Buffered cellulose component for use in biogas generation

Abstract

A buffered biomass component wherein said buffered biomass component comprises: a cellulose component which is substantially free of lignin; a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; water; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 50 %.

Description

[0001] BUFFERED CELLULOSE COMPONENT FOR USE IN BIOGAS GENERATION

[0002] FIELD OF THE INVENTION

[0003] The present invention is directed to the use of a cellulosic component in the generation of biogas, more specifically, a buffered substantially lignin-free cellulose as an additive or partial replacement of a portion of the organic matter (feedstock) fed into an anaerobic digester.

[0004] BACKGROUND OF THE INVENTION

[0005] Biogases are the product of microbial degradation of various organic materials (both plant-based and animal -based products) in the absence of oxygen, i.e., in an anaerobic environment. This microbial degradation in an oxygen-free environment is called anaerobic digestion. Biogas can refer to gas produced naturally and industrially and generally contains between 45-75 % methane (CFL or natural gas), 25-45 % carbon dioxide (CO2), and trace amounts of various other gases.

[0006] Natural sources of biogas include environments such as swamps, which generate methane by action of methanogens. A more common source of biogas is related to industrial activities related to waste disposal, principally related to landfills. A second, less widespread, source of biogas from human activities comes from anaerobic digesters and is used to generate methane and recycle organic waste to be used in fertilizing the field. Biogas is generated when organic waste is exposed to microbes, i.e., bacteria, archaea, and fungi, under anaerobic conditions (no oxygen present) to break down the organic compounds. This biodegradation yields gas (biogas), liquids and solids. The latter two, called digestate, can be used as soil amendments in fields for agriculture. The composition and nutrient content of the digestate is greatly impacted by the feedstock that undergoes anaerobic digestion as well as the operation conditions of the digester.

[0007] One of the end uses of industrially generated biogas is to bum it to provide a source of heat for buildings, boilers and perhaps even the biodigester. Biogas from landfills and digesters can also be refined to separate the methane (natural gas) from the other non-desirable constituents of biogas such as, but not limited to, carbon dioxide, water vapor, hydrogen sulfide, and others. This refining step yields renewable natural gas (RNG) which can be used as is, can be injected into an existing natural gas grid, or even used for vehicles powered by natural gas.

[0008] A significant benefit of biogas recovered from biodigesters or landfills is the reduction of usage of fossil fuels. Use of biogas generated from biodigesters or landfills can provide a clean source of power, which also happens to reduce the amount of methane released into the atmosphere. Since natural gas (methane) is a greenhouse gas which is, pound for pound, over 20 times more dangerous to the atmosphere that carbon dioxide over a 20-year period, it is desirable to reduce the release of this gas into the atmosphere . By controlling the release of this gas from its main industrial sources, it is possible to harness the energy it provides all the while providing a green alternative to power generation. Anaerobic digestion provides additional benefits to communities and the environment such as reducing odours, pathogens, and the risk of water pollution associated with manure coming from livestock and improving soil health.

[0009] The United States currently has over 2,000 biogas systems spread out across the country, but it has the potential to add at least another 10,000 additional plants and thus having a significant positive impact of the environment. In fact, proper harnessing of the potential of biogas in the United States alone would be the equivalent of removing the emissions of millions of cars yearly.

[0010] In addition to environmental benefits, the increased implementation of anaerobic digesters using various agricultural and food waste would inevitably reduce the costs associated with waste management if such were simply directed to landfills. Additional advantages of greater implementation of anaerobic digesters in the United States include the building of thousands of biogas systems, which would support hundreds of thousands of construction jobs and the resulting biodigester plants would employ several tens of thousands of people to operate them.

[0011] Wastewater treatment plants can have on-site anaerobic digesters to treat sewage sludge recovered during treatment. The solids are separated while the water is released and, more often than not, the methane generated is simply burnt into the atmosphere (i.e., it is flared) without benefiting of the energy this combustion generates. Only roughly two thirds of wastewater treatment plants in the United States that have anaerobic digesters actually use the biogas they generate.

[0012] Biogas Feedstocks

[0013] Food waste in landfills is responsible for over 20% of the volume of waste present in U.S. landfills. This food waste is an important source of natural gas as it breaks down. While landfills may capture the resultant biogas, putting organic wastes in landfills does not enable operators to recover the nutrients generated from the source organic material such as fats, oils, and grease collected from the food service industry (added to an anaerobic digester to increase biogas production). Livestock waste is another important source of methane. An average dairy cow weighing 1000 pounds produces approximately 80 pounds of manure per day, which is a non-negligible source of methane. It was assessed, in 2015, that livestock waste contributed to 10 % of all methane emissions in the United States but that only 3 % of all manure was actually being recycled in biodigester plants. This is a significant lost opportunity as well as environmentally careless.

[0014] Organic waste in landfills produces biogas, which is released into the atmosphere. Methane generated from landfills are ranked as the third largest source of such gas (by volume) related to human activities in the United States. Microorganisms present in landfills are similar to those found in anaerobic digestion, in that they are capable of breaking down organic materials and generating biogas. As methane is a potent greenhouse gas, it is desirable to capture these emissions to utilize them as a potential source of energy.

[0015] Crop residues are a source of organic material which can be processed in an anaerobic digester. These residues are meant to include, but not be limited to, stalks, straw, and plant trimmings. There are sufficient crop residues to leave a portion on the field in order to reduce the amount of soil erosion and harvest the remainder for biogas production. It is estimated that there is over 100 million tons of crop residues available which could be used in biogas systems. One drawback of crop residues is that they contain lignin, which is very poorly digested in biodigesters. Crop residues are typically mixed with a variety of other organic materials to generate biogas.

[0016] Composition of biogas

[0017] The composition of biogas is dependent on the feedstock, as well as the conditions of the biodigester such as temperature, pH, organic loading rate, etc. Typical biogas composition is made up of 45-75% methane, 25-45% carbon dioxide and 5% or less of various other gases.

