HK1183291A - High rate anaerobic digester system and method - Google Patents

Description

High efficiency anaerobic digester system and method

Cross Reference to Related Applications

This PCT application claims priority from U.S. provisional patent application No. 61/345,029, filed 5, 14, 2010, the disclosure of which is incorporated herein by reference in its entirety for all purposes.

Background

Technical Field

The present invention generally relates to high efficiency anaerobic digester systems and methods of use thereof.

Description of the related Art

Biological digestion is well known as a method of sewage treatment and environmental protection. Recent biological digestion has emerged in the field of renewable energy generation. Biogas produced in the bio-digestion process can be used to run generators for electricity production and boilers for heating purposes.

FIGS. 1A, 1B and 1C depict a conventional digester system using a single reaction vessel. Figure 1A shows a dry anaerobic composting (Dranco) process. The Dranco digester is a dry, single stage, thermophilic anaerobic digestion system (Verma, 2002). Feed is introduced into the top of the digester and flows into the conical bottom where the auger removes anaerobic digester effluent. A portion of the anaerobic digester effluent is used to inoculate the incoming feed and steam is added to raise the temperature to the high temperature range. The remaining anaerobic digester effluent is dewatered to produce wastewater and a filter cake. The filter cake contains active bacteria, some ammonia and undigested solids that are aerobically stabilized for use as compost. The waste is preferably sorted to maintain compost quality. There was no mixing in the reactor except for some bubbling of the biogas against the substrate plug flow movement. It was reported that the Dranco digesters maintained high average organic loading rates (12-15 kg VS/m)³D) to treat municipal organic solid waste.

Fig. 1B shows a system running the Kompogas process. The Kompogas digester is a high solids plug flow design. The cylindrical reactor is horizontally oriented and contains an inner rotor that aids in degassing and homogenization (Lissens et al 2001; Nichols 2004). The system is prefabricated to 15,000 or 25,000 tons per year (t/y) size. The internal solids content must be carefully maintained at 23-28% for proper flow of the system. Thus, some of the process water and anaerobic digester effluent is mixed with the incoming organic waste, which also provides for inoculation (Lissens et al 200). The retention time is 15-20 days under the high temperature condition.

Figure 1C shows the Valorga system. The Valorga system is a dry, single stage digester that processes plug flow anaerobic digester effluent (Nichols 2004) with a Total Solids (TS) of 25-30%. Unlike other plug flow digesters, the Valorga design uses pressurized biogas for mixing. This eliminates the need for an inoculating loop. The vertical cylindrical digester includes a zoned extension spanning two-thirds of the digester diameter. This forces the material to enter at the bottom to surround the wall flow before exiting (de Laclos et al, 1997). According to Nichols (2004), feedstock with Total Solids (TS) below 20% does not perform well in the Valorga system because sand particles settle and coagulate the biogas injection port. The residence time was 21 days and the biogas yield was reported to be 220-270m³/t VS（Nichols2004）。

FIG. 2 depicts a sequential batch anaerobic composting (SEBAC) system comprising 2 or 3 batches of sequentially loaded bed digesters, whereby percolate can be transferred between digesters by nebulisers (Chynoweth et al, 1991; Chynoweth et al, 1992; Okeefe et al, 1993; Forster-Carneiro et al, 2004). The coarsely shredded municipal solid waste Organic Fraction (OFMSW) was placed in a batch digester. Percolate from the mature digester is sprayed onto the fresh material as inoculum and the percolate is recirculated to the top of the mature heap until methanogenesis stabilizes. The digester then goes to internal recycle until methane production slows as the batch matures. In laboratory testing, the SEBAC process has difficulty starting up when loaded with pure food waste (Forster-Carneiro et al, 2004). Fillers are needed to prevent compaction and allow drainage of leachate. Early pilot studies reported methane production at 21 and 42 days of residence time of 160 and 190m, respectively³Pert VS (Chynoweth et al, 1992). The waste stream contains 60% paper and paperboard, 10% plastic and 6% yard waste, the authors report that the yield represents 80-90% of the final methanogenic capacity.

Conventional Anaerobic Phase Solid (APS) systems break down biodegradable materials to treat waste, generate biogas, or both. The operating principle of existing APS systems is staged heterogeneous anaerobic digestion of solids.

Since anaerobic digestion uses mixed and highly competitive microbial cultures that degrade essentially all the biodegradable components of the organic matter, anaerobic digestion becomes one of the key technologies for waste degradation and treatment. Anaerobic digestion is less costly and more amenable to different sizes of distribution operations than other biomass conversion technologies such as ethanol fermentation. Bacteria and fungi used in anaerobic digestion processes have effective enzyme systems to degrade organic polymers such as fibers (e.g., cellulose and hemicellulose), proteins, and fats. For many years, anaerobic digestion technology has evolved from a single environmental management process to a viable process for generating renewable energy. Anaerobic digestion has gained increased attention as the demand for renewable energy sources and for reducing greenhouse gas emissions and environmental degradation has grown.

Examples of existing high solids and anaerobic digesters are Zhang et al, U.S. patent No. 6,342,378 and Zhang, U.S. patent No. 7,556,737. These patents disclose anaerobic phase solids digesters (APS-digesters) developed by the university of California Davis division (UC Davis). APS-digesters combine the features of both batch and continuous digesters (Zhang and Zhang,1999; Zhang,2002; Hartman, 2004). The exemplary system includes 5 reactors: 4 hydrolysis reactors and 1 biogas production reactor. The raw materials are loaded into the respective hydrolysis reactor and by the action of extracellular enzymes and acidogenic bacteria, the waste is dissolved and converted into simple organic acids. The acids are collected and transferred to a biogas production reactor where they are further reduced to methane by methanogenic bacteria. Multiple hydrolysis reactors allow time intervals between the start of each batch hydrolysis reaction. This time interval contributes to a relatively constant biogas production rate despite the batch loading and operating schedule. After complete digestion of each batch, solids and liquids were removed and stabilized aerobically. In laboratory tests, the APS digester system was able to digest rice straw, reduce TS by 40-60% and generate 400-500m³Biogas/t VS, comparable to the yield seen for more easily degradable substrates (Zhang and Zhang, 1999). Other substrates tested on APS digesters include post-consumer food waste, food processing waste, and animal manure. Restaurant foodBiogas production of the material waste and the green waste (grass clippings) is 600 and 440m respectively³tVS, residence time 12 days and biogas production rate 3-3.5m³/m³/d。

Existing anaerobic digestion technologies are divided into class 2-solid waste treated and waste water treated. The prior art is limited for applications where both solid and liquid materials need to be processed, such as food processing plants.

There remains a need to improve the performance of anaerobic digestion techniques. Existing anaerobic digesters require a significant amount of incubation time to digest and biostabilize the contents before effluent can be discharged. In addition, there is a continuing need to improve efficiency in increasing throughput and reducing costs.

In light of the foregoing, it would be beneficial to have a method and apparatus that overcomes the above-mentioned and other disadvantages of known biodigesters, including anaerobic digesters.

Disclosure of Invention

Aspects of the present invention are directed to an anaerobic digester system for generating biogas from organic material. The system comprises a hydrolysis reactor, a biogas production reactor and a biostabilization reactor, wherein the hydrolysis reactor comprises an acidogenic bacteria and a hydrolytic bacteria culture which take organic materials as hydrolysis substrates, the biogas production reactor comprises an acetogenic bacteria and a methanogenic bacteria culture, and the biostabilization reactor comprises a methanogenic bacteria culture. The hydrolysis reactor also includes an inlet for receiving the organic material, an outlet for discharging a hydrolysis effluent from the hydrolysis reactor, and an air vent for discharging biogas from the hydrolysis reactor. The biogas production reactor further includes a biogas production reactor inlet that receives the hydrolysis effluent from the hydrolysis reactor outlet, a reactor outlet that discharges a biogas production effluent from the biogas production reactor, and a gas vent that discharges biogas from the biogas production reactor. The biostabilization reactor further includes a biostabilization reactor inlet that receives a biogas production effluent from the biogas production reactor outlet, a biostabilization reactor outlet that discharges a biostabilization effluent from the biostabilization reactor, and an air vent that discharges a biogas from the biostabilization reactor.

In various embodiments, the biogas production reactor has a controlled internal pH of about 6.8 to about 8.2. In various embodiments, the biostabilization reactor has a controlled internal pH of about 6.8 to about 8.2. In various embodiments, the biogas production reactor has a controlled internal temperature of about 25 ℃ to about 55 ℃. In various embodiments, the biostabilization reactor has a controlled internal temperature equal to or lower than the biogas production reactor. In various embodiments, the biostabilization reactor has a controlled internal temperature of about 25 ℃ to about 55 ℃.

In various embodiments, the organic material is a member selected from the group consisting of a solid, a liquid, and combinations thereof.

In various embodiments, the biostable reactor bacterial culture is substantially methanogenic. In various embodiments, the biostabilization reactor bacterial culture is substantially free of acid-producing bacteria.

In various embodiments, the system further comprises a grinder upstream of the biogas production reactor for mechanically reducing the size of solid particles in the feedstock. In various embodiments, the system further comprises a solid-liquid separator located between the biogas production reactor and the biostabilization reactor, the separator configured to separate a fibrous solid component from a liquid component from the biogas production reactor effluent. In exemplary embodiments, the fibrous solid component has a moisture content of about 60% to about 75%. An exemplary grinder optionally grinds material from the hydrolysis reactor and returns the ground material to the hydrolysis reactor. In an exemplary system, a grinder grinds the hydrolysis effluent and then moves back to the biogas production reactor.

Aspects of the present invention are directed to a biostabilization reactor system that generates biogas from partially digested organic material. The biostabilization reactor comprises a vessel comprising an inlet for mixing partially digested organic material with a biostabilizing bacterial culture to biodigest the organic material, an air vent for venting biogas produced by biogas production, and an outlet for venting a liquid effluent produced by biogas production from the vessel. The partially digested organic material is methanogenic with a mixture of acidogenic and methanogenic bacterial cultures upstream of the vessel. The biostable bacterial culture is a methanogenic culture.

In various embodiments, the system further comprises a solid-liquid separator for separating a solid component from a liquid component in the partially digested organic material to be passed into the biostabilization vessel. In various embodiments, the biostabilization reactor vessel is configured to maintain an internal temperature of about 25 ℃ to about 55 ℃. The biostable reactor vessel may be configured to maintain a mixture of the organic material and the biostable bacterial culture at a pH of about 6.8 to about 8.2.

