Solvothermal liquefaction of wastes

Abstract

A waste stream of organic matter such as plant and wood sourced streams may be converted to useful hydrocarbon products such as so-called "bio-oil" by selective sourcing of woody and herbaceous feeds having lignan and glucan, among other potential hydrocarbon sources. An intermediate sourced from methane or similar industrial waste by-products enhances useful yields of bio-oil and organic products from high temperature and pressure processes such as hydrothermal liquefaction (HTL). Usage of the low-cost intermediate produced from waste products such as shale gas increases yields of a desired diesel precursor and minimizes char, a low value waste byproducts of hydrothermal processing. The low-cost intermediate is a mixture of methanol, ethanol, and water, and since it may be produced from natural gas that would otherwise be flared or discarded, invocation for conversion of waste biomass into fuels has the advantage of converting two different waste steams into a useful product.

Description

[0001] PATENT APPLICATION

[0002] CJL Attorney Docket No.: WPI25-03(W25-012-03)PCT

[0003] SOLVOTHERMAL LIQUEFACTION OF WASTES

[0004] Inventors: Michael T. Timko, Alex R. Maag,

[0005] Geoffrey A. Tompsett and Emma Neumann Attorney Docket No.: WPI25-03(W25-012-03)PCT

[0006] BACKGROUND

[0007] Substantial attention has been focused on hydrocarbons in view of concerning trends labeled as climate change, global warming and greenhouse gas effects. Collectively, an ongoing balance between the need for hydrocarbons in a modem, industrialized society and the detriment of hydrocarbon-based emissions and waste is continually sought. A plethora of hydrocarbons exist in organic plant based materials, often discarded as waste, however feasible recovery of plant based hydrocarbons has been elusive due to significant thermal and / or chemical treatment needed to harvest hydrocarbons from these natural waste streams.

[0008] SUMMARY

[0009] A waste stream of organic matter such as plant and wood sourced streams may be converted to useful hydrocarbon products such as so-called “bio-oif’ by selective sourcing of woody and herbaceous feeds having lignan and glucan, among other potential hydrocarbon sources. An intermediate or solvent sourced from methane or similar industrial waste by-products enhances useful yields of bio-oil and organic products from high temperature and pressure processes such as hydrothermal liquefaction (HT). Usage of the low-cost intermediate produced from waste products such as shale gas increases yields of a desired diesel precursor and minimizes char, a low value waste byproduct of hydrothermal processing. The low- cost intermediate is a mixture of methanol, ethanol, and water, and since it may be produced from natural gas that would otherwise be flared or discarded, invocationAttorney Docket No.: WPI25-03(W25-012-03)PCT for conversion of waste biomass into fuels has the advantage of converting two different waste steams into a useful hydrocarbon product.

[0010] Configurations herein are based, in part, on the observation that fossil fuel alternatives are appealing for renewability and reduced environmental impact. Unfortunately, conventional approaches to alternative fuels suffer from the shortcoming of cost and energy demands with production of alternatives such as plant based and waste based recycling, limiting yield and profitability. Accordingly, configurations herein substantially improve production of organic products such as bio-oil / biocrude and gas by adding a low cost intermediate such as waste methanol for enhancing the biocrude yield and reducing the resulting char waste. The methanol can be up to 20-30% water, short chain alcohols and other impurities and still achieve the performance and efficiency increases, avoiding the need for highly refined or purified methanol as an input.

[0011] In further detail, configurations herein demonstrate a method for recycling an organic waste stream by combining an organic solvent with the organic waste stream in a containment, and heating the organic waste stream to 280°C - 400 °C under pressure in the containment. Pressure is typically maintained >10 MPa in the containment to obtain bio-oil / bio crude, and recycles the organic solvent, such as a methanol blend, for continued iterations.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The foregoing and other objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

[0014] Fig. 1 is a context diagram of organic waste recycling stream as disclosed herein;

[0015] Figs. 2A-2C are graphs of the biocrude yields and char generation with various ratios of methanol loading;Attorney Docket No.: WPI25-03(W25-012-03)PCT Fig. 3 is a yield comparison of conventional HTL to the methanol loading enhancement as disclosed herein;

[0016] Fig. 4 shows a comparison of char generation from conventional HTL for various feedstocks;

[0017] Figs. 5A-5D show a GC-MS (Gas Chromatography-Mass Spectrometry) analysis for HTL and STL for various feedstocks; and

[0018] Fig. 6A and 6B show an aqueous phase analysis for pinewood and com stover feedstocks.

[0019] DETAILED DESCRIPTION

[0020] Wastes contribute disproportionately to many of the environmental issues of modem society. In particular, waste biomass from agriculture and forestry is one of the most abundant wastes generated in the United States as recently reported by the DOE (U.S. Department of Energy). The strongly interlinked structure of biomass suggests inefficiencies in accommodating these waste feeds.