[0018] Commercial scale anaerobic biodigesters face a number of different issues, with the most common being feedstock variability, low process efficiency, and lower product quality. These issues can be really significant for the asset owner or operator as it could not only translate to a non -economically favorable digester but could have considerable safety hazards to operators and the community (i.e., generation of offensive odours and / or generation of increased amounts of hydrogen sulfide, H2S). Currently, there are a wide range of techniques available to anaerobic digester operators and owners to overcome these challenges. Pretreatment of highly recalcitrant feedstocks has been utilized to improve the hydrolysis rate of certain types of biomasses that are more difficult to degrade by the microbial community present in the anaerobic digester. These pretreatments include physical pretreatments (such as grinding the biomass, chipping, cavitation, mechanical refining, deflaking, dispersing and use of a Hollander beater, etc.), thermal pretreatments (categorized as hydrothermal, microwave, extrusion, torrefaction, steam explosion, and wet oxidation), and chemical pretreatments (which covers acidic, basic, redox reactions and ionic liquids), and combinations thereof. Other pretreatments which have been considered and tested include biological pretreatment; electrochemical pretreatment; and various combination pretreatments also referred to as hybrid approaches. However, in most cases the high capital cost, high consumption of energy and chemicals, low delignification efficiencies, and sophisticated operating conditions are the major factor hindering their full-scale application.

[0019] Lignocellulosic biomass is a widely available resource which can be used in biogas production. When lignin is present in the unprocessed biomass, or in a pulp after incomplete delignification, and it is used as part of the feedstock for a biodigester, it results in a reduction of the rate of hydrolysis of said feedstock by the microbial community. This is due to lignin being highly recalcitrant to biodegradation, especially under anaerobic conditions. It has been observed that there is an inverse relationship between the amount of lignin in plant biomass and the corresponding biomethane potential, in which lignin limits the bioavailability of the more readily degradable cellulose as they are tightly linked together. Lignin, and its corresponding dissolved lignin components, will accumulate as the microbial community preferentially targets the more readily biodegradable compounds, which will eventually limit certain microbial activities and hinder the efficiency of other processes required for adequate anaerobic digestion. As such, it is preferable to minimize the amount of lignin remaining in the feedstock when the latter is used in anaerobic digestion for the generation of biogas in order to maximize the methane yield.

[0020] In addition to that, in jurisdictions where waste lignocellulosic biomass is limited, operators and asset owners have had to resort to the use of very recalcitrant, hard-to-degrade feedstocks (i.e., higher lignin content, high cellulose crystallinity, lower cellulose surface area, etc.). These have proven to be more difficult to incorporate in anaerobic digesters, resulting in inefficient biogas generation. Lignin has a complex aromatic and highly branched structure and is therefore not favoured by microorganisms. This complex structure blocks access to the cellulose part of the biomass that would normally be readily degradable. Lignin is not an ideal source of carbon for biogas generation due to the numerous degradation reactions that must occur making it a time-consuming process that few organisms are capable of. Also, as lignin is biodegraded, it produces oxidants and phenolic compounds, which will act as anti-microbials, hindering other members of the microbial community present in anaerobic digesters. Anaerobic digestion is conducted by a complex community of microorganisms which break down biomass into CO2 and methane. The activities of these microorganisms are broken down into roles: hydrolysis, acidogenesis, acetogenesis, and methanogenesis. The first stage involves hydrolysis of the insoluble biomass into its soluble components including sugars, fatty acids, and amino acids. The second stage, acidogenesis, further degrades these components into organic acids and alcohols. Microbes involved in acetogenesis consume the organic acids and alcohols produced by acidogenesis and produce methanogenic substrates such as acetate, hydrogen, and CO2. Finally, methanogenic archaea convert these substrates into methane. To maintain a healthy digester with a sufficient level of methane production, the microbial community in an anaerobic digester needs to maintain a balance of organisms involved in each of these roles.

[0021] There are many factors that can disrupt the balance of the microbial community involved in anaerobic digestion. One of the most common issues seen in anaerobic digestion, is acidification of the system. There are multiple variables that can lead to acidification, which occurs when there is an imbalance in the production and consumption of volatile fatty acids (VFAs). The accumulation of VFAs results in a drop in the pH of the digester environment. Although many acidogenic species can survive a wide pH range, other microorganisms in the digester are sensitive to changes in the pH, affecting their growth and metabolism. Methanogens in particular require a neutral pH to maintain an active metabolism and produce the final methane product. Thus, acidification of the digester environment leads to a reduction in methane and biogas production and, in some cases, complete failure of the entire anaerobic digestion process; which results in significant economic losses for anaerobic digester owners.

[0022] There are a few common methods used to remedy acidification in anaerobic digesters. Some of those include adjusting digester conditions such as temperature, organic loading rate or retention times, altering feedstock inputs (i.e., particle size), eliminating certain feedstocks all together, and using additives, either chemical (i.e., trace metals, minerals, alkali reagents, etc.) or biological (i.e., enzymes, additional organisms, etc.).

[0023] One of the most common and direct methods for dealing with acidification is the use of an alkali additive. Commonly used reagents include sodium hydroxide, sodium bicarbonate, calcium oxide, ammonium acetate and ammonium bicarbonate. Use of these materials has been shown to successfully reduce acidity in digester environments in multiple studies and is considered an effective method to combat acidification. Although adding an alkali to an acidified digester system can be effective, higher concentrations of said reagent can be inhibitory to the microbial community. It is well known that an optimal VFA to alkalinity ratio is less than 0.9 mg VFA / mg CaCO, If this ratio surpasses 1.25 mg VFA / mg CaCOs, microbial activity will be supressed. In this context, adding an alkali can increase the alkalinity of an anaerobic digester system, thereby decreasing the VFA to alkalinity ratio.

[0024] Another less common but still existent issue with anaerobic digesters is basification or alkalinization, where the pH of the system tends towards higher values. This can be caused by feeds which are rich in protein and contain large amounts of nitrogen, which will lower carbon-to-nitrogen ratios. This increased nitrogen content will result in ammonia being released via mineralization of organic nitrogen compounds. Small increases in pH and temperature can alter the dissociation balance of ammonia and ammonium, with ammonia having inhibitory concentrations between 30 to 100 mg / L and ammonium between 4000 to 6000 mg / L. To combat alkalinization, an acidic additive can be added such as hydrochloric acid, acetic acid or sodium acetate.

[0025] In light of the above, it is clear that biogas production needs to increase in the coming years in order to reduce countries dependence on oil and fossil fuel-based products, especially given the fact that such biogas facilities can be readily implemented. However, in order to optimize biogas production from such biogas facilities it is desirable to be able to provide a more consistent biogas output which is rich in methane, and overcome any challenges associated with anaerobic digestion, such as acidification. The composition of the biogas generated at such facilities may vary during the year depending on the available feedstock which is used. In many areas, farmers having a biogas facility on their farms or close by provide some or all of the feedstock. However, some feedstock is not necessarily available year-round or scarce and thus, changing the composition of the feedstock over the year has a direct impact on the generation of biogas and the composition thereof, which increases the chances of altering the correct functioning of an anaerobic digestion system.