In various embodiments, the biostabilization outlet is configured to discharge liquid effluent from an area adjacent to an inner wall surface of the biostabilization vessel. The vented biogas may be vented from the top of the biostabilization vessel.

In various embodiments, the method further comprises recycling a portion of the separated liquid from the solid-liquid separator to the hydrolysis reactor. The effluent from one or more reactors may be transferred to one or more other reactors. In various embodiments, the biogas production effluent is recycled to the hydrolysis reactor. In various embodiments, the biostable effluent is recycled to the hydrolysis reactor. In various embodiments, the biostable effluent is recycled to the biogas production reactor. In various embodiments, the effluent from the reactors is recycled back to each reactor. The recycled effluent may be a liquid, a solid, or a combination thereof. In various embodiments, the recycled effluent is a liquid that is added to the feed to the hydrolysis reactor to adjust its water content. The liquor may be processed to remove ammonia and other components (e.g., salt elements) before being recycled to the hydrolysis reactor.

Aspects of the present invention are directed to methods of generating biogas from organic material. The method includes delivering feedstock to a hydrolysis reactor of the system, incubating a mixture comprising a hydrolysis effluent and an acidogenic and hydrolytic bacterial culture under anaerobic conditions to produce hydrogen, carbon dioxide and a hydrolysis effluent, transferring at least a portion of the hydrolysis effluent to the biogas production reactor, incubating a biogas production mixture comprising a hydrolysis effluent and an acidogenic and methanogenic bacterial culture under anaerobic conditions to produce methane, carbon dioxide and a biogas production effluent, transferring at least a portion of the biogas production effluent to the biostabilization reactor, incubating a biostabilization mixture comprising a biogas production effluent and a biostabilizing methanogenic bacterial culture under anaerobic conditions to produce methane and a biostabilization effluent.

In various embodiments, the steps are performed substantially simultaneously.

The system and method of the present invention have other features and advantages which are apparent from or are set forth in more detail in the accompanying drawings, which are incorporated in and constitute a part of this specification, and the following detailed description of the invention, which together serve to explain the principles of the invention.

Brief description of the drawings

FIGS. 1A, 1B and 1C are schematic diagrams of a conventional bio-digester.

FIG. 2 is a schematic diagram of a conventional sequential batch anaerobic composting (SEBAC) system.

FIG. 3 is a schematic representation of the biochemical processes involved in the anaerobic digestion process of the present invention.

FIG. 4 is a schematic diagram of an anaerobic digester system according to the present invention.

FIG. 5 is a schematic diagram of an anaerobic digester system similar to the system of FIG. 4, showing the use of an alternative ammonia removal device.

FIG. 6 is a schematic diagram of an anaerobic digester system similar to the system of FIG. 4, showing the use of an optional ammonia removal device and the addition of a fresh liquid feed to the biogas production reactor.

FIG. 7 is a schematic of the anaerobic digester system of the invention in which the hydrolysis reactor effluent is transferred directly to the biostabilization reactor.

FIG. 8 is a schematic of an anaerobic digester system of the invention in which the effluent from the biostabilization reactor is recycled to the digester system, such as through the hydrolysis reactor via valve 37.

FIG. 9 shows the public interest of a biogas product produced according to the system and method of the present invention.

Detailed Description

Reference will now be made in detail to the various embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

Definitions and abbreviations

"biogas" refers to a gas produced by the biological decomposition of organic matter, usually in the absence of oxygen. Examples of biogas include, but are not limited to, methane, hydrogen, and carbon dioxide produced by anaerobic digestion, fermentation, or biogas production of biodegradable materials such as biomass, fertilizers, sewage, municipal waste, green waste, and crops.

"biogas production" generally refers to the production of biogas products from microorganisms derived from organic materials. In various aspects, "biogas production" refers to the generation of biogas in the processing of a liquid or solid feedstock or material of the present invention. In various aspects, "biogas production" refers to a process for generating methane and/or carbon dioxide from organic material by the present processes and systems.

"anaerobic digestion" is understood to be generally used in the industrial, chemical, agricultural and environmental fields. In various aspects, "anaerobic digestion" refers to a series of processes in which microorganisms break down organic or biodegradable materials in the absence of oxygen to treat waste and/or release energy. In various aspects, "anaerobic digestion" refers to the processing of a variety of organic materials, including liquids, solids, and combinations thereof. "anaerobic digestion" is used interchangeably with "AD" and "digestion".

"methanogenesis" and "biogenic methane" are used interchangeably and refer to the formation of methane from methanogens. In various aspects, "methanogenesis" is used interchangeably with "biogenesis". "methanogenesis" is understood to be a general term used in the industrial, chemical, agricultural and environmental fields and generally refers to the formation of methane by microorganisms known as methanogens. In various aspects, methanogenesis is produced by anaerobic fermentation.

"methanogenic organisms" and "methanogenic bacterial cultures" are to be understood as meaning microorganisms which are used in general in the environmental, agricultural and chemical fields and which are capable of producing methane from organic material and/or metabolizing organic material. Exemplary methanogens include, but are not limited to, Methanobacterium austeniticum (Methanobacterium ineliskii), Methanobacterium formate (mb. formicum), Methanobacterium sohnenii (mb. sohngenii), Methanosarcina pasteurianum (Methanosarcina barkeri), Methanosarcina methane (ms. methanoica), and methanococcus equi (mc. mazei), and combinations thereof. Methanobacteriaceae (methanobacterium), Methanosarcinaceae (methanosarcinae), methanomyces (methanomycetetaceae), methanogranulaceae (methanobacterium), Methanomicrobiaceae (methanomicrobioceae), and other archaebacteria are also used.

"acetogenic bacteria" and "acetogenic bacterial cultures" are to be understood as meaning the classes of microorganisms which are commonly used in the environmental, agricultural and chemical fields and which are capable of producing acetic acid as an anaerobic fermentation product.

"acid-producing bacteria" and "acid-producing bacterial cultures" are to be understood as meaning those microorganisms which are customarily used in the environmental, agricultural and chemical sectors and which are capable of producing volatile fatty acids as anaerobic fermentation products.

"bacterial cultures" are understood to be commonly used in the agricultural, chemical and environmental fields. In various aspects, "bacterial culture" refers to a mixed culture. In various aspects, "bacterial culture" includes bacteria and archaea.

"organic substrate," "organic material," and "feedstock" are used substantially interchangeably and refer to materials that can be used in the processes and systems of the present invention to produce biogas products. In some aspects, "organic substrate" refers to a carbonaceous material that can be used in the processes and systems of the present invention. "organic substrate" may refer to a liquid, a solid, or a combination thereof.

In an exemplary embodiment, the organic substrate is food waste and municipal solid waste. Previous studies have shown the availability of anaerobic digestion of food waste and its mixtures with agricultural waste such as livestock manure and municipal solid waste (Zhang et al, 2006; EI-Mashad and Zhang,2010; Zhu et al, 2010). In various aspects, the organic material is pretreated by chemical treatment such as acid treatment, base treatment, radiation treatment, thermal treatment, radiation treatment, ammonia treatment, and combinations thereof.

"organic material" and "feedstock" are used substantially interchangeably. "feedstock" is understood to be used in the agricultural and environmental fields.

"partial digestion" refers to organic material that has undergone a biogas manufacturing process. In various aspects, "partial digestion" refers to organic material in which at least a substantial portion has undergone hydrolysis or at least a substantial portion has undergone culturing by acetogenic and methanogenic bacteria.

"hydrolysis" is understood to be generally used in the industrial, chemical, agricultural and environmental fields. "hydrolysis" generally refers to the division of a molecule into two or more portions by the addition of water molecules. In various aspects, "hydrolysis" refers to the chemical reaction of a water molecule into a hydrogen cation and a hydroxide anion. In various aspects, "hydrolysis" refers to the process of generating hydrogen and/or carbon dioxide from organic material by the processes and systems of the present invention. In various aspects, "hydrolysis" refers to the process of metabolizing organic material to produce hydrogen by hydrolyzing a microorganism.

"hydrolytic microorganisms" are to be understood as meaning those microorganisms which are generally used in the industrial, chemical, agricultural and environmental sectors and which are capable of generating hydrogen as an anaerobic respiration product. Exemplary hydrolyzing microorganisms include, but are not limited to, Clostridium (Clostridium), Lactobacillus (Lactobacillus), and other Firmicutes and Proteobacteria (Proteobacteria), and combinations thereof.

"solid-liquid separator" generally refers to a device for separating a solid component from a liquid component according to the process and system of the present invention. In various aspects, a "solid-liquid separator" refers to a device that increases the amount of separation between a solid component and a liquid component from the level that would occur in the absence of the device. In various aspects, a "solid-liquid separator" refers to a device that separates solid particles having a diameter greater than about 1mm, less than about 3mm, less than about 5mm, less than about 10mm, or less than about 20 mm.

"reactor," "vessel," and "reaction vessel" are used substantially interchangeably to refer to a device that contains materials, and in some aspects, to a device in which the reactions described herein take place.

"incubation" is understood to be the usual use in the chemical, agricultural and environmental fields. As used herein, "incubation" generally refers to allowing the material to remain for a period of time for the desired reaction to occur.

As used herein, "fluid" refers broadly to liquids, with or without suspended solid materials. In various aspects, the amount of solids is such that the "fluid" can flow through the system of the present invention.

"solid" is understood to be generally used in the chemical, agricultural and environmental fields. "solid" includes, but is not limited to, inert solids, soluble solids, biodegradable solids, and non-biodegradable solids. In various aspects, "solid" refers to a biodegradable solid.

"acid", "base" and "salt" are to be understood as such terms are commonly used in the chemical, agricultural and environmental fields.

"HR" refers to "hydrolysis reactor". "BGR" refers to "biogas production reactor". "BSR" refers to "biostabilization reactor".

For convenience in explanation and accurate definition in the appended claims, the terms "upper" or "upper", "lower" or "lower", "within" and "outside", and "top" and "bottom" are used to describe features of the invention with reference to the positions of such features as displayed in the figures.

In various aspects, modifications of the various figures are similar to previous modifications and the same reference numerals and subsequent subscripts "a", "b", "c", "d" and omission symbols designate corresponding parts.

Unless otherwise indicated, the terms and abbreviations used herein are to be understood as commonly used in the industrial, chemical, agricultural and environmental fields. The use of the singular includes the plural and vice versa unless otherwise indicated.

