CN120917135A - Fermenter system and method for producing biogas and optionally useful products, in particular fatty acids and/or proteins - Google Patents

Abstract

The invention relates to a fermenter system (100) for producing biogas and optionally useful products, in particular fatty acids and/or proteins, comprising a first fermenter (1), a second fermenter (2), a pipe (4, 6) connecting the first fermenter (1) and the second fermenter (2), and a heating unit configured to provide a temperature of > 25 ℃ in the first and second fermenter (1, 2) and the pipe (4, 6). Wherein the fermenter system (100) is configured for anaerobic operation. The invention also relates to the use of the fermenter system (100) and to a method for producing biogas and useful products, in particular fatty acids and/or proteins, using the fermenter system (100).

Description

Fermenter system and method for producing biogas and optionally useful products, in particular fatty acids and/or proteins

Technical Field

The present invention relates to the conversion of biological products, in particular biological materials, residues and waste into useful products. More particularly, the present invention relates to a process for producing methane, carbon dioxide and, if applicable, other useful products such as fatty acids and/or proteins, and to an apparatus for carrying out the process.

Background

Biogas (biogas) is a mixture of biogenic methane and biogenic carbon dioxide, currently produced mainly by the so-called wet fermentation process. In these processes, animal manure (in particular pig manure, cow manure, poultry dry manure) is fed to a fermenter. The faeces used help to introduce the active microbial community into the process, thereby enabling degradation of the substrate material to be fermented and biogas production. The process may be carried out in a fermenter. Furthermore, so-called multistage processes are also common, in which the substrate to be fermented is passed through several fermenters in succession.

Since the proportion of fermentable biological dry matter in the manure used is generally low, additional fermentation substrate needs to be supplemented to quantitatively increase the biogas yield. The fermentation substrate used is mainly biological waste, such as food waste, slaughterhouse waste and waste from food production. In addition to biological waste, energy crops, so-called "renewable raw materials", produced in agricultural processes, in particular whole-plant silage (e.g. corn, cereal or grass), can also be used as fermentation substrates.

A fermentation base stream consisting of manure and fermentation substrate is passed through one or more fermentors. During fermentation, part of the biomass in the fermentation substrate is converted into biogas. Furthermore, a fermentation residue is left which consists of solid and liquid components, which is generally used as fertilizer, in particular on agricultural land.

In particular in areas where there is not a sufficient quantity of livestock as a source of faeces for operating biogas plants, an alternative to process engineering is to separate the fermentation residues discharged from the fermenter into solid and liquid fractions in order to reintroduce a part of the liquid phase into the fermentation process together with fresh fermentation substrate.

In these types of processes, the maximum possible solids content of the fermentation substrate-fecal mixture is fundamentally limited, since the mixture must remain pumpable and stirrable. The maximum possible solids content of the fermentation substrate mixture to be fermented or the limitation of the fermentation substrate results in only small amounts of fresh fermentation substrate per cubic meter of fermenter volume per day being fed into the fermenter. The dry matter content of the fermentation substrate mixture to be fermented is, as a rule, below 15% by weight.

Another disadvantage is that the fermentation performance of the microbial community provided by the faeces is rather low. Thus, fermentation processes require a relatively long average hydraulic residence time, typically 30 to 120 days. This in turn requires the use of fermenters of considerable size, typically several hundred to several thousand cubic meters.

The fermentation process is generally carried out continuously. Unless a portion of the liquid phase is separated at the end of the fermentation process in order to be reintroduced into the fermentation process with fresh fermentation substrate, the solid and liquid phases will pass through the fermenter with the same hydraulic residence time. In this case, the hydraulic residence time of each of the solid and liquid phases cannot be controlled or actively regulated individually.

In some cases, discontinuous processes (e.g. so-called batch processes) are also used, wherein the fermentation process is actively terminated or stopped after a period of time, typically when biogas production is significantly reduced. The fermenter is then emptied and the fermentation process is restarted using fresh fermentation substrate.

An alternative process to wet fermentation is the so-called dry fermentation. In this process, the fermentation substrate to be fermented is deposited in solid phase in a vessel used as a fermenter. During fermentation, the substrate is diafiltered by a diafiltration solution, which provides the microbial colonies required for fermenting the substrate.

The procedure in which all steps (hydrolysis, acidification, methanogenesis) of biomass into biogas need to be performed in only a single fermenter is distinguished from the procedure in which at least two fermentors are used.

In these two-stage dry fermentation processes, diafiltration is mainly used to hydrolyze the substrate (solid phase) and remove substances or intermediates released during hydrolysis that are dissolved in the first fermenter permeate. The liquid phase pumped out of the first fermenter (percolate) is then fed to a second fermenter, wherein the substances dissolved in the percolate, which are released from the substrate in the first fermenter by hydrolysis, are subjected to an acidification and methanogenesis step. During this step of the process, most of the biogas is produced. At the same time, the percolate is regenerated in this way and can be recycled to the first vessel, where it is again enriched with intermediate products released by hydrolysis of the substrate.

One common design of such fermenter systems is the so-called garage fermenter, in which a discontinuous process is used for fermenting the substrate (solid phase), because the fermenter is opened at fixed time intervals to remove unfermented substrate and the fermenter is refilled with fresh fermentation substrate.

Due to the microbiological and equipment-specific characteristics on which the process is based, the fermentation performance of the fermentation substrate used to convert it into the desired target product (in particular biogas) is limited.

One particular limiting factor is that all steps of the metabolism of the substance (hydrolysis, acidification, methanogenesis) are carried out simultaneously. Since the microorganisms (biota) responsible for each sub-process of substance metabolism have respective, species-specific requirements for their optimal environmental conditions (in particular the pH of the environment), the fermentation process must be carried out under environmental conditions which allow the microbial strains necessary for all substance metabolism to exert their specific fermentation function, although the environmental conditions are suboptimal for each microbial strain.

Another related limitation of the fermentation performance of the fermentation substrates used in the conversion process described above stems from the fact that the fecal based biocenosis present in the fermentor is mainly composed of microorganisms whose material metabolism is mainly directed towards the degradation of soluble sugars, starches, fats/oils and proteins.

However, plant biomass consists of a large number of so-called fibrous and structural substances, which consist of, inter alia, cellulose and hemicellulose. The biological communities used in the above-described processes have limited ability to degrade these materials. Thus, the above-described process is not effective in degrading this quantitatively highly relevant biomass potential. At the same time, the significant biomass potential is therefore excluded from use as a fermentation substrate. Therefore, energy crops, especially corn, mainly planted in agricultural production frames are widely used, but this has led to ecologically and socioeconomic land use competition. Residues and waste from certain manufacturing sectors (e.g. beverage and food industry), as well as food waste (e.g. canteen and kitchen waste, food waste from the food trade), are suitable as fermentation substrates for the above process, provided that their material composition is mainly characterized by soluble sugars, starches, fats/oils and proteins.

For example, DE 10 2006 012 130 B4 discloses a method and a device for producing biogas.

Disclosure of Invention

It is an object of the present invention to provide an apparatus and a method which at least partly or completely overcome the above-mentioned disadvantages. It is a further object of the present invention to provide an apparatus and a method by means of which a fermentation substrate containing cellulose and hemicellulose can be subjected to substance decomposition to produce biomethane and biocarbon, and if applicable other by-products. It is a further object of the present invention to provide an apparatus and a method by which a fermentation substrate consisting essentially of cellulose and hemicellulose containing material can be used for the production of methane, in particular biogenic methane, carbon dioxide, in particular biogenic carbon dioxide, and other by-products. It is another object of the present invention to provide an apparatus and method that achieves high space-time yields by eliminating capacity limiting points (bottlenecks).