[0026] Because of these factors, it is desirable to provide an alternative substrate which will replace or supplement at least a portion of the organic material (feedstock) being used in the production of biogas and simultaneously help overcome acidification and / or alkalinization challenges. Accordingly, there is a need to provide a method to delignify biomass to obtain a cellulose that is substantially free of lignin and that contains a neutralization agent that can be used as part of the feedstock in combination with other organic materials to generate consistent methane-rich biogas. SUMMARY OF THE INVENTION

[0027] The addition of cellulose with a neutralizing agent would combine the positive effects of the addition of low lignin cellulose with the positive effects of buffer on the acidification in a digester system. A low-lignin content cellulosic product which comprises a readily available, consistent source of carbon and which promotes a stable microbial community will increase the methane production of a biogas digester.

[0028] A drawback to the use of chemical additives is that they are prone to altering biogas production. This is why the addition of a low-lignin cellulose containing a neutralizing agent allows for the control the acidification or alkalinization issues while combating biogas production. This allows for consistent biogas production.

[0029] According to an aspect of the present invention, there is provided a buffered cellulose component which combines a low-lignin content cellulose additive with a buffering agent, which introduces a stable and readily biodegradable source of carbon, coupled with the positive effect of mitigating system acidification with a buffer.

[0030] According to an aspect of the present invention, there is provided a buffered cellulose component which combines a low-lignin content cellulose additive with a buffering or neutralizing agent which ensures that any negative effects potentially observed in biogas production when adding a neutralization agent can be counteracted by the beneficial effects of the cellulose. The combination of a buffer or neutralization agent with a cellulose with high biochemical methane potential (BMP) is particularly desirable as it remedies a considerable drawback linked to the addition of neutralizing agents on their own. This buffered cellulose can allow to maintain localized pH constant where the buffer component is present, it is balanced by the presence of a cellulose with high BMP. The addition of cellulose with a buffering agent combines the positive effects of the cellulose as described in previous patent applications by the Applicant as well as the positive effects of buffer on the acidification of the digester system. A low-lignin content cellulosic product which comprises a readily available, consistent source of carbon and which promotes a stable microbial community will increase the methane production of a biogas digester (also referred as a biodigester).

[0031] The combining of buffer with a low-lignin content cellulose is particularly desirable as it will result in increased methane potential from biodigesters and allow the system to sustain an optimal pH range for the microorganism present. According to an aspect of the present invention, there is provided a buffered biomass component wherein said buffered biomass component comprises: a cellulose component which is substantially free of lignin; water; and a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 50 %. Preferably, said component capable of neutralizing and / or buffering the pH is present in a concentration ranging from 0.5 to 5 M.

[0032] According to a preferred embodiment of the present invention, said solids content of said buffered biomass ranges from 15 to 25 %.

[0033] According to a preferred embodiment of the present invention, the alkali reagent is selected from the group consisting of: sodium hydroxide, potassium hydroxide, calcium oxide and other alkali and alkali earth metals.

[0034] According to a preferred embodiment of the present invention, the acidic reagent is selected from the group consisting of: a strong acid; a weak acid; and a combination thereof. Preferably, the strong acid is selected from the group consisting of: an inorganic acid; and an organic acid. Also preferably, the weak acid is selected from the group consisting of: an inorganic acid; and an organic acid.

[0035] According to a preferred embodiment of the present invention, a component capable of neutralizing and / or buffering the pH is selected from the group consisting of: bicarbonate buffers; phosphate buffers; acetate buffers; and combinations thereof. Preferably, said bicarbonate buffer is sodium bicarbonate.

[0036] According to a preferred embodiment of the present invention, said cellulose component which is substantially free of lignin is a cellulose where there remains less than 10 % of the amount of lignin prior to a lignocellulosic biomass being delignified. Preferably, said cellulose component which is substantially free of lignin is a cellulose where there remains less than 5 % of the amount of lignin prior to a lignocellulosic biomass being delignified. More preferably, said cellulose component which is substantially free of lignin is a cellulose where there remains less than 2.5 % of the amount of lignin prior to a lignocellulosic biomass being delignified. Even more preferably, said cellulose component which is substantially free of lignin is a cellulose where there remains less than 1 % of the amount of lignin prior to a lignocellulosic biomass being delignified.

[0037] According to a preferred embodiment of the present invention, said cellulose component which is substantially free of lignin is the result of the delignification of a recalcitrant biomass by exposure to a modified Caro’s acid.

[0038] According to an aspect of the present invention, there is provided a method to generate biogas, said process comprising the steps of: providing a digester adapted to receive a feed and capture a biogas composition resulting from anaerobic digestion; providing a feed comprising: o a feedstock component comprising of:

[0039] ■ a buffered biomass component which is substantially free of lignin in an amount that ranges between 1 % w / w to 100 % w / w of the feedstock; o optionally, at least one other organic material; and o at least one inoculum capable of converting a portion of said feedstock into methane under anaerobic conditions; wherein said buffered biomass component comprising: a cellulose component which is substantially free of lignin; water; and a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%. adding said feed to said digester; allowing sufficient time for a portion of allowing sufficient time for a portion of said feedstock and optionally, said at least one other organic material to be degraded (i.e. at least a portion of said buffered biomass and optionally, at least a portion of said organic material) to yield a biogas composition comprising methane; capturing said biogas composition; and optionally, storing at least a portion of said biogas.

[0040] Preferably, said cellulose component which is substantially free of lignin is present in an amount ranging from 1 % w / w to 100 % w / w of the total organic feedstock added to the biodigester. More preferably, said cellulose component which is substantially free of lignin is present in an amount ranging from 1 to 50 % w / w of the total organic feedstock added to the biodigester. Even more preferably, said cellulose component which is substantially free of lignin is present in an amount ranging from 2 to 40 % w / w of the total organic feedstock added to the biodigester.

[0041] According to an aspect of the present invention, there is provided a use of a buffered biomass component to reduce the acidity or alkalinity in a biogas reactor, wherein said buffered biomass component wherein said buffered biomass component comprises: a cellulose component which is substantially free of lignin; water; and a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%.

[0042] According to a preferred embodiment of the present invention, a portion of the digester’s contents is removed daily from said digester and a substantially equivalent replacement amount comprised of said inoculum, said low-lignin content cellulose additive with a buffering or neutralizing agent and optionally, said least one organic material is added to the digester. Preferably, said low-lignin content cellulose additive with a buffering or neutralizing agent comprises up to 100% of the equivalent feedstock replacement amount. Preferably, said low-lignin content cellulose additive with a buffering or neutralizing agent comprises from 1% to 100% of the equivalent feedstock replacement amount. More preferably, said low- lignin content cellulose additive with a buffering agent comprises from 1% to 10% of the equivalent feedstock replacement amount.