[0021] Concurrently, another energy related inefficiency is denoted by waste methane from industrial processes, often related to petroleum refining. Methane and other gases are often “flared” - burned into the environment / atmosphere as a most favorable approach. However, emerging technology converts methane from stranded gas into a methanol-rich liquid form that can be brought to market.

[0022] Currently, this methanol rich liquid intermediate must be refined before it can be sold on the market, primarily as methanol. While this crude methanol has limited commercialization potential without further refinement and cost, configurations herein leverage the crude, intermediate methanol for a solvothermal liquefaction (STL) process which produces enhanced biocrude and bio-oil yields from the waste biomass.

[0023] The disclosed approach embraces a process that can efficiently convert both waste biomass and the crude methanol into a useful product through solvothermal liquefaction (STL). STL achieves rapid conversion of wet organic wastes in the presence of an organic solvent or co-solvent, producing an energy dense oil precursor to useful fuels and chemicals. The advantage of using crude methanol for STL is its low cost. The advantage of combining crude methanol with biocrudeAttorney Docket No.: WPI25-03(W25-012-03)PCT from STL of biomass waste is production of a more valuable and energy-dense product. Both the crude methanol and biomass waste are low carbon footprint substances. Combining them into a single product has potential as a large source of renewable fuel or diesel.

[0024] Configurations disclosed herein discuss yields in terms of bio-oil, referring to a hydrocarbon rich liquid that serves as an equivalent or near equivalent for many petroleum products often generated from industrial refinement of commodity, mined natural crude oil. Bio-oil, also referred to as bio-diesel, is applicable in a broad range of contexts as a substitute for more traditional, refined petroleum products. Bio-oil can often replace certain products with little to no additional refinement, such as diesel, heating oil, and so-called “bunker fuel” for oil fired boilers. Other products may be provided with various levels of refinement, based on the hydrocarbon sources for the bio-oil and the hydrogen and carbon compositions required by the target application. Regardless of the intended target use, the bio-oil yield as disclosed herein stands as a useful, carbon-rich organic product for hydrocarbon fueled contexts.

[0025] The description below presents an example of methods for the STL technology which greatly increases the yields of desirable products such as bio-oil that are obtained from thermal treatment of wastes under pressure. Although parallels are drawn to HTL as a comparative approach, the disclosed process delivers specific results from selected feedstocks and hydrocarbon inputs over conventional HTL processes.

[0026] Fig. 1 is a context diagram of organic waste recycling stream as disclosed herein. Referring to Fig. 1, In a recycling environment 100, a natural growth recycling stream 101 includes forestry residues 110. Concurrently, a natural geological production stream 102 generates stranded gas 120 from petroleum and / or gas drilling and gathering operations. These two production streams generate recyclable content that symbiotically contribute to the STL process for providing a value greater than either alone.

[0027] Following the two streams 101, 102 until merging, the forestry residues 110 include any suitable plant material, although typically more “woody” rather than herbivorous “leavy” materials perform superior, as disclosed below. In particularAttorney Docket No.: WPI25-03(W25-012-03)PCT configurations, corn stover, switchgrass, sorghum, pinewood sawdust and red oak sawdust were employed, however other suitable feedstocks may be employed. The forestry residues undergo manual cutting and grinding 112 for suitable physical granularity, followed by transport 114 as a biomass. Lumber and paper industry residues may be considered sources of discarded wood and sawdust materials, for example.

[0028] Continuing from the geological production stream 102, typically in conjunction with oil or gas refining, methanol is generated 122 from waste methane, typically by industrial syngas generation (steam reforming followed by synthesis) or direct catalytic oxidation, or other suitable process. The resulting methanol from the waste methane stream typically has a composition of between 70%-80% methanol, between 20%-30% water and up to 5% short chain alcohols. Higher purity (greater methanol percentage), such as up to 90 or 95% may be achieved but is not required. It is expected that the organic solvent is an alcohol such as methanol of at least 70% purity. Ethanol may also be present. The organic waste stream 101 preferable includes ample quantities of a wet, woody biomass. By way of background, methanol is the simplest alcohol with only one carbon atom (CH3OH), often abbreviated as MeOH. Ethanol has two carbon atoms (C2H5OH) Other alcohols that may have value as solvents include methanol, ethanol, alcohol denat, isopropyl alcohol (IP A), propanol, and benzyl alcohol.

[0029] The short -chain alcohols that may comprise the non-methanol component include low-molecular-weight organic compounds containing a hydroxyl (-OH) group attached to a small carbon chain (typically C1-C5). They are highly soluble in water, volatile, and often used as solvents or fuels, with key examples including methanol, ethanol, propanol, and isopropyl.