Aspects of the present invention relate to the DIGESTER systems and methods disclosed in U.S. patent No. 6,342,378, entitled 1/29 in 2002 and entitled ANAEROBIC digestion ingredient WASTE WITH AN and ANAEROBIC solid DIGESTER DIGESTER SYSTEM (manufactured with solid WASTE biogas of an ANAEROBIC SOLIDS DIGESTER system) and U.S. patent No. 7,556,737, entitled ANAEROBIC digested ingredient FOR generating biogas FROM ORGANIC solid WASTE, entitled ANAEROBIC phase SOLIDS DIGESTER and method, entitled ANAEROBIC phase SOLIDS DIGESTER in 2009, 7/7 in 2009, which are incorporated herein by reference in their entirety FOR all purposes. In contrast to existing anaerobic digester systems, the system according to the present invention achieves higher processing rates and higher energy conversion efficiencies.

Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is directed to FIGS. 3 and 4. FIG. 3 is a generalized illustration of biochemical processes involved in the anaerobic digestion process. As shown in fig. 3, in anaerobic digestion, organic matter is hydrolyzed by extracellular enzymes of microorganisms into soluble compounds such as amino acids, sugars, and long chain fatty acids. The hydrolysis step product is then fermented to short chain Volatile Fatty Acids (VFA), alcohol, ammonia and hydrogen sulfide. The VFA (in addition to acetate) and alcohol are further converted by acetogenic bacteria to acetic acid, hydrogen and carbon dioxide, which is subsequently converted by methanogenic bacteria to methane and carbon dioxide. The biogas produced by anaerobic digestion may contain hydrogen, methane, carbon dioxide as the main components and can be used as a fuel for power generation and heat generation, or a fuel for transport carriers.

In an exemplary embodiment, the organic material or feedstock is agricultural waste, such as rice straw. Previous studies have shown the feasibility of anaerobically digesting mixtures of straw (rice and wheat straws) with other Agricultural and food Wastes such as animal manure, green leaves and molasses using conventional batch or semi-continuous feed digestion reactors (Hills, D.J. and D.W.Roberts, Agricultural waste waters 3:179-189(1981); Dar, G.H. and S.M.tandon, Biological waters 21:75-83(1987); Adbellah et al, Journal of Agricultural Sciences119:255-263(1992); Somayaji, D.and S.Khanna, World Journal of biology & technology10:521-523 (1994)). Hills and Roberts (1981) showed that the addition of shredded rice straw or shredded wheat straw to cow dung enhances the anaerobic digestion process and increases methane production. Rice straw is a ligno-cellulosic material consisting mainly of cellulose (37.4%), hemicellulose (44.9%), lignin (4.9%) and silica fume (13.1%) (Hills, D.J. and D.W.Roberts, Agricultural products 3:179-189 (1981)). The straw contained about 0.4% nitrogen and the carbon to nitrogen ratio (C/N) was about 75. Suitable C/N ratios for anaerobic digestion range from 25 to 35 (Hills, D.J. and D.W.Roberts, Agricultural temperatures 3:179-189 (1981)). Therefore, nitrogen supplementation may be required to affect anaerobic digestion of rice straw.

Nitrogen may be added in inorganic form such as ammonia or in organic form such as organic nitrogen contained in urea, animal manure or food waste. However, once nitrogen is released from the organic matter, it becomes water-soluble ammonia (NH)⁴⁺). Recycling nitrogen in the digestion liquor reduces the amount of nitrogen required to continuously operate the anaerobic digester. Animal manureAnd food waste is a good source of nutrients if readily available in the vicinity of rice straw production. Nitrogen fertilizers such as ammonia or urea are simply added to the straw as another source of nitrogen and may be more suitable for the area when it is not feasible to treat other waste types. Thus, in various embodiments, the organic material is supplemented with a nitrogen source. In various embodiments, the nitrogen source is a member selected from the group consisting of urea, livestock manure, food waste, inorganic nitrogen fertilizer, and combinations thereof.

In various embodiments, the organic material, particularly agricultural waste (such as rice straw), is pre-treated by a chemical treatment process selected from the group consisting of: bicarbonate treatment, alkaline peroxide treatment, radiation treatment, ammonia treatment, and combinations thereof.

In various embodiments, the organic material is a solid, a liquid, or a combination thereof. Exemplary systems have solid materials and liquid materials such as wastewater.

Fig. 4 shows an anaerobic digester system, generally designated 30, for producing biogas from organic material or feedstock. In the exemplary system, solid feedstock 32 enters a grinder 33 to reduce the solid particle size.

The ground feedstock is fed by a pump 37 into a hydrolysis vessel (hydrolysis reactor) 35. The exemplary system optionally includes a wet mill 39 to further continuously reduce the particle size of the solid components in the reactor.

The exemplary hydrolysis reactor includes an inlet 40 for receiving feed from a pump and a first outlet 42 for discharging hydrolysis effluent. The gas vent 44 may vent the biogas from the hydrolysis vessel 35. The inlet of any reaction vessel may be configured to accept solids, liquids, or combinations thereof.

The hydrolysis effluent from the hydrolysis reactor 35 enters the biogas production reactor 46 via a biogas production pump 47. The biogas production reactor includes a biogas-producing bacterial culture to produce biogas from an organic material containing a hydrolysis effluent. The organic material is fed through inlet 49 and exits through outlet 51 to discharge a biogas production effluent from the biogas production reactor. A BGR vent 53 to vent biogas production products is provided on the biogas production reactor.

The effluent from the biogas production reactor 46 may optionally be fed through a solid-liquid separator 54. An exemplary separator is a conventional device for separating particles of a desired size from a mixed organic material. An exemplary separator is provided in series between the biogas production reactor and the biostabilization reactor.

A BSR pump 56 downstream of the solid-liquid separator 54 transfers the organic material (biogas production effluent) to a biostabilization reactor 58. The biostabilization reactor includes a first inlet 60 that receives the outlet effluent from the biogas production reactor and an outlet 61 that discharges the biostabilization effluent from the biostabilization reactor. Gas vent 63 discharges biogas products from the biostabilization reactor.

The components of the system 30 will now be described in more detail.

In various embodiments, pump 37 is a chopper pump. During the incubation period, the mixed contents of the hydrolysis reactor 35 are pumped through a pump with a chopper to reduce the particle size of the solid components in the feedstock. By reducing the particle size, the energy conversion efficiency of the system 30 (and in particular the hydrolysis reactor 35) can generally be increased. The system 30 is also adapted to add liquid feed as described below.

The hydrolysis reactor 35 is configured to hold a mixture or solution. In various embodiments, the hydrolysis reaction vessel 35 comprises a compartment with one or more internal vertical partitions, similar to the vessel of the' 378 patent. An exemplary reaction vessel includes a single undivided compartment. An exemplary vessel is a sealed compartment configured to hold ground material in an oxygen-free environment. An exemplary hydrolysis reactor is a standard cylindrical vessel without a stirrer, auger, or other mixing device. However, it will be appreciated that the vessel may be provided with means for mixing or agitating the material for use in the process of adding or removing organic material or for use during all or part of the incubation period as described herein. Such devices include, but are not limited to, overhead stirrers, gas or electrically driven stirrers, magnetic stirrers, shakers, homogenizers, sonicators, bubble tubes, and bubblers.

In various embodiments, the hydrolysis outlet 42 is in fluid communication with any interior surface of the hydrolysis reaction vessel. In an exemplary reactor, the outlet is in fluid communication with a vertical surface of the hydrolysis reaction vessel. The outlet may be connected directly or indirectly to the side wall of the container in a known manner so as to minimize the passage of unwanted material which is normally collected in the central region of the container. In various embodiments, the biogas is vented from the interior of the reaction vessel. In an exemplary system, the vent is connected to the top of the container. In various embodiments, the gas vent is connected to the top of the container above the surface of the liquid contents.

An exemplary hydrolysis reactor comprises a suspension or mixture of an acidogenic and a hydrolyzing bacterial culture. The bacterial culture may be mixed with an aqueous base such as water. In an exemplary system, the bacterial culture is introduced into the hydrolysis reactor via an inlet. The hydrolytic bacterial culture is used as a hydrolysis substrate for the organic feedstock during incubation.

In operation, the hydrolytic bacterial culture is mixed with feedstock within the hydrolysis reactor. In various embodiments, the hydrolysis vessel comprises a mixture of organic feedstock, bacterial culture and aqueous liquid, equal to at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% and even more preferably at least 90%, 95% or substantially 100% of the internal capacity of the hydrolysis vessel.

In various embodiments, the internal temperature of hydrolysis reactor 35 is maintained in the range of about 25 ℃ to about 55 ℃, preferably in the range of about 50 ℃ to about 55 ℃ during incubation. In various embodiments, the internal pH of the feedstock and bacterial culture in hydrolysis reactor 35 during incubation is from about 4.0 to about 7.0. In various embodiments, chemicals are added to adjust the pH. The chemicals may be added via the inlet or by other known methods.

The mixture of feedstock and hydrolyzed bacterial culture is hydrolyzed by the extracellular enzymes of the microorganism into soluble compounds such as amino acids, sugars and long chain fatty acids. It is understood that any active mesophilic or thermophilic organism that produces hydrolysis can be used for the hydrolyzed bacterial culture. The hydrolyzed bacterial culture may include, but is not limited to, microorganisms from the species Clostridium, Lactobacillus, and Eubacterium (Eubacterium). Clostridia species include, but are not limited to, clostridium thermosaccharium (c), clostridium thermohydrosulfiricum (c), clostridium succinicium (c), clostridium butyricum (c), clostridium pasteurianum (c), and clostridium beijirincki (c). Lactobacillus includes, but is not limited to Lactobacillus paracasei (Lactobacillus paracasel). Eubacteria include, but are not limited to, enterobacter aerogenes (e. Other useful microorganisms and microorganism mixtures for use in hydrolysis reactor 35 will be apparent to those skilled in the art from the description herein.

Exemplary efficient mixed culture microorganisms can maintain themselves indefinitely as long as a fresh supply of organic material is added, since the primary product of the fermentation process is a gas that escapes the culture medium and leaves little, if any, toxic growth inhibitory product. Mixed cultures generally provide the most complete fermentation. Nutritional balance and pH adjustment may be performed to facilitate hydrolytic activity as described herein.