[0043] According to an aspect of the present invention, there is provided a method to generate biogas, said process consisting of the steps of: providing a biodigester adapted to receive a feed and capture a biogas composition resulting from anaerobic digestion; providing a feed comprising: o a feedstock component comprising of:

[0044] ■ a buffered biomass component which is substantially free of lignin in an amount that ranges between 1 % w / w to 100 % w / w of the feedstock; o optionally, at least one other organic material; and o at least one inoculum capable of converting said feedstock and said at least one other organic material into methane under anaerobic conditions; wherein said buffered biomass component comprising: a cellulose component which is substantially free of lignin; a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; water; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%. adding said feed to said biodigester; allowing sufficient time for a portion of said feedstock and optionally, said at least one other organic material to be degraded to yield a biogas composition comprising methane; capturing said biogas composition; and optionally, storing at least a portion of said biogas.

[0045] According to an aspect of the present invention, there is provided a use of a buffered biomass component to reduce the acidity or alkalinity in a biogas reactor, wherein said buffered biomass component wherein said buffered biomass component consists of: a cellulose component which is substantially free of lignin; a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; water; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%.

[0046] According to an aspect of the present invention, there is provided a buffered biomass component wherein said buffered biomass component consisting of: a cellulose component which is substantially free of lignin; water; and a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 50 %.

[0047] It will be understood by the person skilled in the art that biogas is generated after organic materials (plant and animal products) are broken down when exposed to bacteria, archaea and fungi, in an anoxic environment (i.e., under anaerobic conditions). This is also referred to as anaerobic digestion. Anaerobic digestion of organic material yields biogas and residual solids and liquids which is called the digestate. The digestate is rich in nutrients that were present in the original organic material but is now more readily available for plants and soil. The amount, composition, and nutrient content of the digestate is determined by the type of feedstock used in the decomposition of the organic matter added to the digester.

[0048] According to a preferred embodiment of the present invention, there is provided a method to generate biogas which employs a substantially lignin-free cellulosic component obtained from the exposure of a lignocellulosic feedstock to a modified Caro's acid under substantially milder conditions than other conventionally employed pulping processes (such as Kraft pulping). This approach allows for a greener process across the board as the lignocellulosic feedstock does not divert food resources away from animals or humans, as well as uses a very low energy input delignification process.

[0049] According to a preferred embodiment of the present invention, the feedstock is a cellulose wherein said cellulose has a content of hemicellulose of less than 15 %, preferably less than 10 % and more preferably less than 5 %, and a Kappa number of less than 10, more preferably less than 5, and even more preferably, less than 2.

[0050] According to a preferred embodiment of the present invention, the feedstock is a low -lignin, low- hemicellulose containing cellulose additive with a buffering agent which may include sodium hydroxide, sodium bicarbonate, calcium oxide and / or ammonium bicarbonate. Preferably, said buffering or neutralization agents are coupled with the cellulose additive component in concentrations between 0.01 to 10 M, more preferably between 0. 1 and 5 M, and even more preferably, between 0.5 and 1 M.

[0051] Biogas comprises several gases including, but not limited to, methane, carbon dioxide, hydrogen sulfide, and volatile fatty acids. In most cases, the residual solids and liquids (“digestate”) can be used as fertilizer for soils.

[0052] BRIEF DESCRIPTION OF THE FIGURES

[0053] Features and advantages of embodiments of the present application will become apparent from the following detailed description and the appended figures, which:

[0054] Figure 1 is a graphical depiction of the buffered cellulose solution pH at increasing volumes of titrant (where the titrant used was 0.1 N acetic acid); and

[0055] Figure 2 is a graphical depiction of the cumulative methane produced over time in buffered and unbuffered cellulose as per Experiment #3.

[0056] DETAILED DESCRIPTION OF THE INVENTION

[0057] One of the technical barriers to greater adoption of biogas as an alternative fuel source is related to infrastructural challenges. One of such challenges is the variance in the availability of the feedstock used in anaerobic digesters. It is known that various organic materials may be added to an anaerobic digester and produce biogas, however, what is not as well understood or appreciated is that there are several gases which are formed during such anaerobic digestion. The varying composition of the biogas is correlated to the feed (organic material) added for anaerobic digestion as well as the operating conditions and feed input. The availability of feedstock, being of organic nature, naturally varies throughout the year as based on the growing seasons. Moreover, the winter season is generally associated with a reduced biogas production which causes a number of problems.

[0058] According to a preferred embodiment of the present invention, there is provided a method to increase or maintain the methane production from an anaerobic digester while simultaneously addressing issues related to acidification and / or alkalization.

[0059] It has been surprisingly found that when using a substantially lignin-free cellulose as a component or as the main component of the feedstock into an anaerobic digester, the methane gas volume produced increases when compared to a similar situation where a non-delignified biomass or an insufficiently delignified substrate is added to the same digester.

[0060] According to a preferred embodiment of the present invention, there is provided a method to increase and stabilize the volume of methane produced from a biogas digester by using a substantially lignin-free cellulose as part of or as the feedstock for biogas production. It has been surprisingly found that using a substantially lignin-free cellulose as part of or as the feedstock to anaerobic digestion can increase the methane gas volume produced. It has also been surprisingly found that using a substantially lignin-free cellulose that contains a buffering or neutralization agent can stabilize the pH of the digester while maintaining or increasing the biogas and methane volume generation.

[0061] According to a preferred embodiment of the present invention, the composition of gases comprises at least 60 % methane to be used as an efficient source of energy.

[0062] Currently, most biomass fed to anaerobic digesters is not delignified and the presence of lignin causes inhibition of the biodegradation of said biomass by microorganisms present in the biodigester and consequently hindering optimal methane production from such units. Preferably, by using cellulose obtained from a delignification of lignocellulosic biomass using a modified Caro’s acid, as a lesser component or the main component of the feedstock added to anaerobic digesters, the cellulose is in a more readily accessible form for the microorganisms in the biodigester.