[0030] A pressurized containment 130, autoclave or reactor is employed to combine the methanol stream 102, effectively acting as an organic solvent, with the organic waste stream 101 in the containment 130. The containment 130 heats the organic waste stream to 280°C -400 °C, methanol and optional additional water under pressure in the containment for maintaining a pressure > 10 MPa in the containment to complete the hydrothermal process, however pressures as low as 300 psi / 2 MPa may be employed. A nitrogen atmosphere in the containment may be provided fromAttorney Docket No.: WPI25-03(W25-012-03)PCT pressurized N2. The combination of the organic waste stream 101, methanol and water is heated for around 1-120 minutes. A particular configuration provides an improvement over a standard HTL by STL reactions performed in the reactor 130 at 300 °C and autogenic + 300 psi N2 conditions for 20 minutes prior to quenching the reaction.

[0031] The high temperatures and pressure of the reactor containment 130 generate char as a less desirable waste product, removable via a solids filter 132, sieve or other suitable separation scheme. A three phase separator 134 generates the remaining products 140. The oil phase 136 is received as the bio-oil / biocrude yield, and a distillation column 138 can separate residual water and alcohol for recirculating methanol back into the reactor 130. Thus, the generated useful products 140 include

[0032] an oil, a gas, an aqueous mixture of oil and water, and char.

[0033] Figs. 2A-2C are graphs of the biocrude yields and char generation with various ratios of methanol loading. Referring to Figs. 1 and 2, methanol loading between 25%-75% varies the ratio of beneficial biocrude to generated char. For the results of Figs.2A-2C, the operating conditions were as follows. The reactor 130 was maintained at 300 °C for 20 min, varying methanol loading as shown across the horizontal axis. A 15wt% solid loading relative to water and methanol solvent was maintained, and it can be observed that a 25 wt% MeOH STL treatment for both woody (poplar Fig. 2A and poplar Fig. 2B) and herbaceous (switchgrass, Fig. 2C) feeds optimizes biocrude yield, while 25 - 50% wt% MeOH STL treatment is optimal for solid (char) reduction. In general, herbaceous feeds may be characterized by plants that do not have a woody stem and die down to the ground after blooming or seasonally, while woody growths tend to have a rigid stem with lignified stems or cellulose defining the rigid upright structure.

[0034] Fig. 3 is a yield comparison of conventional HTL to the methanol loading enhancement as disclosed herein. Fig. 3 compares oil yield improvements from the disclosed STL with conventional HTL approaches. If can be seen that herbaceous feedstocks have minimal improvement in oil yield with methanol addition, however woody feedstocks have >90% improvement in STL oil yield compared to HTL. However, the improvement in oil yield is most prominent with woody feedstocks,Attorney Docket No.: WPI25-03(W25-012-03)PCT

[0035] namely sawdust from pinewood and red oak. The same improvement is not observed

[0036] for other feeds such as switchgrass, however, all feeds have a noticeable reduction in

[0037] the solid char byproduct.

[0038] Fig. 4 shows a comparison of char generation from conventional HTL for

[0039] various feedstocks. Fig. 4 demonstrates that all feedstocks have a marked solid

[0040] reduction with methanol addition, with a significant solid reduction for STL of

[0041] woody feedstocks compared to HTL. The reduction in char yield with addition of

[0042] methanol can be attributed to either an improved reactivity of the primary char,

[0043] which more readily partitions compounds into a fluid state or a minimization of

[0044] secondary reactions that redeposit as a secondary char phase. These results highlight

[0045] the potential benefits of a solvothermal approach with a "crude" methanol feed by

[0046] reducing the required waste disposal costs of residual solids for a wide variety of

[0047] green wastes, as well as improve the process reaction efficiency of a liquefaction

[0048] process by upwards of 20% to produce a biocrude 136 phase.

[0049] Table 1 shows an analysis of the various feedstocks for constituent

[0050] composition. Woody feeds evaluated include Pine and Red Oak, while herbaceous

[0051] feeds evaluated include Com Stover, Sorghum and Switchgrass. Bamboo was also

[0052] evaluated. Several patterns emerge from the results of Figs. 3 and 4. The

[0053] performance of the woody species of pine and red oak is exemplified when the

[0054] organic waste stream includes less than 5% ash. It may be further observed that the

[0055] woody species define an organic waste stream that has a higher percentage of lignin

[0056] than ash, and that the percentage of lignin in the woody waste stream components is

[0057] at least 400% greater (greater than 30%) than a percentage of ash, while the

[0058] herbaceous species have only about 2x the percentage of lignin to ash. It may be

[0059] apparent to provide an organic waste stream sourced from at least 95% pine or oak,

[0060] or other woody species, or that the organic waste stream includes at least 25 %

[0061] lignin sourced from woody source feeds.