The above object is achieved by a fermenter system for the production of biogas and, if applicable, of useful products, in particular fatty acids and/or proteins, by the use of a fermenter system according to claim 9, and by a method for the production of biogas and, if applicable, of useful products, in particular fatty acids and/or proteins, according to claim 10. Advantageous embodiments are specified in the dependent claims and in the description.

The fermenter system according to the invention is preferably operated continuously. In the method according to the invention, a fermenter system according to the invention is preferably used.

The term "biogas" or "biogas" as used herein refers to biogenic methane and, if applicable, other short chain bioalkanes such as bioethane, biopropane and biobutane, as well as biohydrogen and biocarbon dioxide. Biogas can be distinguished from conventional gases by its source. For example, the distinction between biogenic methane and natural gas may be determined based on the content of impurities and/or the isotope C14.

The term "fatty acid" as used herein refers to short chain fatty acids and salts thereof. The short chain fatty acids generally have a molecular weight of 500g/mol or less, preferably 400g/mol or less, 300g/mol or less, 200g/mol or less, or more preferably 150g/mol or less. Exemplary fatty acids include formate, acetate, propionate, butyrate, lactate, and succinate.

The term "fermenter" as used herein refers to a bioreactor. The fermenter comprises a vessel for culturing biological material, in particular microorganisms or a mixture of microorganisms, or a biological community. For this purpose, the fermenter provides the most optimal conditions possible. The fermenter is used in particular for the fermentation or cultivation of "anaerobic microorganisms" and provides the necessary environmental conditions for this purpose, in particular with a substantially complete barrier to oxygen.

The fermenter is preferably designed to be airtight, thermally insulating and heatable. More preferably, the fermenter is designed as a cylindrical vessel, even more preferably the cylindrical vessel is arranged horizontally, i.e. with horizontally oriented sides (surfaces). The feeding means, the pipe and the discharging means may be arranged on the circular surface, respectively. Thus, the feeding means may be arranged on a first circular surface of the first fermenter, the discharging means may be arranged on a second circular surface of the second fermenter, and the pipe may be arranged between the second circular surface of the first fermenter and the first circular surface of the second fermenter.

The fermenter can be made of plastic, in particular polyethylene and polypropylene, stainless steel or glass fiber reinforced plastic (GRP).

Preferably, the fermenter has external dimensions that enable it to be housed or mounted in the frame of a 20 foot or 40 foot standard container. The length of the fermenter is preferably 6 to 12 meters, more preferably 4 to 6 meters in the frame of a 20 foot standard container and 10 to 12 meters in the frame of a 40 foot standard container. The outer diameter of the fermenter may be 2.2 to 2.4 meters.

Preferably, a layer of insulation having a material thickness of at least 5cm, preferably at least 8cm or at least 10cm is provided between the outer or outer surface and the inner or inner surface of the fermenter (in contact with the culture medium). This minimizes heat loss. Conventional insulation materials, such as mineral wool, polystyrene (foam) or cardboard, can be used as insulation material, so that the front and rear sides of the cylindrical container (lid) are also correspondingly insulated. Polyurethane foam, wool, crushed straw, or plastic bubble film may also be used to insulate the container.

The term "fermentation substrate" as used herein refers to biological material, in particular fibrous-rich plant biomass, such as agricultural residues or waste, residues or waste of the food and beverage industry, and residues or waste produced, for example, in landscapes and water management. Aquatic plants and algae, particularly algae from the marine ecosystem, can also be used as fermentation substrates.

If the fermentation substrate relates to agriculturally produced biomass, the fruit parts of these plants may be co-fermented, but this is not essential. In this way, the competition between the food use and the energy or raw material use of plant production is facilitated by enabling agricultural crops to be used both as food or animal feed and for dual use in energy production, in particular by biogas production.

Thus, a large number of suitable fermentation substrates are available, which can be produced in a broad, ecologically advantageous agricultural framework. The use of fiber-rich plants and plant components also allows plants to serve as fermentation substrates, while playing an important ecological role in soil protection, protection of drinking water and water sources, and protection of biodiversity.

Other cellulose-containing and/or hemicellulose-containing materials may also be used as fermentation substrates, such as waste paper, cardboard, leaves, plant stems, straw material, grass and straw, as well as production residues from the paper and pulp industry, the pharmaceutical or chemical industry and from cereal mills and breweries.

A particular advantage is that the process according to the invention makes it possible to obtain renewable raw materials (cellulose and hemicellulose) of the world's most importance, estimated to be renewable only in quantities of about 10 ¹¹ tons per year worldwide.

The term "treatment solution" as used herein refers to an aqueous solution preferably containing an electrolyte. The first and second treatment solutions preferably have corresponding compositions at the initial stage (i.e., prior to contact with a biological community and fermentation substrate).

Advantageous embodiments of the treatment solutions, in particular of the first and/or second treatment solutions, may, for example, where applicable, comprise 120 to 210mmol/l, preferably 140 to 180mmol/l, sodium and potassium, where the sodium content may be greater than 100mmol/l, preferably 120 to 160mmol/l, 20 to 60mmol/l, preferably 30 to 50mmol/l, 70 to 130mmol/l, preferably 80 to 110mmol/l, bicarbonate, 5 to 15mmol/l hydrogen phosphate, 5 to 15mmol/l dihydrogen phosphate, 0.3 to 0.9mmol/l magnesium, and 0.1 to 0.4mmol/l calcium in deionized water.

The environmental conditions within the first and second fermenters require anaerobic conditions to facilitate the microbial community established therein, wherein, particularly in the first fermenters, entry of small amounts of atmospheric oxygen can be tolerated. Since some of the microbial strains forming the microbial community in the first fermenter are facultative anaerobes, they can metabolize a certain amount of oxygen, thereby removing it from the environment. Preferably, the redox potential in the first and second fermentors should be maintained in the range of-400 to-200 mV.

The inner barrel arranged in the first fermentation tank can be used for mixing the content of the first fermentation tank. Preferably, the cartridge has an at least partly closed design in the direction of the feed device, in particular near the first side of the first fermenter.

The inner barrel may be set in rotational motion by a suitable drive system (e.g., a motor). The rotational speed of the inner drum may be adjusted according to certain parameters, such as the nature of the supplied fermentation substrate, the rate of hydrolysis of the fermentation substrate and/or the organic load level. The rotational speed of the inner drum is preferably 2 to 30 revolutions per hour, more preferably 3 to 15 revolutions per hour, particularly preferably 4 to 6 revolutions per hour. The rotation of the inner cylinder may be performed continuously or at predetermined time intervals. The direction of rotation may be clockwise, counter-clockwise or alternating.

During mixing through the inner drum, the fermentation substrate particles having a further increased degree of hydrolysis may be contacted with fermentation substrate particles having a still lesser degree of hydrolysis. In this way, the microbial community present in the first fermenter can be transferred strongly to the fermentation substrate to be hydrolyzed under conditions which are gentle to the microbial community. Furthermore, the use of an inner barrel enables the solid and liquid phases to be thoroughly mixed. Due to the high organic dry matter content of many fermentation substrates, it is often not possible to mix and move the fermentation substrates in the first fermentation tank by means of conventional agitators, as in wet fermentation equipment. Preferably, the first fermenter does not contain a stirrer.