The biogas production reactor 46 is physically configured similarly to the hydrolysis reactor 35. In various embodiments, the biogas production outlet 51 is in fluid communication with any interior surface of the biogas production reaction vessel. In an exemplary reactor, an outlet is in fluid communication with a vertical surface of the biogas production reaction vessel. The outlet may be connected directly or indirectly to the side wall of the vessel in a known manner so as to minimise the introduction of unwanted material which is normally collected in the central region of the vessel. In various embodiments, the biogas is vented from the interior of the reaction vessel. In an exemplary system, the vent is connected to the top of the container. In various embodiments, the gas vent is connected to the top of the container above the surface of the liquid contents.

In various embodiments, the biogas production reactor 46 is configured to process a member selected from the group consisting of liquids, solids, and combinations thereof. In the exemplary system, the wet mill 39 reduces the size of solid particles in the hydrolysis effluent from the hydrolysis reactor 35. In an exemplary embodiment, the organic material retains a small solid component for processing by the biogas production reactor. Any solids remaining in the organic material after processing in the biogas production reactor may optionally be removed downstream from the solid-liquid separator 54.

An exemplary biogas production reactor comprises an acetogenic and methanogenic bacterial culture, collectively referred to as a biogas production bacterial culture. In various embodiments, the biogas producing bacterial culture comprises one of acid producing bacteria, acetogenic bacteria, alkane producing organisms and combinations thereof in varying amounts. The bacterial culture may be mixed with an aqueous base such as water by known processes. In various embodiments, the contents of one or more reactors are mixed with a mixing device. Exemplary mixing devices include, but are not limited to, impellers, agitators, sparging, and thermal cycling. In operation, the biogas producing bacterial culture is mixed with effluent within the biogas production reactor. In various embodiments, the biogas production vessel comprises a mixture of organic material (effluent), bacterial culture and aqueous liquid, equal to at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% and even more preferably at least 90%, 95% or substantially 100% of the internal volume of the biogas production vessel.

Anaerobic systems for methane production use acid-forming bacteria and methanogenic organisms, collectively known as methanogens, which can be used to produce methane. A review of Microbiology for Anaerobic Digestion is set forth in Anaerobic Digestion, The Microbiology of Anaerobic Digestion, D.F. Toerien and W.H. J.Hattingh, Water Research, Vol.3, p.385 and 416, Paegon Press (Pergamon Press), which is incorporated herein by reference for all purposes. As listed in the toeinen review, the acid-forming species may include species from genera including, but not limited to: aerobacter (Aerobacter), Aeromonas (Aeromonas), Alcaligenes (Alcaligenes), Bacillus (Bacillus), Bacteroides (Bacteroides), Clostridium (Clostridium), Escherichia (Escherichia), Klebsiella (Klebsiella), Leptospira (Leptospira), Micrococcus (Micrococcus), Neisseria (Neisseria), Escherichia (Paracolium), Proteus (Proteus), Pseudomonas (Pseudomonas), Rhodopseudomonas (Rhodopseudomonas), Sarcina (Sarcina), Serratia (Serratia), Streptococcus (Streptococcus), and Streptomyces (Streptomyces). The present invention also uses a microorganism selected from the group consisting of: methanobacterium austenitalis, methanobacterium formis, methanobacterium sojae, methanosarcina pasteurii, methanosarcina, methanococcus equi and combinations thereof. Also used are methanobacteriaceae, methanosarcinaceae, methanomyceliaceae, methanobacteraceae, methanomicrobiaceae and other archaebacteria.

A wide variety of substrates can be utilized by methanogenic bacteria, but it is believed that each species is characteristically limited to the use of some compounds. Thus, it is believed that complete fermentation of certain organic substrates, such as compounds present in wastewater, requires some methanogenic bacterial species. For example, complete fermentation of valeric acid requires as many as 3 methanogenic bacteria. Pentanoic acid is oxidized by methanobacterium suboxydans (mb. suboxydans) to acetate and propionate, which is not further attacked by the organism. The second species, such as methanobacterium propionate (mb. propionicum), can convert propionic acid to acetic acid, carbon dioxide and methane. A third species such as Methanosarcina methanolica is required for acetic acid fermentation.

The internal environment of an exemplary biogas production reactor is controlled to promote methanogenesis. In various embodiments, the internal temperature of the biogas production reactor 46 is maintained above about 30 ℃. In various embodiments, the internal temperature of the biogas production reactor is maintained at about 25 ℃ to about 55 ℃. In various embodiments, the biogas production reactor has a controlled internal pH of about 6.8 to about 8.2. In various embodiments, chemicals are added to adjust the pH.

The biostabilization reactor inlet 60 is in fluid communication with the biogas production outlet 51. In various aspects, the biostabilization reactor 58 is configured similarly to the biogas production reactor 46. Biostabilization reactor 58 includes a vessel that maintains organic material (e.g., effluent) and bacterial culture in an anaerobic environment. An exemplary container is cylindrical. However, it should be understood that the vessel may have other shapes and configurations similar to hydrolysis reactors and biogas production reactors according to the present invention.

In various embodiments, one or more of the reactors comprises a solid support for bacterial culture such as a sheet, plastic pellet, sand, biofilm, and the like. The solid support promotes bacterial retention and increases bacterial populations. Other substances such as silica may also be added to the reactor to facilitate chemical and biochemical reactions therein.

In various embodiments, biostable outlet 61 is in fluid communication with any interior surface of the biostable reaction vessel. In an exemplary reactor, the outlet is in fluid communication with a vertical surface of the biostable reaction vessel. The outlet may be connected directly or indirectly to the side wall of the container in a known manner so as to minimize the intake of unwanted material which would normally collect in the central region of the container. In various embodiments, the biogas is vented from the interior of the reaction vessel. In an exemplary system, the vent is connected to the top of the container. In various embodiments, the gas vent is connected to the top of the container above the surface of the liquid contents.

The exemplary biostabilization reactor does not include a mixing device. It is understood that known mixing devices may be provided to mix and agitate, including but not limited to a stirrer or auger. In various embodiments, the biostabilization outlet is in fluid communication with a vertical surface of the biostabilization reaction vessel. The outlet may be connected directly or indirectly to the side wall of the container in a known manner so as to minimize the passage of unwanted material which is normally collected in the central region of the container. In an exemplary system, a biostable vent is coupled to the top of the container. In various embodiments, the gas vent is connected to the top of the container above the surface of the liquid contents.

In various embodiments, biostabilization reactor 58 is configured to process a member selected from the group consisting of a liquid, a solid, and combinations thereof. In various embodiments, the biostabilization reactor is configured to process substantially liquid organic material, meaning a liquid with no solids or only small, small amounts of solid particles. In the exemplary system, an optional solid-liquid separator 54 separates relatively large particles from the biogas production effluent before it enters the biostabilization reactor. In this way, the biostabilization reactor can operate efficiently on liquid components, while solid components are mainly treated in the hydrolysis reactor 35 and the biogas production reactor 46. In various embodiments, the separated solid particles are added to the hydrolysis reactor feedstock. In various embodiments, the separated solid particles are processed off-line, such as in a separate composting system.

In various embodiments, the biostabilization reactor is fed with partially digested organic material. An exemplary biostabilization reactor receives a partially digested biogas production effluent. One skilled in the art will understand from the description herein how to adjust the process level of a biogas production reactor prior to transfer to a biostabilization reactor. The level of processing depends largely on the composition of the organic material entering the system. In the exemplary case where food waste is used as a feedstock, the hydrolyzed effluent may be incubated in the biogas production reactor for a period of time sufficient to deplete substantially all of the solid components. In contrast, the solid components in straw feedstocks are not readily digestible. In various embodiments, the amount of solid components digested in the biogas production reactor prior to transfer to the biostabilization reactor is about 70%, more preferably 75%, more preferably 80%, more preferably 85%, more preferably 90%, and more preferably 95%. In various embodiments, the organic material (hydrolysis effluent) is incubated in the biogas production reactor until substantially all of the solid components are digested.

It will be understood from the description herein that the minimum size of particles to be separated from a biogas production reactor depends on the application and system conditions. In various embodiments, the solid particles entering biostabilization reactor 58 are greater than or equal to about 20mm in diameter, preferably about 10mm in diameter, and more preferably about 1mm in diameter.

Unlike the biogas production reactor 46, the exemplary biostabilization reactor 58 comprises a methanogenic bacterial culture, but is substantially free of an acetogenic bacterial culture. As the organic material (e.g., effluent) for the biostabilization reactor enters the exemplary biogas production reactor comprising the acetogenic bacterial culture and the methanogenic bacterial culture, the organic material is partially digested prior to entering the biostabilization reactor. In various embodiments, the solid component is depleted from the acetogenic bacterial culture in the biogas production reactor, such that the biostabilization reactor is adapted for maximum energy conversion efficiency of the soluble component.

In various embodiments, the methanogenic bacterial culture in biostabilization reactor 58 is substantially free of acetogenic bacteria. By "substantially free of acetogenic bacteria" is meant that the culture contains minimal acetogenic bacteria and a small amount of acidification reaction. In various aspects, "substantially free of acetogenic bacteria" means that the hydrolyzable components react little or not at all. In various aspects, "substantially free of acetogenic bacteria" means less than about 10%, more preferably less than about 5%, more preferably less than about 3% and even more preferably less than about 1%. In various embodiments, the bacterial culture in the biostabilization reactor comprises one of acid-producing bacteria, acetogenic bacteria, alkane-producing organisms, and combinations thereof in varying amounts. In various embodiments, the bacterial culture in the biostabilization reactor includes acetogens, methanogens, and combinations thereof in varying amounts

Any undigested solid components are separated by optional solid-liquid separator 54 and composted. The separated components may optionally be transferred back to the biogas production reactor 46. In various embodiments, the solid component in the biogas production effluent is a fibrous solid. In various embodiments, the moisture content of the solid component in the biogas production effluent is from about 60% to about 75%. In various embodiments, the solid-liquid separator is a filter. In various embodiments, the solid-liquid separator is one of a grinder, a mesh, a filter, a screen, a filter, a slat, and combinations thereof, for modifying solid particle size, separating solid particles, or both in a conventional manner. In certain exemplary embodiments, a filter is used.

Because the solid components enter the biogas production reactor and then enter the biostabilization reactor after separation, neither the exemplary biogas production reactor nor the exemplary biostabilization reactor need a filter or similar device at each inlet to prevent solids from entering. In contrast, existing anaerobic digestion systems include a single reaction vessel that generates methane and thus require filters or the biogas production reactor is configured to efficiently use up solid and liquid components, such as by extending incubation time or increasing vessel size.

