify) at least some of the digestate. Densifying at least some of the digestate (e.g., via the formation of pellets and / or brickettes) is advantageous in that it can improve some thermochemical processes (e.g., combustion and / or gasification) and / or can facilitate storage of that part of the digestate (e.g., short term storage and / or seasonal storage). For example, the resulting pellets and / or brickettes can have a relatively consistent size and / or density, can have a relatively high and / or consistent calorific value, and / or can have a relatively low moisture content (e.g., 5-10%). Accordingly, the thermochemical processing (e.g., combustion or gasification) of the digestate can be improved when at least some of the digestate is densified. Storing the densified solid digestate can improve the process by facilitating providing a more consistent feed for thermochemical processing (e.g., in terms of quantity and / or calorific value).

[0027] In general, the process(es) of the instant disclosure include preparing lignocellulosic feedstock for anaerobic digestion, feeding feedstock (i.e., containing the prepared lignocellulosic feedstock) into one or more anaerobic digesters configured to convert the feedstock to biogas and digestate. At least some of the biogas is processed (e.g., to produce upgraded biogas and / or other product derived from the biogas). At least some of the digestate is processed to produce: (i) energy product (e.g., heat and / or power), and (ii) carbon- containing material (e.g., carbon dioxide) that is used to reduce GHG emissions (e.g., reduce a carbon intensity of the upgraded biogas and / or other product derived from the biogas).Feedstock

[0028] In general, the feedstock for anaerobic digestion will include one or more types of lignocellulosic feedstock. The term “lignocellulosic feedstock,” as used herein, refers to any type of plant biomass or feedstock derived from plant biomass that contains cellulose, hemicellulose, and lignin, and that has not been consumed by an animal. For example, some examples of different types of lignocellulosic feedstock include, but are not limited to, agricultural crop residues, energy crops, forestry residues, etc. For purposes herein, manure is not a lignocellulosic feedstock (e.g., any lignocellulosic material in cattle, poultry, or swine manure would have been consumed by an animal).

[0029] The composition of lignocellulosic feedstock can vary with the type of biomass, its age, and / or its growing environment. For example, wheat straw can have a cellulose content of about 35%, a hemicellulose content of about 25%, and a lignin content of about 25%, by weight (w / w) on a dry basis. In some embodiments, the lignocellulosic feedstock contains cellulose in an amount greater than about 25%, hemicellulose in an amount greater than about 15%, and lignin in an amount greater than about 5%, by weight (w / w) on a dry basis. In some embodiments, the lignocellulosic feedstock contains cellulose in an amount between about 25% and about 50%, hemicellulose in an amount between about 15% and about 40%,and lignin in an amount between about 5% and about 30%, by weight (w / w) on a dry basis. In some embodiments, the lignocellulosic feedstock has a combined content of cellulose, hemicellulose and lignin greater than about 25% by weight (w / w) on a dry basis. Lignocellulosic feedstock also often contains extractives and / or ash.

[0030] In some embodiments, the lignocellulosic feedstock is or contains at least one type of energy crop. Energy crops are crops specifically grown for fuel and / or energy production (e.g., are non-food crops). Energy crops are often grown on marginal land (land not suitable for traditional food crops like com and soybeans). In some embodiments, the lignocellulosic feedstock is or contains miscanthus, giant reed grass (Arundo donax reed canary grass, switchgrass, maize, eucalyptus, willow, millet, hemp energy cane, sorghum (including sweet sorghum), cord grass, and / or rye grass.

[0031] In some embodiments, the lignocellulosic feedstock is or contains at least one type of agricultural crop residue. Agricultural crop residues, which are often considered waste products and / or byproducts of crop production, may be used to produce fuel and / or energy without concerns about the feedstock competing with food crops for arable land. Agricultural crop residues can refer to field residues or processing residues. Field residues, which are materials left after harvesting a crop (e.g., left in an agricultural field or orchard), can include straw, stubble, stover, etc. The term straw refers to the stalk / stem of cereal plants and grasses after the removal of the grain and chaff (e.g., after threshing). The term stover refers to the leaves and stalks of field crops such as com (maize), sorghum, or soybean that are commonly left in a field after harvesting the grain (e.g., includes stalks, leaves, husks, and cobs). Process residues are materials left after the crop is processed into a usable resource (e.g., sugarcane bagasse). In some embodiments, the lignocellulosic feedstock is or contains soybean stover, corn stover, rice straw, sugar cane tops and / or leaves, sugar cane bagasse, rice straw, barley straw, wheat straw, canola straw, oat straw, cotton burr, and / or any cereal grain straw. In some embodiments, the lignocellulosic feedstock is straw (e.g., rice, barley, wheat, triticale, oat, rye, rape seed, pea, canola, and / or flax straw).

[0032] In some embodiments, the lignocellulosic feedstock is or contains a crop feedstock (e.g., an energy crop or an agricultural crop residue). In some embodiments, thelignocellulosic feedstock is or comprises maize silage. In some embodiments, the lignocellulosic feedstock is or comprises whole crop silage (e.g., a mixture of silage made up of grain and / or legume, optionally blended with grasses).

[0033] In some embodiments, the feedstock for anaerobic digestion only contains a single lignocellulosic feedstock (i.e., the anaerobic digestion is a mono-digestion). In some embodiments, the feedstock for anaerobic digestion contains at least two feedstocks (e.g., is a co-digestion). For example, in some embodiments, the anaerobic digestion is a co-digestion of a lignocellulosic feedstock (e.g., an energy crop or an agricultural crop residue) and another type of feedstock (e.g., manure, food scraps, algae, sewage sludge, etc.).

[0034] In some embodiments, the anaerobic digestion is a co-digestion where the feedstock contains (i) an agricultural crop residue and (ii) another feedstock (e.g., manure, food scraps, energy crops, etc.). In some embodiments, the anaerobic digestion is a co-digestion where the feedstock contains (i) an agricultural crop residue or an energy crop and (ii) manure (e.g., swine manure, cow manure, chicken manure, etc.). In some of these embodiments, the agricultural crop residue makes up at least about 50%, at least about 60%, at least about 70%, at least about 80%, or at least about 90% of the total feedstock fed to the anaerobic digestion, where the percentage is based on dry weight.Preparing the Lignocellulosic Feedstock

[0035] In general, there will be some preparation of the lignocellulosic feedstock upstream of the anaerobic digestion. Some non-limiting examples of such feedstock preparation can include feedstock handling, size reduction, water addition (e.g., slurrying and / or soaking), debris removal (e.g., screening), and / or pretreatment (e.g., thermal, mechanical, chemical, and / or biological pretreatment).

[0036] Feedstock handling can use equipment for receiving the lignocellulosic feedstock (e.g., delivered by truck or tractor), storing the lignocellulosic feedstock (e.g., short term queuing and / or for off-season use), unbaling the lignocellulosic feedstock (i.e., if baled), weighing the lignocellulosic feedstock, mixing different types of feedstock (if applicable), and / or moving the lignocellulosic feedstock within the facility (e.g., dry and / or as a slurry).

[0037] Size reduction reduces the average size of the lignocellulosic feedstock particles, which can make the lignocellulosic feedstock easier to handle (e.g., in a conveying system and / or in downstream processing) and can improve the performance of the anaerobic digestion. For example, the size reduction of lignocellulosic feedstock, such as straw, has been shown to enhance biogas production (e.g., with biogas production typically increasing with decreasing particle size). Size reduction of the lignocellulosic feedstock can also reduce the risk of blockages (e.g., in the conveying equipment, digester(s), and / or downstream processing equipment). Size reduction can be achieved using any suitable size reduction method or combination of methods (e.g., wet and / or dry), including but not limited to, milling, grinding, cutting, agitation, shredding, chipping, compression / expansion, and / or other types of mechanical action. Size reduction by mechanical action can be performed by any type of equipment adapted for the purpose, for example, but not limited to, hammer mills, choppers, shredders, tub-grinders, roll presses, refiners, and hydrapulpers. In some embodiments, size reduction includes processing the lignocellulosic feedstock with a hammer mill. In some embodiments, the lignocellulosic feedstock is subjected to size reduction that results in at least 80% of the resultant particles having a length less than about 30 cm, less than about 20 cm, less than about 10 cm, less than about 5 cm, less than about 3 cm, less than about 2 cm, less than about 1 cm, between about 0.05 mm and about 3 cm, between about .05 mm and about 2 cm, or between about .05 mm and about 1 cm. In some embodiments, the size reduction includes passing the feedstock through a sieve. In some embodiments, the sieve is a 1 inch sieve (e.g., about 25.4 mm), a3 / 4 inch mesh sieve (e.g., about 19 mm), a 14 inch sieve (e.g., about 12.7 mm), a 3 / 8 inch sieve (e.g., about 9.51 mm), a 14 inch sieve (e.g., about 6.35 mm), a 3 / 16 inch sieve (e.g., about 4.76 mm), a No. 5 mesh sieve (e.g., about 4 mm), a No. 10 mesh sieve (e.g., about 2 mm), a No. 12 mesh sieve (e.g., about 1.68 mm), a No. 14 mesh sieve (e.g., about 1.41 mm), a No. 16 mesh sieve (e.g., about 1.2 mm), a No. 18 mesh sieve (e.g., about 1 mm), a No. 20 mesh sieve (e.g., about 0.841 mm), or a No. 40 mesh sieve (e.g., about 0.42 mm), or smaller. In some embodiments, at least 80% of the particles by mass that pass through such sieves will be retained by a No. 270 mesh sieve (e.g., about 0.053), a No. 325 mesh sieve (e.g., about 0.044), or a No. 400 mesh sieve (e.g., about 0.037). In general, a good methane yield has been obtained when wheatstraw is milled to have an average particle size of between about 1 mm and about 7 mm (e.g., about 2 mm to about 5 mm).

[0038] Slurrying refers to adding liquid (e.g., water) to the lignocellulosic feedstock (or vice versa) to form an aqueous slurry (e.g., after a size reduction). Slurrying, which may allow the lignocellulosic feedstock to be readily conveyed (e.g., pumped), can be achieved using any suitable equipment, including but not limited to a batch or continuous mixing vessel. Slurrying can be conducted separately from or simultaneously with other water addition steps (e.g., slurrying can be integrated with soaking). In general, slurrying can produce an aqueous stream of any suitable solids content, which for example, can be selected to facilitate pumping and / or providing water for the anaerobic digestion.

[0039] Soaking the lignocellulosic feedstock can allow aqueous liquid to permeate the lignocellulosic biomass, and thus may reduce or prevent complications associated with floating feedstock particles in the anaerobic digestion and / or may improve other feedstock handling steps (e.g., pretreatment). In general, soaking may be carried out at any suitable temperature and / or for any suitable duration.

[0040] Lignocellulosic feedstock can contain a significant amount of debris such as sand, grit, and / or stones (e.g., as a result of the harvesting process). The presence of such debris can negatively affect various pieces of equipment used in the process (e.g., reduce the reliability and / or service life of the equipment). For example, sand can negatively affect equipment used upstream of the anaerobic digestion (e.g., mechanical pretreatment), within the anaerobic digestion (e.g., mixing and / or agitation), and / or downstream of the anaerobic digestion (e.g., processing the digestate). In addition, sand can settle and accumulate at the bottom of a digester, and over time may substantially solidify, and thus can reduce the capacity the digester. Accordingly, digesters may need to be periodically shut down to remove accumulated sand. Subjecting the lignocellulosic feedstock to a sand removal process prior to pretreatment and / or prior to anaerobic digestion can increase the reliability and / or service life of the equipment, and / or can reduce or obviate the need for periodic shutdowns of the anaerobic digestion to remove accumulated sand. After an anaerobic digestion is shut down, it can take some time (e.g., 1 to 2 months) before full biogas operation resumes. Theterm “sand removal”, as used herein with regard to the lignocellulosic feedstock, refers to one or more processes for removing debris such as sand, grit, and / or stones from the lignocellulosic feedstock. In general, sand removal from the lignocellulosic feedstock can involve any dry or wet process known in the art. For example, sand removal can be achieved using one or more hydrocyclones, screens, and / or sieves.

[0041] Lignocellulosic feedstock can have a recalcitrant structure that results in a reduced biogas yield. One approach for increasing the biogas yield from lignocellulosic feedstocks is to treat the lignocellulosic feedstock upstream of the anaerobic digestion (i.e., to pretreat the feedstock). Pretreatment, which can at least partially degrade the recalcitrant structure of the lignocellulosic feedstock, and thus increase biogas yield, can include any suitable process or combination of processes, including, for example, thermal pretreatment (e.g., adding steam or liquid hot water), mechanical pretreatment (e.g., chopping, crushing, pressing, macerating, and / or pelletizing), chemical pretreatment (e.g., adding acid, alkali, etc.), and / or biological pretreatment (e.g., adding fungi, enzymes). For example, some examples of pretreatment chemicals include sodium hydroxide, potassium hydroxide, calcium carbonate, ammonia, acetic acid, phosphoric acid, sulfuric acid, carbon dioxide, etc.

[0042] As will be appreciated by those skilled in the art, some of these feedstock preparation steps may be optional and the steps selected may be dependent on the type of lignocellulosic feedstock, the feedstock supplier, the selected pretreatment conditions, and / or the design of the biogas plant.

[0043] For example, while pretreatment is generally viewed as beneficial for improving the performance of anaerobic digestion (e.g., in terms of increasing biogas yield and reducing the amount of solids in the digestate), it can be costly, can be energy intensive, can be challenging to scale-up, and / or can complicate the process (e.g., depending on the pretreatment). In some cases, pretreatment can result in a negative energy balance (e.g., where the energy output of the process is less than the energy input), particularly if the pretreatment is severe. While the process(es) disclosed herein can include pretreatment, including a relatively severe pretreatment (e.g., a pretreatment with a severity greater than about 3 according to Eq. 1), one advantage of various process(es) disclosed herein is thatwhen the goal is to only generate sufficient energy product for the process and to not export energy product (e.g., which may be at least partially achieved via an incomplete anaerobic digestion), pretreatment, and in particular, a severe pretreatment may not be necessary and / or desirable. In some embodiments, preparation of the lignocellulosic feedstock does not include chemical pretreatment (e.g., adding chemicals and heat). In some embodiments, preparation of the lignocellulosic feedstock does not include: (i) chemical pretreatment (e.g., using acids, bases, oxidizing agents, solvents), (ii) pretreatment based on irradiating the feedstock (e.g., using ultrasound, gamma ray, microwave), and / or (iii) pelletizing and / or briquetting. In some of these embodiments, preparation of the lignocellulosic feedstock also does not include biological pretreatment (e.g., fungal).

[0044] For purposes herein, the severity of pretreatment is expressed using a severity factor, log Ro, which is defined as: log (t-e(T'100) / 14-75) (1) where t is the time (in min), and T is the temperature (in °C), of the reaction. Those skilled in the art will appreciate that for systems where the temperature varies with time, the quantity inside the brackets of Eq (1) is integrated with respect to time to calculate the severity. In some embodiments, preparation of the lignocellulosic feedstock includes a pretreatment having a severity that is not more than about 2.5, not more than about 2, not more than about 1.5, not more than about 1.3, or not more than about 1. In some embodiments, such pretreatment is or includes a thermal pretreatment (e.g., with hot water at a temperature between about 50°C and about 100°C). In some embodiments, such pretreatment is or includes adding steam (e.g., saturated or unsaturated).Anaerobic Digestion

[0045] Anaerobic digestion is a biological process that involves the degradation of organic matter by microorganisms (e.g., bacteria, fungi, and / or archaea) to produce biogas. Anaerobic digestion is often described as having four phases, namely, 1) hydrolysis, 2) acidogenesis, 3) acetogenesis, and 4) methanogenesis. In the first phase, the carbohydrates, proteins, and / or fats in the organic matter are broken down into smaller molecules such assugars, amino acids, and fatty acids (e.g., via one or more reactions catalyzed by extracellular enzymes secreted by hydrolytic bacteria). In the second phase, acidogens (e.g., fermentative bacteria) break down the smaller molecules into volatile fatty acids (e.g., acetate, propionate, and / or butyrate) and often other products (e.g., ethanol, hydrogen, and / or carbon dioxide). In the third phase, acetogens break down the larger fermentation products into hydrogen, carbon dioxide and acetate. In the fourth phase, methanogens convert acetate, hydrogen, and / or carbon dioxide to methane. The overall process is often described using the following chemical reactions for the digestion of glucose and xylose:C6HI2O63 CO2 +3 CH4(2)C5H10O5 2.5CO2+2.5CH4(3)

[0046] The anaerobic digestion of the feedstock (i.e., containing at least one lignocellulosic feedstock) will be conducted in at least one digester. The term “digester”, as used herein, refers to any receptacle (e.g., vessel and / or space) in which at least part of the anaerobic digestion occurs. For example, each digester can be a holding tank, or other contained volume, such as a covered lagoon or a sealable structure, designed to facilitate the breakdown of organic matter by microorganisms under anaerobic or low oxygen conditions and the collection of biogas. If more than one digester is used, the digesters can be connected in series and / or in parallel.