In addition, the inner drum is effective in preventing the formation of a scum layer and a sediment layer, which may be formed when the fermentation substrate is not mixed or is insufficiently mixed. In general, fermentation substrates tend to spontaneously separate into distinct phases (sediment, mixed and scum layers). Fresh fermentation substrate, as well as fermentation substrate which is only slightly hydrolysed, tend to precipitate on its boundary region between Fang Yexiang and the gas phase, forming a so-called scum layer. The gases produced by the ongoing fermentation process in the fermenter rise through the scum layer, gradually displacing the liquid phase in the scum layer, so that the continuation of the fermentation (hydrolysis) is largely arrested, and the fermenter is also at increased risk of being blocked by the fermentation substrate. As hydrolysis of the fermentation substrate proceeds, its particle size decreases and density increases, causing substrate particles to sink in the fermenter and accumulate at the bottom of the vessel. In contrast, the rotational movement of the inner barrel can effectively prevent the formation of a scum layer and a deposit layer.

In this way, a homogeneous fermentation substrate mixture can be maintained in the first fermenter. The first biological community of the first microorganism present in the first fermenter can be gently mixed with the fermentation substrate and the treatment solution.

According to a preferred embodiment, the first fermenter comprises a feed device which is adapted to heat the fermentation substrate and/or the treatment solution to a temperature of > 25 ℃ and to convey a defined amount of the fermentation substrate and/or the treatment solution into the first fermenter. The feed device may treat and add the fermentation substrate and/or the treatment solution under anaerobic conditions (i.e., substantially free of air).

The fermentation substrate may be heated in the feed device to a temperature in the first fermenter of ≡25 ℃, for example 25 ℃ to 60 ℃, preferably 35 ℃ to 45 ℃, more preferably 38 ℃ to 42 ℃, for example 39 ℃ to 41 ℃ and 39.5 ℃ to 40 ℃, before being introduced into the first fermenter. This enables the environmental conditions in the fermenter, in particular the temperature as relevant process parameter, to be kept constant.

The supply of the fermentation substrate to the first fermenter can be carried out by means of a conveying device, in particular a screw conveyor or a screw auger. The feeding device provided with the conveying device, in particular a screw conveyor or a screw auger, may be made of, for example, stainless steel or plastic. Alternatively, the substrate feed may be carried out using a solid pump, in particular a rotor pump or a screw pump.

Furthermore, the fermentation substrate to be fed to the first fermenter can be mixed with a quantity of treatment solution which can be adapted individually to the moisture/water content contained in the fermentation substrate, wherein the treatment solution is preferably heated to or maintained at the temperature in the first fermenter. This enables the supply of various fermentation substrates without being affected by their moisture content, while maintaining the organic load rate (per cubic meter of dry matter) in the first fermenter at a constant level.

According to a further preferred embodiment, the inner drum is arranged rotatable about a longitudinal axis of the first fermenter and/or is adapted to move the content of the first fermenter to the second fermenter, preferably wherein the first fermenter comprises an inner tube passing through the inner drum with a conveying unit, such as a screw conveyor or a screw auger.

The inner drum may be designed in such a way that the spatial mixing of the contents of the first fermenter is further improved. For example, means may be mounted on the inner wall of the inner vessel to enable continuous (preferably horizontal) propulsion of the fermentation substrate located within the inner vessel in the direction of the conduit or towards the second fermenter. Furthermore, other means may be mounted on the inner wall of the inner barrel to enable mixing in a direction substantially perpendicular to the direction of advancement. By simultaneously performing a continuous (preferably horizontal) pushing and mixing in a direction substantially perpendicular to the pushing direction, an optimal continuous mixing of the fermentation substrate in the first fermenter and optimal conditions for the cultivation of the first anaerobic microorganism can be ensured.

Biogas produced in the first fermenter can leave the fermenter via the first outlet.

Substrate specificity and predictable process engineering control of the hydraulic residence time of the fermentation substrate can be achieved by continuously or intermittently supplying the fermentation substrate into the fermentor, in combination with rotation of the inner drum and continuously or intermittently discharging incompletely hydrolyzed fermentation substrate and treatment solution from the first fermentor.

By arranging an inner tube along the longitudinal axis of the inner tube, part of the fermentation substrate can be transported through the inner tube by means of a transport device, preferably a screw conveyor or screw auger, to the fermentation substrate feed zone on the other side of the cylindrical fermenter vessel, whereby an alternative method of influencing the hydraulic residence time of the solid fermentation substrate phase can be provided. Thus, the inner tube is capable of transporting the fermentation substrate from the second side to the first side of the first fermenter. This not only brings the freshly supplied fermentation substrate into sufficient contact with the hydrolysed fermentation substrate, but also the fresh fermentation substrate is sufficiently transferred (contaminated) with the microbial community responsible for hydrolysing the fermentation substrate. In this way, hydrolysis of the fermentation substrate can be initiated rapidly.

The average hydraulic residence time of the fermentation substrate (solid phase) in the first fermenter can be from 24 to 120 hours, preferably from 48 to 96 hours. The average hydraulic retention time depends on the mass composition and quality of the fermentation substrate. During this time, most of the cellulose, hemicellulose, and other components in the fermentation substrate, such as sugars, starches, and proteins, may be hydrolyzed under anaerobic conditions present in the first fermenter and converted to short chain fatty acids.

The design of the fermenter system enables the mean hydraulic residence time of the solid and liquid phases in the fermenter to be influenced actively and independently, so that it is adapted to specific requirements, for example the composition of the fermentation substrate. By using a control system to control the residence time of the solid and liquid phases, respectively, the hydrolysis process can be further targeted.

In wet fermentation processes, such a targeted effect on the solid and liquid phase residence times cannot be achieved. In wet fermentation, the solid and liquid phases pass through the fermenter with the same average hydraulic residence time.

According to another preferred embodiment, the fermenter system comprises a first separation unit located between the first and the second fermenter, which is adapted to remove solids from the fermenter system at least partly, preferably substantially completely.

Downstream of the first fermenter, the fermentation substrate exiting from the first fermenter can be separated into a solid phase and a liquid phase. The first separation unit is disposed between the first and second fermenters and provides a stream to the second fermentor, wherein the stream is devoid of or substantially free of fermentation substrate.

Or preferably, the fermentation substrate-depleted stream or the substantially fermentation substrate-free stream is fed to a second separation unit described below. Preferably, the fermenter system comprises a first separation unit downstream of the first fermenter, a second separation unit downstream of the first separation unit, and a second fermenter downstream of the second separation unit. More preferably, the first and second separation units are arranged on a pipe and are fluidly connected to each other and to the first and second fermenters by a pipe.

The solid phase (unhydrolyzed or incompletely hydrolyzed fermentation substrate, and the microbial cell mass attached thereto) can be separated by using the first separation unit. For this purpose, apparatuses for solid-liquid separation known in the art can be used. The first separation unit is preferably based on a sieve. The screen may be made of stainless steel or plastic. Preferably, a plastic sieve made of plastic material with little or no colonization (biofilm formation) of microorganisms is used. For this purpose, for example, polyamides may be used.

The mesh size of the screen may be from 10 μm to 2mm, preferably from 50 μm to 1mm, more preferably from 100 μm to 500 μm.

The solid-liquid separation provided by the first separation unit may also ensure that no solid fermentation substrate particles enter the treatment solution circuit with liquid phase (treatment solution) which may otherwise lead to a reduced flow rate or flow rate due to material deposition or clogging.