In an exemplary system, the solid component is digested or removed prior to entering the biostabilization reactor. Thus, the exemplary biostabilization reactor may be configured similarly to a biomass retention reactor. Examples of such biomass retention reactors are biofilm reactors, upflow chute black-out (upflow batch) reactors and anaerobic sequential batch reactors. Biomass retention reactor type reactors are commonly used for processing wastewater and other organic materials that are free of solid components.

In various embodiments, the biostable container comprises a mixture of organic material, bacterial culture, and aqueous liquid equal to at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80%, and even more preferably at least 90%, 95%, or substantially 100% of the internal volume of the biostable container. In various embodiments, the hydrolysis vessel, biogas production vessel, biostabilization vessel, or combinations thereof, comprise a headspace void volume above solid and liquid contents for safety considerations. In various embodiments, the headspace is equal to about 5% of the volume of the container.

In various embodiments, the internal temperature of biostabilization reactor 58 is from about 25 ℃ to about 55 ℃, preferably from about 25 ℃ to about 30 ℃. In various embodiments, the internal temperature of the biostabilization reactor 58 is lower than the internal temperature of the biogas production reactor 46. It is to be understood that the actual temperature within the reaction vessel may in fact fluctuate, and thus the internal temperature may refer to an average temperature or a temperature range. In various embodiments, biostabilization reactor 58 has an internal pH of about 6.8 to about 8.2 in organic material and bacterial culture incubations.

In various embodiments, mechanical degradation or chemical treatment of the organic material (e.g., feedstock) may be required at any point or points in the system to obtain a suitable particle size or to make the carbonaceous component of the organic material more readily available to the respective digestive bacterial culture. Known methods of mechanical degradation can be used according to the invention. Various pretreatments of the organic substrate are suitable for use with the present invention, such as acid or alkaline hydrolysis.

It was found that the reduction of the mechanical size of organic materials and raw materials aids biodegradation for several reasons. A decrease in physical size corresponds to an increase in the active surface area of the particles to be digested. The mechanical size reduction may also rupture the cells, thereby making the biodegradable component more accessible to the microorganism. In various embodiments, the organic material is pretreated with a process comprising milling the feedstock to a size of about 5 millimeters to about 50 millimeters. In various embodiments, the feedstock is heated to a temperature of from about 50 ℃ to about 120 ℃, more preferably from about 60 ℃ to about 90 ℃. In various embodiments, the feedstock is pretreated by a physical process selected from the group consisting of: grinding, cutting, heating, and combinations thereof. The pretreatment may be upstream of a biogas production reactor.

In various embodiments, hydrolysis reactor 35 and biogas production reactor 46 comprise a bacterial culture to produce biogas by bio-digesting organic material containing at least some solid components and biostabilization reactor 58 comprises a bacterial culture to produce biogas by bio-digesting organic material substantially free of solid components. "substantially free" with respect to the presence of solid components means less than about 10%, in various aspects less than about 5%, in various aspects less than about 3%, and in various aspects less than about 1%. In various aspects, an organic material that is "substantially free" of solid components refers to liquid wastewater.

A method of using the anaerobic digester system according to the invention will now be described. In various aspects, the system operates similar to the digester systems disclosed in U.S. patent nos. 7,556,737 ('737 patent) and 6,342,378 (' 378 patent), which are incorporated herein by reference for all purposes. In various aspects, the components of the system operate similarly to the systems disclosed in U.S. patent nos. 4,316,961 and 4,722,741, which are incorporated herein by reference for all purposes.

The exemplary hydrolysis reactor 35 and biogas production reactor 46 may optionally be intermittently heated and/or cooled and sequentially fed in batches to facilitate energy conversion. Biostabilization reactor 65 may or may not be heated depending on a variety of factors understood by the description herein, including, but not limited to, climatic conditions and specific contents and distribution of organic materials. In various embodiments, the hydrolysis reactor 35 and the biogas production reactor 46 are thermally insulated to conserve heat. In various embodiments, all reactors-hydrolysis reactors, biogas production reactors, and biostabilization reactors-are thermally insulated to conserve heat.

In an exemplary process, organic material having a solids content greater than about 10% is first passed to a mill 33 for mechanical size reduction. The resulting mixture comprises an aqueous solid solution. In an exemplary system, the solid particles have a diameter of less than or equal to about 20 mm. In various embodiments, the size of the solid particles is continuously reduced in the mill and the organic feedstock is continuously fed into the hydrolysis reactor.

The solids-containing material is then used as a feedstock for the hydrolysis reactor 35. The feedstock is decomposed by a combination of chemical and biochemical reactions in a hydrolysis reactor to produce a mixture of sugars, organic acids (such as amino acids and fatty acids) and alcohols (such as ethanol). Chemical hydrolysis occurs due to the presence of water, hydrolysis and acidogenic bacterial culture, and enzymes in the hydrolysis reactor. The biochemical reaction is completed by acid-producing and hydrolyzing microorganisms.

The hydrolysis reactor feed and contents, including the hydrolysis and acidogenic bacterial culture, comprise the hydrolysis mixture in the reactor. The hydrolysis mixture is maintained in the reactor under sufficient conditions for a sufficient period of time to produce biogas. In an exemplary system, the biogas includes hydrogen and carbon dioxide as major components and hydrogen sulfide and ammonia as minor components. The biogas is removed through gas port 44 and transferred to another location or stored.

After the hydrolysis reaction has been allowed to proceed to completion of an incubation period contained in the hydrolysis reactor 35, the hydrolysis effluent is transferred via an optional wet grinder 39 and a pump 47 to a biogas production reactor 46. In an exemplary system, the hydrolysis effluent and the acetogenic and methanogenic bacterial cultures in the reactor form a biogas production mixture. In the biogas production reactor 46, sugars, organic acids, alcohols and other compounds in the biogas production mixture are converted to biogas by the acetogenic and methanogenic bacterial culture. The biogas produced by the biogas production reactor 46 comprises methane and carbon dioxide, with hydrogen sulfide and ammonia being minor components. The biogas is removed through the gas vent 53 and transferred to another location or stored. The biogas produced by the biogas production reactor may be mixed with the gases produced by the hydrolysis reactor, wherein the gas components may later be separated. Alternatively, the biogas from each reactor may be kept separate.

After a period of incubation to allow most of the biogas production to occur, the biogas production effluent is transferred to biostabilization reactor 58 via solid-liquid separator 54. In an exemplary method, the biogas production mixture is incubated under sufficient conditions for a sufficient period of time to deplete all or a portion of the solid components. Existing anaerobic digester systems require incubation of the organic material in the biogas production reactor until the contents are biostable, and systems and methods according to the present invention provide biostable in biostable reactor 58. The exemplary biogas production reactor will achieve about 80% to about 90% of the maximum biogas generation potential of the biodegradable solid component.

In various embodiments, system 30 includes one or more processes to recycle process liquids, solids, or combinations thereof. In various embodiments, at least a portion of the effluent from the one or more system reactors is transferred to the one or more reactors. All or part of the hydrolysis effluent may be transferred back to the hydrolysis reactor. All or a portion of the biogas production effluent may be transferred to the hydrolysis reactor. All or a portion of the biostable effluent may be transferred to a hydrolysis reactor, a biogas production reactor, or a combination thereof. In various embodiments, the effluent from each reactor is not recycled.

In the exemplary system, the biogas production effluent is primarily liquid with only a small fraction of small solid particles after passing through optional solid-liquid separator 54. In the exemplary system 30, this liquid portion is recycled to the hydrolysis reactor 35. The recycled liquid may enter the mill 33 as eluent, be added to the hydrolysis reactor feed, and/or directly enter the hydrolysis reactor. The recycled liquid from the hydrolysis reactor may be added to a feed mixing device such as a mixing tank or mixing pump prior to entering the hydrolysis reactor. The recycled liquid may replenish water and nutrients in the hydrolysis reactor feed.

The process of recycling biogas to make effluent according to the present invention is different from the recycle process of Zhang, U.S. patent No. 7,556,737. Unlike continuous recycling of Zhang, the recycling process of the present invention is carried out in one or more batches as the feedstock is fed to the mill. Recycling is performed to partially conserve liquid and reduce municipal water usage. In the exemplary system, the effluent from the biogas production reactor 46 is diverted to the grinder 33 or pump 37 to adjust the water content of the hydrolysis reactor 35 feedstock. In an exemplary system, the effluent is primarily liquid. The remaining organic material, including organic acids, is converted to biogas in biostabilization reactor 58.

The biostable effluent may be used or treated in a conventional manner. For example, the biostable effluent may be further processed for water and nutrient recovery. The biostable effluent may also be used for crop irrigation. In various embodiments, the biostabilization is recycled to the hydrolysis reactor, the biogas production, or both. The process of recycling the liquid component of the biostable effluent is similar to the process described above for recycling biogas to make the effluent.

In an exemplary system, solid feedstock such as crop residue, rice straw, green waste, municipal waste, and the like is introduced into the hydrolysis reactor in batch or semi-batch. Meanwhile, the biogas production reactor continuously generates biogas in a large amount. In various embodiments, the solid feedstock enters the hydrolysis reactor from the top of the reactor in a batch or semi-batch manner.

The system may include more than one hydrolysis reactor and other components understood from the description herein. For example, the system may include a buffer tank. After the feedstock is hydrolyzed in multiple hydrolysis tanks, the effluents from different hydrolysis tanks are collected and transferred to a buffer tank for equilibration. Hydrogen and carbon dioxide gas may also be generated in the hydrolysis tank. The equilibrated soluble species is intermittently transferred to a biogas production reactor for continuous biogas generation. After completion of the digestion cycle, the digested straw is removed from the hydrolysis reactor before a new batch of straw is added. In various embodiments, the system includes more than one hydrolysis reactor, a biogas production reactor, and a biostabilization reactor.

The manner in which the incubation conditions of each of the hydrolysis reactor, biogas production reactor, and biostabilization reactor are adjusted is understood in light of the description herein. In various embodiments, at least one of the temperature, pressure, and incubation time is maintained within a desired or predetermined range. In various embodiments, the system includes a controller and microprocessor that monitors and controls conditions and flow rates within one or more reactors.