[0047] In general, each digester or the combination of digesters can be designed and engineered to operate using a number of different configurations and / or a number of different operating conditions, including but not limited to, single stage versus multistage, batch versus continuous mode, mixed versus unmixed, and / or mesophilic versus thermophilic.

[0048] In a single-stage digestion, the anaerobic reactions in the different phases occur within a single, sealed digester (e.g., simultaneously). In a multi-stage digestion (e.g., a two-stage digestion, where two digesters are connected in series), different digesters can be optimized for different phases (e.g., optimized for certain bacterial communities). For example, two- stage systems are often provided to separate the hydrolysis and methanogenesis phases.

[0049] In batch mode, the feedstock is added to the digester at the start of the process, and digestate is removed only once the anaerobic digestion is complete. In continuous mode or semi-continuous mode, feedstock is introduced into the digester throughout the anaerobic digestion (e.g., continuously or periodically), while the digestate is also removed throughout the anaerobic digestion (e.g., continuously or periodically). In each mode (e.g., batch, continuous mode, or semi-continuous mode), the biogas may be removed from the digester throughout the process. Batch mode anaerobic digestions can be, for example, conducted in lagoon-type digesters or batch digesters. Continuous mode or semi-continuous mode anaerobic digestions can be, for example, conducted in continuous stirred-tank digesters or plug flow digesters. In some embodiments, the anaerobic digestion is carried out in at least one anaerobic digester operated in semi-continuous mode, wherein effluent is removed and feedstock is added periodically (e.g., once a day, twice a day, three times a day, four times a day, five times a day, or six times a day), while biogas is removed substantially continuously.

[0050] In a mixed digestion, stirring and / or another form of agitation is provided (e.g., continuously or periodically). For example, mixing (e.g., stirring and / or agitation) can be provided via mechanical mixing and / or hydraulic mixing. Mixing is often required in an anaerobic digestion to maximize contact of the microorganisms with the substrate (e.g., the lignocellulosic feedstock), to prevent the formation of layers (e.g., including floating layers and sediment layers), and / or to avoid forming scum at the surface. In some embodiments, the anaerobic digestion is conducted in at least one complete stirred reactor (e.g., which operates as a Continuous Stirred Tank Reactor or CSTR), wherein the feedstock is continuously / periodically fed into a tank configured to provide mixing.

[0051] The anaerobic digestion can be carried out at any suitable temperature or combination of temperatures (e.g., depending on the microorganisms involved and / or the configuration of the system). In some embodiments, at least one digester is operated in a mesophilic temperature range (i.e., about 20°C to about 45°C). In some embodiments, at least one digester is operated in a thermophilic temperature range (i.e., about 46°C to about 60°C, or higher). In general, biogas production tends to increase with increasing temperature (e.g., up to the optimum temperature for the microorganisms involved, after which biogas productioncan drop). Digesters are often heated (e.g., in the winter months) so as to maintain the temperature within the desired range.

[0052] In general, the factors affecting the anaerobic digestion process are known, and those skilled in the art can readily select process conditions to promote biogas production based on the description herein. For example, in addition to temperature, some conditions known to affect biogas production include pH, C / N ratio, salinity, solids content, substrate to inoculum ratio, organic loading rate, retention time, etc. In general, any suitable conditions can be selected. For example, the anaerobic digestion of lignocellulosic feedstock is typically conducted at a pH within the range between about 6 and about 8.5 (and often between about 6.5 and about 7.8), at a temperature in the range between about 20°C and about 70°C (e.g., with an optimum often about 35 °C for a mesophilic system and about 55°C for a thermophilic system), with a C / N ratio in the range between about 20 and about 40 (e.g., with an optimum often between about 20 and about 30), and / or with a salinity in the range between about 0 and about 8%. In multi-stage anaerobic digestions (i.e., that use multiple digesters), the temperature, solids content, pH, and / or added nutrients can be substantially the same or different in different digesters. For example, at pH values lower than about 5.5, acidogenic bacteria may be active but methanogenic bacteria may be inhibited.

[0053] The term “solids content,” as used herein, can refer to the total solids of a material or the undissolved solids of the material, unless otherwise specified. Total solids (TS) is a measurement of the total amount of solids (i.e., dissolved and undissolved) in a material. For purposes herein, the TS of a sample is measured by weighing a sample, heating the sample at 105°C to constant weight, and weighing the resulting dried solids; the TS is the weight of the dried solids to the weight of the original sample, and can be expressed as a percent. Undissolved solids (UDS) is a measurement of the amount of solids in a material that is not in solution (e.g., cannot pass through a given filter). For purposes herein, the UDS of a sample is measured by weighing the sample, separating solid particles in the sample from at least some of the liquid (i.e., using a 1.6 pm glass filter and optionally using a centrifuge if it does not filter readily), washing the solid particles, and drying the solid particles at 37°C to constant weight; the UDS is the weight of the dried solid particles to the weight of the sample, and can be expressed as a percentage. Dissolved solids (DS) is a measurement of theamount of solids that that are in solution (e.g., dissolved) in the sample. For purposes herein, the DS of a sample is determined by subtracting the UDS from the TS.

[0054] The wet anaerobic digestion of lignocellulosic feedstock is typically conducted with a solids content in the range between about 1% and about 20%. When determining the solids content at which a batch anaerobic digestion is conducted, the solids content is determined for the initial phase of the anaerobic digestion (i.e., is an initial solids content as the solids content will decrease as the anaerobic digestion progresses). When determining the solids content at which a continuous anaerobic digestion is conducted, the solids content can be measured from within the digester and / or from the effluent. In general, it can be advantageous when the solids content, and in particular the UDS, is at least about 2% (e.g., to improve accessibility of substrate to the microorganisms and / or reduce water usage) and less than about 15% (e.g., to facilitate mixing and / or dilution of potential toxins). In some embodiments, the TS is between about 2% and about 15%, between about 4% and 10%, or between about 5% and about 9%. In some embodiments, the UDS is between about 4% and about 15%, between about 4% and 10%, or between about 5% and about 9%.

[0055] In general, the solids content will be dependent on how much liquid is present. For example, liquid can be added directly to the digester and / or upstream of the anaerobic digestion, as fresh water, as a recycled liquid, and / or when introducing various materials (e.g., chemicals, nutrients, and / or microbial inoculum). Such materials can be added together or individually, prior to starting the anaerobic digestion and / or at one or more points during the anaerobic digestion. For example, water can be mixed with the feedstock to form a slurry before it is fed to the anaerobic digester. Chemicals (e.g., calcium carbonate, lime) can be added to adjust the pH of the digester contents (e.g., proactively and / or in response to changing pH conditions) and / or to provide buffering. Nutrients (e.g., in the form of natural or synthetic fertilizing reagents) can be added when the feedstock does not contain a sufficient amount of nutrients to promote microbial growth (e.g., nutrients such as nitrogen (N), phosphorus (P), sulfur (S), iron (Fe), nickel (Ni), molybdenum (Mo), cobalt (Co), and / or tungsten (W)). Adding some chemicals, such as ammonia (NH3) or urea, can both add nutrients (e.g., increase the C / N ratio) and adjust the pH.

[0056] In order to conduct a rapid and successful anaerobic digestion, a microbial inoculum is typically added near the beginning of the anaerobic digestion. The terms “microbial inoculum” or “inoculum”, as used herein, refers to a population of microorganisms or cells associated with the anaerobic digestion. An inoculum, which can include any suitable microorganisms (e.g., mesophilic and / or thermophilic bacteria), typically includes hydrolytic bacteria, acidogens, acetogens, and methanogens (e.g., archaea). For example, microorganisms that can be found in an inoculum can include, but are not limited to, those found in the following: Clostridium, Pseudomonas, Eubacterium, Methanosarcina, Methanosaeta, Methanobacterium, Methanobrevibacter . In general, the source of the inoculum can be a cultured source (e.g., fresh culture, which can be genetically engineered) and / or a natural source (e.g., pre-existing soil, decomposing material, semi-liquid manure, digestate) and / or can be provided in any suitable medium (e.g., a liquid or solid medium). For example, some non-limiting examples of sources of inoculum include digested sludge from agricultural wastes, digested sludge from wastewater plants, discarded food, restaurant wastes, and cattle and swine excrement. In some embodiments, the source of inoculum is digestate produced from livestock waste (e.g., digested manure). In some embodiments, the inoculum is prepared by subjecting the microorganisms or cells from a given inoculum source to pretreatment (e.g., dewatering, sieving, and / or degassing) and / or incubation. Inoculums for anaerobic digestion are well known, and one skilled in the art will be able to select the source of inoculum and / or the amount added for the given operating conditions (e.g., for a given amount and type of feedstock held in the digester, the amount of water added to the digester, temperature range, retention time, etc.).

[0057] In general, the retention time for anaerobic digestion can vary with the type of feedstock and / or any pretreatment thereof, the configuration of the anaerobic digestion system, and / or the operating conditions. The term “retention time”, as used herein, refers to the average time the substrate stays within the anaerobic digestion. For a batch anaerobic digestion, the retention time is the duration of the digestion. For a continuous or semi- continuous anaerobic digestion (e.g., conducted in a complete stirred reactor, which functions as a CSTR), the retention time is calculated as the volume of the tank (e.g., in m3) divided by the influent flow rate (e.g., in m3 / day). In multistage anaerobic digestions, wherein multipledigesters are arranged in series, the retention time is the sum of the retention times of the multiple digesters.

[0058] For lignocellulosic feedstocks, suitable retention times are typically between about 5 and about 90 days, more commonly between about 10 and about 60 days, and often between about 15 and about 40 days (e.g., depending on whether the feedstock is pretreated, the average particle size of the feedstock, whether the feedstock is co-digested, the operating temperature(s), and / or the completeness of the anaerobic digestion). For example, conventionally, for an anaerobic digestion of wheat straw that has not been pretreated, where the anaerobic digestion is conducted in a semi-continuous CSTR system operated under mesophilic conditions, the retention time can be at the higher end of these ranges.

[0059] As will be appreciated by those skilled in the art, many of the operating conditions (e.g., temperature, pH, C / N ratio, salinity, solids content, substrate to inoculum ratio, organic loading rate, retention time) are interdependent. For example, relatively short retention times and / or relatively high organic loading rates can reduce the pH within the digester.

[0060] Those skilled in the art having regard to the instant disclosure will also appreciate that the various operating conditions can be selected to reduce life cycle greenhouse gas emissions of the biogas (or product derived from the biogas), to reduce costs, and / or to improve scalability of the anaerobic digestion.

[0061] For example, while increasing the retention time can generally increase the biogas yield (e.g., up to some level), long retention times are not ideal for reducing costs and / or for large-scale biogas productions. For example, long retention times can be associated with additional heating and / or mixing costs (e.g., as heating and / or mixing may be conducted over a longer time period) and / or relatively large digester volumes. Large digester volume can require constructing more and and / or larger reactors, and thus can be costly and / or require a relatively large land area. Larger reactors can be particularly costly to construct (e.g., may be fabricated from concrete, carbon steel, and / or stainless steel) and / or can be more challenging to mix.

[0062] In addition, while the C / N can be decreased by adding a nitrogen-rich substrate (e.g., manure) to the anaerobic digestion (e.g., the co-digestion of manure and agricultural crop residue), thereby increasing the biogas yield from the lignocellulosic feedstock, the use of substrates such as manure can limit the scale (e.g., limited by the supply of manure). In addition, the addition of another substrate (e.g., manure) can complicate obtaining credits, particularly if GHG emissions and / or GHG removals from each substrate and / or the digestate needs to be estimated and / or if applicable regulations for obtaining the credits require monodigestion (i.e., anaerobic digestion of a single feedstock). In some embodiments, the C / N ratio is decreased by adding nutrients (e.g., a nutrient solution containing nitrogen) to the anaerobic digestion (e.g., in one or more digesters). Adding nutrients instead of adding a nitrogen-rich substrate, such as manure, can make it easier to scale up biogas production.

[0063] The anaerobic digestion of the feedstock produces biogas (e.g., raw biogas) and digestate (e.g., whole digestate).Biogas Processing

[0064] The gas produced from anaerobic digestion is often referred to as raw biogas. Raw biogas is a gas mixture that is predominantly methane (CH4) and carbon dioxide (CO2), and that can contain water (H2O), hydrogen sulfide (H2S), and / or ammonia (NH3). The composition and / or properties of raw biogas can vary depending on the feedstock (e.g., whether it is mono-digestion or co-digestion) and / or various conditions of the anaerobic digestion (e.g., retention time).

[0065] The raw biogas produced from the anaerobic digestion will be collected and subjected to biogas processing. In general, the biogas processing produces one or more target products derived from the biogas (e.g., upgraded biogas, hydrogen, methanol, ammonia, etc.) and / or produces one or more intermediates derived from the biogas (e.g., upgraded biogas, hydrogen, methanol, ammonia, syngas, etc.) provided for producing one or more target products (e.g., hydrogen, methanol, ethanol, ammonia, fertilizer, dimethyl ether (DME), methyl tert-butyl ether (MTBE), or gasoline, diesel, jet fuel, or other transportation fuel having renewable content). In preferred embodiments, the biogas processing also produces carbon-containing material (e.g., carbon dioxide) used to reduce life cycle GHG emissions ofthe target product and / or process. Biogas processing typically includes one or more purification processes (e.g., biogas cleaning and / or biogas upgrading).

[0066] The term “biogas cleaning”, as used herein, refers to a process where biogas (e.g., raw biogas) is treated to remove one or more non-methane components (e.g., H2O, H2S, O2, NH3, etc.), but does not remove a significant amount of carbon dioxide and / or nitrogen (e.g., the calorific value of the biogas may not change significantly as a result of biogas cleaning).

[0067] The term “biogas upgrading”, as used herein, refers to a process where biogas (e.g., raw or cleaned biogas) is treated to remove one or more components (e.g., CO2, N2, H2O, H2S, O2, NH3, etc.), wherein the treatment increases the calorific value of the biogas. For example, biogas upgrading typically includes removing carbon dioxide and / or nitrogen (e.g., if present in significant amounts). Biogas upgrading, which can include biogas cleaning, produces upgraded biogas. The term “upgraded biogas”, as used herein, refers to biogas that has been upgraded (i.e., can refer to partially purified biogas or fully upgraded biogas, such as RNG). The term “biogas,” as used herein, can refer to raw biogas, cleaned biogas, or upgraded biogas, unless otherwise specified.

[0068] In general, the one or more purification processes (e.g., biogas cleaning and / or biogas upgrading) can use any suitable technology or combination of technologies that can separate methane from one or more non-methane components in the biogas (e.g., from CO2, N2, H2S, H2O, NH3, and / or O2) and / or separate carbon dioxide from methane or from one or more other non-methane components. Such technologies can include, but are not limited to, absorption, adsorption, membrane, and / or cryogenic separations.

