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

Abstract

The invention relates to a fermenter system (100) for producing biogenic gases and, optionally, useful products, in particular fatty acids and proteins, comprising a first fermenter (1), a second fermenter (2) and a pipeline (4, 6) which fluidically connects the first fermenter (1) and the second fermenter (2), a heating unit which is designed to provide a temperature of ≥ 25°C in the first and second fermenter (1, 2) and the pipeline (4, 6), the fermenter system (100) being designed for anaerobic process control. The present invention also relates to the use of the fermenter system (100) and to a method for producing biogenic gases and useful products, in particular fatty acids and / or proteins, using a fermenter system (100).

Description

Fermenter system and process for the production of biogenic gases and qqf. Useful products, in particular fatty acids and / or proteins

[0001] The present invention relates to the conversion of biogenic products, in particular biogenic products, residues, and waste, into useful products. In particular, the present invention relates to a process for producing methane, carbon dioxide, and optionally other useful products, e.g., fatty acids and / or proteins, as well as a device for carrying out the process.

[0002] Biogas, a mixture of biomethane and biocarbon dioxide, is currently predominantly produced using wet fermentation processes. In these processes, animal feces (especially pig manure, cattle manure, and poultry manure) are fed into a fermenter. The feces used serve to provide the process with a viable microbial biocenosis, enabling the material degradation of the substrates to be fermented and the production of biogas. The process can be carried out in a single fermenter. Multi-stage processes are also common, in which the substrate to be fermented flows sequentially through several fermenters.

[0003] Since the proportion of fermentable biogenic dry matter in the feces used is generally low, additional fermentation substrates are added to quantitatively increase the amount of biogas that can be produced. The fermentation substrates used are primarily organic waste, such as food and slaughterhouse waste, as well as waste from food production. In addition to biogenic waste, energy crops produced in agricultural production, so-called "renewable raw materials," particularly whole-crop silage (e.g., corn, grain, or grass), are also used as fermentation substrates.

[0004] The digestate stream, consisting of feces and digestate, flows through the digester(s). Part of the digestate's biomass is converted into biogas as a result of fermentation. A digestate consisting of solid and liquid components also remains, which is typically applied as fertilizer, particularly on agricultural land.

[0005] Particularly in regions that do not have a sufficient livestock population as a source of faeces for the operation of biogas plants, a process-related alternative is to separate the digestate leaving the fermenter into a solid and liquid portion in order to reintroduce part of the liquid phase into the fermentation process together with fresh fermentation substrate.

[0006] The maximum possible solids content of the digestate-feces mixture is fundamentally limited in these types of processes, as the mixture must remain pumpable and stirrable. This limitation of the maximum possible solids content or digestate of the digestate mixture to be fermented means that only a small amount of fresh digestate can be fed into the digester per cubic meter of digester volume per day. Typically, the dry matter content of the digestate mixture to be fermented is less than 15% by weight.

[0007] A further disadvantage is that the fermentative capacity of the microbial biocenoses provided by the faeces is rather low. Accordingly, the fermentation processes require a longer time, usually between 30 and 120 The average hydraulic retention time is 10 days. This, in turn, requires a considerable size of the fermenters used, which are usually between a few hundred and a few thousand cubic meters.

[0008] The fermentation process is usually continuous. Unless a portion of the liquid phase is separated at the end of the fermentation process to be reintroduced into the fermentation process together with fresh fermentation substrate, the solid and liquid phases pass through the fermenter with identical hydraulic residence times. Individual control or active influence of the respective hydraulic residence times of the solid and liquid phases is not possible.

[0009] In some cases, discontinuous processes (e.g., so-called batch processes) are also used, in which the fermentation process is actively terminated or stopped after a certain period of time, usually when the biogas yield drops significantly. The fermenter is emptied, and the fermentation process is then restarted with fresh fermentation substrate.

[0010] An alternative process approach to wet fermentation is dry fermentation. In this process, the fermentation substrate to be fermented is layered as a solid phase in a container serving as a fermenter. During fermentation, a percolation solution trickles through the fermentation substrate, providing the microbial biocenosis required for fermentation.

[0011] A distinction must be made between a process in which all steps of converting biomass to biogas (hydrolysis, acidification, methane formation) take place in a single fermenter and a process in which at least two fermenters are used.

[0012] In these two-stage dry fermentation processes, percolation primarily serves to hydrolyze the substrate (the solid phase) and remove the released substances or intermediate products that dissolve in the percolation solution from the first fermenter. The liquid phase pumped out of the first fermenter The percolation solution is then fed to a second fermenter, where the substances dissolved in the percolation solution, released from the substrate by hydrolysis in the first fermenter, undergo acidification and methane formation. The majority of the biogas is produced during this process step. At the same time, the percolation solution regenerates and can be fed back into the first container to be enriched with intermediate products released by hydrolysis of the substrate.

[0013] A common design of such fermenter systems is the so-called garage fermenter, in which a discontinuous process is present with regard to the fermentation substrate (solid phase), since the fermenter is opened at regular intervals to receive the fermentation substrate, to remove unfermented substrate and to refill the fermenter with fresh fermentation substrate.

[0014] The fermentative performance for converting the fermentation substrates used into the desired target products, especially biogas, is limited due to the microbiological and equipment-related specifics underlying the processes described.

[0015] A particular limiting factor is the fact that all steps of material metabolism (hydrolysis, acidification, methane formation) occur in parallel. Since the microorganisms (biocenosis) that carry out the various subprocesses of material metabolism each have their own species-specific requirements for optimal environmental conditions (particularly with regard to the pH value of the environment), the fermentation process must be carried out under environmental conditions that allow all the microorganism strains necessary for material metabolism to perform their specific fermentative tasks, albeit under suboptimal environmental conditions for the respective microorganism strains.