The thermal and chemical conditions may be varied in order to increase the reaction rate and efficiency of each reactor. In various embodiments, the hydrolysis reactor is operated at a temperature of about 50 ℃ to about 55 ℃, the biogas production reactor is operated at a temperature of about 35 ℃ to about 40 ℃, and the biostabilization reactor is operated at a temperature of about 25 ℃ to about 30 ℃. In various embodiments, the hydrolysis reactor is operated at a temperature of about 35 ℃ to about 45 ℃, the biogas production reactor is operated at a temperature of about 35 ℃ to about 40 ℃, and the biostabilization reactor is operated at a temperature of about 25 ℃ to about 35 ℃.

In various embodiments, the hydrolysis reactor operates at a pH of about 4.5 to about 6.5, the biogas production reactor operates at a pH of about 6.8 to about 8.0, and the biostabilization reactor operates at a pH of about 6.8 to 8.0. In various embodiments, the hydrolysis reactor, the biogas production reactor, and the biostabilization reactor are all operated at a pH of about 6.5 to about 8.2.

In various embodiments, the process achieves a Total Solids (TS) reduction of at least about 50%, preferably at least about 60% and more preferably at least about 90%. In various embodiments, the Volatile Solids (VS) are reduced by at least about 60%, more preferably at least about 70% and even more preferably at least about 80%. In various embodiments, the reduction in TS and VS is: at least about 70% and at least about 80% for food waste, at least about 70% and at least about 80% for a mixture of food and green waste, and at least about 50% and at least about 70% for green waste. In various embodiments, the average biogas production of the systems and methods of the invention is at least 300mL/gVS, preferably at least 400mL/gVS, and more preferably at least 500 mL/gVS. In various embodiments, the system produces at least about 200mL/gVS, preferably at least 300mL/gVS and more preferably at least 400 mL/gVS. In another embodiment, the concentration of hydrogen collected from the hydrolysis reactor is from about 10% to about 60%, more preferably from about 20% to about 50%.

In various embodiments, the methane gas concentration collected from the biogas production reactor is from about 40% to about 80%, more preferably from about 50% to about 70% and most preferably about 60%. In various embodiments, the methane gas concentration collected from the biostabilization reactor is from about 60% to about 80%, more preferably from about 65% to about 80% and most preferably about 70%.

Turning to fig. 5, an anaerobic digester system 30a according to the invention is shown. System 30a is similar in many respects to system 30, but includes an optional ammonia removal device 67. System 30a includes 3 anaerobic reactors: a hydrolysis reactor 35, a biogas production reactor 46, and a biostabilization reactor 58.

An ammonia removal unit 67 removes ammonia, salts and other elements prior to recycling. The device 67 separates and removes the unwanted excess ammonia and salts. This may be required for the treatment of organic materials with high protein content and salt, such as meat products.

The method of use of system 30a is similar to the method of use of system 30. In various embodiments, the liquid separated by the solid-liquid separator 54 is passed through an ammonia removal device 67 to remove ammonia from the liquid prior to recycling to the hydrolysis reactor. The ammonia removal process may be a chemical, mechanical, or ionic process, including gas stripping, membrane separation, and other conventional techniques. In an exemplary embodiment, the liquid is treated with alkali chemistry (lime or sodium hydroxide) to increase the pH to above about 9, and simultaneously a gas (air or biogas) is passed through the liquid (e.g., bubbled) to remove ammonia from the liquid. The ammonia in the gas may later be removed from the gas and collected as an ammonia product. One ammonia collection process is to react an ammonia-laden gas with an acid (e.g., sulfuric acid or nitric acid). The ammonia will react with the acid to form ammonium sulfate or nitrate, which is used as a fertilizer product or for other purposes.

With respect to FIG. 6, an exemplary anaerobic digester system 30b according to the present invention is shown. System 30b is similar in many respects to system 30a, except that biogas production reactor 46 receives a fresh liquid feed 68 from an external source. In an exemplary system, the fresh liquid feed is wastewater. Liquid feed 68 is added to the biogas production reactor along with the effluent from hydrolysis reactor 35. System 30b is generally useful for applications where both solid and liquid feedstocks require treatment, such as solid waste and wastewater.

In operation and application, the system 30b is used in substantially the same manner as the system 30a and the system 30 described above.

With respect to fig. 7, the exemplary anaerobic digester system 30c also includes a second hydrolysis effluent port 42a for diverting hydrolysis reactor effluent to the biostabilization reactor 58 via a second biostabilization inlet 60 a.

Fig. 8 shows an exemplary system 30d of the present invention wherein the hydrolysis reactor second effluent port 42a diverts the hydrolysis reactor effluent to the biostabilization reactor 58 via the biostabilization reactor second inlet 60 a. The system also includes a line 80 through which effluent from the biostabilization reactor is recycled back to the system (e.g., back to the hydrolysis reactor) (e.g., via valve 37).

As one of the increasingly important biofuel production technologies, anaerobic digestion offers many public benefits, relating to bioenergy production, environmental quality protection, and public health improvement. Figure 9 shows many of the public benefits of anaerobic digestion and its byproducts.

In contrast to conventional high solids digesters, the high efficiency anaerobic bio-digester system according to the present invention provides increased energy efficiency in terms of conversion of organic material to biogas energy. The system of the present invention can also be used for more applications than any of the prior art. The system can be used to treat a wide range of organic solid materials having a wide range of chemical compositions by using an optional water recycle and ammonia-salt separation process.

The system and method according to the present invention provides the ability and flexibility to treat solid waste and wastewater in one system. The system can be used to treat solid waste and wastewater and generate biogas (e.g., hydrogen and methane gas) to produce energy. Thus, the system may increase energy efficiency and reduce system cost.

In the exemplary system, the biostabilization reactor 58 and the biogas production reactor 46 differ in function and structure. In the exemplary system, the solid components are digested by the biogas production reactor, separated by the solid-liquid separator 54 for composting, or a combination thereof. Thus, the biostabilization reactor operates primarily on liquid wastewater. The bacterial culture contained in each reactor is generally different due to the difference in the entry into the biogas production reactor and the biostable organic material. Partly for the reasons described above, biostabilization reactors allow for higher processing rates and shorter residence times than systems with biogas production facilities and processes only.

The system according to the invention allows to reduce the organic content of waste and effluent compared to the existing systems.

In addition, the exemplary system utilizes features to make the bio-digestion process more efficient and generate more biogas from a given organic material than existing anaerobic digestion systems. These optional features and benefits include at least (1) 3 biological and temperature phased anaerobic digestion processes to achieve optimal thermal, chemical and biochemical conditions for rapid conversion of organic material to biogas; (2) simultaneously mechanically and biologically decomposing the organic solids to increase the rate of chemical and biochemical reactions; (3) water recycle to reduce clean water usage and wastewater discharge; and (4) treating the solid waste and wastewater in one system.

The system according to the invention can be used to generate biogas energy from organic materials such as food and yard waste, agricultural residues, food processing by-products and animal manure.

The system according to the invention provides a more energy efficient way of converting organic material to biogas energy than existing high solids digesters. The system can be used for more applications than in the prior art. Because the optional water recycle and ammonia-salt separation process is incorporated into the digester system, the system can be used to treat a wide range of organic solid materials with a wide range of chemical compositions.

Anaerobic digestion systems according to the present invention have higher energy conversion efficiency and lower costs, including capital, operating, and maintenance costs, than existing anaerobic digestion systems. Furthermore, the system is easier to operate and maintain.

In summary, in various preferred embodiments, the present invention provides:

an anaerobic digester system for generating biogas from organic material, the system comprising: a hydrolysis reactor containing a culture of a hydrolyzing bacterium, said organic material being a hydrolysis substrate for said culture, said hydrolysis reactor further comprising: a hydrolysis inlet to receive organic material; a first hydrolysis outlet for discharging hydrolysis effluent from the hydrolysis reactor; and a vent for venting biogas from the hydrolysis reactor; a biogas production reactor containing therein a culture of acetogenic and methanogenic bacteria, said biogas production reactor further comprising: a biogas production reactor inlet receiving a hydrolysis effluent from the hydrolysis reactor outlet; a biogas production reactor outlet for discharging a biogas production effluent from the biogas production reactor; a gas vent for discharging biogas from the biogas production reactor; and a biostabilization reactor having a methanogenic bacterial culture therein, the biostabilization reactor further comprising: a first biostabilization reactor inlet that receives a biogas production effluent from a biogas production reactor outlet; a biostabilization reactor outlet for discharging biostabilization effluent from the biostabilization reactor; and a vent for venting biogas from the biostabilization reactor.

An anaerobic digestion system for generating biogas from organic material according to the preceding paragraph, said system comprising: a hydrolysis reactor containing a bacterial culture therein for the production of biogas from organic material containing biodegradable solids, the hydrolysis reactor further comprising: a hydrolysis inlet to receive organic material; a hydrolysis outlet for discharging a hydrolysis effluent from the hydrolysis reactor; and a vent for venting biogas from the hydrolysis reactor; a biogas production reactor having a bacterial culture contained therein for producing biogas from organic material containing biodegradable solids, the biogas production reactor further comprising: a biogas production reactor inlet receiving a hydrolysis effluent from the hydrolysis reactor outlet; a biogas production reactor outlet for discharging a biogas production effluent from the biogas production reactor; and a vent for venting biogas from the biogas production reactor; and a biostabilization reactor having a bacterial culture therein for producing biogas from an organic material substantially free of biodegradable solids, the biostabilization reactor further comprising: a biostabilization reactor inlet that receives a biogas production effluent from a biogas production reactor outlet; a biostabilization reactor outlet for discharging biostabilization effluent from the biostabilization reactor; and a vent for venting biogas from the biostabilization reactor.

A system according to any preceding paragraph, the biostabilization reactor comprising a vessel for maintaining a methanogenic bacterial culture, wherein the biostabilization reactor outlet communicates with a vertical surface of the biostabilization reactor vessel.

A system according to any preceding paragraph, the biogas production reactor comprising a vessel that maintains a methanogenic bacterial culture, wherein the biogas production reactor outlet communicates with a vertical surface of the biogas production reactor vessel.

The system according to any preceding paragraph, wherein the biogas production reactor has a controlled internal temperature above about 30 ℃.

The system according to any preceding paragraph, wherein the biogas production reactor has a controlled internal temperature of about 25 ℃ to about 55 ℃.

The system according to any preceding paragraph, wherein the biogas production reactor has a controlled internal pH of about 6.8 to about 8.2.