[0069] As will be understood by those skilled in the art, the technology used can be dependent on the composition of the biogas and the desired purity of the resulting gas (e.g., upgraded biogas). For example, biogas upgrading units often include carbon dioxide removal based on absorption (e.g., water scrubbing, organic physical scrubbing, chemical scrubbing), adsorption (e.g., pressure swing adsorption (PSA), temperature swing adsorption (TSA)), membrane separation (e.g., carbon dioxide selective membranes based on polyimide, polysulfone, cellulose acetate, polydimethylsiloxane, and / or methane selective membranes),or cryogenic separation, and often include one or more other systems (e.g., dehydration units, H2S removal units, N2 rejection units, etc.).

[0070] In some embodiments, the biogas processing produces upgraded biogas having a methane content of at least about 90%, at least about 92%, at least about 94%, at least about 95%, at least about 96%, or at least about 98%. In some embodiments, the biogas processing produces upgraded biogas that meets applicable standards required for injection into a natural gas pipeline (e.g., RNG specifications) and / or for transportation purposes (e.g., CNG specifications). The percentages used to quantify gas composition and / or a specific gas content, as used herein, are expressed as mol%, unless otherwise specified. More specifically, they are expressed by mole fraction at standard temperature and pressure (STP), which is equivalent to volume fraction.

[0071] In some embodiments, the biogas processing also produces carbon dioxide provided to reduce life cycle GHG emissions of the upgraded biogas, and / or a target product derived from the upgraded biogas. In some embodiments, the biogas processing produces carbon dioxide containing gas (i.e., CCh-containing gas) having a carbon dioxide content of at least about 90%, at least about 92%, at least about 94%, at least about 95%, at least about 96%, or at least about 98%. In some embodiments, the CCh-containing gas is captured from the biogas in a relatively pure form (e.g., when biogas is subjected to absorption-based carbon dioxide capture, regeneration of the absorbent often produces relatively pure carbon dioxide). In some embodiments, the CCh-containing gas, which is enriched in carbon dioxide relative to the raw biogas, is captured from an off gas produced from biogas upgrading.

[0072] In some embodiments, the biogas processing includes processing the upgraded biogas. Such processing can include compression, liquefaction, odorization, and / or blending with a relatively high calorific value gas. For example, the upgraded biogas typically will need to be compressed if it is to be transported like compressed natural gas (CNG) or liquefied natural gas (LNG), or if it is to be injected into a natural gas distribution system (e.g., a pipeline). Upgraded biogas typically is required to meet or exceed certain specifications before being injected into a natural gas distribution system (e.g., certain pipeline specifications) and / or being used for transportation purposes (e.g., CNG specifications). For example, depending onthe pipeline, pipelines specifications may require the RNG to have a CH4 level that is at least 95% or have a heating value of at least 950 BTU / scf. Processing of the upgraded biogas can include increasing the calorific value of the upgraded biogas (e.g., by adding propane and / or blending with natural gas) and / or can include odorizing the upgraded biogas (e.g., to improve detection).

[0073] In some embodiments, the biogas processing includes processing the carbon dioxide provided to reduce life cycle GHG emissions of the upgraded biogas, and / or a target product derived from the upgraded biogas (e.g., processing a CCh-containing gas produced from biogas upgrading). Such processing can include further purification (if required), dehydration, compression, cooling, and / or liquefaction (e.g., to facilitate transport). For example, when carbon dioxide is transported by vehicle (e.g., truck, ship, rail car) it is often transported as a liquid (e.g., a pressure of about 290 psig and a temperature of about -20°C, or a pressure of about 100 psig and a temperature of about -50°C). When carbon dioxide is transported by a carbon dioxide distribution system (e.g., a carbon dioxide pipeline) it is often transported as a supercritical fluid (critical point is ~31°C, -1070 psig). For example, many carbon dioxide pipelines are operated between about 1250 psig and about 2200 psig, or higher.

[0074] In some embodiments, the target product is the upgraded biogas (e.g., RNG, bio-CNG, and / or bio-LNG). In some embodiments, the process produces upgraded biogas (e.g., RNG, bio-CNG, and / or bio-LNG) that is an intermediate for producing the target product.

[0075] In some embodiments, the target product is produced in a process comprising methane reforming (e.g., the upgraded biogas can be subjected to methane reforming close to the biogas production, and / or the RNG, bio-CNG, and / or bio-LNG intermediate can be transported for methane reforming). Methane reforming includes technologies such as steam methane reforming (SMR), autothermal reforming (ATR), partial oxidation (POX), and / or dry methane reforming (DMR). SMR, ATR, and DMR, which are types of catalytic reforming, may operate by exposing natural gas and / or upgraded biogas to a catalyst at high temperature and pressure. POX reactions, which include thermal partial oxidation reactions (TPOX) and catalytic partial oxidation reactions (CPOX), may occur when a sub-stoichiometric fuel-oxygen mixture is partially combusted in a reformer. Methane reforming typically produces syngas. The term “syngas”, as used herein, refers to a gas mixture that contains hydrogen (H2) and one or more carbon oxides (e.g., carbon monoxide (CO) and / or carbon dioxide (CO2)). While syngas is predominately hydrogen and one or more carbon oxides (e.g., H2in addition to CO and / or CO2 collectively make up more than 50% of the gas), it can also contain unreacted feedstock (e.g., methane) and / or smaller amounts of other gases (e.g., argon and / or nitrogen).

[0076] 0f the various types of methane reforming, SMR is the most common. In SMR, which is an endothermic process, methane is reacted with steam under pressure in the presence of a catalyst to produce carbon monoxide (CO) and hydrogen according to the following reaction:CH4+ H2O + heat CO + 3H2(4)

[0077] Often this reaction occurs in the SMR reactor tubes, which contain the reforming catalyst. Without being limiting, the catalyst may be nickel-based, the operating pressure may be between 200 psig (1.38 MPa) and 600 psig (4.14 MPa), and the operating temperature may be between about 450 to 1000°C. The heat required for the catalytic reforming of Eq. 4 can be provided by the combustion in the SMR burners (e.g., the combustion chamber may surround the reformer tubes in which the reaction is conducted). The syngas produced from Eq. (4) may be further reacted in a water gas shift (WGS) reaction, wherein carbon monoxide is converted to carbon dioxide and hydrogen:CO + H2O — CO2 + H2 + small amount of heat (5)

[0078] Providing WGS downstream of SMR increases the yield of hydrogen, and thus is commonly included in hydrogen production. When included, the WGS is considered to be part of the methane reforming. The syngas produced as result of the SMR and WGS reactions can be used as a fuel or as an intermediate for producing one or more products (e.g., can product of the overall process, or can be intermediate for producing product of the overall process).

[0079] In some embodiments, the methane reforming is part of hydrogen production, methanol production, ammonia production, or another production process. In someembodiments, the methane reforming is part of a process that produces the target product (e.g., hydrogen, methanol, ammonia, or another product (e.g., syngas)). In other embodiments, the methane reforming is part of a process that produces an intermediate product (e.g., hydrogen, methanol, ammonia, or other intermediate product (e.g., syngas)) provided for producing the target product.

[0080] In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to hydrogen production to produce hydrogen that is the target product or is an intermediate for producing the target product. Hydrogen production typically includes methane reforming and hydrogen purification, and produces gas enriched in hydrogen (e.g., having a hydrogen content of at least about 80%, at least about 90%, at least about 95%, at least about 97%, or at least about 98%). Since the feed is at least partially derived from the biogas, the hydrogen production will produce renewable hydrogen. Such renewable hydrogen can be used to power fuel cell electric vehicles (FCEVs), produce electricity (e.g., at a power plant), as rocket fuel, or as feedstock for one or more industrial processes (e.g., at an oil refinery, steel production facility, etc.). In some embodiments, the renewable hydrogen is used in the hydroprocessing (e.g., hydrocracking and / or hydrotreating) of crude-oil derived liquid hydrocarbon such that at least some of the hydrogen is incorporated into the crude-oil derived liquid hydrocarbon to produce the target product (e.g., gasoline, diesel, and / or jet fuel, and / or waxes having renewable content). The term “crude oil derived liquid hydrocarbon”, as used herein, refers to any carbon-containing material obtained and / or derived from crude oil that is liquid at standard ambient temperature and pressure. The term “crude oil”, as used herein, refers to petroleum extracted from geological formations (e.g., in its unrefined form). Crude oil includes liquid, gaseous, and / or solid carbon-containing material from geological formations, including oil reservoirs, such as hydrocarbons found within rock formations, oil sands, or oil shale. In some embodiments, the renewable hydrogen is used in the hydroprocessing (e.g., hydrocracking and / or hydrotreating) of renewable fats and / or oils (e.g., algae, jatropha, tallows, camelina, pyrolysis oil produced from biomass, etc.) to produce fuel (e.g., gasoline, diesel, and / or jet fuel).

[0081] In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to methanol production to produce methanol (e.g., the methanol canbe the target product or an intermediate for producing the target product). Methanol can, for example, be used as a fuel (e.g., mixed with gasoline) or can be used to produce fuel (e.g., biodiesel) or chemicals (e.g., acetic acid, formaldehyde, methyl methacrylate). Methanol can, for example, be produced from syngas according to the following catalytic reaction:CO + 2H2CH3OH (6)

[0082] Without being limiting, the catalyst may be copper based, the operating pressure may be between 600 psig (4.1 MPa) and 1700 psig (11.7 MPa), and the operating temperature may be between 200 to 315°C.

[0083] In some embodiments, the syngas is produced from steam methane reforming. Since the reaction in Eq. (6) only consumes two moles of hydrogen per mole of carbon monoxide, whereas syngas produced by steam methane reforming can produce three moles of hydrogen for every mole of carbon monoxide, additional carbon dioxide can be injected into the methane synthesis, to produce additional methanol according to the following reaction:CO2+ 3H2CH3OH + H2O (7)In this case, the additional carbon dioxide can be obtained from the biogas upgrading and / or collected from the methane reforming (e.g., collected from flue gas from steam methane reforming).

[0084] In some embodiments, the syngas is produced via dry methane reforming (DMR) wherein methane and carbon dioxide react according to the following reaction.CH4+ CO22CO + 2H2(4b)

[0085] In this case, the feed to the DMR can include raw or partially purified biogas (e.g., preferably cleaned biogas that contains methane and carbon dioxide). Without being limiting, the catalyst may be nickel based, the temperature can be relatively high (e.g., 700°C to 900°C), and the pressure can be relatively low (e.g., 0.1 MPa). Since the reaction in Eq. (6) consumes two moles of hydrogen per mole of carbon monoxide, but the syngas produced from dry methane reforming only contains one mole of hydrogen for every mole of carbonmonoxide (e.g., in theory), additional hydrogen (e.g., produced from electrolysis of water) can be added to the methanol synthesis.

[0086] In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to ammonia production to produce ammonia (e.g., the ammonia can be the target product or an intermediate for producing a target product, such as fertilizer). In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to ammonia production to produce ammonia that is used as an energy carrier for energy storage and transportation (e.g., the target product can be hydrogen, where the ammonia is used to store the hydrogen) Ammonia, can for example, be produced from the Haber-Bosch process (e.g., conducted at a temperature in the range of about 400-500°C, a pressure in the range of about 150-300 bar, in the presence of an iron (Fe) based catalyst), according to the following reaction:N2+ 3H22NH3(8)

[0087] The hydrogen for this reaction can be provided from the syngas produced from methane reforming, while the nitrogen can be provided by introducing air into a secondary reformer. Alternatively, or additionally, the nitrogen can be obtained from an air separation unit.

[0088] In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to a production process that includes methane reforming to produce syngas that is the target product or is an intermediate for producing the target product. For example, syngas can be used as a fuel, or as feedstock for producing products such as fuels (e.g., alcohols produced via gas fermentation, DME produced via a single step or two-step reaction, liquid fuels and lubricants produced from a Fischer-Tropsch-like process).

[0089] In some embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is fed to hydrogen production based on methane cracking. Methane cracking, which has been proposed as an alternative to methane reforming for hydrogen production, typically produces relatively pure hydrogen and solid carbon.

[0090] In some of the above embodiments, feed at least partially derived from the biogas (e.g., cleaned or upgraded biogas) is provided for producing the target product. In many of these embodiments, it can be advantageous to provide feed containing upgraded biogas. More specifically, it is often advantageous to remove excess amounts of carbon dioxide (e.g., in order to make the process for producing the product more efficient and / or to facilitate delivery of the biogas via a natural gas distribution system). However, in some embodiments, it can be advantageous to provide feed at least partially derived from the biogas that contains biogas that has not been upgraded (e.g., raw or cleaned biogas). For example, some technologies such as DMR can require carbon dioxide.

[0091] As described above, biogas processing can produce: (i) the target product and / or (ii) intermediate provided for producing the target product. In some embodiments, providing the intermediate for producing the product includes introducing a quantity of upgraded biogas into a natural gas distribution system and transferring the environmental attributes of the quantity of upgraded biogas to the producer of the target product.Digestate Processing

[0092] The slurry removed from an anaerobic digestion (e.g., removed at the end of a batch process or removed periodically or continuously during a continuous process) is often referred to as whole digestate. Whole digestate contains liquid and solids (e.g., suspended solids such as undigested cellulose, undigested hemicellulose, lignin, nutrients, by-products of the anaerobic digestion, and / or microbial biomass). The composition of whole digestate (e.g., including the amount of nutrients, cellulose, hemicellulose, lignin, and microbial biomass) can be dependent on the feedstock for anaerobic digestion and / or various conditions of the anaerobic digestion (e.g., retention time).

[0093] In general, at least some of the digestate from the anaerobic digestion (e.g., whole digestate, liquid digestate, and / or solid digestate) will be subjected to one or more processing steps (e.g., a solids-liquid separation, drying, one or more thermochemical processes, etc.) to generate energy product (e.g., heat and / or power) and / or to produce carbon-containing material (e.g., carbon dioxide) used to reduce GHG emissions associated with the process and / or target product (e.g., upgraded biogas and / or product derived from biogas). Forpurposes herein, the term “energy product” refers to thermal product, electricity product, and / or mechanical work product (e.g., heat and / or power). In some embodiments, the energy product is and / or includes thermal product (e.g., hot water, steam, and / or chilled water). In some embodiments, the energy product is and / or includes mechanical work product (e.g., steam turbine driven compression or steam turbine driven pumping). Turbine driven compression can, for example, be used for compressing upgraded biogas, carbon dioxide, and / or refrigerant gas used in liquefaction processes. In some embodiments, the energy product is and / or includes electricity product. In some embodiments, the energy product includes electricity product, thermal product, and / or mechanical work product.

[0094] In some embodiments, the digestate (e.g., whole digestate) undergoes at least one solids-liquid separation. In some embodiments, a solids-liquid separation is the first step in digestate processing. The term “solids-liquid separation,” as used herein, refers to methods wherein one or more devices separate at least some of the solids in a material (e.g., a slurry such as whole digestate) from at least some of the liquid in the material (e.g., based on centrifugation, filtration, sedimentation, pressing and / or other dewatering technologies). Such devices include, but are not limited to, centrifuges (e.g., decanter centrifuge or discontinuous centrifuge), screw presses, filter presses (e.g., belt filter press, plate and frame filter press), screens, settling tanks, cyclone cleaners, and / or the like. Optionally, a flocculant, coagulant, and / or surfactant is added to enhance the solids-liquid separation. In some embodiments, the digestate (e.g., whole digestate) is fed to a screw press. The use of a screw press can be advantageous for digestate produced from lignocellulosic feedstocks as such digestate can have a relatively high fiber content. In some embodiments, the digestate (e.g., whole digestate) is fed to a filter press. The use of a filter press can be advantageous as it can provide solid digestate having a relatively low moisture content and / or can efficiently dewater fine solids.

[0095] A solids-liquid separation carried out on digestate typically produces a liquid fraction (e.g., also termed “liquid digestate” or “liquid”) and a solids fraction (e.g., also termed “solid digestate” or “solids”). In general, the solids fraction has a higher undissolved solids (UDS) than the feed to the solids-liquid separation, and typically contains the larger suspended solid particles in the digestate (e.g., undigested cellulose, undigested hemicellulose, lignin, andmicrobial biomass). The liquid fraction, which has a lower UDS than the feed to the solids- liquid separation, is typically aqueous and may contain smaller suspended solids (e.g., fines). Depending on the solids-liquid separation technology used, the liquid fraction may be referred to as filtrate or centrate.