[0062] Corn Pinewood Red Oak

[0063] Green Feed Switchgrass Sorghum

[0064] Stover Sawdust Sawdust Biochemical Analysis

[0065]

[0066] Attorney Docket No.: WPI25-03(W25-012-03)PCT

[0067] Glucan % 37.2% 34.2% 35.2% 41.2% 42.0%

[0068] Xylan % 18.7% 17.1% 16.9% 18.0% 18.5%

[0069] Arabinan % 2.1% 1.5% 1.7% 0% 0%

[0070] K-Lignin % 17.6% 20.3% 13.3% 30.6% 30.9%

[0071] Ash % 12.7% 6.6% 10.2% 0.35% 0.36%

[0072] Other % 11.7% 20.3% 22.7% 9.9% 8.2%

[0073] Ultimate Analysis Carbon 46.1% 45.4% 40.0% 48.0% 47.8% Hydrogen 6.0% 5.9% 5.1% 5.8% 5.8% Nitrogen 0.7% 0.5% 1% 0.9% 0.6% Oxygen143.5% 44.7% 53.9% 45.3% 45.8%

[0074]

[0075] TABLE I

[0076] In particular configurations, K-lignin may be provided for the lignin

[0077] component. K-lignin is extracted from wood during the Kraft pulping process,

[0078] which uses strong alkaline chemicals to separate lignin from cellulose. Kraft lignin

[0079] is usually sulfur-bearing, hydrophobic, and has a relatively high molecular weight.

[0080] Figs. 5A-5D show a GC-MS (Gas Chromatography-Mass Spectrometry)

[0081] analysis for HTL and STL for various feedstocks at a 50:50 MeOH: water loading

[0082] for five different feedstocks.

[0083] Fig. 6A and 6B show an aqueous phase analysis for pinewood and com

[0084] stover feedstocks. Variations in feedstocks and woody / herbaceous blends may be

[0085] performed. The temperature and pressure may be varied by any suitable increment.

[0086] In particular configurations, temperature may be varied above 300 °C, 325 °C, 350

[0087] °C, 375 °C, 400 °C, 425° C or greater. Pressure may be adjusted from around 300

[0088] psi, or 2 MPa in 1 MPa increments 10 MPa or above for achieving hydrothermal

[0089] activity.

[0090] In addition to improving yields, the STL biocrude is higher quality than HTL

[0091] biocrude. In particular, the STL biocrude has many methoxy side chains that benefit

[0092] fuel properties. The solvothermal process has been experimentally shown to result a

[0093] dramatic improvement in biocrude yield of up to 20% when compared to the moreAttorney Docket No.: WPI25-03(W25-012-03)PCT traditional hydrothermal liquefaction of green wastes. This result is also paired with a >50% reduction in solid yield which minimizes waste disposal costs. Further economic and sustainability benefits are realized when combining liquefaction with the low-cost crude methanol feed that valorizes flare gas emissions.

[0094] While the system and methods defined herein have been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

Claims

Attorney Docket No.: WPI25-03(W25-012-03)PCT CLAIMSWhat is claimed is:

1. A method for recycling an organic waste stream, comprising:combining an organic solvent with the organic waste stream in a containment;heating the organic waste stream to 280°C -400 °C under pressure in the containment; andmaintaining a pressure >10 MPa in the containment to obtain at least two of: an oil, a gas, an aqueous mixture of oil and water, and char.

2. The method of claim 1 wherein the solvent is an alcohol of at least 70% purity.

3. The method of claim 1 wherein the solvent is at least 70% methanol.

4. The method of claim 3 wherein the organic stream includes a wet, woody biomass and the methanol results from waste methane and having a purity less than 95% or less than 90%.

5. The method of claim 3 further comprising receiving the methanol from a waste methane stream, the methanol having a composition of between 70%-80% methanol, between 20%-30% water and up to 5% short chain alcohols.

6. The method of claim 1 wherein the organic waste stream includes at least 25 % lignin sourced from woody source feeds.

7. The method of claim 1 wherein the organic waste stream includes less than 5% ash.

8. The method of claim 1 wherein the percentage of lignin in the organic wasteAttorney Docket No.: WPI25-03(W25-012-03)PCT stream is at least 400% greater than a percentage of ash.

9. The method of claim 1 wherein the organic waste stream has a higher percentage of lignin than ash.

10. The method of claim 1 wherein the organic waste stream is sourced from at least 95% pine or oak.

11. The method of claim 3 further comprising heating the organic waste stream, methanol and water in an autoclave for 1-120 minutes.1 . A method for recycling an organic waste stream, comprising:combining methanol with water and the organic waste stream sourced from woody and herbaceous materials in a containment;heating the organic waste stream to greater than 300 °C under pressure in the containment;maintaining a pressure >2 MPa in the containment to obtain at least two of: an oil, a gas, an aqueous mixture of oil and water, and char; andvarying a ratio of the methanol and water for increasing a bio-oil yield and mitigating generation of char.

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