A plurality of first separation units may be provided. Preferably, a first one of the first separation units may be adapted to remove larger fermentation substrate particles, e.g. using a sieve having a pore size of 5mm to 2mm (e.g. 2.5mm to 2 mm). The second first separation unit, which is arranged downstream of the first separation unit, may be adapted to remove smaller fermentation substrate particles, for example using a screen having a pore size of 500 μm to 10 μm (e.g. 200 μm to 100 μm). This may increase the throughput of the treatment solution through the first separation unit and thus the throughput of the fermenter system.

According to a preferred embodiment, the fermenter system comprises a second separation unit between the first and the second fermenter, which second separation unit is adapted to separate the first treatment solution from the second treatment solution such that only small molecules can enter the second treatment solution from the first treatment solution, preferably wherein the second separation unit comprises a membrane with a cut-off value of 1000g/mol or less. The second separation unit is preferably arranged downstream of the first separation unit and upstream of the second fermenter. The second separation unit may be a permeation unit having a membrane with a cut-off value of 1000g/mol or less. Mass transfer through the membrane may be based on alternating changes in hydraulic pressure. Acid transfer may also occur due to the pH gradient between the first and second treatment solutions. Optionally, the second separation unit may be a reverse osmosis unit or an ultrafiltration unit.

The second separation unit, or SCFA exchange unit (short chain fatty acid exchange unit), is capable of transferring small molecules (e.g., molecules having a molecular weight of 1000g/mol or less) from the first treatment solution into the second treatment solution. For this purpose, it is preferable to use a membrane having a rejection value of 750g/mol or less, 500g/mol or less, more preferably 400g/mol or less, 300g/mol or less, even more preferably 150g/mol or less.

The second separation unit may contact the treatment solution enriched in short chain fatty acids hydrolyzed and acidified in the first fermenter with the treatment solution depleted in fatty acid content from the second fermenter, thereby enabling transfer of fatty acids into the treatment solution loop of the second fermenter.

The treatment solutions of the treatment solution circuits of the first and second fermenter are subjected to substance exchange with each other by means of the second separation unit. By transferring the fermentation substrate to the first fermenter, both organic and inorganic components of the fermentation substrate enter the treatment solution circuit of the first fermenter. By means of the first separation unit, separation of the solid phase from the liquid phase can be achieved. The solid phase consists mainly of plant biomass which is not completely degraded, whereas the liquid phase contains water-soluble mineral components, so-called ash, in the plant biomass or in the fermentation substrate in addition to short-chain fatty acids formed during the fermentation. Ash is preferably removed periodically by the first separation unit to prevent its accumulation in the process solution loop of the first fermenter over time and the consequent deterioration of environmental conditions.

Furthermore, depending on the water or moisture content of the fermentation substrate, a corresponding amount of water may enter the first fermenter through the substrate feed. Typical fermentation substrates, especially agricultural substrates, typically have a water or moisture content of between 60% and 80%. Biomass from aquatic environments is typically much higher in water content, while some residues and wastes, such as paper and board, straw, etc., may be much lower in water content. In addition, to remove this excess water, it is necessary to drain from the treatment solution circuit of the fermenter system.

The SCFA exchange unit may have a partial separation effect on the treatment solution loops of the first and second fermentors. Thus, the treatment solution exiting the first fermenter (including the short chain fatty acids and electrolyte dissolved therein) can enter the treatment solution circuit of the second fermenter.

Short chain fatty acids, electrolytes and excess water may be transferred from the treatment solution circuit of the first fermenter to the treatment solution circuit of the second fermenter, which may be done through a membrane of limited permeability, and optionally with the application of pressure changes. After transfer of the substances (fatty acids, electrolytes, excess water) to the treatment solution circuit of the second fermenter, the treatment solution of the first fermenter is preferably pumped out and recycled using the pump of the SCFA exchange unit, optionally after heating to the temperature in the first fermenter, to the feed device of the first fermenter.

A plurality of second separation units may be provided. For example, a first one of the second separation units may comprise a first membrane having a cutoff of 2000 to 1000g/mol, and a second one of the second separation units downstream of the first one of the second separation units may comprise a second membrane having a cutoff of 500g/mol or less. The plurality of second separation units may be osmosis units. Alternatively or additionally, the plurality of second separation units may be designed as ultrafiltration units and/or reverse osmosis units. The osmosis unit, ultrafiltration unit and/or reverse osmosis unit may be combined in any desired manner. For example, a first of the plurality of second separation units may be a osmosis unit and a second of the plurality of second separation units may be a reverse osmosis unit. Alternatively or in addition to the above-described series connection of a plurality of second separation units, a plurality of second separation units may also be connected in parallel, wherein each second separation unit preferably comprises a membrane having the same cut-off value.

In this way, the throughput of the treatment solution through the second separation unit, and thus the throughput of the fermenter system, can be increased.

Larger fermentation substrate particles may be removed by the first separation unit before entering the second separation unit. To this end, the first separation unit may comprise, for example, a sieve, in particular a sieve having a pore size of 2mm to 0.25mm (e.g. 1.5mm to 0.5mm, 1.25mm to 0.75mm or 1.0mm to 0.9 mm). A plurality of first separation units may be provided. The second first separation unit arranged downstream of the first separation unit may be adapted to remove smaller fermentation substrate particles than the first separation unit. This may increase the throughput of the treatment solution. For example, the first separation unit may comprise a sieve having a pore size of 2mm to 1.5mm, and the second first separation unit may comprise a sieve having a pore size of 1.0mm to 0.9 mm.

The process solution of the second fermenter process solution loop is enriched in short chain fatty acids in the SCFA exchange unit, which can be recycled to the second fermenter by a pump.

In the second fermenter, the short-chain fatty acids formed in the first fermenter can undergo a significant amount of material degradation by hydrolysis and acidification, yielding methane and carbon dioxide.

This can be achieved by a second anaerobic microorganism, for example using microorganisms listed below as Methanothrix (Methanotrix), methanocaulis (Methanosarcina), methanobacillus ruminants (Methanobrevibacter ruminantium), microbacterium methanotrophic (Methanomicrobium mobile), microbacterium Wo Lin (Syntrophobacter wolinii), micromonospora mutilans (Syntrophomonas), propionibacterium (Propionibacterium), clostridium propionicum (Clostridium propionicum) and/or Propionibacterium mesopropionicum (Propionigenium modestum).

The conversion of simultaneously formed hydrogen and carbon dioxide to methane and water may be performed by, for example, methanobacteria (methanogens) as described herein.

The second treatment solution may have the composition described above. The pH of the second treatment solution is preferably about neutral to slightly alkaline, preferably in the range of 6.8 to 8.0, more preferably in the range of 7.0 to 7.5. The temperature of the second treatment solution is preferably from 35 ℃ to 41 ℃, more preferably from 37 ℃ to 40.5 ℃, for example from 38 ℃ to 40 ℃.

Biogas produced in the second fermenter can leave the fermenter via the second outlet.

According to another preferred embodiment, the second fermenter comprises a feed device adapted to distribute the treatment solution evenly into the second fermenter. For this purpose, the treatment solution provided by the first fermenter can be introduced into the second fermenter, preferably after passing through the first and/or second separation unit, via one or more pipes with a plurality of perforations.