[0096] In some embodiments, the whole digestate undergoes a single solids-liquid separation (i.e., a single-step solids-liquid separation). In some embodiments, the whole digestate undergoes multiple solids-liquid separations (e.g., a multi-step separation where multiple liquid fractions and / or multiple solids fractions are produced). In such embodiments, the different liquid fractions can be combined or can have different fates, and / or the different solids fractions can be combined or can have different fates. For example, in some embodiments, the whole digestate is subjected to a first solids-liquid separation that produces a first solids fraction and a first liquid fraction (e.g., using a screw press), and the first liquid fraction is subjected to a second solids-liquid separation (e.g., for enhanced solids removal) to produce a second solids fraction (e.g., containing fine particles and / or colloids) and a second liquid fraction. In this embodiment, the first and second solids fractions can be combined upstream of and / or for the thermochemical processing, or the first solids fraction can be fed to thermochemical processing while the second solids fraction is recycled back to the anaerobic digestion. Optionally, one or more treatment steps (e.g., precipitation) is conducted between two solids-liquid separations.

[0097] In some embodiments, at least some of the liquid fraction produced by one or more solids-liquid separations is further processed (e.g., for nutrient recovery and / or to facilitate direct discharge into receiving waters). Such processing can include filtration (e.g., using vibrating sieves, reverse osmosis, ultrafiltration, nanofiltration, and / or microfiltration), evaporation (e.g., falling film evaporator), stripping (e.g., ammonia stripping), ion exchange, struvite precipitation, and / or biological treatment (e.g., aerobic biological treatment). For example, liquid digestate can be treated to recover nitrogen and / or phosphorus. Recovered nitrogen and / or phosphorus can be provided for use as a fertilizer and / or for producing fertilizer.

[0098] In some embodiments, at least some of the liquid fraction produced by one or more solids-liquid separations is recycled within the process (e.g., without treatment or following processing). Recycling at least some of the liquid fraction can reduce water usage for the process. Recycling at least some of the untreated liquid can reduce treatment efforts and / or costs. For example, at least some of the liquid produced by one or more solids-liquid separations (e.g., treated or untreated) can be used to prepare a slurry containing the incoming feedstock and / or can be fed into one or more of the anaerobic digesters).

[0099] In some embodiments, at least some of the liquid fraction produced by one or more solids-liquid separations is provided for use as a fertilizer and / or soil conditioner (e.g., with or without treatment) that is used within the process (e.g., to return nutrients to land from which at least some of the lignocellulosic feedstock was harvested). For example, in some embodiments, at least some of the liquid digestate is used directly as a fertilizer and / or soil conditioner for the process (e.g., without further treatment), thereby reducing life cycle GHG emissions of the upgraded biogas as a result of reduced reliance on fossil-based fertilizer. In some embodiments, at least some of the liquid digestate is treated to recover nutrients that are used to produce a fertilizer for the process. In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations is provided for use as a fertilizer and / or soil conditioner for the process (e.g., with or without treatment). Using liquid and / or solid digestate as a fertilizer and / or soil amendment can be advantageous as the anaerobic digestion can make the nutrients more readily recoverable and / or available for plant absorption.

[0100] In general, at least some of the solids in the digestate (e.g., the solids fraction produced by at least one solids-liquid separation) will be processed (e.g., dried, mechanically processed, and / or thermochemically processed). In some embodiments, at least about 60%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95%, of the solids produced from the anaerobic digestion by weight are provided for thermochemical processing (e.g., as whole digestate or as a solids fraction).

[0101] In some embodiments, at least some of the solids fraction produced by a solids- liquid separation on whole digestate is further processed (e.g., dried, mechanically processed,and / or thermochemically processed). Depending on the specific technology used, solids- liquid separations conducted on whole digestate will typically produce a solids fraction having a UDS between about 15% and about 60%, more commonly between about 15% and about 50%, and often between about 20% and 40%. For example, without being limiting in any way, a decanter centrifuge may produce solids having a UDS between about 20% and about 30%, a screw press may produce solids having a UDS between about 20% and about 40%, and a plate-and-frame filter press may produce solids having a UDS between about 40% and about 50%.

[0102] In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations is dried (e.g., upstream of one or more thermochemical processes). Drying the solids fraction produced by one or more solids-liquid separations, and in particular, the solids fraction produced from a solids-liquid separation of whole digestate, can be advantageous in that it can help stabilize the solids (e.g., for storage and / or land application) and / or can remove a sufficient amount of water to improve the efficiency of some thermochemical processes, such as combustion, gasification, and / or pyrolysis. For example, using dry biomass in a direct combustion boiler can result in improved efficiency, increased steam production, reduced ancillary power requirements, reduced fuel use, lower emissions, and / or improved boiler operation.

[0103] The drying of the solids fraction can be carried out using any suitable drying technology (e.g., suitable for biomass). Such technology, which can be based on direct and / or indirect heating, often includes heat generation (e.g., produces hot gases, steam, and / or hot water). For example, such technology can include, but is not limited to, belt dryers, drum dryers, feed-and-turn dryers, fluidized bed dryers, solar dryers, evaporators and / or thermal dryers. In some embodiments, at least some of the dried solids fraction is fed to a direct fired drum dryer.

[0104] In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations is dried to produce dried solids having a moisture content that is between about 5% and about 40%, between about 5% and about 30%, between about 5% and about 20%, between about 10% and about 20%, or is between about 10% and about 15%. Insome embodiments, at least some of the solids fraction produced by one or more solids-liquid separations is dried to produce dried solids having a moisture content that is less than about 15%, is less than about 10%, or is less than about 8%. For purposes herein, the “moisture content” is expressed as a percent on a weight basis.

[0105] In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations (e.g., dried or not dried) is provided as a fertilizer and / or soil amendment for the land from which the feedstock was collected. In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations (e.g., fines) is recycled back to the anaerobic digestion.

[0106] In some embodiments, at least some of the solids fraction produced by one or more solids-liquid separations (e.g., dried or not dried) is mechanically treated (e.g., to produce pellets and / or brickettes). Such mechanical treatment may facilitate transport and / or storage, and / or be carried out for the downstream thermochemical processing (e.g., gasification). In some embodiments, the solids fraction is not mechanically treated to form pellets and / or brickettes. In some embodiments, at least some of the solids fraction is mechanically treated to form pellets and / or brickettes that are fed to the one or more thermochemical processes. In some embodiments, the pellets and / or brickettes are stored prior to being fed to the one or more thermochemical processes (e.g., short term storage or seasonal storage).

[0107] In general, at least some of the solids from the digestate (e.g., at least some of the solids fraction produced by one or more solids-liquid separations) will be subjected to one or more thermochemical processes that generate energy product (e.g., heat and / or power) and / or produce carbon-containing material (e.g., carbon dioxide) used to reduce GHG emissions associated with the process and / or target product (e.g., upgraded biogas and / or hydrogen). “Thermochemical processes” use heat to promote chemical transformations of biomass (e.g., into energy and / or chemical products). For example, thermochemical processes such as combustion, gasification, pyrolysis, and / or wet oxidation can be used to convert lignocellulosic feedstock and / or digestate (e.g., solid digestate) into energy (e.g., heat, steam, electricity, fuels) and / or chemical products. Thermochemical processes are distinct from biochemical conversion processes such as anaerobic digestion.

[0108] In some embodiments, at least some of the digestate is combusted (e.g., at least some of the solids fraction produced by a solids-liquid separation carried out on whole digestate). Without being limiting in any way, combustion may be conducted at temperatures between about 750°C and about 1500°C with a sufficient supply of oxygen. Combustion of digestate can be carried out using well-known combustion or incineration methods and systems (e.g., boilers or furnaces configured to combust biomass, which may or may not have multi-fuel firing capability). For example, the digestate can be combusted in a grate furnace, rotating kiln, or fluidized bed (e.g., fixed bed, bubbling bed, circulating bed). In some embodiments, at least some of the digestate (e.g., dried digestate) is combusted in a fluidized bed boiler. The use of fluidized bed boilers can be advantageous due to the relatively low combustion temperatures (e.g., 800-900°C) and / or relatively high combustion efficiency. To improve efficiency, such combustion systems often require that the material being combusted have a moisture content that is less than about 35%, more commonly less than about 15%, and often less than about 10%. In some embodiments, the digestate that is combusted is dried upstream of being combusted (e.g., such that the moisture content is less than about 10% or less than about 15%).

[0109] The combustion of digestate (e.g., the combustion of at least some of the solids) facilitates the generation of energy product (e.g., thermal product, electricity product, or mechanical work product). For example, the combustion of digestate converts the chemical energy in the digestate into thermal energy (e.g., in the form of steam and / or hot water). This thermal energy can be used within the process and / or at the facility (e.g., for drying digestate, heating one or more anaerobic digesters, biogas upgrading (e.g., for regenerating absorbents), space heating, chilling, producing liquefied RNG and / or liquefied carbon dioxide, etc.). Alternatively, and / or additionally, at least some of this thermal energy can be converted to power (e.g., electrical power and / or mechanical work). For example, steam produced as a result of the combustion can be used to turn a steam turbine, which is used to run a generator that generates electricity, and / or which is configured to produce mechanical work (e.g., to drive one or more compressors directly). The steam leaving the steam turbine can be further used to provide useful thermal energy. The electricity and / or mechanical work can be used within the process and / or at the facility (e.g., for pretreatment, size reduction, heating one or more anaerobic digesters, mixing / agitation, pumping, gas compression, biogas upgrading,drying digestate, solids-liquid separations (e.g., screw presses), producing pellets and / or brickettes, producing liquefied RNG and / or liquefied carbon dioxide, etc.).

[0110] The combustion of at least some of the digestate and the generation of energy product (e.g., thermal product, electricity product, or mechanical work product) at least partially derived from the digestate can be carried out using any suitable device or combination of devices, including any of the well-known combined heat and power (CHP) systems (e.g., one or more co-generation plants suitable for biomass). Such CHP systems often include a combustion unit (e.g., boiler) in which combustion occurs and a motor unit (e.g., steam turbine or steam engine) for producing the power. In some embodiments, the heat and power are generated from a CHP utilizing a steam turbine. In some embodiments, the heat and power are generated from a CHP utilizing on another technology (e.g., steam engine, Stirling engine, the Organic Rankine Cycle (ORC)). In some embodiments, the heat and power are generated using a heat recovery steam generator (HRSG).[0011 l]When the thermochemical processing includes combustion, carbon-containing material derived from the digestate and produced as a result of the combustion typically is provided to reduce GHG emissions associated with the process and / or the target product (e.g., upgraded biogas and / or other product derived from the biogas). In general, this carbon- containing material will be obtained from an off gas produced from the combustion (e.g., flue gas) and will contain carbon oxides (e.g., can be a gas stream that contains carbon dioxide and / or carbon monoxide). In some embodiments, the carbon-containing material provided to reduce GHG emissions associated with the process and / or biogas is produced by subjecting the off gas (e.g., flue gas) to one or more purification processes (e.g., one or more carbon capture processes). For example, flue gas, which typically contains carbon dioxide, is often fed to a flue gas cleaning system (e.g., to remove larger particles, nitrogen oxides, sulfur oxides, and / or other pollutants) before it is emitted to the atmosphere. In some embodiments, the carbon-containing material provided to reduce GHG emissions associated with the process and / or target product is carbon dioxide (e.g., gas, liquid, or solid) produced by capturing carbon dioxide from the off gas (e.g., flue gas). While the carbon dioxide can be captured from the flue gas at any point in time (e.g., before flue gas cleaning, as part of flue gas cleaning, and / or subsequent to flue gas cleaning), it can be advantageous to capture thecarbon dioxide following flue gas cleaning (e.g., so that various pollutants do not foul any absorbents, adsorbents, and / or membranes used in the carbon capture). In some embodiments, the carbon-containing material provided to reduce GHG emissions associated with the process and / or the target product (e.g., upgraded biogas and / or other product derived from the biogas) is a gas having a carbon dioxide content of at least 80%, at least 85%, at least 90%, at least 95%, or at least 98%.

[0112] In addition to the energy product and the carbon dioxide containing off gas (e.g., flue gas), combustion systems typically produce ash. In some embodiments, at least some of the ash, which may contain nutrients and / or unburnt digestate, is provided for use as a fertilizer and / or soil amendment for the process. Advantageously, the use of ash in this fashion can reduce GHG emissions from the process (e.g., related to the displacement of fossil-based fertilizers).

[0113] In some embodiments, at least some of the digestate (e.g., at least some of the solids fraction produced by a solids-liquid separation carried out on whole digestate) is gasified. Without being limiting in any way, gasification may be conducted at temperatures between about 600°C and about 1200°C with a limited supply of oxygen. Gasification of digestate can be carried out using well-known gasification methods and systems (e.g., suitable for biomass). Gasification of the digestate typically produces solids (e.g., bio-char) and syngas (e.g., typically containing carbon monoxide, hydrogen, carbon dioxide, and / or methane). The energy product is generated from heat associated with the gasification and / or from one or more products of the gasification. For example, the chemical energy in at least some of the syngas (e.g., in the hydrogen, methane, and / or carbon monoxide) and / or the solids (e.g., biochar) can be converted into energy product (e.g., heat and / or power). For example, in some embodiments, the syngas (e.g., after cooling and optionally after one or more purification steps to remove carbon dioxide) is fed to a system that produces heat and / or power therefrom. Such systems can include a combustion system configured to combust the syngas (e.g., an internal combustion engine, or a gas turbine) or a fuel cell.

[0114] When the thermochemical processing includes gasification, carbon-containing material derived from the digestate and produced from the gasification and / or downstream ofthe gasification typically is provided to reduce GHG emissions associated with the process and / or target product (e.g., upgraded biogas and / or other product derived from the biogas). In some embodiments, this carbon-containing material includes the solids (e.g., bio-char) produced from the gasification. In some embodiments, this carbon-containing material includes carbon dioxide produced from the gasification and / or carbon dioxide produced from the combustion of at least some of the syngas or the solids (e.g., bio-char). Such carbon dioxide can be captured from the syngas (e.g., pre-combustion), or from an off gas (e.g., exhaust gas) from the combustion unit (e.g., post-combustion), using any suitable carbon capture technology (e.g., based on absorption, adsorption, membrane, cryogenic technologies, chemical looping). In some embodiments, at least some of the digestate (e.g., dried digestate) is fed to an integrated gasification combined cycle (IGCC) system, which facilitates carbon capture of carbon dioxide from the syngas.

[0115] In some embodiments, at least some of the digestate (e.g., at least some of the solids fraction produced by a solids-liquid separation carried out on whole digestate) is pyrolized. Without being limiting in any way, pyrolysis may be conducted at temperatures between about 300°C and about 700°C with a restricted supply of oxygen (e.g., no oxygen). The pyrolysis of the digestate typically produces bio-oil, solids (e.g., bio-char), and / or syngas (e.g., typically containing carbon monoxide, hydrogen, carbon dioxide, and / or methane). In general, lower temperatures (e.g., between about 400°C and about 500°C) may favour solids (e.g., bio-char) production, higher temperatures (e.g., about 700°C) may favour syngas production, while moderate temperatures may favour bio-oil production. Pyrolysis of digestate can be carried out using well-known pyrolysis methods and systems (e.g., suitable for biomass). The energy product is generated from heat associated with the pyrolysis and / or from one or more products of the pyrolysis. For example, the chemical energy in at least some of the syngas (e.g., in the hydrogen and / or carbon monoxide), in at least some of the bio-oil, and / or in at least some of the solids (e.g., bio-char), can be converted into energy product (e.g., heat and / or power). In some embodiments, the syngas (e.g., after cooling and optionally after one or more purification steps to remove carbon dioxide) is fed to a system that produces heat and / or power from the syngas (e.g., is fed to an internal combustion engine, a gas turbine, or a fuel cell).