The system according to any preceding paragraph, wherein the organic material is a member selected from the group consisting of a solid, a liquid, and combinations thereof.

A system according to any preceding paragraph, wherein the hydrolysis reactor further comprises an acetogenic bacterial culture.

A system according to any preceding paragraph, wherein the biostabilization reactor has a controlled internal temperature equal to or lower than the biogas production reactor.

A system according to any preceding paragraph, wherein the biostable bacterial culture is substantially free of acetogenic bacteria.

The system according to any preceding paragraph, wherein the biostabilization reactor has a controlled internal pH of about 6.8 to about 8.2.

The system according to any preceding paragraph, wherein the biogas production reactor is configured to process a member selected from the group consisting of a liquid, a solid, and combinations thereof.

A system according to any preceding paragraph, further comprising a grinder upstream of the biogas production reactor for mechanically reducing the size of solid particles in the organic material.

A system according to any preceding paragraph, the system further comprising: a solid-liquid separator located between the biogas production reactor and the biostabilization reactor, the separator configured to separate a fibrous solid component from a liquid component of a biogas production effluent.

A system according to any preceding paragraph, wherein the fibrous solid component has a moisture content of about 60% to about 70%.

A system according to any preceding paragraph, further comprising a filter means fluidly located between the biogas production reactor and the biostabilization reactor.

The system according to any preceding paragraph, wherein the filter means is selected from one of a grinder, a mesh, a filter, a screen, a filter, a slat, and combinations thereof.

A system according to any preceding paragraph, wherein the biogas discharged from the hydrolysis reactor comprises hydrogen and carbon dioxide, the biogas discharged from the biogas production reactor comprises methane and carbon dioxide, and the biogas discharged from the biostabilization reactor comprises methane.

The system according to any preceding paragraph, wherein the organic material has a high salt content.

A system according to any preceding paragraph, further comprising a removal device to remove one of ammonia, salt, and combinations thereof from the biogas production effluent.

A system according to any preceding paragraph, further comprising a liquid line that transfers at least a portion of the biogas production effluent to the hydrolysis reactor via the removal device.

A system according to any preceding paragraph, further comprising a biostabilization reactor second inlet that receives a biogas production effluent from the hydrolysis reactor second outlet.

A system according to any preceding paragraph, further comprising a biostabilization reactor effluent recycle line feeding biostabilization reactor effluent to an element selected from the group consisting of the hydrolysis reactor, the biogas production reactor, and combinations thereof.

A method of generating biogas, the method comprising: delivering organic material as feedstock to the systematic hydrolysis reactor of any preceding claim; incubating a hydrolysis mixture comprising a hydrolysis effluent and an acidogenic and hydrolyzing bacterial culture under anaerobic conditions to produce hydrogen, carbon dioxide, and a hydrolysis effluent; transferring a minor portion of the hydrolysis effluent to the biogas production reactor; incubating a biogas production mixture comprising a hydrolyzed effluent and an acetogenic and methanogenic bacterial culture under anaerobic conditions to produce methane, carbon dioxide, and a biogas production effluent; transferring a minor portion of the biogas production effluent to a biostabilization reactor; incubating a biostable mixture comprising a biogas production effluent and a biostable methanogenic bacterial culture under anaerobic conditions to produce methane and a biostable effluent. The method can be, but need not be, implemented using any of the devices or systems listed herein. In various embodiments, the method includes transferring a portion of the effluent from the hydrolysis reactor to a biostabilization reactor.

A biostabilization reactor system for generating biogas from partially digested organic material, the reactor system comprising: a vessel comprising an inlet for mixing partially digested organic material and a biostable bacterial culture for biogas production of the organic material; a gas vent for discharging biogas generated by biogas production; and an outlet for discharging a biogas production produced liquid effluent from the vessel; wherein the partially digested organic material is methanogenic with a mixture of an acetogenic and a methanogenic bacterial culture upstream of the vessel, and the biostable bacterial culture is a methanogenic bacterial culture. The biostabilization reactor system may, but need not, be used in any device or system or to perform any of the methods listed herein. The partially digested organic material is transferred from the biogas production reactor, the hydrolysis reactor, or a combination of both to the biostabilization reactor.

A system according to any preceding paragraph, wherein the methanogenic bacterial culture is substantially free of acetogenic bacteria.

A system according to any preceding paragraph, further comprising a solid liquid separator for separating a solid component from a liquid component in the partially digested organic material to be injected into the vessel.

A system according to any preceding paragraph, wherein the vessel is configured to be maintained at an internal temperature of about 25 ℃ to about 55 ℃.

The system according to any preceding paragraph, wherein the vessel is configured to maintain the mixture of the organic material and the biostable bacterial culture at a pH of about 6.8 to about 8.2.

A system according to any preceding paragraph, wherein the outlet is configured to discharge liquid effluent from an area adjacent an inner wall surface of the vessel.

A system according to any preceding paragraph, wherein the vented biogas is vented from a top of the vessel.

A system according to any preceding paragraph, wherein the inlet is operatively fluidly connected to the hydrolysis reactor such that the hydrolysis reactor effluent is transferred to the system.

A method of generating a biogas that is a member selected from the group consisting of methane, hydrogen, carbon dioxide, and combinations thereof, the method comprising: delivering a feedstock to a hydrolysis reactor, a portion of the feedstock comprising ground solid organic material, the hydrolysis reactor comprising a culture of hydrolyzing and acetogenic bacteria, the solid organic material being a hydrolysis substrate for the culture; incubating a hydrolysis mixture comprising the feedstock and a culture of hydrolytic and acetogenic bacteria under substantially anaerobic conditions for a period of time to produce hydrogen, carbon dioxide, and a hydrolysis effluent; transferring the first portion of the hydrolyzed effluent to a biogas production reactor having an acetogenic and methanogenic biogas production bacterial culture therein; incubating a biogas production mixture comprising a second portion of said hydrolyzed effluent and a culture of biogas producing bacteria under sufficiently anaerobic conditions for a period of time to produce methane, carbon dioxide, and a biogas production effluent; transferring a minor portion of the biogas production effluent to a biostabilization reactor having a biostabilization bacterial culture therein; incubating the biostable mixture comprising the biogas production effluent and the biostable bacterial culture under sufficiently anaerobic conditions for a period of time to produce methane and carbon dioxide. The method may also optionally include transferring at least a portion of the hydrolysis effluent to a biostabilization reactor. The methods can be, but are not necessarily, practiced using any apparatus or system or as a component of or in addition to any of the methods listed herein.

A method according to any preceding paragraph, wherein the biostable incubation is performed at a temperature equal to or lower than the biogas production incubation.

A method according to any preceding paragraph, further comprising providing different liquid feedstocks to the biogas production reactor prior to the biogas production incubation.

A method according to any preceding paragraph, further comprising separating a solid component from a liquid of the biogas production effluent prior to transferring to the biostabilization reactor.

The method according to any preceding paragraph, further comprising recycling a portion of the separated liquid to the hydrolysis reactor.

A method according to any preceding paragraph, wherein the steps are performed substantially simultaneously.

A method according to any preceding paragraph, wherein the biostable bacterial culture is a methanogenic bacterial culture substantially free of acetogenic bacteria.

A method according to any preceding paragraph, further comprising diverting at least a portion of the biogas production effluent to the biostabilization reactor.

Examples

Example 1: tested high efficiency anaerobic digester system

The high efficiency anaerobic digester system (HR biodigesterter) shown in figure 1 was tested for treating vegetable waste. The HR biodigister system has 3 reactors-a Hydrolysis Reactor (HR), a biogas production reactor (BR) and a biostabilization reactor (BSR). The working volumes of HR, BR and BSR are 5, 5 and 9 liters, respectively. All reactors were operated at 35 degrees celsius. Hydraulic retention time for HR was 5 days, BR was 20 days and BSR was 12 days. A mixture of 3 vegetables (including cabbage, green pepper and celery) was used as a feedstock for the digester system and tested for HR biodigister for about 70 days. The vegetable mixture was prepared from fresh vegetables using a laboratory food processor. The vegetable mixture has Total Solids (TS) and Volatile Solids (VS) contents of 6-7% and 5.5-6.5%, respectively, and is composed of 55% cabbage, 27% pepper and 17% celery.

The vegetable mixture is first injected into HR. In HR, vegetables are hydrolyzed and mostly converted to volatile fatty acids (acetic acid is the major acid produced) by microbial reactions. The pH in HR is maintained between 5 and 6 (mostly between 5.6 and 5.8). HR mixed intermittently (3 minutes per hour) and then allowed to settle for 2 hours before the effluent was discharged. The effluent of HR is discharged at 2 ports located on the reactor wall, one at approximately mid-height (called upper port) and one near the bottom (lower port). The effluent removed from the upper port contains less suspended solids than the effluent removed from the lower port. The effluent from the upper port is sent directly to the BSR and the effluent from the lower port is sent to the BGR for conversion to biogas. The effluent from the BGR is injected into the BSR for further treatment after passing through a solid-liquid separator (pressure) to remove the solid fraction. Effluent from the BSR was discharged. The BGR and BSR were mixed intermittently (3 minutes per hour) and allowed to settle (no mixing) for 2 hours before the effluent was discharged. The pH in BGR and BSR was maintained in the 7.4-7.8 range.

2 tests were performed. The first test was used for system (a) of fig. 1 and lasted for approximately 50 days, with the first 30 days of system startup and the last 20 days of system performance data collected. After the first test, the second test was used for system (b) of fig. 1 and continued for 30 days. The first test fed HR with only the vegetable mix, the second test vegetable mix and recycled water taken from BSR effluent. In the first test, ammonium hydroxide was added to HR to increase nitrogen content and alkalinity to control pH. The second test was for nutrients in the recycle system, avoiding the need to add ammonia. The amount of circulating water is the same as the amount of vegetable mixture. The vegetables and the circulating water are mixed before being injected into the HR.

Test results

The biogas produced by HR contains 5-30% hydrogen, 70-93% carbon oxide and 2-4% methane. The biogas composition in HR varies depending on the feed conditions. The biogas generated by BGR and BSR has a stable composition with 70-72% methane and 30-28% carbon oxide. In the first test, the average biogas production from the digester system in the first test stage was 624ml/gVS, calculated from the raw vegetable mix injected with HR. The distributed biogas production in HR, BGR and BSR was 80, 116 and 428ml/gVS, respectively. In the second test, the average biogas production was 557 ml/gVS. The distributed biogas production in HR, BGR and BSR was 76, 122 and 359ml/gVS, respectively. The solids reduction achieved by the 2 systems was 86-88% for Total Solids (TS) and 92-93% for Volatile Solids (VS). Due to the high digestibility of vegetables, the solids removed from the BGR reactor effluent by pressing were less, about 2% solids. More than 85% of the total solids and more than 90% of the volatile solids are converted to biogas by a microbial digestion process.