In this way, the short-chain fatty acid-rich treatment solution in the second separation unit or SCFA exchange unit can be pumped by a pump into the bottom region of the fermenter and distributed evenly over the introduction surface by means of the installed pipe system. For this purpose, a structure of a plurality of pipes may be provided in the bottom region of the second fermenter, which pipes extend in parallel along the longitudinal axis of the horizontally placed second fermenter. The tubing may have a diameter of about 1.75cm to about 5cm, preferably 1.875cm to 4.25cm, more preferably 2.4cm to 2.6cm, for example 2.5 cm. The pipes may be connected to the inner wall of the second fermenter adjacent to each other or at a distance. The number, diameter and spacing of the parallel arranged pipes may be related to the amount of treatment solution to be fed to the fermenter per day. For example, the amount of treatment solution may be up to twice the volume of the fermenter.

The conduit may have perforations through which the treatment solution may pass into the interior of the second fermenter. The pitch and diameter of the perforations may be related to the amount of treatment solution that is supplied to the fermenter per day.

The perforated pipe is provided to gently transport the second treatment solution into the microbial colonies in the second fermenter. This may at least partially (optionally completely) prevent undesired separation of the second microorganisms, which may be immobilized in the second fermenter. In addition, by introducing the treatment solution into the second fermenter at a plurality of points, the lowering of the pH value can be prevented. Thus, the pH of the treatment solution in the bottom region of the fermenter is only minimally affected, although the fatty acid load enters this region. The environmental conditions thus maintained increase the conversion of the short-chain fatty acids contained in the supplied treatment solution into biogas by the biological colonies established in the second fermenter. Advantageously, the buffering action of the bicarbonate, phosphate and dihydrogen phosphate ions contained in the treatment solution also contributes to this.

According to another preferred embodiment, the second fermenter comprises a mesh adapted to provide a sedimentation surface for anaerobic microorganisms, preferably wherein the mesh comprises packing elements fixed within the mesh. The packing element may be integrated into the net structure such that the packing element is prevented from floating or sinking in the second fermenter. Or the packing element may be removably attached to the mesh structure.

The mesh structure may be a two-dimensional or three-dimensional mesh fixed within the second fermenter. The treatment solution may flow vertically through the second fermenter (preferably horizontally arranged) and in the opposite direction to the gravity vector. The mesh structure is arranged above the feeding device. Preferably, the mesh structure occupies approximately the same area as the feeding means. More preferably, the mesh structure covers substantially the entire horizontal cross section of the horizontally oriented second fermenter.

The network may comprise a plurality of packing elements that provide a settling surface for the biofilm to form for the biological community established in the second fermenter. These packing elements may be pall rings, as well as other like structures, such as cylindrical rings, saddles or lattice structures, and are preferably made of polypropylene or polyethylene. To prevent the packing elements from floating or sinking in the second fermenter, they can be integrated, for example, into a net structure. The mesh of the mesh structure may have a smaller size than the packing elements so that the packing elements remain in the mesh structure.

Preferably, pall rings made of polypropylene, nominal size 25 (length 25mm, diameter 25 mm) are used as packing elements. In this case, the mesh structure may be a rectangular mesh with a side length of less than 25mm, for example 20 mm.

The treatment solution passes through the network and flows out from above, whose fatty acid load has been reduced by microbial degradation of the biological communities within the network, and can then be discharged from the second fermenter through a discharge device. The discharge device can be designed as a perforated pipe which is arranged in the upper region of the horizontally placed second fermenter, i.e. above the net structure.

The conduit provided with perforations is preferably constructed according to the feed device.

For example, it is preferred that the treatment solution is supplied to the second fermenter through a first pipe system arranged below the mesh structure. The first pipe system may include 10 to 20 first pipes with a pipe pitch of 10 to 20cm. The length of each first conduit may be 5 to 10m. Each first conduit may have an inner diameter of 1.5 to 3.5 cm. Each first conduit may comprise first perforations spaced 10 to 50cm apart. The number of first perforations may be 10 to 100. The first perforations may independently have a diameter of 0.3 to 0.5 cm.

For example, the treatment solution is preferably collected or drained from the second fermenter through a second pipe system arranged above the mesh structure. The second tubing may comprise 1 to 10 second tubing with a tubing spacing of 2 to 10cm. The length of each second conduit may be from 5 to 10m. Each second pipe may have an inner diameter of 2 to 10cm. Each second conduit may comprise second perforations spaced 10 to 100cm apart. The number of second perforations may be 10 to 30. The second perforations may independently have a diameter of 1 to 2 cm.

The treatment solution can be removed from the second fermenter by a pump, which can be designed as a magnetically coupled centrifugal pump.

The outgoing flow of treatment solution can be fed into two ducts which can be selectively opened or closed by one or more valves. An electrically operated solenoid valve, preferably a pneumatic valve that can be actuated by a pilot valve, can be used as the valve.

One of the two pipes may be connected to the SCFA exchange unit. The conduit may be equipped with a pump. If the conduit is actuated by a valve, the treatment solution with reduced fatty acid loading in the second fermenter can be supplied to the SCFA exchange unit in order to be enriched again with fatty acids formed in the fermenter.

Through another conduit, the treatment solution may be withdrawn from the treatment solution circuit of the fermenter system when the valve is correspondingly activated. In this way, the water supplied to the fermenter system together with the fermentation substrate can be removed from the fermentation process and the amount of circulating water in the fermenter system can be adjusted to a suitable level.

The excess treatment solution withdrawn from the fermentation process contains, among other components, electrolytes and microbial cell clusters. The liquid may be processed into, for example, a plant fertilizer. Depending on the composition, sterilization methods may be advantageously employed to ensure microbial safety, and methods such as reverse osmosis processes may also be employed to increase the solution concentration.

According to a preferred embodiment, the second fermenter comprises a drain and optionally a return line fluidly connecting the second fermenter with the first fermenter, preferably the drain is provided on the return line.

According to another preferred embodiment, the method according to (iii) comprises the step (iia) of substantially removing solids from the fermenter system. This may be done using a first separation unit.

According to another preferred embodiment, the method according to (iii) comprises the step (iiib) of contacting the first treatment solution with the second treatment solution such that substances, in particular short chain fatty acids, substantially dissolved in the first treatment solution are at least partially transferred into the second treatment solution. This may be done using a second separation unit.

Preferably, steps (iii), (iiia) and (iiib) are performed in this order.

According to another preferred embodiment, the fermentation substrate and the treatment solution are heated to a substantially constant temperature prior to step (i), and/or the first and/or second treatment solution are adjusted to a substantially constant pH.

According to another embodiment, interfering substances contained in the biogas, preferably oxygen, hydrogen sulfide and/or ammonia, are removed. Preferably, the biogas is supplied to a utilization unit, such as a cogeneration unit, and/or a separation unit for separating the biogas into a hydrocarbon-containing fraction and a carbon dioxide-containing fraction. The removal of such interfering substances is well known to those skilled in the art.

According to a preferred embodiment, the first anaerobic microorganism comprises a species of the genus Cellulars (Fibrobacter succinogenes), ruminococcus albus (Ruminococcus albus), cellulars fibrinolyticus (Butyrivibrio fibrisolvens), clostridium rochaete (Clostridium lochheadii), ruminococcus flavus (Ruminococcus flavefaciens) or Paenibacillus succinogenes (Bacteroides succinogenes), a protozoa, such as Geopogonium (Isotricha), myxoplasma (DASYTRICHA), euglena (Eutodinium) or Bipilus (Diplodinium), and/or a fungus, such as a species of the genus Cellulars (Neocilimastix), pi Luomo Nana (Piromonas) or Sphaeromonas (Sphaeromonas), and/or wherein the gastric content of the foregut system, in particular the rumen of ruminants, such as cattle, sheep and/or goats, is used as the first anaerobic microorganism. The first anaerobic microorganism forms a first biological community.