[0116] When the thermochemical processing includes pyrolysis, carbon-containing material derived from the digestate and produced from the pyrolysis and / or downstream of the pyrolysis typically is provided to reduce GHG emissions associated with the process and / or the target product (e.g., upgraded biogas and / or other product derived from the biogas). In some embodiments, this carbon-containing material includes the solids (e.g., bio-char) and / or bio-oil produced from the pyrolysis (e.g., bio-oil can be sequestered in geological formations). In some embodiments, this carbon-containing material includes carbon dioxide produced from the pyrolysis and / or from the combustion of at least some of the syngas, the bio-oil, or the solids (e.g., bio-char). Such carbon dioxide can be captured from the syngas (i.e., pre-combustion), or from an off gas (e.g., exhaust gas) from the combustion unit (i.e., post-combustion), using any suitable separation technology (e.g., based on absorption, adsorption, membrane, cryogenic technologies, chemical looping).

[0117] In some embodiments, at least some of the digestate is subjected to wet oxidation (e.g., at least some of the solids fraction produced by a solids-liquid separation carried out on whole digestate). In general, the term “wet oxidation” refers to an aqueous phase oxidation, which may take place through a family of related oxidation and hydrolysis reactions. Without being limiting in any way, wet oxidation may be conducted at temperatures between about 100°C and about 374°C (e.g., often between about 170°C and about 200°C), with a sufficient supply of oxygen (e.g., with an oxidant such as air or oxygen), and at pressures between about 0.5 MPa and about 22 MPa (e.g., often between about 0.5 MPa and about 2 MPa). In some embodiments, a catalyst (e.g., base) is added. Wet oxidation of digestate can be carried out using well-known wet oxidation systems (e.g., Zimpro® wet oxidation unit available from Siemens). Wet oxidation systems can produce off gas that contains carbon dioxide, nitrogen, and / or steam. The energy produced from the wet oxidation can be recovered directly from the steam (e.g., the thermal product can include the steam) or by passing the steam through a turbine (e.g., to generate electricity product or mechanical work product).

[0118] When the thermochemical processing includes wet-oxidation, the carbon dioxide in the off gas can be provided for carbon capture and storage.

[0119] As described herein, at least some of the digestate is converted into energy product (e.g., heat and / or power) via one or more thermochemical processes (e.g., combustion, gasification, pyrolysis, wet oxidation). Depending on the technology adopted, it may be advantageous to dry digestate upstream of the one or more thermochemical processes. For example, while the moisture content of the digestate may not be an issue for wet oxidation systems, some combustion, gasification, and / or pyrolysis systems may have a recommended moisture content of about 10% or less. While it is possible to dry whole digestate for use as feed to the one or more thermochemical processes, it can be advantageous to instead dry a solids fraction produced from a solids-liquid separation of the digestate (e.g., because it requires less energy and / or because the liquid digestate has other potential uses). In general, drying of digestate (e.g., solid digestate or whole digestate) is energy intensive, and thus may increase the GHG emissions of the process when the energy is at least partially derived from fossil sources. In some embodiments, at least some of the heat and / or power required for drying the digestate is obtained from processing at least some of the digestate (e.g., including one or more thermochemical processes that produce heat and / or power). For example, in some embodiments, the heat generation for the drying technology is integrated with one or more of the thermochemical processes.

[0120] In some embodiments, the digestate provided to the one or thermochemical processes is first mixed with a portion of the incoming lignocellulosic feedstock (i.e., that hasn’t undergone anaerobic digestion). For example, fresh lignocellulosic feedstock, which may or may not have been subjected to size reduction, can be mixed with the solids fraction produced from one or more solids-liquid separation to increase the total solids (TS) of the feed to the thermochemical process(es), or can be mixed with whole digestate upstream of a solids-liquid separation. In some embodiments, the heat and / or power needs for the process is met by combusting a portion of the fresh lignocellulosic feedstock and / or some of the biogas (e.g., raw biogas, some of the upgraded biogas, and / or at least some of the off gas from biogas upgrading), together with at least some of the solid digestate (e.g., using the same or different combustion systems).

[0121] In some embodiments, at least some of the solid digestate is recycled back to the anaerobic digestion (e.g., with or without processing). For example, in some embodiments,solids (e.g., bio-char) and / or bio-oil produced by the one or more thermochemical processes is recycled back to the anaerobic digestion. In some embodiments, fines produced from a solids-liquid separation are recycled back to the anaerobic digestion.

[0122] In some embodiments, one or more of the systems for generating the energy product (e.g., thermal product, electricity product, and / or mechanical work product) that is at least partially derived from the digestate is / are located on-site (e.g., operated by the biogas producer or a third party) or in close proximity to the biogas production (e.g., adjacent to).GHG Emissions Reduction

[0123] In general, carbon-containing material derived at least from the lignocellulosic feedstock is provided to reduce GHG emissions of the overall process and / or to reduce life cycle GHG emissions of the target product (e.g., upgraded biogas and / or other product derived from the biogas). The term “derived from”, as used herein, encompasses the terms "originated from," "obtained from," "obtainable from," "isolated from," “produced from,” and "created from," and generally indicates that one specified material finds its origin in another specified material and / or has features (e.g., environmental attributes) that can be described with reference to another specified material. The term “provide,” “provided,” “providing,” as used herein, encompasses directly or indirectly obtaining a specified material and / or making the specified material available for use.

[0124] In general, the carbon-containing material provided to reduce GHG emissions typically includes carbon-containing material derived from the digestate (e.g., produced during digestate processing). In some embodiments, the carbon-containing material derived from the digestate is or includes carbon oxides (e.g., is a CCh-containing gas) that is stored and / or used as part of at least one carbon capture and storage process. In some embodiments, the carbon-containing material derived from the digestate is bio-char, bio-oil, or a combination thereof, that is stored and / or used as part of at least one carbon capture and storage process. In some embodiments, the carbon-containing material provided to reduce GHG emissions includes (i) carbon-containing material derived from the digestate (e.g., produced during digestate processing), and (ii) carbon dioxide derived from the biogas.

[0125] Carbon capture and storage (CCS) is a climate change mitigation technology that leads to a reduction in atmospheric carbon dioxide relative to the option of not using the technology. The terms “carbon capture and storage” or “CCS”, as used herein, refers to one or more processes wherein carbon dioxide is captured from the atmosphere, or captured from a process that otherwise would release it to the atmosphere, and wherein the captured carbon is stored and / or used in a way that reduces the level of carbon dioxide in the atmosphere. Carbon capture can be carried out naturally (e.g., via photosynthesis) and / or using any suitable technology or combination of technologies.

[0126] In general, the carbon-containing material provided to reduce GHG emissions includes carbon dioxide (e.g., captured from a gas mixture such as raw biogas, flue gas, or syngas), which can be captured using any suitable carbon capture technology (e.g., membrane, absorption, adsorption, cryogenic, chemical looping, and / or gas hydration technologies). Optionally, such carbon capture can be integrated with another process (e.g., can be part of biogas upgrading). It can be particularly advantageous to use carbon capture techniques that provide a relatively pure carbon dioxide stream. Such techniques may, for example, include vacuum PSA (VPSA), absorption processes (e.g., based on amines), and / or cryogenic separations (e.g., using temperatures below -10°C or below -50°C). In some embodiments, the carbon-containing material provided to reduce GHG emissions includes carbon monoxide, bio-oil, and / or bio-char.

[0127] Storage of carbon-containing material can be carried out using any suitable technology and / or combination of technologies that prevents and / or delays the release of the captured carbon dioxide, or an equal quantity of carbon dioxide displaced physically by the captured carbon dioxide, to the atmosphere. For example, storage of captured carbon dioxide can include injecting it into a carbon dioxide pipeline configured to transport the injected carbon dioxide to a location where it can be sequestered in a subsurface formation (e.g., trapped it in a geological formation, such as a saline aquifer, oil and natural gas reservoir, unmineable coal seam, organic-rich shale, or basalt formation). Storage of the captured carbon can also include storage in a product (e.g., storing carbon dioxide within concrete, aggregates, chemicals, beverages, building materials, etc. or storing bio-oil within plastic).

[0128] Use of the carbon-containing material can be carried out using any suitable technology and / or combination of technologies that reduces the level of carbon dioxide in the atmosphere. For example, the carbon-containing material derived from the digestate can be used within a process that displaces the use of a fossil equivalent (e.g., using carbon dioxide captured from the biogas and / or one or more thermochemical processes in enhanced oil recovery (EOR)).

[0129] As will be understood by those skilled in the art, it can be advantageous for the CCS technology to be selected such that it is recognized by the applicable regulatory authority for reducing life cycle GHG emissions and / or mitigating climate change. For example, some regulations may require storage of carbon dioxide in geological formations to have a maximum leakage rate (e.g., monitoring of carbon dioxide leakage from storage for a certain time period may be mandatory).

[0130] In some embodiments, the carbon dioxide derived from the biogas and carbon dioxide derived from the digestate is stored (e.g., sequestered) in at least one geological formation. In some embodiments, the at least one geological formation includes at least one saline aquifer and / or at least one oil / natural gas reservoir (e.g., is stored as part of an EOR process).[0013 l]In some embodiments, at least about 52%, at least about 55%, at least about 57%, at least about 58%, at least about 60%, at least about 62%, or at least about 65% of the carbon originally present in the feedstock, is carried through to the digestate as determined (e.g., measured and / or calculated) by mass balance. In some embodiments, at least about 40%, at least about 45%, at least about 50%, at least about 55%, or at least about 60% of the carbon originally present in the feedstock, as calculated by mass balance, is eventually provided so as to reduce life cycle GHG emissions of the process and / or target product (e.g., is sequestered as carbon dioxide in a geological formation). In some embodiments, at least about 30%, at least about 35%, at least about 40% at least about 45%, or at least about 50% of the carbon originally present in the feedstock is recovered from the digestate (e.g., as carbon dioxide) and used so as to reduce life cycle GHG emissions of the target product (e.g., is sequestered as carbon dioxide in a geological formation).

[0132] Advantageously, appropriate storage and / or use of the carbon-containing material derived from at least the lignocellulosic feedstock (e.g., from the digestate) can mitigate climate change and / or reduce GHG emissions (e.g., can provide a GHG emissions reduction). The terms “GHG emissions reduction” or “emissions reduction”, as used herein with regard to a specific action, refers to the difference between the life cycle GHG emissions if the action had not been taken (e.g., the baseline or reference case) and the life cycle GHG emissions when the action is taken. In some embodiments, appropriate storage and / or use of the carbon-containing material derived from at least the lignocellulosic feedstock can reduce the life cycle GHG emissions of the target product (e.g., upgraded biogas, and / or any fuel, chemical, and / or product produced from the upgraded biogas, such as hydrogen), to about zero or less, relative to no CCS (e.g., provide so-called negative emissions). The term “carbon intensity” or “CI” refers to the quantity of life cycle GHG emissions associated with a product (e.g., fuel) for a given production process and is often expressed in grams of CO2 equivalent emissions per unit of product produced (e.g., gCChe / MJ of fuel, gCO2e / MMBTU of fuel, gCChe / kWh of electricity, or kgCChe / kg of fuel / product).

[0133] As will be appreciated by those skilled in the art, life cycle GHG emissions and / or carbon intensity are often determined using a Life Cycle Analysis (LCA), which identifies and estimates all “GHG emissions” and “GHG removals” in producing product (e.g., fuel), from the growing or extraction of raw materials, to the production of the product, through to the end use (e.g., well-to-wheel). The term “greenhouse gas removal” or “GHG removal”, as used herein, refers to a negative GHG emissions contribution to the life cycle GHG emissions. For example, the carbon intensity and / or life cycle GHG emissions of the upgraded biogas can account for GHG emissions associated with feedstock production (e.g., fertilizer use), biogas upgrading (e.g., compression), and / or transport via natural gas pipeline (e.g., methane losses), and for GHG removals associated with feedstock (e.g., using a waste feedstock associated with avoided GHG emissions) and / or digestate processing (e.g., CCS of carbon-containing material derived from the digestate).

[0134] Those skilled in the art will appreciate that life cycle GHG emissions and / or carbon intensity of product (e.g., upgraded biogas and / or product produced using the upgraded biogas) can be dependent upon the LCA methodology used and / or that the LCA analysis canbe aided by software (e.g., GREET ®, SimaPro®, or GaBi). Those skilled in the art will also appreciate that when product (e.g., one or more products such as upgraded biogas and / or a product produced using the upgraded biogas) is treated as meeting a certain life cycle GHG emission reduction threshold under certain regulations and / or when one or more credits for the product or its production are obtained, the LCA methodology will be selected to comply with the prevailing rules and regulations in the applicable jurisdiction (e.g., relevant to desired credits).

[0135] Those skilled in the art will also appreciate that since life cycle GHG emissions are expressed per unit of production, these calculations can be relatively complex when there is co-product produced in addition to target product. The term “product,” as used herein, refers generally to one or more things produced from a process (e.g., including a process that is part of the overall process), and is not limited to being associated with a certain fate (e.g., being sold, stored, traded, further processed, or an intermediate for another product). The term “target product,” as used herein, refers to product around which the overall process is designed (e.g., is the driver for the overall process). The term “co-product”, as used herein, refers to product produced from the process other than target product and other than the carbon-containing material provided for CCS. In general, co-product is desirable product (e.g., goods or services that can be sold or reused profitably) and can be exported from the overall process. The terms “export” or “exported,” as used herein with reference to product, refers to the product being provided for use outside of the overall process (i.e., exported product is not used in the overall process apart from optionally being accounted for in GHG analyses). The terms “export” or “exported,” as used herein with reference to product, are not limited to the provision being across a specific geographic boundary.

[0136] One approach for determining life cycle GHG emissions when there is co-product exported from the process is the allocation approach. In the allocation approach, GHG emissions and GHG removals of the total system are allocated to the co-product and target product. Such allocation is typically proportional (e.g., based on energy, mass, or economic value (e.g., typically energy if suitable)), although equal allocation has been also proposed. For example, in one common energy allocation approach, the relative amounts of each of the co-product(s) and target product(s) are calculated on an energy basis and are used toproportionally allocate the total system GHG emissions and GHG removals to the corresponding products. For example, if the process produces a target product (e.g., upgraded biogas) that contains 55% of the total energy output from the process, and a co-product (e.g., electricity) that contains 45% of the total energy output from the process, then the target product would be allocated 55% of the GHG emissions / removals of the total system (e.g., the GHG removals are shared between the target product and co-product).

[0137] Another approach for determining life cycle GHG emissions when there is coproduct exported from the process is the displacement approach. In general, this approach involves identifying a conventional product that the co-product will replace, and expanding the system boundaries to include GHG emissions and GHG removals contributions that would have occurred if the conventional product had been produced, and crediting any GHG emissions / removals resulting from the displacement to the target product. For example, consider biogas production where some of the digestate is combusted to produce electricity that is fed into the electrical grid. In this case, the exported electricity, which is at least partially sourced from renewable material, can displace the use of electricity produced from natural gas. In the system expansion approach, a GHG removal is calculated using the yield of exported electricity and the life cycle GHG emissions of the natural gas and is credited to the upgraded biogas.

[0138] Yet another approach for determining life cycle GHG emissions when there is coproduct exported from the process is process subdivision. In the process subdivision approach, the overall process is divided into subprocesses for the purposes of life cycle GHG emissions calculations (e.g., different boundaries are set for the target product and a coproduct rather than using a common system boundary). For example, the production of upgraded biogas can have separate system boundaries than the production of product derived from the digestate (e.g., electricity). In this case, the digestate may be considered a wastebased feedstock (e.g., is not assigned upstream product emissions) and any GHG emissions and GHG removals arising from its processing are allocated only to the product of the digestate processing (e.g., electricity product, heat product, mechanical work product, fertilizer, animal bedding, etc.) and typically does not affect the life cycle GHG emissions ofthe upgraded biogas or product derived from the upgraded biogas (i.e., unless some of the product from digestate processing is used in the biogas production process).