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The references referred to above are incorporated herein by reference for all purposes.

Claims (41)

1. An anaerobic digester system for generating biogas from organic material, the system comprising:

a hydrolysis reactor containing a culture of a hydrolyzing bacterium, said organic material being a hydrolysis substrate for said culture, said hydrolysis reactor further comprising:

a hydrolysis inlet to receive organic material;

a first hydrolysis outlet for discharging hydrolysis effluent from the hydrolysis reactor; and

a vent for venting biogas from the hydrolysis reactor;

a biogas production reactor containing therein a culture of acetogenic and methanogenic bacteria, said biogas production reactor further comprising:

a biogas production reactor inlet receiving a hydrolysis effluent from the hydrolysis reactor outlet;

a biogas production reactor outlet for discharging a biogas production effluent from the biogas production reactor; and

a gas vent for discharging biogas from the biogas production reactor; and

a biostabilization reactor having a methanogenic bacterial culture contained therein, the biostabilization reactor further comprising:

a first biostabilization reactor inlet that receives a biogas production effluent from a biogas production reactor outlet;

a biostabilization reactor outlet for discharging biostabilization effluent from the biostabilization reactor; and

a vent for venting biogas from the biostabilization reactor.

2. An anaerobic digestion system for generating biogas from organic material, the system comprising:

a hydrolysis reactor containing a bacterial culture therein for the production of biogas from organic material containing biodegradable solids, the hydrolysis reactor further comprising:

a hydrolysis inlet to receive organic material;

a hydrolysis outlet for discharging a hydrolysis effluent from the hydrolysis reactor; and

a vent for venting biogas from the hydrolysis reactor;

a biogas production reactor having a bacterial culture contained therein for producing biogas from organic material containing biodegradable solids, the biogas production reactor further comprising:

a biogas production reactor inlet receiving a hydrolysis effluent from the hydrolysis reactor outlet;

a biogas production reactor outlet for discharging a biogas production effluent from the biogas production reactor; and

a gas vent for discharging biogas from the biogas production reactor; and

a biostabilization reactor having a bacterial culture therein for the production of biogas from organic material substantially free of biodegradable solids, said biostabilization reactor further comprising:

a biostabilization reactor inlet that receives a biogas production effluent from a biogas production reactor outlet;

a biostabilization reactor outlet for discharging biostabilization effluent from the biostabilization reactor; and

a vent for venting biogas from the biostabilization reactor.

3. The system of claim 1 or 2, wherein the biostabilization reactor comprises a vessel for maintaining a methanogenic bacterial culture, wherein the biostabilization reactor outlet is in communication with a vertical surface of the biostabilization reactor vessel.

4. The system of any one of claims 1-3, wherein the biogas production reactor comprises a vessel that maintains a methanogenic bacterial culture, wherein the biogas production reactor outlet is in communication with a vertical surface of the biogas production reactor vessel.

5. The system of claim 1 or 2, wherein the biogas production reactor has a controlled internal temperature above about 30 ℃.

6. The system of any one of the preceding claims, wherein the biogas production reactor has a controlled internal temperature of about 25 ℃ to about 55 ℃.

7. The system of any one of the preceding claims, wherein the biogas production reactor has a controlled internal pH of about 6.8 to about 8.2.

8. The system of claim 1 or 2, wherein the organic material is a member selected from the group consisting of a solid, a liquid, and combinations thereof.

9. The system of claim 1 or 2, wherein the hydrolysis reactor further comprises an acetogenic bacterial culture.

10. The system of claim 1 or 2, wherein the biostabilization reactor has a controlled internal temperature equal to or lower than the biogas production reactor.

11. The system of any one of the preceding claims, wherein the biostable bacterial culture is substantially free of acetogenic bacteria.

12. The system of any one of claims 1-6, wherein the biostabilization reactor has a controlled internal pH of about 6.8 to about 8.2.

13. The system of any one of claims 1, 2, or 12, wherein the biogas production reactor is configured to process a member selected from the group consisting of a liquid, a solid, and combinations thereof.

14. The system of claim 1 or 2, further comprising a grinder upstream of the biogas production reactor for mechanically reducing the size of solid particles in the organic material.

15. The system of any one of claims 1, 2 or 13, further comprising:

a solid-liquid separator located between the biogas production reactor and the biostabilization reactor, the separator configured to separate a fibrous solid component from a liquid component of a biogas production effluent.

16. The system of claim 15, wherein the fibrous solid component has a moisture content of about 60% to about 70%.

17. The system of any one of the preceding claims, further comprising a filter means fluidly located between the biogas production reactor and the biostabilization reactor.

18. The system of claim 17, wherein the filter means is selected from one of a grinder, a mesh, a filter, a screen, a filter, a slat, and combinations thereof.

19. The system of claim 1 or 2, wherein the biogas discharged from the hydrolysis reactor comprises hydrogen and carbon dioxide, the biogas discharged from the biogas production reactor comprises methane and carbon dioxide, and the biogas discharged from the biostabilization reactor comprises methane.

20. The system of any one of the preceding claims, wherein the organic material has a high salt content.

21. The system of any one of the preceding claims, further comprising a removal device that removes one of ammonia, salt, and combinations thereof from the biogas production effluent.

22. The system of claim 21, further comprising a liquid line that transfers at least a portion of the biogas production effluent to the hydrolysis reactor via the removal device.

23. The system of any one of the preceding claims, further comprising a biostabilization reactor second inlet that receives a biogas-making effluent from a hydrolysis reactor second outlet.

24. The system of any one of the preceding claims, further comprising a biostabilization reactor effluent recycle line feeding the biostabilization reactor effluent to an element selected from the group consisting of the hydrolysis reactor, the biogas production reactor, and combinations thereof.

25. A method of generating biogas, the method comprising:

delivering organic material to the system hydrolysis reactor of any of the preceding claims as feedstock;

incubating a hydrolysis mixture comprising a hydrolysis effluent and an acidogenic and hydrolyzing bacterial culture under anaerobic conditions to produce hydrogen, carbon dioxide, and a hydrolysis effluent;

transferring a minor portion of the hydrolysis effluent to the biogas production reactor;

incubating a biogas production mixture comprising a hydrolyzed effluent and an acetogenic and methanogenic bacterial culture under anaerobic conditions to produce methane, carbon dioxide, and a biogas production effluent;

transferring a minor portion of the biogas production effluent to a biostabilization reactor; and

incubating a biostable mixture comprising a biogas production effluent and a biostable methanogenic bacterial culture under anaerobic conditions to produce methane and a biostable effluent.

26. A biostabilization reactor system for generating biogas from partially digested organic material, the reactor system comprising:

a vessel comprising an inlet for mixing partially digested organic material and a biostable bacterial culture for biogas production of the organic material;

a gas vent for discharging biogas generated by biogas production; and

an outlet for discharging a biogas production produced liquid effluent from the vessel;

wherein the partially digested organic material is methanogenic with a mixture of an acetogenic and a methanogenic bacterial culture upstream of the vessel, and the biostable bacterial culture is a methanogenic bacterial culture.

27. The system of claim 26, wherein the methanogenic bacterial culture is substantially free of acetogenic bacteria.

28. The system of claim 26, further comprising a solid-liquid separator for separating a solid component from a liquid component in the partially digested organic material to be injected into the vessel.

29. The system of claim 26, wherein the vessel is configured to be maintained at an internal temperature of about 25 ℃ to about 55 ℃.

30. The system of any one of claims 26-29, wherein the container is configured to maintain the mixture of the organic material and the biostable bacterial culture at a pH of about 6.8 to about 8.2.

31. The system of claim 26, wherein the outlet is configured to discharge liquid effluent from an area adjacent to the inner wall surface of the vessel.

32. The system of claim 26, wherein the vented biogas is vented from a top of the vessel.

33. The system of any one of claims 26 to 32, wherein the inlet is in operative fluid communication with the hydrolysis reactor such that the hydrolysis reactor effluent is diverted into the system.

34. A method of generating a biogas that is a member selected from the group consisting of methane, hydrogen, carbon dioxide, and combinations thereof, the method comprising:

delivering a feedstock to a hydrolysis reactor, a portion of the feedstock comprising ground solid organic material, the hydrolysis reactor comprising a culture of hydrolyzing and acetogenic bacteria, the solid organic material being a hydrolysis substrate for the culture;

incubating a hydrolysis mixture comprising the feedstock and a culture of hydrolytic and acetogenic bacteria under substantially anaerobic conditions for a period of time to produce hydrogen, carbon dioxide, and a hydrolysis effluent;

transferring the first portion of the hydrolyzed effluent to a biogas production reactor having an acetogenic and methanogenic biogas production bacterial culture therein;

incubating a biogas production mixture comprising a second portion of said hydrolyzed effluent and a culture of biogas producing bacteria under sufficiently anaerobic conditions for a period of time to produce methane, carbon dioxide, and a biogas production effluent;

transferring at least a portion of the biogas production effluent to a biostabilization reactor having a biostabilization bacterial culture therein; and

incubating the biostable mixture comprising the biogas production effluent and the biostable bacterial culture under sufficiently anaerobic conditions for a period of time to produce methane and carbon dioxide.

35. The method of claim 34, wherein the biostable incubation is performed at a temperature at or below the temperature of the biogas production incubation.

36. The method of claim 34, further comprising providing a different liquid feedstock to the biogas production reactor prior to the biogas production incubation.

37. The method of any one of claims 34-36, further comprising separating a solid component from a liquid of the biogas production effluent prior to transferring to the biostabilization reactor.

38. The method of claim 37, further comprising recycling a portion of the separated liquid to the hydrolysis reactor.

39. The method of any one of claims 34-38, wherein the steps are performed substantially simultaneously.

40. The method of claim 34, wherein the biostable bacterial culture is a methanogenic bacterial culture substantially free of acetogenic bacteria.

41. The method of any one of claims 34 to 40, further comprising transferring at least a portion of the hydrolysis effluent to the biostabilization reactor.