Hydrolysis of the cellulosic and hemicellulose fractions in the fermentation substrate may be performed by the first anaerobic microorganism (cellulase-producing microorganism) having cellulolytic activity listed above. Exemplary end products of microbial metabolism of the first anaerobic microorganism include short chain fatty acids such as acetate, formate, propionate, butyrate, lactate, succinate, and hydrogen and carbon dioxide. Hydrogen and carbon dioxide can in turn be converted into methane and water by certain microorganisms (archaea).

Alternatively or additionally, the gastric content of the foregut system of ruminants (Ruminantia), in particular ruminants related to human nutrition (cattle (Bovini), sheep (Ovis), goats (Capra)), may be used. To this end, the rumen content of ruminants (e.g. obtained from slaughterhouses) may be advantageously used as starter inoculants. If such starter inoculums are added in a fermenter together with additional fermentation substrate and mixed with fresh fermentation substrate, a continuously fermenting biota is formed throughout the fermenter, which hydrolyses in particular cellulose and hemicellulose into its monomers and converts these monomers (intermediates) into short-chain fatty acids.

The cell wall components of plant fermentation substrates and monomers formed by hydrolysis of structural materials can be converted into pyruvate by anaerobic glycolysis (Embden-Meyerhof pathway) and pentose phosphate pathway. Pyruvic acid is a core intermediate of microbial carbohydrate metabolism, which is rapidly converted to short chain fatty acids, in particular acetic acid, propionic acid and butyric acid.

To facilitate establishment of a microbial community therein, the environmental conditions in the first fermenter generally require a pH value in the range of weak acidity to weak alkalinity, for example 5.5 to 7.5, preferably 6.0 to 7.0, more preferably 6.5 to 6.8.

The microbial community established in the first fermenter, due to its specific microbial composition, can particularly rapidly hydrolyze cellulose and hemicellulose contained in the fermentation substrate and other fermentation substrate components that are degradable under anaerobic conditions, forming a mixture of short chain fatty acids, in particular acetic acid, propionic acid and butyric acid, and valeric acid and isovaleric acid.

The rates of hydrolysis and acid formation (acidification) are so high that the pH drops rapidly, resulting in a significant negative change in the environmental conditions within the first fermenter.

Preferably, the short chain fatty acid rich treatment solution is removed from the first fermenter rapidly, for example during the residence time described above, to avoid possible acidosis and replaced with fresh treatment solution. This can be achieved in particular by continuous operation of the fermenter system comprising the second separation unit.

By means of suitable process control techniques, by simultaneous control of substrate feed, treatment solution feed, inner drum rotation, internal substrate recirculation and substrate discharge, it is ensured that the treatment solution on the one hand and the solid fermentation substrate phase on the other hand each have a residence time which is adapted to the type and quality of the fermentation substrate.

By targeted control of the residence time of the solid phase (fermentation substrate), the degree of substrate degradation (conversion of biomass to biogas) can also be optimized. Shorter residence times may lead to undesirable degradation of the substrate because a significant portion of the plant biomass supplied to the fermentation process is undegraded and is discharged from the first fermenter as a solid fermentation residue, while longer residence times may lead to undesirable utilization of the available fermenter volume because, with increasing residence time, components of the fermentation substrate that are difficult or impossible to degrade under anaerobic conditions may accumulate more and more in the fermenter. This applies in particular to lignin, which is usually present in the plant biomass of terrestrial plants and which cannot be degraded under the anaerobic conditions prevailing in the fermenter.

According to another preferred embodiment, the second anaerobic microorganism comprises methanobacteria, in particular methanobacteria (methanobacteria), methanobacteria (Methanobrevibacter), in particular methanobacteria ruminants (m.ruminantium), methanococcus (Methanococcus), methanomicro-bacteria (Methanomicrobium), in particular methanomicro-bacteria mobilis (m.mobile), methanobacteria (Methanogenium), methanospirobacteria (Methanospirillum), methanoplankton bacteria (Methanoplanus), methanogran bacteria (Methanocorpusculum), methanoculleus (Methanoculleus) and/or methanosarcina (Methanosarcina), methanosilk bacteria (methanotricx), wo Lin camping bacteria (Syntrophobacter wolinii), campylobacter ani (Syntrophomonas), propionibacteria (propionibacteria), clostridium propionicum (Clostridium propionicum) and/or mesopropiobacteria (Propionigenium modesty), and/or wherein an active degraded sludge from a wastewater treatment plant or a fermentation tank is used as the second anaerobic microorganism. The second anaerobic microorganism is typically an archaea capable of converting hydrogen and carbon dioxide into methane and water. The second anaerobic microorganism forms a second biological community.

The second anaerobic microorganism may be cultivated at a pH value of 6.8 to 8.0, preferably 7.0 to 7.5.

As the starting inoculum, a microbial community, for example a microbial community present in aquatic sediments, an activated degraded sludge from a wastewater treatment plant or a microbial community in a fermenter of a biogas plant, can be used.

In order to establish a biocenosis that is capable of converting more highly loaded short chain fatty acids into biomethane and biocarbon at a sufficiently high rate to prevent accumulation of such acids in the treatment solution, and in particular to prevent the pH of the treatment solution from decreasing as a result of such accumulation, it has proven advantageous to produce an enriched culture containing high population density fatty acid converting microorganisms. Such an enriched culture may be produced by supplying a specific mixture of short chain fatty acids to the fermenter under continuous monitoring of the pH value in a closed treatment solution loop after introduction of the initial inoculum of the second anaerobic microorganism. As a result of this particular substrate supply, those microorganisms which are able to metabolize the short-chain fatty acids supplied to the fermenter are enriched in the biological community, while those microorganism populations which are not able to do so are gradually replaced.

For transporting the treatment solution, the fermenter system may comprise one or more pumps, preferably one or more centrifugal pumps, more preferably magnetically coupled centrifugal pumps. The magnetic coupling of the pump impeller ensures that no sealing of the pump housing or the drive shaft connected to the drive motor is required. Thus, leakage that may occur due to the corrosion process on the drive shaft and the drive seal can be effectively prevented. The pump or pumps preferably comprise a pump housing made of plastic, in particular polyethylene or polypropylene. This may prevent corrosion or other damage to the drive shaft and seals by the treatment solution (particularly due to the electrolyte contained therein). Magnetic coupling centrifugal pumps with housings made of plastic, in particular polyethylene or polypropylene, have proven to be particularly advantageous.

Biogas discharged from the first fermenter through the first outlet and biogas discharged from the second fermenter through the second outlet can be fed to a common central gas line. A measuring device for continuously measuring the gas quantity and the gas composition can be integrated into the collecting channel.

Biogas that is removed or withdrawn from the fermenter system contains mainly methane and carbon dioxide, and may also contain small amounts of oxygen, hydrogen sulfide or ammonia, as well as other trace gases. Furthermore, biogas may contain moisture, in particular water, which is mainly dependent on the temperature in the fermenter.

Oxygen, hydrogen sulphide and/or ammonia contained in the biogas are preferably removed, preferably hydrogen sulphide and ammonia, before the biogas is subjected to energy or substance utilization. This may be done in any manner known in the art.