[0139] In general, the production of co-product from biogas production has been viewed as advantageous because the co-product can generate additional revenue. For example, coproduct derived from digestate, which can include energy product (e.g., heat and / or power), fertilizer product (e.g., liquid digestate, recovered nutrients, and / or fertilizer) and / or fiber product (e.g., soil amendment, composted solids, animal bedding, and / or horticultural fiber), is often considered valuable product that can be sold to generate revenue. In addition, such co-products have been viewed as advantageous in terms of reducing the carbon intensity of the biogas. For example, using the displacement approach, a GHG removal associated with exporting renewable electricity to the grid, and thus displacing non-renewable electricity, can be allocated to the biogas (e.g., an emissions credit can be applied to biogas production for displacement of non-renewable electricity).

[0140] In the instant disclosure, the export of energy product and / or other co-product derived from the digestate (e.g., fertilizer product and / or fiber product) from the process is minimized and / or avoided (e.g., to simplify the life cycle GHG emissions analysis and / or reduce the carbon intensity of the target product).

[0141] Minimizing the export of energy product and / or other co-product can be advantageous when the life cycle GHG emissions of the target product (e.g., upgraded biogas and / or product derived from the upgraded biogas) is determined using the allocation approach (e.g., since the target product is allocated a relatively high percentage of the GHG removal). In some embodiments, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% of the energy product, by energy, is used within the process and / or is not exported.

[0142] Preventing the export of energy product and / or other co-product can be advantageous when the life cycle GHG emissions of the target product is determined using the allocation approach (e.g., since the target product can be allocated all of the GHG removal) and / or where process subdivision is appropriate. With regard to the latter, in preventing the export of co-product derived from the digestate (e.g., energy product), processsubdivision between the production of the target product and the production of digestate- derived co-product (e.g., energy product) is no longer an option, and the GHG removals associated with the carbon-containing material being provided for CCS are all allocated to the target product and are not allocated to exported co-product.

[0143] In some embodiments, one or more credits are generated, obtained, and / or provided (e.g., associated with the target product and / or with one or more GHG emission reductions associated with the process). Credits can be used to incentivize at least partially renewable products and / or products associated with reduced carbon or GHG emissions (e.g., fuels used in the transportation sector). For example, credits such as fuel credits can be used to demonstrate compliance with some government initiative, standard, and / or program, where the goal is to reduce GHG emissions (e.g., reduce carbon intensity in transportation fuels as compared to some baseline level related to conventional petroleum fuels) and / or produce a certain amount of biofuel (e.g., produce a mandated volume or a certain percentage of biofuels). The target GHG emission reductions and / or target biofuel amounts may be set per year or for a given target date. Some non-limiting examples of such initiatives, standards, and / or programs include the Renewable Fuel Standard Program (RFS2) in the United States, the Renewable Energy Directive (RED II) in Europe, the Fuel Quality Directive in Europe, the Renewable Transport Fuel Obligation (RTFO) in the United Kingdom, and / or the Low Carbon Fuel Standards (LCFS) in California, Oregon, or British Columbia). Credits can also be used to incentivize other products associated with reduced carbon or greenhouse gas emissions, such as, for example, producer or production credits for clean hydrogen or credits for products made using clean hydrogen.

[0144] The term “credit”, as used herein, refers to any rights and / or benefits relating to GHG emission reductions (e.g., carbon reductions) and / or the renewable origin of a specific material (e.g., fuel or other product), including but not limited to rights to credits, revenues, offsets, GHG gas rights, tax benefits, government payments, or similar rights or quantifiable benefits, whether created from or through a government authority, a private contract, or otherwise. A credit can be a certificate, record, serial number or guarantee, in any form, including electronic, which evidences production of a quantity of a product meeting certain life cycle GHG emission reductions relative to a baseline (e.g., a gasoline baseline) set by agovernment authority. Non-limiting examples of fuel credits include RINs and LCFS credits. A Renewable Identification Number (or RIN), which is a certificate that acts as a tradable currency for managing compliance under the RFS2, may be generated for each gallon of biofuel (e.g., ethanol, biodiesel, etc.) produced. A Low Carbon Fuel Standard (LCFS) credit, which is a certificate which acts as a tradable currency for managing compliance under California’s LCFS, may be generated for each metric ton (MT) of CO2 reduced.

[0145] In general, the requirements for obtaining, generating, or causing the generation of credits can vary by country, the agency, and or the prevailing regulations in / under which the credit is generated. In some cases, credit generation may be dependent upon a compliance pathway (e.g., predetermined or applied for) and / or the product (e.g., upgraded biogas) meeting a predetermined GHG emission threshold.

[0146] In some embodiments, the process includes generating, obtaining, and / or providing credits for the target product (e.g., upgraded biogas and / or product derived from the biogas, such as hydrogen) and / or its production. For example, in some embodiments, the process includes obtaining, and / or providing producer or production credits for clean hydrogen produced using the upgraded biogas, or credits for products made using clean hydrogen.

[0147] In some embodiments, the process includes introducing at least some of the upgraded biogas into a natural gas distribution system (e.g., pipeline), wherein it is transported as a fungible batch to some destination (e.g., a production facility, such as a fuel production facility). When upgraded biogas (e.g., RNG) is transported by a natural gas distribution system, a quantity of upgraded biogas (e.g., in MJ) is injected into the natural gas distribution system at one location and an equal quantity of gas, or less (e.g., in MJ) is withdrawn from the natural gas distribution system at another location. Since the transfer or allocation of the environmental attributes of upgraded biogas injected into a natural gas distribution system to gas withdrawn at a different location is typically recognized, the withdrawn gas is recognized as the upgraded biogas and / or is treated as the upgraded biogas under applicable regulations (e.g., even though the withdrawn gas may not contain actual molecules from the original feedstock and / or contains methane from fossil sources). Such transfer may be carried out on a displacement basis, where transactions within the natural gas distribution system involve amatching and balancing of inputs and outputs. Typically, the direction of the physical flow of gas is not considered. The term “environmental attributes”, as used herein, encompasses a recognition or entitlement, in any form and any jurisdiction, associated with a product (e.g., upgraded biogas) and relating to a reduction in GHG emissions resulting from such products’ use or to the renewable origin of the product itself, including, but not limited to, all environmental attributes necessary to generate credits (e.g., RINs, LCFS credits, and / or European fuel credits).Incomplete Anaerobic Digestion

[0148] In some embodiments, the anaerobic digestion will be substantially incomplete such that at least some of the cellulose and / or hemicellulose and / or other anaerobically digestible organic compounds derived from the lignocellulosic feedstock (e.g., including sugar monomers and / or oligomers and / or organic acids) is converted to: (i) energy product (e.g., heat and / or power) and / or (ii) carbon-containing material used to reduce GHG emissions, instead of being converted to biogas via the anaerobic digestion.

[0149] There are various ways to determine the completion of an anaerobic digestion, including but not limited to, those that use the biomethane potential of the feedstock, the residual biomethane potential of the digestate, the amount of volatile solids in the digestate, the amount of methane produced (e.g., methane yield), and / or compositional analysis of the feedstock and / or the digestate.

[0150] The biomethane potential (BMP) of a specific material (e.g., feedstock) defines the maximum amount of methane that can be produced from the material by anaerobic digestion. The measurement of BMP is well-known and automated BMP test equipment is available. For example, BMP tests are typically carried out under mesophilic conditions for a set time period (typically at least 30 days) with an appropriate inoculum to substrate ratio and nutrient supplement to avoid inhibition of biogas production. BMP is often expressed as L of biogas per gram of VS.[0015 l]The residual biomethane potential (RBP) test is often used for determining the quality and / or stability of digestate (e.g., to demonstrate to the environmental regulators thatthe digestate has been adequately processed). RBP tests are typically carried out under mesophilic conditions for a set time period (typically at least 28 days) with an appropriate inoculum to substrate ratio and nutrient supplement to avoid inhibition of biogas production. The RBP value is also often expressed as L biogas / g VS. In general, the RBP test can be used for whole digestate, solid digestate, and / or liquid digestate. For purposes herein, when the RBP test is used to determine the completion of an anaerobic digestion, the test is conducted on whole digestate or solid digestate.

[0152] The term “volatile solids” or “VS”, as used herein, refers generally to the organic part of dry matter. The quantity of volatile solids in a sample (e.g., of feedstock or inoculum) is measured by heating a dry sample (dried at 105°C) at a temperature typically between about 450°C and about 575°C so that only ash remains. The VS is calculated as the weight of the solids lost upon heating to the weight of the dried sample, and is typically expressed as a percentage.

[0153] In some embodiments, the completion of the anaerobic digestion is determined using the RBP and / or residual VS of the digestate (i.e., the RBP and VS of whole digestate or solid digestate). According to some governments, digestate is considered to be relatively stable (e.g., suitable for land application) if it has a RBP limit of 0.45 L biogas / g VS (28 day incubation) (e.g. U.K. PAS 110:2014). A recommended RBP limit of 0.25 L biogas / g VS (28 day incubation) has also been proposed. In some embodiments, the anaerobic digestion is carried out such that it is incomplete as determined by a RBP that is greater than or equal to about 0.3 L biogas / g VS, greater than or equal to about 0.35 L biogas / g VS greater, than or equal to about 0.40 L biogas / g VS, or greater than or equal to about 0.45 L biogas / g VS. In some of these embodiments, the RBP is also less than about 0.47 L biogas / g VS, less than about 0.45 L biogas / g VS, or less than about 0.40 L biogas / g VS. For example, in some embodiments, the RBP is between about 0.465 L biogas / g VS and about 0.310 L biogas / g VS, is between about 0.450 L biogas / g VS and about 0.335 L biogas / g VS, or between about 0.440 L biogas / g VS and about 0.360 L biogas / g VS. For purposes herein, RBP is determined according to PAS 110:2014. Advantageously, producing digestate having such a relatively large RBP means that there is more potential energy in the digestate, which can be converted to heat and / or power without further anaerobic digestion.

[0154] In some embodiments, the completion of the anaerobic digestion is determined using the composition of the digestate. For purposes herein, when the composition of the digestate (e.g., residual carbohydrate content) is used to determine the completion level of an anaerobic digestion, the compositional analysis is conducted on whole digestate or solid digestate. For example, in some embodiments, the anaerobic digestion is carried out such that it is incomplete as determined by a carbohydrate assay of the digestate (i.e., whole digestate or solid digestate), wherein the residual carbohydrate content therein (i.e., the collective relative amounts of arabinan, galactan, glucan, xylan, and mannan, including any monomers and / or oligomers, in the digestate as determined by the carbohydrate assay discussed herein), makes up greater than about 20% of the digestate, makes up greater than about 22% of the digestate, makes up greater than about 25% of the digestate, makes up greater than about 30% of the digestate, makes up greater than about 35% of the digestate, makes up greater than about 40% of the digestate, or makes up greater than about 45% of the digestate (e.g., with the remainder of the digestate largely being lignin, microbial biomass, and ash), on a dry basis. In some of these embodiments, the residual carbohydrate content of the digestate is also less than about 50%, less than about 45%, or less than about 40% (e.g., is between about 45% and about 25%). For example, in some embodiments, the residual carbohydrate content of the digestate is between about 23% and about 50%, is between about 27% and about 46%, or is between about 32% and about 44%, on a dry basis. Advantageously, producing digestate having such relatively large residual carbohydrate content means that at least some of the carbohydrates that could have been converted to biogas, are instead used to produce heat and / or power (e.g., for the process) and / or carbon-containing material that can be used to reduce GHG emissions (e.g., for the process). In some embodiments, the residual carbohydrate content of the digestate is between about 23% and about 50%, while the lignin content of the digestate is at least 15%, at least 20%, or at least 25%, on a dry basis.

[0155] In some embodiments, the completion of the anaerobic digestion is determined using the theoretical methane yield and the methane yield (i.e., measured). In such embodiments, the completion of the anaerobic digestion is defined as the ratio between the methane yield and the theoretical methane yield, and can be expressed as a percentage as follows:

[0156] For example, in some embodiments, the completion of the anaerobic digestion is less than about 75%, less than about 70%, less than about 65%, less than about 60%, less than about 55%, less than about 50%, less than about 45%, less than about 40%, less than about 35%, or less than about 30%. In some of these embodiments, the completion of the anaerobic digestion is also greater than about 20%, greater than about 25%, or greater than about 30%. For example, in some embodiments, the completion of the anaerobic digestions is between about 30% and about 70%, between about 35% and about 65%, or between about 40% and about 60%. Modelling has indicated that there is a good balance between a successful anaerobic digestion and a good amount of energy produced from the combustion of digestate when the completion is between about 45% and about 65%. In some embodiments, the completion of the anaerobic digestions is between about 45% and about 65%.

[0157] The term “theoretical methane yield”, as used herein, refers to the theoretical maximum methane yield from the feedstock and is determined as follows:1) Determine the composition of the dry feedstock (with a carbohydrate assay based on the Determination of Structural Carbohydrates and Lignin in Biomass-LAP (Technical Report NREL / TP-510-42618)). For example, see Example 1.2) Use the composition of the feedstock and stoichiometry (the Buswell equation shown in Eq. 11) to determine the volume of methane produced per gram of digestible volatile solids (DVS). The term “digestible volatile solids” or “DVS”, as used herein, refers to the volatile solids in the feedstock (i.e., determined on a dry basis) that are normally anaerobically degradable (e.g., carbohydrates, proteins, and lipids, but not the lignin). See Example 2.

[0158] The term “methane yield”, as used herein, refers to the measured volume of methane collected from an anaerobic digestion per gram of DVS fed to the anaerobic digestion. For an anaerobic digestion conducted in batch mode, the methane yield is determined for a given batch. For an anaerobic digestion conducted in continuous mode, where feed is introduced and digestate is removed at substantially constant rates, the methane yield is determined over a suitable time period (e.g., daily or weekly), outside periods of startup or shutdown. For an anaerobic digestion conducted in semi-continuous mode with a substantially regular feeding / digestate removal pattern, the methane yield is determined for the feeding cycle (i.e.,the shortest repeating pattern). For example, if digestate is removed and feed is subsequently added 2 times a day or 5 days a week, the feeding cycle is daily or weekly, respectively. When the methane yield is determined for a given feeding cycle, the methane production and DVS feed values are averaged over the feeding cycle. An example of a system run with a feeding cycle of 1 week is shown in Example 3. For an anaerobic digestion conducted in semi-continuous mode with an irregular feeding / digestate removal schedule (i.e., no repeating pattern), the methane yield is determined over a sufficiently long time period (e.g., preferably at least one retention time).

[0159] Using the ratio of methane yield to theoretical methane yield, which is determined using the DVS, is advantageous over methods that only consider the VS (e.g., BMP).

[0160] In some embodiments, the completeness of the anaerobic digestion is selected to provide a certain amount of heat and / or power for the process (e.g., to meet the energy needs of the process) and / or to produce target product (e.g., upgraded biogas and / or hydrogen) having a carbon intensity that is lower than a certain value (e.g., a negative value, less than about -10 gCChe / MJ, less than about -20 gCChe / MJ, or less than about -30 gCChe / MJ). There are a number of factors that determine the completeness of an anaerobic digestion (e.g., an anaerobic digestion may be incomplete as a result of inadequate size reduction, no pretreatment, insufficient mixing, a relatively high substrate to inoculum ratio, insufficient nutrients, poorly selected total solids content, and / or a relatively short retention time).

[0161] In some embodiments, the incomplete digestion is achieved by selecting a sufficiently short retention time. In some embodiments, the incomplete digestion is achieved by providing a limited supply of added nutrients (e.g., reducing and / or stopping nutrient addition for at least a portion of the retention time). In some embodiments, the incomplete digestion is achieved by reducing and / or stopping mixing (e.g., for at least a portion of the retention time). In some embodiments, the incomplete digestion is achieved by providing limited heating (e.g., reducing and / or stopping heating of at least one anaerobic digester for at least a portion of the retention time). In some embodiments, the incomplete digestion is achieved by providing limited pH control (e.g., shifting the pH out of the optimal range). In some embodiments, the incomplete digestion is achieved by providing any combination of: asufficiently short retention time, a limited amount of nutrients, limited mixing, limited heating, or limited pH control. As will be appreciated by those skilled in the art, it can be advantageous to reduce the completion level while still using operating conditions that maintain the health of the anaerobic microorganisms and / or facilitate substantially stable operation of the anaerobic digestion. In some embodiments, the completion level is achieved at least by selecting a retention time that is less than a retention time needed to achieve 70% completion when the operating conditions are otherwise substantially the same. In some embodiments, the completion level is achieved at least by selecting a retention time that is less than a retention time needed to achieve 65% completion when the operating conditions are otherwise substantially the same. In some embodiments, the completion level is achieved at least by selecting a retention time that is less than a retention time needed to achieve 60% completion when the operating conditions are otherwise substantially the same.