[0063] According to a preferred embodiment of the present invention, the feedstock used in anaerobic digestion is a cellulose which has been processed to be substantially free of lignin. Preferably, the addition of a substantially-free of lignin component allows for an increase in the generation of methane in an anaerobic digester when all or part of the feedstock is replaced with said substantially lignin-free cellulose. Preferably, said substantially lignin-free component is cellulose and is present in an amount ranging from 1 % w / w to 100 % w / w of the total feedstock amount added daily in the biodigester. Preferably, the cellulose is hydrated, in some cases the water may be up to 90 % of the weight of the cellulose. According to a preferred embodiment, the cellulose is present in an amount ranging from 1 to 50 % w / w of the total organic feedstock in the biodigester. According to a more preferred embodiment of the present invention, the cellulose is present in an amount ranging from 2 to 40 % w / w of the total organic feedstock in the biodigester. Preferably, the amount of biomass component may be adjusted based on the composition of the organic content present in the digester. It is also desirable that given the possible fluctuations between various biodigesters (due to their different organic content and microbial communities), a pre -determination be done to assess the optimal concentration of the biomass component to be incorporated with the other organic content inside the digester so as not to incorporate an amount which is not optimal as the component may be more costly than the other organic content inside the biodigester.

[0064] It is generally accepted that biogas is formed mainly by the degradation of organic materials such as: carbohydrates, proteins, and lipids. The lignin fraction present in various feedstock added to digesters is known to be difficult to degrade by the microorganisms present in the digesters. While anaerobic digestion of lignin has been observed in certain environments, it requires a variety of microorganisms whose main pathway involves the enzymatic depolymerization of lignin. Even when these organisms are present, the process tends to be slow. Because of the complexity of the microbial community present in those systems, they are very difficult to reproduce on an industrial scale, making the applicability of the anaerobic digestion of lignin a complicated and difficult topic.

[0065] Recalcitrant biomass or highly recalcitrant biomass is another way of labelling such difficult to degrade biomass. The US Department of Energy has referred to biomass recalcitrance as being the resistance of plants to release their sugars for fermentation or upgrading. It is this recalcitrance which has been labelled to be the primary barrier to efficient and economical production of advanced biofuels. Types of recalcitrant biomass include but are not limited to: lignocellulosic biomass such as forestry by-products (such as wood shavings and the like); agricultural waste or by-products (such as but not limited to, com stover, rice straw, and wheat straw); paper industry waste; and other such as, but not limited to hemp, switch grass, etc. Within those categories, highly recalcitrant biomass is that containing large amounts of lignin, high crystallinity of the cellulosic portion or a high degree of polymerization of the cellulosic portion. By adding a cellulose-rich component which is essentially devoid of lignin, it has been made possible to increase the generation of methane in an anaerobic digester. The delignification of biomass according to conventional pulping approaches typically results in pulp which is still high in lignin. Typically, further removal of the remaining lignin is performed through a bleaching process, which involves harsh chemicals and conditions that are not energy and environmentally conscious. To employ a bleached pulp in a biodigester is simply not commercially viable or applicable on an industrial scale as it would be highly cost-prohibitive. In addition, any potential bleaching agent residues would negatively affect the digester health.

[0066] According to a preferred embodiment of the present invention, the biomass component is an unbleached cellulose. Preferably, the cellulose is obtained by the delignification of biomass through the exposure of such to a modified Caro’s acid as per the following processes. A preferred embodiment of the process to delignify biomass, comprises the steps of: providing a vessel; providing biomass comprising lignin, hemicellulose and cellulose fibers into said vessel; providing an aqueous acidic composition comprising an acid selected from the group consisting of: sulfuric acid; an alkylsulfonic acid; an arylsulfonic acid and combinations thereof; providing a modifier component; providing a peroxide component; exposing said biomass to said acidic composition, said peroxide component and said modifier component to create a reaction mass for a period of time sufficient to a delignification reaction to occur and remove over 90 wt % of said lignin and hemicellulose from said biomass; separating the dissolved lignin and hemicellulose form the solid cellulose; neutralizing the solid cellulose to a neutral pH; and, optionally, rinsing the cellulose to remove any acidic component remaining therein.

[0067] Preferably, the recalcitrant biomass comprises lignin, hemicellulose and cellulose fibers and is exposed to said acidic composition, said peroxide component and said modifier component which form a modified Caro’s acid composition selected from the group consisting of: composition A; composition B and Composition C; wherein said composition A comprises:

[0068] - sulfuric acid in an amount ranging from 20 to 70 wt % of the total weight of the composition; - a modifier compound comprising an amine moiety and a sulfonic acid moiety selected from the group consisting of: taurine; taurine derivatives; and taurine- related compounds; and

[0069] - a peroxide; wherein said composition B comprises:

[0070] - an alkylsulfonic acid; and

[0071] - a peroxide; wherein the acid is present in an amount ranging from 40 to 80 wt % of the total weight of the composition and where the peroxide is present in an amount ranging from 10 to 40 wt % of the total weight of the composition; wherein said composition C comprises:

[0072] - sulfuric acid;

[0073] -a two-part modifier comprising:

[0074] - a compound comprising an amine moiety; and

[0075] - a compound comprising a sulfonic acid moiety; and

[0076] - a peroxide.

[0077] According to a preferred embodiment of the present invention, exposing said biomass to said modified Caro’s acid composition will allow the delignification reaction to occur and remove over 90 wt % of said lignin and hemicellulose from said biomass.

[0078] Preferably, the delignification reaction is carried out at a temperature below 55°C by a method selected from the group consisting of:

[0079] - adding water into said vessel;

[0080] - adding biomass into said vessel; and

[0081] - using a heat exchanger.

[0082] Preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 1: 1: 1. Preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 1: 1. Also preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no more than 15: 1: 1. Preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no more than 15: 1. More preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety and said peroxide are present in a molar ratio of no less than 3: 1 : 1. More preferably, said sulfuric acid, said compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3: 1.

[0083] According to a preferred embodiment of the method to delignify biomass as set out herein, said modifier compound comprises an amine moiety and a sulfonic acid moiety is selected from the group consisting of: taurine; taurine derivatives; and taurine -related compounds.

[0084] According to a preferred embodiment of the method to delignify biomass as set out herein, said taurine derivative or taurine -related compound is selected from the group consisting of: taurolidine; taurocholic acid; tauroselcholic acid; tauromustine; 5-taurinomethyluridine and 5-taurinomethyl-2- thiouridine; homotaurine (tramiprosate); acamprosate; and taurates; as well as aminoalkylsulfonic acids where the alkyl is selected from the group consisting of C1-C5 linear alkyl and C1-C5 branched alkyl. Preferably, said linear alkylaminosulfonic acid is selected form the group consisting of: methyl; ethyl (taurine); propyl; and butyl. Preferably, said branched aminoalkylsulfonic acid is selected from the group consisting of: isopropyl; isobutyl; and isopentyl.

[0085] According to a preferred embodiment of the present invention, said modifier compound comprising an amine moiety and a sulfonic acid moiety is taurine.