For example, ammonium sulfate may be formed by applying an acidic solution (e.g., dilute sulfuric acid at a concentration of 1% to 25%) to substantially remove ammonia from the gas mixture, which in turn may be used as a fertilizer.

After this process step, hydrogen sulfide may be substantially quantitatively removed from the gas mixture. For example, an acidic solution of a water-soluble lead salt (e.g., lead chloride, lead acetate, or lead nitrate) may be used. Since lead sulfide has a low solubility product even in an acidic aqueous solution, hydrogen sulfide contained in a gas stream can be effectively removed. The obtained lead sulfide can be supplied to the lead processing industry for utilization.

The remaining biogas mainly comprises methane and carbon dioxide, preferably after pre-drying, can be supplied to a power plant, such as a cogeneration plant, for power generation and/or heat supply. Can also be directly used for heat supply.

Further alternative uses of biogas may require additional gas treatment processes. This may be used to separate methane and/or carbon dioxide. This can be done, for example, by adsorption processes (e.g. pressure swing adsorption), absorption processes (e.g. amine washing), membrane processes (in which a membrane with a suitable cut-off is used (e.g. made of metal, ceramic or plastic) to separate the gas), and low temperature processes (in which the gas contained in the mixture is continuously liquefied by lowering the temperature) as known in the art.

After purification, the methane or carbon dioxide obtained can be used directly. For example, methane may be delivered to a natural gas network.

The fermentation residue may be sterilized. The sterilized or unsterilized fermentation residue may, for example, be separated into a fiber component and a protein. The fiber component can be further used in industrial production. The protein may, for example, be added to animal feed.

The liquid extracted from the second fermenter can be sterilized, for example, for use as fertilizer. Or the extracted liquid may be sterilized and separated, for example by reverse osmosis, to yield a concentrated liquid fertilizer and water.

The term "substantially" may include deviations of +10% and/or-10%. For example, the term "substantially perpendicular" includes angles of 81 ° to 99 °. For example, the term "substantially complete" includes 90% to 100% removal.

Preferably, the first fermenter and/or the second fermenter does not contain a stirrer. More preferably, the fermenter system does not contain a stirrer. In the context of the present disclosure, a stirrer or stirrer comprises one or more shafts or axes, which are typically provided with blades and/or paddles.

It is to be understood that the features mentioned above and those yet to be explained below can be used not only in the respective combination indicated, but also in other combinations or alone without departing from the scope of the invention.

The present invention will now be explained in more detail by way of examples. Features mentioned in the examples are not only regarded as belonging to the invention in connection with the specific examples but also as belonging to the invention when used alone. Please refer to the accompanying drawings.

Drawings

In the drawings:

FIG. 1 shows a schematic view of an exemplary fermenter system according to the present invention, and

FIGS. 2a-c show schematic diagrams of utilization of fermentation products obtained from exemplary fermenter systems.

Detailed Description

Examples

FIG. 1 shows a schematic diagram of an exemplary fermenter system 100 according to the present invention. The fermenter system 100 comprises a first fermenter 1 and a second fermenter 2, which are connected to one another via pipes 4,6 provided with pumps. The first fermenter 1 and the second fermenter 2 are designed as cylindrical vessels which are placed horizontally.

The first fermenter 1 comprises on its first circular side a feed device 3 with a motor 24, through which feed device 3a first treatment solution and a fermentation substrate, for example plant residues, can be added to the first fermenter 1, wherein a first biological community of first anaerobic microorganisms is present in the first treatment solution in the first fermenter 1.

The first fermenter 1 is equipped with an inner cylinder 8 arranged therein, mixing devices 9,10, and an inner tube 11 provided with screw conveyors, in order to be able to spatially homogeneously mix the fermentation substrate, the first treatment solution and the biological communities of the first anaerobic microorganisms along the flow directions 26, 27 schematically indicated by the arrows and to convey them to the second circular side of the first fermenter 1.

During spatially uniform mixing of the fermentation substrate, the first treatment solution and the microbiota of the first anaerobic microorganism, the fermentation substrate degrades or ferments to form short chain fatty acids. The mixture of the partially degraded fermentation substrate or fermentation residue and the first treatment solution containing short chain fatty acids exits the first fermenter 1 and enters the first separation unit 13, which separation unit 13 separates the fermentation residue from the first treatment solution containing short chain fatty acids. The first separation unit may, for example, comprise a screw or auger adapted to lift the solid component upwardly out of the liquid phase while the liquid phase remains substantially. The first separation unit may also comprise a screen. After the liquid phase passes through the sieve, the liquid phase, can be pumped out by, for example, a pump.

Fermentation residues may be removed from the fermenter system 100, for example using a motor 25, and may be utilized as shown in FIG. 2 a.

The first treatment solution containing short chain fatty acids is conveyed via a pump-equipped conduit 4 to a second separation unit 14. The second separation unit 14 is designed as a reverse osmosis unit and comprises a membrane 15 with a cut-off value of 150g/mol or less. The first treatment solution containing short chain fatty acids may be separated from the second treatment solution by a membrane 15. The membrane 15 is capable of transferring small molecules, in particular short chain fatty acids and electrolytes, into the second treatment solution. Molecules with a molecular weight >150g/mol remain in the first treatment solution.

The first treatment solution from which the short-chain molecules are removed can be recycled to the feed device 3 via a pipe 5 equipped with a pump.

The second treatment solution containing short-chain fatty acids is introduced into the second fermenter 2 via a feed device 17 via a pump-equipped line 6. In the second fermenter 2, there is a second treatment solution and a second biological community of anaerobic second microorganisms. The biocenosis is partially fixed on a packing element, which is designed as a pall ring, on the inner network 18 of the second fermenter 2. The mesh structure 18 extends through the entire (horizontal) cross section of the horizontally arranged second fermenter 2.

The second treatment solution containing short chain fatty acids flowing from the feed device 17 into the second fermenter 2 flows through substantially the entire cross section of the network 18, so that the anaerobic second microorganisms degrade the short chain fatty acids contained in the second treatment solution substantially into carbon dioxide and biomethane. The discharge means 19 present in the second fermenter 2 enable the second treatment solution, the biomethane and the carbon dioxide to be discharged from the second fermenter 2.

The feed means 17 and the discharge means 19 are arranged on opposite sides of the mesh structure 18 and each comprise a pipe with a plurality of perforations to enable a uniform flow of the treatment solution along a flow direction 28 schematically indicated by arrows through the entire cross section of the mesh structure 18.

The liquid from the second fermenter 2 is discharged at the discharge 19, which can be supplied to the liquid discharge unit 23 via the line 7 equipped with the pump and the valve 21, and is discharged from the fermenter system 100. Alternatively or additionally, the discharged liquid may be recycled to the second separation unit 14 through a conduit 22 provided with a pump and valve 20. The liquid withdrawn from the fermenter system 100 can be utilized as schematically shown in FIG. 2 c.

The first and second fermentors 1, 2 are further provided with a first outlet 12 and a second outlet 16 for the utilization of the generated (bio) gas, as schematically shown in fig. 2 b.

The process parameters, including the constant temperature of the process solution, the pH values in the first and second fermenters 1,2, etc., are controlled by a control unit (not shown) such that the two biota are cultivated under their respective optimal conditions.

FIGS. 2a-c illustrate schematic diagrams of utilization of fermentation products obtained by exemplary fermenter system 100.

As can be seen from fig. 2a, the fermentation residues taken out of the first fermenter 1 can be sterilized and separated. The resulting fiber component may, for example, be further used in industrial production. The resulting protein may, for example, be added to animal feed.