[0162] In some embodiments, the operating conditions of the anaerobic digestion are selected to substantially optimize biogas production, except for the retention time, which is selected to provide the desired completeness. In some embodiments, the particle size and / or some of the operating conditions of the anaerobic digestion (e.g., degree of mixing, temperature, added nutrients, and / or total solids content) are selected increase (e.g., maximize) methane yield, except for retention time, which is selected to decrease methane yield. In general, it may be advantageous if the decrease in methane yield is not associated with the production of an excess amount of volatile organic acids (VOAs). In some embodiments, the ratio of mass of methane produced to mass of VOAs produced is between 3 and 9. In some of these embodiments, the ratio of mass of methane produced to mass of VOAs produced is greater than 3 and less than about 9, less than about 8, less than about 7, less than about 6, or less than about 5.

[0163] In some embodiments, the anaerobic digestion (e.g., mono-digestion) of lignocellulosic feedstock (e.g., such as wheat straw) is carried out with sufficient mixing, at a reasonable mesophilic temperature, an appropriate inoculum to substrate ratio, and sufficient nutrient supplement selected to avoid inhibition of biogas production, and the retention time is selected to be between about 10 days and about 40 days, between about 15 days and about 30 days, or between about 18 days and about 25 days, or any time in between. Additionally,in some of these embodiments, the lignocellulosic feedstock is subjected to size reduction that produces lignocellulosic particles having an average size that is less than about 2 cm. A retention time between about 16 and about 30 days for a mesophilic mono-digestion of wheat straw is relatively short (e.g., could expect it to be between 55 and 90 days for a complete anaerobic digestion if there is no high-severity pretreatment) and thus can be expected to significantly reduce costs (e.g., can facilitate the use of smaller digesters).

[0164] In some embodiments, the anaerobic digestion (e.g., mono-digestion) of lignocellulosic feedstock (e.g., such as wheat straw) is carried out with sufficient mixing, at a reasonable thermophilic temperature, an appropriate inoculum to substrate ratio, and sufficient nutrient supplement selected to avoid inhibition of biogas production, and the retention time is selected to be between about 8 days and about 25 days, between about 10 days and about 22 days, or between about 12 days and about 20 days, or any time in between (e.g., 16-18 days). Additionally, in some of these embodiments, the lignocellulosic feedstock is subjected to size reduction that produces lignocellulosic particles having an average size that is less than about 2 cm. A retention time between about 10 and about 22 days for a thermophilic mono-digestion of wheat straw is relatively short (e.g., could expect it to be between 25 and 70 days (e.g., 50 days) for a complete anaerobic digestion if there is no high- severity pretreatment) and thus can be expected to significantly reduce costs (e.g., can facilitate the use of smaller digesters).

[0165] Advantageously, the instant disclosure provides various embodiments wherein at least some of the digestate is processed (i.e., including one or more thermochemical processes) to generate: (1) energy product (e.g., heat and / or power), at least some of which is used in the process, and (2) carbon-containing material (e.g., such as carbon dioxide), at least some of which is used to reduce GHG emissions associated with the process and / or target product (e.g., upgraded biogas and / or hydrogen). Such processing is advantageous as:(i) the heat and / or power that is generated is at least partially renewable and can be used to at least partially meet the energy needs of the process, thereby reducing and / or obviating the use of fossil fuel (e.g., fossil fuel used to generate grid electricity), and providing cost savings and GHG emission reductions;(ii) the GHG emission reduction obtained by using the carbon-containing material (e.g., carbon dioxide produced from thermochemical processing) can supplement a GHG emission reduction obtained by using and / or storing the carbon dioxide from the biogas (i.e., produced during anaerobic digestion);(iii) the energy product (e.g., heat and / or power) and the carbon-containing material (e.g., carbon dioxide produced from thermochemical processing) used to reduce GHG emissions, are at least partially derived from a part of the lignocellulosic material that otherwise may be considered waste (e.g., digestate is often landfilled); and / or(iv) subjecting at least some of the digestate to processing, including thermochemical processing, instead of applying it to land and / or recycling it back to the anaerobic digestion or another anaerobic digestion, helps manage the digestate in a manner that is compatible with large-scale biogas production.

[0166] With regard to (i), when the heat and / or power is generated in close proximity to the biogas production (e.g., on site), it can reduce the amount of electricity that is withdrawn from the electrical grid or can obviate the need to withdraw electricity from the electrical grid, thereby improving both economics and life cycle GHG emissions. Even when power is generated off-site (e.g., when dried and / or pelletized digestate is transported for electricity production), and the renewable electricity derived from the lignocellulosic feedstock is provided via the electrical grid, the life cycle GHG emissions for the process can be reduced as it can reduce and / or obviate the need for fossil-based electricity (e.g., credit for avoided emissions).

[0167] With regard to (ii), processing the digestate so as to be able to capture and store at least some of the carbon from the digestate can significantly reduce life cycle GHG emissions of the product.

[0168] With regard to (iv), since at least some of the solids are combusted, at least this part of the digestate does not need to be processed and / or trucked for land application. This can be particularly advantageous for large-scale biogas production, as effective management and beneficial utilization of digestate can be a bottleneck when increasing biogas production.

[0169] While processing the digestate (e.g., at least some of the solid digestate) to generate energy product (e.g., heat and / or power) that is at least partially used in the process is generally advantageous, it is particularly advantageous when the anaerobic digestion is substantially incomplete (i.e., there are one or more synergistic advantages).

[0170] In a substantially complete anaerobic digestion, much of the cellulose and hemicellulose will be converted to biogas, while most of the lignin will remain in the digestate (i.e., lignin is normally anaerobically non-degradable). Since the lignin contains an energy potential, it can be processed to produce heat and / or power for the process (e.g., can be combusted). In an incomplete anaerobic digestion, in addition to the lignin, the digestate will contain a relatively high amount of undigested cellulose and / or hemicellulose (e.g., which could be converted to biogas with enough time). Providing an incomplete anaerobic digestion can improve the process because the undigested cellulose and / or hemicellulose in the digestate increases its residual energy potential (i.e., relative to the digestate from a complete anaerobic digestion), thereby facilitating the generation of relatively high amount of heat and / or power for the process. Advantageously, this additional heat and / or power can be produced from digestate wherein the residual DVS were not readily digested. Since more energy product (e.g., heat and / or power) can be generated, without having to consume some of the biogas produced (or consuming a reduced amount of biogas), and while using relatively small anaerobic digesters, it can improve economics and / or life cycle GHG emissions of the process.

[0171] In some embodiments, substantially all of the energy product is provided for the process. The term “substantially all,” as used herein with reference to providing product (e.g., energy product), refers to most of, as in at least about 90%, of the product that is to be used. The term “provided for the process”, as used herein with reference to product (e.g., energy product), refers to providing the product for any part or parts of an overall process that can impact life cycle GHG emissions of the target product(s). While exporting energy product out of the process (e.g., providing renewable electricity to an electrical grid) can be advantageous in that both a financial credit and an emissions credit may be received, the instant disclosure recognizes that minimizing and / or preventing the export of co-product, such as energy product, can be more advantageous as the life cycle GHG emissions of thetarget product can be relatively low (e.g., the target product can have a higher value). The combination of minimizing and / or preventing export of co-product, such as energy product, in combination with producing a relatively high amount of energy product (e.g., resulting from an incomplete digestion) can be particularly advantageous as the biogas and / or digestate processing can have high energy requirements. In particular, digestate processing, such as drying of the solids, thermochemical processing, capture of carbon dioxide, and / or processing of the captured carbon dioxide (e.g., compression and / or liquefaction) can be energy intensive. For example, drying digestate (e.g., solid digestate) can be energy intensive as a result of its high water content, while carbon capture based on amine scrubbing can be energy intensive as a result of absorbent regeneration.

[0172] In some embodiments, the heat produced is provided for preparing the lignocellulosic feedstock, for the anaerobic digestion, for drying, for carbon capture (e.g., preparing hot potassium), or any combination thereof. Additionally, or alternatively, in some embodiments, the power (e.g., electricity or mechanical work product) produced is provided for preparing the lignocellulosic feedstock, for the anaerobic digestion (e.g., agitation), for a solids-liquid separation, for compression, for regenerating carbon capture (e.g., amine regeneration), or any combination thereof. In some embodiments, at least part of the anaerobic digestion is thermophilic (e.g., includes a mesophilic digester followed by a thermophilic digester), and at least some of the heat is used to provide heat for the thermophilic digester.

[0173] Providing an incomplete anaerobic digestion can also increase the amount of carbon- containing material (e.g., carbon dioxide) derived from the lignocellulosic feedstock that that is used to reduce life cycle greenhouse gas (GHG) emissions associated with the process and / or target product (e.g., upgraded biogas and / or hydrogen).

[0174] An additional synergistic advantage of combining an incomplete digestion with processing of the digestate (e.g., to produce heat and / or power used in the process and / or carbon-containing material used to reduce GHG emissions) can include a more efficient solids-liquid separation (e.g., a digestate that is relatively easy to separate into liquids and / or solids).

[0175] Advantageously, various embodiments of the instant disclosure can increase the profits of biogas production from agricultural crop residues and / or other lignocellulosic feedstock by reducing the carbon intensity of the biogas or product derived therefrom, thereby increasing the value of the biogas / product. The carbon intensity of the biogas / product is reduced as a result of: (i) at least some of the energy needs for the process being met using a renewable resource (e.g., by recovering energy from the digestate); and / or (ii) increasing an amount of carbon dioxide and / or other carbon-containing material derived from the lignocellulosic feedstock that is used in carbon capture and storage (CCS), which can also increase the number and / or value of credits that can be obtained (e.g., associated with the biogas and / or one or more products produced using the biogas).

[0176] Further advantageously, various embodiments of the instant disclosure can increase the profits of biogas production from agricultural crop residues and / or other lignocellulosic feedstock by providing cost savings related to conducting a relatively incomplete anaerobic digestion. Such cost savings can include, but are not limited to, cost savings associated with using shorter retention times, using smaller digester volumes, obviating the need for severe pretreatment (e.g., adding chemicals), and / or exploiting the faster earlier kinetics.

[0177] Accordingly, while the incomplete anaerobic digestion of the lignocellulosic feedstock can be associated with a relatively low biogas yield, in the instant disclosure, any profits losses associated with a low biogas yield can be at least partially offset by profits associated with producing upgraded biogas (e.g., RNG) having a relatively low carbon intensity (e.g., a negative carbon intensity), using a smaller digester, avoiding consuming an excessive amount of biogas or upgraded biogas for combustion, and / or cost savings associated with requiring less fossil fuel (e.g., natural gas). Advantageously, these cost savings can be significant as the energy demands for biogas production can be high, particularly when the biogas is upgraded and / or when carbon dioxide from the biogas is purified and / or compressed (e.g., for carbon capture and storage). For example, in addition to the pretreating and / or feedstock handling energy demands upstream of the anaerobic digestion, and the heating and / or mixing energy demands for the anaerobic digestion, a significant amount of energy can be required providing relatively pure CF and / or CO2product gases (e.g., biogas upgrading), for compressing the CH4 and / or CO2 product gases (e.g., for transport and / or liquefaction), and / or drying the digestate.

[0178] Advantageously, the various embodiments described herein can promote the anaerobic digestion of lignocellulosic feedstocks such as straw at a relatively large scale. In some embodiments, the process is carried out with at least about 250 tonnes of lignocellulosic feedstock being fed into the anaerobic digestion per day. In some embodiments, the process is carried out with at least about 500 tonnes of lignocellulosic feedstock being fed into the anaerobic digestion per day. In some embodiments, the process is carried out with at least about 1000 tonnes of lignocellulosic feedstock being fed into the anaerobic digestion per day.

[0179] Certain non-limiting embodiments of the instant disclosure are discussed further with regard to Figs, la to If.

[0180] Referring to Fig. la, there is shown a flow diagram of an embodiment of a process 100a that includes converting lignocellulosic feedstock to biogas (i.e., a biogas production process). The process includes several phases, including: feedstock preparation 110, anaerobic digestion 120, biogas processing 130, digestate processing 140, and GHG emissions reduction 170.

[0181] In the feedstock preparation phase 110, lignocellulosic feedstock (e.g., one or more types of feedstock, such as agricultural crop residue) is received and prepared for anaerobic digestion. The prepared feedstock is fed to the anaerobic digestion 120, which produces biogas and digestate. In the biogas processing phase 130, the biogas is processed to produce product derived from the biogas (e.g., upgraded biogas, or product derived from the upgraded biogas) and a CCh-containing gas 131. For example, in some embodiments, the biogas processing includes one or more purification steps, and produces upgraded biogas. In the digestate processing stage 140, the digestate is processed in one or more steps, to generate energy product 150 (e.g., heat and / or power), and to produce carbon containing material 160. The CCh-containing gas 131 produced from biogas processing 130 and the carbon-containing material 160 produced from digestate processing 140 are used to reduce the GHG emissions 170 from the process.

[0182] In this embodiment, the carbon containing material 160 includes a CO2-containing gas 161, and the GHG emissions reduction stage 170 includes providing carbon dioxide derived from the lignocellulosic material for at least one CCS process (i.e., providing carbon dioxide provided in and / or removed from the CO2-containing gas 131 and / or 161 for storage and / or use). Depending on the configuration of the system, the CCh-containing gas 131 from the biogas processing and / or the CCh-containing gas 161 can be at least partially processed using the same equipment (e.g., using at least some of the same purification systems, dehydrators, compressors, and / or liquefaction system). For example, in some embodiments, each of the CCh-containing gases 131 and / or 161 is relatively pure, but are processed using the same dehydrating, compressing, and / or liquifying equipment. In some embodiments, each of the CCh-containing gases 131 and / or 161 is fed to a same purification system (e.g., at the same stage or at different stages), thereby producing C Ch-enriched gas that is provided for at least one CCS process.

[0183] Substantially all of the energy product (e.g., heat and / or power) 150 generated from digestate processing 140 is provided for the process (e.g., is used for feedstock preparation, anaerobic digestion, biogas processing, and / or digestate processing).

[0184] Referring to Figs, lb, there is shown a flow diagram of another embodiment of a process 100b that includes converting lignocellulosic feedstock to biogas. In this embodiment, the digestate processing includes a solids-liquid separation 142. The liquid can be used in any suitable manner (e.g., at least a portion of the liquid can be treated, land applied, and / or recycled back into the anaerobic digestion). For example, the liquid digestate can be treated to recover nitrogen. At least some of the solids are subjected to further processing, including thermochemical processing 146 (e.g., one or more thermochemical processes). Such further processing can include drying the solids 143, as shown in the process 100c illustrated in Fig. 1c.

[0185] Referring to Figs. Id, there is shown a flow diagram of another embodiment of a process lOOd that includes converting lignocellulosic feedstock to biogas, wherein the thermochemical processing includes combustion 146a of the dried digestate. For example, the biogas plant can include a combined heat and power (CHP) system powered by adigestate-fired boiler. The combustion of the dried digestate generates energy product 150 and an off gas (e.g., flue gas) that contains carbon dioxide. The carbon dioxide in the off gas is captured and used to reduce GHG emissions 170. Optionally, at least some of the carbon dioxide derived from the off gas is least partially processed using the same equipment that processes CO2-contain stream 131. Such processing can include compression and / or liquefaction, and depending on the purity of the CO2-containing gases, one or more purification processes.