[0086] According to a preferred embodiment of the present invention, said sulfuric acid and compound comprising an amine moiety and a sulfonic acid moiety are present in a molar ratio of no less than 3: 1.

[0087] According to a preferred embodiment of the present invention, said compound comprising an amine moiety is an alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine; and combinations thereof.

[0088] According to a preferred embodiment of the present invention, said compound comprising a sulfonic acid moiety is selected from the group consisting of: alkylsulfonic acids and combinations thereof.

[0089] According to a preferred embodiment of the present invention, said alkylsulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from Ci-Ce and are linear or branched; and combinations thereof. According to a preferred embodiment of the present invention, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2- propane sulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butane sulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof.

[0090] According to a preferred embodiment of the present invention, said alkylsulfonic acid; and said peroxide are present in a molar ratio of no less than 1: 1.

[0091] According to a preferred embodiment of the present invention, said compound comprising a sulfonic acid moiety is methane sulfonic acid.

[0092] According to a preferred embodiment of the present invention, in Composition C, said sulfuric acid and said a compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio of no less than 1: 1: 1.

[0093] According to a preferred embodiment of the present invention, in Composition C, said sulfuric acid, said compound comprising an amine moiety and said compound comprising a sulfonic acid moiety are present in a molar ratio ranging from 28: 1: 1 to 2: 1: 1.

[0094] According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,678) comprises: sulfuric acid; a heterocyclic compound; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1: 1. Preferably, the sulfuric acid and said heterocyclic compound are present in a molar ratio ranging from 28: 1 to 2: 1 More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 24: 1 to 3: 1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 20 : 1 to 4: 1. More preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 16: 1 to 5: 1. Preferably, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12: 1 to 6: 1. Also preferably, said heterocyclic compound has a molecular weight below 300 g / mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g / mol. More preferably, said heterocyclic compound is a secondary amine. According to a preferred embodiment of the present invention, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; and N-methylimidazole. According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,677) comprises: sulfuric acid; a modifying agent comprising a compound containing an amine group; and wherein sulfuric acid and said compound containing an amine group; are present in a molar ratio of no less than 1: 1. Preferably, the sulfuric acid and said compound containing an amine group are present in a molar ratio ranging from 28: 1 to 2: 1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 24: 1 to 3: 1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 20: 1 to 4: 1. More preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 16: 1 to 5: 1. Preferably, the sulfuric acid and compound containing an amine group are present in a molar ratio ranging from 12: 1 to 6: 1. According to a preferred embodiment of the present invention, the modifying agent is selected in the group consisting of: TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; diethylamine; triethylamine; morpholine; MEA -triazine; and combinations thereof. According to a more preferred embodiment of the present invention, the modifying agent is TEOA; MEOA; pyrrolidine; DEOA; ethylenediamine; triethylamine.

[0095] According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,676) comprises: sulfuric acid; a modifying agent comprising an alkanesulfonic acid; and wherein sulfuric acid and said alkane sulfonic acid are present in a molar ratio of no less than 1: 1. Preferably, said alkanesulfonic acid is selected from the group consisting of: alkanesulfonic acids where the alkyl groups range from Ci-Ce and are linear or branched; and combinations thereof. Preferably, said alkanesulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2 -propane sulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. More preferably, said alkanesulfonic acid is methanesulfonic acid. Also preferably, said alkanesulfonic acid has a molecular weight below 300 g / mol. Also preferably, said alkanesulfonic acid has a molecular weight below 150 g / mol. Preferably, the sulfuric acid and said alkanesulfonic acid and are present in a molar ratio ranging from 28: 1 to 2: 1. More preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 24: 1 to 3 : 1. Preferably, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 20: 1 to 4: 1. More preferably, the sulfuric acid and alkane sulfonic acid are present in a molar ratio ranging from 16: 1 to 5: 1. According to a preferred embodiment of the present invention, the sulfuric acid and alkanesulfonic acid are present in a molar ratio ranging from 12: 1 to 6: 1. According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,675) comprises: sulfuric acid; a substituted aromatic compound; and wherein sulfuric acid and said substituted aromatic compound; are present in a molar ratio of no less than 1: 1. Preferably, the substituted aromatic compound comprises at least two substituents. More preferably, at least one substituent is an amine group and at least one of the other substituent is a sulfonic acid moiety. According to a preferred embodiment, the substituted aromatic compound comprises three or more substituent. According to a preferred embodiment of the present invention, the substituted aromatic compound comprises at least a sulfonic acid moiety. According to another preferred embodiment of the present invention, the substituted aromatic compound comprises an aromatic compound having a sulfonamide substituent, where the compound can be selected from the group consisting of: benzenesulfonamides; toluenesulfonamides; substituted benzenesulfonamides; and substituted toluenesulfonamides. Preferably, the sulfuric acid and said substituted aromatic compound and are present in a molar ratio ranging from 28: 1 to 2: 1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 24: 1 to 3 : 1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 20: 1 to 4: 1. More preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 16: 1 to 5: 1. Preferably, the sulfuric acid and substituted aromatic compound are present in a molar ratio ranging from 12: 1 to 6: 1.

[0096] According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,674) comprises: sulfuric acid; a modifying agent comprising an arylsulfonic acid; and optionally, a compound containing an amine group; wherein sulfuric acid and said a arylsulfonic acid; are present in a molar ratio of no less than 1: 1. Preferably, the compound containing an amine group is selected from the group consisting of: imidazole; N-methylimidazole; triazole; monoethanolamine (MEO A); diethanolamine (DEO A); triethanolamine (TEO A); pyrrolidine and combinations thereof. According to a preferred embodiment of the present invention, sulfuric acid and the peroxide are present in a molar ratio of approximately 1: 1. Preferably, the sulfuric acid and said arylsulfonic acid and are present in a molar ratio ranging from 28: 1 to 2: 1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 24: 1 to 3: 1. Preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 20: 1 to 4: 1. More preferably, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 16: 1 to 5: 1. According to a preferred embodiment of the present invention, the sulfuric acid and arylsulfonic acid are present in a molar ratio ranging from 12: 1 to 6: 1. Also preferably, said arylsulfonic acid has a molecular weight below 300 g / mol. Also preferably, said arylsulfonic acid has a molecular weight below 150 g / mol. Even more preferably, said arylsulfonic acid is selected from the group consisting of: orthanilic acid; metanilic acid; sulfanilic acid; toluenesulfonic acid; benzenesulfonic acid; and combinations thereof.