Fig. 2b shows the use of the (bio) gas discharged from the first and second fermenter 1, 2. Interfering substances, in particular hydrogen sulfide and ammonia, in the (bio) gas may be removed, after which they are converted into electrical and thermal energy after drying in the heat utilization process of a Combined Heat and Power (CHP) plant. In addition, methane and carbon dioxide may be separated and then liquefied and/or compressed.

Fig. 2c shows the use of the liquid discharged from the second fermenter 2. The liquid may be subjected to a sterilization treatment and used, for example, as a fertilizer. Alternatively, the removed liquid may be disinfected and separated, for example by reverse osmosis, to provide a concentrated liquid fertilizer and water.

Claims (15)

1. A fermenter system (100) for producing biogas and optionally useful products, in particular fatty acids and/or proteins, comprising:

a first fermenter (1),

A second fermenter (2), and

A conduit (4, 6) fluidly connecting the first fermenter (1) and the second fermenter (2),

A heating unit configured to provide a temperature of > 25 ℃ in the first and second fermentors (1, 2) and the pipes (4, 6),

Wherein the fermenter system (100) is configured for anaerobic operation, and

Wherein the first fermenter (1) comprises a rotatable inner drum (8) arranged inside the first fermenter.

2. The fermenter system (100) according to claim 1, wherein the first fermenter (1) comprises a feed device (3) configured to heat the fermentation substrate and/or the treatment solution to a temperature of > 25 ℃ and to provide a defined delivery of the fermentation substrate and/or the treatment solution into the first fermenter (1).

3. Fermenter system (100) according to any of the preceding claims, wherein the inner drum is rotatably arranged about a longitudinal axis of a first fermenter and/or is configured to move the content of the first fermenter (1) in the direction of the second fermenter (2), preferably wherein the first fermenter comprises an inner tube extending through an inner drum, which has a conveying unit.

4. The fermenter system (100) according to any of the preceding claims, wherein the fermenter system (100) comprises a first separation unit (13) between the first and second fermenter (1, 2) configured to substantially remove solids from the fermenter system (100).

5. Fermenter system (100) according to any of the preceding claims, wherein the fermenter system (100) comprises a second separation unit (14) between the first and the second fermenter (1, 2) configured to separate the first treatment solution from the second treatment solution such that only small molecules can enter the second treatment solution from the first treatment solution, preferably wherein the second separation unit (14) comprises a membrane (15) having a cut-off value of 1000g/mol or less.

6. The fermenter system (100) according to any of the preceding claims, wherein the second fermenter (2) comprises a feed device (17) configured to distribute a treatment solution evenly into the second fermenter (2).

7. The fermenter system (100) according to any of the preceding claims, wherein the second fermenter (2) comprises a mesh (18) configured to provide a colonization surface for anaerobic microorganisms, preferably wherein the mesh (18) comprises a packing element immobilized within the mesh (18).

8. Fermenter system (100) according to any of the preceding claims, wherein the second fermenter (2) comprises a drain (19) and optionally a return line fluidly connecting the second fermenter (2) to the first fermenter (1), preferably wherein the drain (19) is arranged on the return line.

9. Use of a fermenter system (100) according to one of the preceding claims for producing biogas and optionally useful products, in particular fatty acids and/or proteins.

10. A method of producing biogas and useful products, in particular fatty acids and/or proteins, using a fermenter system (100) comprising a first fermenter (1), a second fermenter (2), and a pipe (4, 6) fluidly connecting the first fermenter (1) and the second fermenter (2), wherein the first fermenter (1) comprises a rotatably arranged inner barrel (8), the method comprising the steps of:

(i) Providing a first anaerobic microorganism and a first treatment solution to a first fermenter (1), and providing a second anaerobic microorganism and a second treatment solution to a second fermenter (2);

(ii) Feeding a fermentation substrate comprising cellulose and/or hemicellulose and a first treatment solution into a first fermenter (1);

(iii) Transferring the first treatment solution to a second fermenter (2), and

(Iv) Removing biogas from the first and second fermenters (1, 2) and removing fermentation substrate from the first fermentor (1);

wherein the temperatures of the first and second fermenters (1, 2) and the pipes (4, 6) are not less than 25 ℃;

Wherein a first anaerobic microorganism, a fermentation substrate and a first treatment solution are mixed, and

Wherein the first anaerobic microorganism is configured to degrade a fermentation substrate to short chain fatty acids via an intermediate product and the second anaerobic microorganism is configured to convert short chain fatty acids to biogas.

11. The method of claim 10, further comprising the step (iiia) of substantially removing solids from the fermenter system (100) after step (iii).

12. The method according to claim 10 or 11, further comprising the step (iiib) of contacting the first treatment solution with the second treatment solution after step (iii) such that substances, in particular short chain fatty acids, mainly dissolved in the first treatment solution are at least partially transferred into the second treatment solution.

13. The method according to any one of claim 10 to 12,

Wherein the fermentation substrate and the treatment solution are heated to a substantially constant temperature prior to step (i), and/or

Wherein the first and/or second treatment solution is adjusted to a substantially constant pH value, and/or

Including removal of contaminants, preferably oxygen, hydrogen sulfide and/or ammonia, present in the biogas, preferably by supplying the biogas to a utilization unit, such as a Cogeneration (CHP) plant, and/or to a separation unit for separating the biogas into a hydrocarbon-containing fraction and a carbon dioxide-containing fraction.

14. The method according to any one of claims 10 to 13, wherein the first anaerobic microorganism comprises a species of the genus Cellobacter (Fibrobacter succinogenes), the genus Ruminococcus albus (Ruminococcus albus), the genus Cellobrio (Butyrivibrio fibrisolvens), the genus Clostridium rochei (Clostridium lochheadii), the genus Ruminococcus flavus (Ruminococcus flavefaciens) or the genus Bacteroides succinogenes (Bacteroides succinogenes), a species of protozoa, such as the genus Celloides (Isotricha), the genus Celloides (DASYTRICHA), the genus Eubacterium (Eutodinium) or the genus Bisolarium (Diplodinium), and/or a species of fungi, such as the genus Celloides (neopalimastix), the genus Pi Luomo, the genus Nannomonas (Piromonas) or the genus globomonas (Sphaeromonas), and/or wherein the gastric contents of the foregut system, in particular the rumen of ruminants (e.g. cattle, sheep and/or goats), are used as the first anaerobic microorganism.

15. The method according to any one of claims 10 to 14, wherein the second anaerobic microorganism comprises methanobacteria, in particular methanobacteria (Methanobacterium), methanobacteria (Methanobrevibacter), methanobacteria (in particular ruminant methanobacteria (m. Ruminium), methanococcus (Methanococcus), methanomicro-bacteria (Methanomicrobium), in particular methanomicro-bacteria mobilis (m. Mobile), methanobacteria (Methanogenium), methanospira (Methanospirillum), methanoplankton (Methanoplanus), methanogran (Methanocorpusculum), methanobagging bacteria (Methanoculleus) and/or methanosarcina (Methanosarcina), methanothrix (metapatrix), wo Lin camping bacilli (Syntrophobacter wolinii), campylobacter (Syntrophomonas), propionibacteria (Propionibacterium), clostridium propionicum (Clostridium propionicum) and/or mesopropionibacteria (Propionigenium modestum), and/or wherein an active degraded sludge from a wastewater treatment plant or a fermenter is used as the second anaerobic microorganism.