[0186] Referring to Figs, le, there is shown a flow diagram of another embodiment of a process lOOe that includes converting lignocellulosic feedstock to biogas, wherein the thermochemical processing includes gasification 146b of the dried digestate, which normally produces solids (e.g., bio-char) and syngas. The syngas is processed 146c, where the processing includes a combustion step (e.g., at least some of the syngas can be combusted in a CHP system to generate energy product 150). Depending on the configuration of the system, the processing 146c can include capturing carbon dioxide from the syngas precombustion to provide the CCh-containing gas 161. Alternatively, carbon dioxide produced during gasification can be captured from an exhaust of the combustion (e.g., can be captured post combustion). For example, the biogas plant can include a CHP system powered by a syngas-fired turbine or internal combustion engine (ICE).

[0187] Referring to Figs. If, there is shown a flow diagram of another embodiment of a process lOOf that includes converting lignocellulosic feedstock to biogas, wherein the thermochemical processing includes pyrolysis 146d of the dried digestate, which normally produces bio-oil, solids (e.g., bio-char), and syngas. In general, the pyrolysis product processing 146e can include processing (e.g., combusting) at least some of the syngas and / or bio-oil to generate energy product 150 (Fig. If shows the syngas being combusted). Depending on whether some of the syngas or the bio-oil is combusted, the carbon-containing material 160 provided to the GHG emissions reduction stage 170 can include bio-oil (e.g., bio-oil can be sequestered in geological formations) and / or carbon dioxide 161 (e.g., captured pre- or post-combustion of the syngas). Fig. If shows bio-oil being used for the GHG emissions reduction 170.

[0188] Referring to Figs. 1g, there is shown a flow diagram of an embodiment of a process 100g that includes converting lignocellulosic feedstock to hydrogen. In this embodiment, the biogas processing includes biogas upgrading 132, which produces upgraded biogas, and hydrogen production 134, which produces hydrogen product 135. In addition to the upgraded biogas, biogas upgrading 132 also produces CCh-containing gas 131 that is used to reduce GHG emissions from the process. Optionally, the upgraded biogas is provided to hydrogen production via a natural gas distribution system. In this embodiment, hydrogen production 134 is based on SMR and / or ATR and includes one or more carbon capture steps (e.g., capturing carbon dioxide from flue gas and / or from syngas) such that it also produces CO2- containing gas 136 that is also used to reduce GHG emissions from the process. Additional CCh-containing gas 161 used to reduce GHG emissions from the process is captured from flue gas from the combustion 146a. This embodiment is particularly advantageous as it produces hydrogen (e.g., associated with no carbon emissions at the point of use) and because much (e.g., more than 80% by mass) of the carbon originally present in the lignocellulosic biomass, which is biogenic, is used to reduce GHG emissions (e.g., including carbon derived from methane in the biogas).

[0189] Referring to Fig. 2, there is shown schematic diagram of an embodiment wherein solid digestate is combusted in a fluidized bed boiler 147 (optionally after a drying step) to generate energy product 150 (e.g., heat and / or power). More specifically, the solid digestate is fed into the boiler 147 having bed material, wherein the combustion thereof heats up the boiler water to produce steam that is used to drive the steam turbine 148. The flue gas (e.g., after cooling) is subjected to carbon capture 171, wherein relatively pure carbon dioxide is obtained and provided for storage.Example 1

[0190] A carbohydrate assay based on Determination of Structural Carbohydrates and Lignin in Biomass-LAP (Technical Report NREL / TP-510-42618) was carried out on milled wheat straw (20 mesh) having a moisture content of 8.58% (and a UDS of 91.42%). The carbohydrate assay provided the relative amounts of each of arabinan, galactan, glucan, xylan, mannan, insoluble lignin, and acid soluble lignin present in the sample as shown in Table 1. Fordiscussion purposes, the contribution of each of these components (mc) can be viewed as the mg of each component found in 1 gram of dried straw, or about 1.09 gram of the undried straw.

[0191] The total solids (TS) were measured by pre-weighing a crucible, dispensing a sample of the wheat straw (i.e., a fixed amount) into the crucible, drying the contents of crucible in a 105°C oven or muffle furnace overnight, and determining the weight of the dried contents of the crucible. The total solids is the number of grams of dry solids per gram of the sample, and is often expressed as a percentage. TS measurements are performed in duplicate and averaged. The TS of the wheat straw sample was 91.42%.

[0192] The volatile solids (VS) were measured by pre-weighing a crucible, dispensing a sample of dried wheat straw (i.e., a fixed amount) into the crucible, heating the contents of crucible in a muffle furnace programed to ramp from room temperature to about 105°C at 15°C / min, hold at about 105°C for about 12 minutes, ramp to about 250°C at 10°C / min, hold at about 250°C for about 30 minutes, ramp to about 575°C at 20°C / min, hold at about 575°C for about 180 minutes, and cooled to 105°C. The contents of the crucible, which corresponds to the ash, are further cooled in the crucible in a desiccator and their weight determined. The VS is calculated as:

[0193] The VS of the wheat straw sample was 95.90% (on a dry basis), which corresponds to 87.67% on a wet basis.

[0194] Non-volatile solids, which corresponds to the percentage of ash in the sample, is determined by subtracting the VS from the TS. The non-volatile solids of the wheat straw was 4.10% (on a dry basis), which corresponds to 3.75% on a wet basis.

[0195] The VS accounts for any carbohydrates (e.g., arabinan, galactan, glucan, xylan, and mannan), lignin (e.g., insoluble and acid soluble), protein, lipids, and other organics (e.g., organic acids) present in the wheat straw. While lignin is not expected to degrade anaerobically to produce biogas, the carbohydrates, protein, lipids, and / or other organics typically can degrade anaerobically. Instead of directly measuring the protein, lipid, andother organic content in the wheat straw, these components are generally accounted for in the “miscellaneous volatile solids,” which are determined by mass balance. For example, in Table 1, the contribution from miscellaneous volatile solids (i.e., 92.18 mg / g dry) is determined by difference (e.g., by subtracting the contributions from arabinan, galactan, glucan, xylan, mannan, lignin, and ash from the total dry solids).

[0196] In order to determine the percentage of volatile solids that are digestible, the contributions for the various components (e.g., arabinan, galactan, glucan, xylan, mannan, and miscellaneous volatile solids) except for the ash and lignin (e.g., insoluble and acid soluble) were used to calculate the digestible volatile solids. The percentage of digestible volatile solids of the wheat straw sample was 69.36% on a dry basis.00197]Table 1. Composition of wheat strawExample 2

[0198] The Buswell equation, shown below, was used to stoichiometrically determine the moles of methane that are produced from various components of the lignocellulosic feedstock via anaerobic digestion.

[0199] The theoretical moles of methane were then used, with the molar volume of an ideal gas at STP (e.g., 22.4 L) and the molecular weight of the monomeric component, to determine the volume of methane produced (in L) per gram of monomeric unit as shown in Table 2. A volume of methane for the miscellaneous VS was estimated as 0.373.

[0201] For a 55.3 g sample of the wheat straw having a UDS of 91.42% (i.e., 50.6 g of dry feedstock), the theoretical maximum amount of methane produced is calculated as:= 50.6 g x 274.81 L per 1000 g= 13.9 L methane

[0202] Since the sample has a DVS of 69.36%, the theoretical methane yield is calculated as:> 13.9 L methane50.6 g X0.69.36 gDVS per g feedstock= 0.396 L methane / g DVSIt is worth noting that, in practice, the value of 0.396 L methane / g DVS typically cannot be reached as, on average, about 10% to about 15% of the digestible volatile solids will be consumed for microbial growth.Example 3

[0203] Methane yield experiments were conducted in a 10 L digester (i.e., a continuous stirred tank reactor) initially charged with 9 kg total weight. The inoculum was sourced from an industrial anaerobic digester processing cow manure. For 5 out of 7 days of the week, some of the digestate was removed and new feed (i.e., slurry containing straw, nutrients, and fresh water) was subsequently added such that total weight was substantially constant. The newly added feed slurry weighed about 460 g, contained about 50.6 g of dry wheat straw, and had a UDS content of about 11%. For the remaining two days of the week, there was no digestate removal and no new feed added. The feeding cycle was seven days (1 week). The resulting retention time was 27 days. The biogas was collected substantially continuously from the digester, was passed through a scrubber to remove carbon dioxide, and the amount of the gas that passed through the scrubber, which is primarily methane, was measured usinga gas volume and flow meter (i.e., BPC® Go from BPC Instruments, which provides the methane volume at STP). The anaerobic digestion was conducted in an incubator set at 37°C. The methane yield was measured as:(volume of methane produced over 7 days)(g dry feedstock fed over 7 days) x g DVS per g feedstock> 32.94 L~ (253 g )* 0.6936= 0.188 L methane / g DVS

[0204] The completion of the anaerobic digestion is calculated as:0.188 L / gDVS x 100%0.396 L / g DVS= 47.54%

[0205] The terminology used herein is for the purpose of describing certain embodiments only and is not intended to be limiting of the invention. For example, as used herein, the singular forms "a," "an," and "the" may include plural references unless the context clearly dictates otherwise. The terms “comprises”, "comprising", “including”, and / or “includes”, as used herein, are intended to mean "including but not limited to." The term “and / or”, as used herein, is intended to refer to either or both of the elements so conjoined. The phrase “at least one” in reference to a list of one or more elements, is intended to refer to at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements. Thus, as a non-limiting example, the phrase “at least one of A and B” may refer to at least one A with no B present, at least one B with no A present, or at least one A and at least one B in combination. In the context of describing the combining of components by the “addition” or “adding” of one component to another, or the separating of components by the “removal” or “removing” of one component from another, those skilled in the art will understand that the order of addition / removal is not critical (unless stated otherwise). The terms “remove”, “removing”, and “removal”, with reference to one or more impurities, contaminants, and / orconstituents of biogas, includes partial removal. The terms “cause” or “causing”, as used herein, may include arranging or bringing about a specific result (e.g., a withdrawal of a gas), either directly or indirectly, or to play a role in a series of activities through commercial arrangements such as a written agreement, verbal agreement, or contract. The term “associated with”, as used herein with reference to two elements, is intended to refer to the two elements being connected with each other, linked to each other, related in some way, dependent upon each other in some way, and / or in some relationship with each other. The terms “first”, “second”, etc., may be used to distinguish one element from another, and these elements should not be limited by these terms. The terms “upstream” and “downstream”, as used herein, refer to the disposition of a step / stage in the process with respect to the disposition of other steps / stages of the process. For example, the term upstream can be used to describe a step / stage that occurs at an earlier point of the process, whereas the term downstream can be used to describe a step / stage that occurs later in the process. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0206] 0f course, the above example and / or embodiments have been provided as examples only. It will be appreciated by those of ordinary skill in the art that various modifications, alternate configurations, and / or equivalents will be employed without departing from the scope of the invention. Accordingly, the scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

Claims1. A process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) processing at least some of the digestate, the processing comprising one or more thermochemical processes and producing energy product, the processing further producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide; e) providing the energy product for the process so as to avoid export of the energy product from the process and such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

2. The process according to claim 1, wherein the processing in d) comprises subjecting the digestate to at least one solids-liquid separation that produces a solids fraction and a liquid fraction.

3. The process according to claim 2, wherein the one or more thermochemical processes comprises combustion, wherein at least some of the solids fraction is fed to the combustion, and wherein the combustion generates at least some of the energy product.

4. The process according to claim 2, wherein the one or more thermochemical processes comprises gasification, wherein at least some of the solids fraction is fed to the gasification, and wherein the gasification produces syngas, bio-char, or a combination thereof.

5. The process according to claim 2, wherein the one or more thermochemical processes comprises pyrolysis, wherein at least some of the solids fraction is fed to the pyrolysis, and wherein the pyrolysis produces syngas, bio-char, bio-oil, or any combination thereof.

6. The process according to claim 4 or 5, wherein the one or more thermochemical processes comprises combustion, wherein at least some of the syngas is fed to the combustion, and wherein the combustion generates at least some of the energy product.

7. The process according to claim 6, wherein at least some of the biogas produced in b) is fed to the combustion, wherein an amount of the biogas fed to combustion on an energy basis is selected to substantially meet energy needs of the process, and wherein the biogas fed to the combustion comprises raw biogas, some of the upgraded biogas, or a combination thereof.

8. The process according to any of claims 1 to 7, comprising providing part of the lignocellulosic feedstock not fed to the anaerobic digestion to at least one of the one or more thermochemical processes, wherein an amount of the lignocellulosic feedstock provided to the at least one thermochemical process is selected to substantially meet energy needs of the process.

9. The process according to any of claims 1 to 8, wherein the biogas processing comprises capturing at least some of the carbon dioxide from the biogas and providing the captured carbon dioxide for carbon capture and storage.

10. The process according to any of claims 1 to 9, wherein the processing in d) produces fertilizer product, fiber product, or a combination thereof, and wherein the process comprises comprising providing substantially all of the fertilizer product, the fiber product, or the combination thereof for use in the process.

11. The process according to any of claims 1 to 10, wherein the energy product comprises mechanical work product, wherein the mechanical work product comprises compression, pumping, or a combination thereof.

12. The process according to any of claims 1 to 11, wherein the energy product comprises electricity product, and wherein e) comprises providing the electricity product for preparingthe lignocellulosic feedstock, for the anaerobic digestion, for the biogas processing, for processing the digestate, or any combination thereof.

13. The process according to any of claims 1 to 12, wherein the lignocellulosic feedstock is agricultural residue.

14. The process according to any of claims 1 to 12, wherein the lignocellulosic feedstock comprises straw.

15. The process according to any of claims 1 to 14, comprising providing the upgraded biogas for producing a product, the product comprising hydrogen, methanol, ammonia, or any combination thereof.

16. The process according to claim 15, wherein the product is produced from a process comprising methane reforming, the methane reforming producing syngas comprising carbon dioxide, at least some of the carbon dioxide from the syngas provided for carbon capture and storage.

17. The process according to any of claims 2 to 8, wherein the processing in d) comprises drying at least some of the solids upstream of the one or more thermochemical processes.

18. The process according any of claims 1 to 17, wherein the processing in d) comprises densification of part of the digestate, and wherein the densification is powered with excess energy product.

19. The process according to any of claims 1 to 17, comprising carrying out the anaerobic digestion, the biogas processing, the processing of the digestate, or any combination thereof with conditions selected such that the energy product substantially meets energy needs of process.

20. The process according to any of claims 1 to 19, comprising carrying out the anaerobic digestion such that it is less than 75% complete.

21. The process according to any of claims 1 to 20, wherein at least some of the upgraded biogas is introduced into a natural gas distribution system.

22. A process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least a portion of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) generating energy product, the energy product derived from the lignocellulosic feedstock provided in a), the generating comprising subjecting at least some of the digestate to processing, the processing comprising one or more thermochemical processes, the processing further producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide; and e) providing the energy product for the process so as to avoid export of the energy product from the process and such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

23. A method of reducing a carbon intensity of upgraded biogas, product derived from the upgraded biogas, or a combination thereof, wherein the upgraded biogas is produced from a process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; and c) subjecting at least some of the biogas to biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; and wherein the method comprises:(i) processing at least some of the digestate, the processing comprising one or more thermochemical processes, the processing producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide, the processing further producing energy product derived from the digestate, the co-product comprising energy product; and(ii) providing the energy product for the process so as to avoid export of the energy product from the process such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported energy product.

24. A process of producing upgraded biogas, the process comprising: a) providing lignocellulosic feedstock; b) feeding at least some of the lignocellulosic feedstock to an anerobic digestion that produces biogas and digestate, the biogas comprising methane and carbon dioxide; c) providing at least some of the biogas for biogas processing, the biogas processing comprising biogas upgrading and producing the upgraded biogas; d) processing at least some of the digestate, the processing comprising one or more thermochemical processes, the processing producing carbon-containing material provided for carbon capture and storage, the carbon-containing material comprising carbon dioxide, the processing further producing co-product derived from the digestate, the co-product comprising energy product; and e) avoiding export of the co-product from the process such that a greenhouse gas removal resulting from the carbon capture and storage is allocated to the upgraded biogas and is not allocated to exported co-product.

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