[0097] According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,673) comprises: sulfuric acid; a heterocyclic compound; an alkanesulfonic acid; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1: 1. Preferably, said aqueous acidic composition comprising: sulfuric acid; a heterocyclic compound; an arylsulfonic acid; and wherein sulfuric acid and said a heterocyclic compound; are present in a molar ratio of no less than 1: 1. Preferably, the arylsulfonic acid is toluenesulfonic acid. Preferably, the sulfuric acid, the heterocyclic compound and the alkane sulfonic acid are present in a molar ratio ranging from 28: 1: 1 to 2: 1: 1. More preferably, the sulfuric acid the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 24: 1 : 1 to 3 : 1 : 1. Preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 20: 1: 1 to 4: 1: 1. More preferably, the sulfuric acid, the heterocyclic compound and the alkanesulfonic acid are present in a molar ratio ranging from 16: 1: 1 to 5: 1: 1. According to a preferred embodiment of the present invention, the sulfuric acid and heterocyclic compound are present in a molar ratio ranging from 12: 1: 1 to 6: 1: 1. Also preferably, said heterocyclic compound has a molecular weight below 300 g / mol. Also preferably, said heterocyclic compound has a molecular weight below 150 g / mol. Even more preferably, said heterocyclic compound is selected from the group consisting of: imidazole; triazole; n-methylimidazole; and combinations thereof. Preferably, the alkanesulfonic acid is selected from the group consisting of: alkylsulfonic acids where the alkyl groups range from Ci-Ce and are linear or branched; and combinations thereof. Preferably, said alkylsulfonic acid is selected from the group consisting of: methanesulfonic acid; ethanesulfonic acid; propanesulfonic acid; 2-propanesulfonic acid; isobutylsulfonic acid; t-butylsulfonic acid; butanesulfonic acid; iso-pentylsulfonic acid; t-pentylsulfonic acid; pentanesulfonic acid; t-butylhexanesulfonic acid; and combinations thereof. More preferably, said alkylsulfonic acid is methanesulfonic acid.

[0098] According to preferred embodiment of the present invention, the modified Caro’s acid (as disclosed in Canadian patent application 3,128,672) comprises: sulfuric acid; a carbonyl-containing nitrogenous base compound; and wherein sulfuric acid and said a carbonyl -containing nitrogenous base compound; are present in a molar ratio of no less than 1: 1. According to a preferred embodiment of the present invention, the carbonyl-containing nitrogenous base compound is selected from the group consisting of: caffeine; lysine; creatine; glutamine; creatinine; 4-aminobenzoic acid; glycine; NMP (N-methyl-2-pyrrolidinone); histidine; DMA (N,N-dimethylacetamide); arginine; 2,3-pyridinedicarboxylic acid; hydantoin; and combinations thereof. Preferably, the sulfuric acid and said carbonyl -containing nitrogenous base compound and are present in a molar ratio ranging from 28: 1 to 2: 1. More preferably, the sulfuric acid and carbonyl -containing nitrogenous base compound are present in a molar ratio ranging from 24: 1 to 3: 1. Preferably, the sulfuric acid and carbonyl -containing nitrogenous base compound are present in a molar ratio ranging from 20: 1 to 4: 1. More preferably, the sulfuric acid and carbonyl -containing nitrogenous base compound are present in a molar ratio ranging from 16: 1 to 5: 1. According to a preferred embodiment of the present invention, the sulfuric acid and carbonyl -containing nitrogenous base compound are present in a molar ratio ranging from 12: 1 to 6: 1.

[0099] According to a preferred embodiment of the present invention, the biomass additive is a cellulose wherein said cellulose has a content of hemicellulose of less than 15 %, preferably less than 10 % and more preferably less than 5 %, and a Kappa number of less than 10, more preferably less than 5, and even more preferably, less than 2.

[0100] Lab Scale Testing

[0101] Serum bottles were used to conduct anaerobic digestion experiments. The serum bottles were set up by adding manure, digestate from a commercial scale digester and in some cases, feedstock comprised of agricultural waste and / or cellulose obtained via a delignification process involving the use of a modified Caro’s acid as described earlier. Biogas production and methane concentrations were regularly measured throughout the experiments.

[0102] Experiment #1 - Titration of buffered cellulose

[0103] Procedure

[0104] Buffered cellulose was prepared by adding sodium bicarbonate dissolved in RO water to cellulose derived from hardwood, to obtain a final sodium bicarbonate buffer concentration of 0.5 M. The final solids content of the buffered cellulose was 19.44 %. Using the same starting cellulose, an unbuffered batch of cellulose was prepared to the same solids content using RO water.

[0105] For the titration, two solutions of cellulose were prepared using the buffered and unbuffered celluloses. These solutions were 5 % of the relevant cellulose wet. The starting pH of the buffered and unbuffered celluloses were 9.45 and 6.54, respectively. To make the two comparable, the unbuffered cellulose solution was brought up to a pH of 9.51 using 0.1 M NaOH prior to titration. The solutions were titrated simultaneously using 0.1 N acetic acid, 1 mL at a time. The pH readings were recorded 2 minutes after the titrant was added for each increment. A total of 24 mL of titrant was added. Results

[0106] The unbuffered cellulose showed a drastic change in pH after the initial addition of titrant, while the buffered cellulose very slowly decreased in pH. Throughout the titration, the unbuffered cellulose reduced in pH incrementally while the buffered cellulose showed a gradual decrease. Although both solutions started at a similar pH, the final pH was significantly different at 6.05 for the buffered cellulose and 3.40 for the unbuffered cellulose. The results of this experiment are found in Figure 1 which depicts the pH of the cellulose solution at increasing volumes of titrant. The titrant used was 0.1 N acetic acid.

[0107] Experiment #2 - Determination of theoretical methane potential (TMP) of buffered and unbuffered cellulose

[0108] Procedure

[0109] The purpose of this experiment was to determine the TMP of buffered cellulose and compare it with the TMP of an unbuffered cellulose. The buffered and unbuffered celluloses both had a total solids content of 16.84 % wt. These substrates were then suspended in water and analyzed for Chemical Oxygen Demand (COD) determination. COD is a measure of the amount of oxygen that can be consumed by reactions during the decomposition of organic matter suspended in water. This value describes how much energy is available in the organic matter and can be used to calculate the theoretical amount of methane that could be produced from the complete decomposition of that organic matter. The same samples were characterized by testing their total solids (TS) as well as volatile solids (VS). This was performed as per US EPA method 1684. The percentage of volatile solids is a measure of the amount of material lost after a sample is ignited. The results of these tests are reported in Table 1. The COD results are the average of two determinations while TS and VS are performed in duplicate.

[0110] Table 1: Theoretical methane potential for buffered and unbuffered substantially lignin-free cellulose samples Results

[0111] The results of this experiment demonstrate the TMP of the buffered cellulose to be nearly identical to the unbuffered cellulose. This indicates that no noteworthy difference should be expected in the amount of methane that can be produced from buffered vs. unbuffered cellulose.

[0112] Experiment #3 - Determination of biochemical methane potential (BMP) of buffered cellulose Procedure

[0113] Buffered cellulose was prepared by adding sodium bicarbonate dissolved in RO water to cellulose derived from hardwood, to obtain a final sodium bicarbonate buffer concentration of 0.402 M. The final solids content of the buffered cellulose was 18.00 %. Using the same starting cellulose, an unbuffered batch of cellulose was prepared to a solids content of 16.28 % using RO water.

[0114] This experiment was designed to corroborate the theoretical results obtained from Experiment #2. For the experiment preparation, the Total Solids (TS) and Volatile Solids (VS) were measured for both substrates, as well as the inoculum (digestate). Substrates were added to serum bottles containing the prepared inoculum in an inoculum-to-substrate ratio of 2.0, calculated based of the volatile solids of the materials. Corresponding substrate-free blank bottles were prepared by adding water in place of the substrate. Bottles were incubated at 35 °C for the duration of the experiment. Biogas and methane production of test samples were measured three times a week or as needed.

[0115] For analysis, the methane measurements were normalized to Standard Temperature Pressure (STP) conditions (101.35 kPa, 0 °C) and the methane generated from the substrate -free blanks was subtracted from the methane generated from the experimental substrates. This was done to ensure that the results are a reflection of the amount of methane produced from the addition of the substrate alone. The results for this experiment are shown in Figure 2.

[0116] Results

[0117] The results of this experiment show that there was no significant difference in BMP between the two celluloses. This, along with the results from Experiment #2 suggest that there should be no difference between the two celluloses when it comes to methane production. Both have high biochemical methane potentials, and the addition of a buffer does not have any negative effects on the production of methane.

[0118] While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by those skilled in the relevant arts, once they have been made familiar with this disclosure that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.

Claims

CLAIMS1. A buffered biomass component wherein said buffered biomass component comprises: a cellulose component which is substantially free of lignin; water; and a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 50 %.

2. The buffered biomass component according to claim 1, wherein said component capable of neutralizing and / or buffering the pH is present in a concentration ranging from 0.5 to 5 M.

3. The buffered biomass component according to claim 1, wherein said solids content of said buffered biomass ranges from 15 to 25 %.

4. The component capable of neutralizing and / or buffering the pH according to claim 1 wherein the alkali reagent is selected from the group consisting of: sodium hydroxide, potassium hydroxide, calcium oxide and other alkali and alkali earth metals.

5. The buffered biomass component according to claim 1, wherein the acidic reagent is selected from the group consisting of: a strong acid; a weak acid; and a combination thereof.

6. The buffered biomass component according to claim 1, wherein the acidic reagent is selected from the group consisting of: a strong acid; a weak acid; and a combination thereof.

7. The buffered biomass component according to claim 6 wherein the strong acid is selected from the group consisting of: an inorganic acid; and an organic acid.

8. The buffered biomass component according to claim 6 wherein the weak acid is selected from the group consisting of: an inorganic acid; and an organic acid.

9. The buffered biomass component according to claim 1 wherein component capable of neutralizing and / or buffering the pH is selected from the group consisting of: bicarbonate buffers; phosphate buffers; acetate buffers; and combinations thereof.

10. The buffered biomass component according to claim 9, wherein said bicarbonate buffer is sodium bicarbonate.

11. The buffered biomass component according to any one of claims 1 to 10, wherein said cellulose component which is substantially free of lignin is a cellulose where there remains less than 10 % of the amount of lignin prior to a lignocellulosic biomass being delignified.

12. The buffered biomass component according to any one of claims 1 to 11, wherein said cellulose component which is substantially free of lignin is a cellulose where there remains less than 5 % of the amount of lignin prior to a lignocellulosic biomass being delignified.

13. The buffered biomass component according to any one of claims 1 to 12, wherein said cellulose component which is substantially free of lignin is a cellulose where there remains less than 2.5 % of the amount of lignin prior to a lignocellulosic biomass being delignified.

14. The buffered biomass component according to any one of claims 1 to 13, wherein said cellulose component which is substantially free of lignin is a cellulose where there remains less than 1 % of the amount of lignin prior to a lignocellulosic biomass being delignified.

15. The buffered biomass component according to any one of claims 1 to 14 wherein said cellulose component which is substantially free of lignin is the result of the delignification of a recalcitrant biomass by exposure to a modified Caro’s acid.

16. A method to generate biogas, said process comprising the steps of: providing a biodigester adapted to receive a feed and capture a biogas composition resulting from anaerobic digestion; providing a feed comprising: o a feedstock component comprising of:■ a buffered biomass component which is substantially free of lignin in an amount that ranges between 1 % w / w to 100 % w / w of the feedstock; o optionally, at least one other organic material; and o at least one inoculum capable of converting said feedstock and said at least one other organic material into methane under anaerobic conditions; wherein said buffered biomass component comprising: a cellulose component which is substantially free of lignin; a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; water; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%. adding said feed to said biodigester; allowing sufficient time for a portion of said feedstock and optionally, said at least one other organic material to be degraded to yield a biogas composition comprising methane; capturing said biogas composition; and optionally, storing at least a portion of said biogas.

17. The method according to claim 16 wherein said cellulose component which is substantially free of lignin is present in an amount ranging from 1 % w / w to 100 % w / w of the total feedstock added to the biodigester.

18. The method according to any one of claims 16 to 17 wherein said cellulose component which is substantially free of lignin is present in an amount ranging from 1 to 50 % w / w of the total feedstock added to the biodigester.

19. The method according to any one of claims 16 to 17 wherein said cellulose component which is substantially free of lignin is present in an amount ranging from 2 to 40 % w / w of the total feedstock added to the biodigester.

20. A use of a buffered biomass component to reduce the acidity or alkalinity in a biogas reactor, wherein said buffered biomass component wherein said buffered biomass component comprises: a cellulose component which is substantially free of lignin; a component capable of neutralizing and / or buffering the pH, wherein said component can be selected from the group consisting of: o an alkali reagent; o an acidic reagent; and o a buffering agent; water; wherein the concentration of said component capable of neutralizing and / or buffering the pH ranges from 0.1 to 10 M and wherein a solids content of said buffered biomass ranges from 10 to 25%.

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