[0016] A further relevant limitation of the fermentative performance of the conversion of the fermentation substrates used in the processes described above is due to the fact that the faecal-based biocenosis in the fermenters consists predominantly of such composed of microorganisms whose metabolism is particularly focused on the breakdown of soluble sugars, starch, fats / oils and proteins.

[0017] Plant biomass, however, consists to a high extent of so-called fiber and structural substances, which consist primarily of cellulose and hemicelluloses. The biocenoses used in the processes described above, however, have only limited capacity for the material degradation of these substances. As a result, the processes described above are not capable of effectively degrading this quantitatively extremely significant biomass potential. At the same time, significant biomass potential for use as a fermentation substrate is therefore ruled out. Therefore, energy crops grown predominantly in agricultural production are used, particularly maize, which, however, creates ecologically and socio-economically relevant competition for land use. Residues and waste materials from certain production sectors, e.g. the beverage and food industries, as well as food waste (e.g.Canteen and kitchen waste, food waste from the food trade) are suitable as fermentation substrates for the processes described above, provided that their material composition is essentially characterized by soluble sugars, starch, fats / oils and proteins.

[0018] For example, DE 10 2006 012 130 B4 discloses a method and a device for producing biogas.

[0019] The invention is based on the object of providing a device and a method which at least partially or completely overcome the disadvantages described above. A further object of the invention is to provide a device and a method with which cellulose- and hemicellulose-containing fermentation substrates can be materially digested to produce biomethane and biocarbon dioxide and optionally other co-products. Yet a further object of the present invention is to provide a device and a method with which predominantly fermentation substrates made of cellulose- and hemicellulose-containing materials are used to produce methane, in particular biomethane, carbon dioxide, in particular biocarbon dioxide, and other co-products. A further object is to provide a device and a method which, by Elimination of capacity-limiting points (bottlenecks) provides a high space-time yield.

[0020] The above objects are achieved by the fermenter system for producing biogenic gases and optionally useful products, in particular fatty acids and / or proteins, according to claim 1, the use of the fermenter system according to claim 9, and the method for producing biogenic gases and optionally useful products, in particular fatty acids and / or proteins, according to claim 10. Advantageous embodiments are listed in the dependent claims and the description.

[0021] The fermenter system according to the invention is preferably operated continuously. The fermenter system according to the invention is preferably used in the process according to the invention.

[0022] The term "biogenic gas" or "biogas," as used herein, refers to biomethane, possibly other short-chain bioalkanes, e.g., bioethane, biopropane, and biobutane, biohydrogen, and biocarbon dioxide. Biogenic gas can be distinguished from conventional gas based on its origin. For example, a difference between biomethane and natural gas can be due to impurities and / or a content of the isotope C 14 be determined.

[0023] The term "fatty acids," as used herein, refers to short-chain fatty acids and their salts. Short-chain fatty acids generally have a molecular weight of <500 g / mol, preferably <400 g / mol, <300 g / mol, <200 g / mol, or more preferably <150 g / mol. Exemplary fatty acids include formate, acetate, propionate, butyrate, lactate, and succinate.

[0024] The term "fermenter," as used herein, refers to a bioreactor. The fermenter comprises a container in which biological material, in particular microorganisms or mixtures of several microorganisms, or a biocenosis, is cultivated. The fermenter provides the most optimal conditions possible for this purpose. The fermenter is used in particular for the fermentation or cultivation of "anaerobic microorganisms." and provides the necessary environmental conditions, in particular a substantially complete exclusion of oxygen.

[0025] The fermenters are preferably designed to be gas-tight, thermally insulated, and heatable. More preferably, the fermenters are designed as cylindrical containers; even more preferably, the cylindrical containers are designed horizontally, thus with a horizontally arranged outer surface. The feed device, the pipeline, and the removal device can each be arranged on the circular surfaces. Thus, the feed device can be arranged on a first circular surface of the first fermenter, the removal device on a second circular surface of the second fermenter, and the pipeline between the second circular surface of the first fermenter and the first circular surface of the second fermenter.

[0026] A fermenter can be made of a plastic, especially polyethylene and polypropylene, as well as stainless steel or glass fiber reinforced plastic (GRP).

[0027] Preferably, the fermenters have external dimensions that allow them to be accommodated or installed in the frame of a 20- or 40-foot standard container. The length of the fermenters is preferably 6 to 12 meters, particularly preferably 4 to 6 meters for a frame of a 20-foot standard container, and 10 to 12 meters for a frame of a 40-foot standard container. The external diameter of the fermenters can be 2.2 to 2.4 meters.

[0028] Preferably, an insulation layer with a material thickness of at least 5 cm, preferably at least 8 cm, or at least 10 cm is provided between the fermenter's outer wall or outside and the fermenter's inner wall or inside (with media contact). This minimizes heat loss. Conventional insulation materials, such as mineral wool, Styrofoam, or cardboard, can be used as insulation; the front and back of the cylindrical containers (lids) can also be appropriately insulated. Thermal insulation of the containers using polyurethane foam, wool, shredded straw, or plastic bubble wrap is also possible.

[0029] The term "fermentation substrate," as used herein, refers to biogenic materials, especially fiber-rich plant biomass, such as agricultural residues or waste, residues or waste from the food and beverage industry, and residues or waste generated, for example, in the field of landscape and water management. Aquatic plants and algae, especially algae from marine ecosystems, can also be used as fermentation substrates.

[0030] If the fermentation substrate is agriculturally produced biomass, co-fermentation of the fruit portion of these plants is possible, but not required. This can contribute to ending the competition between the production of plants for food purposes and for energy or raw material purposes by enabling the dual use of agriculturally produced crops as food or feed, or for energy production, particularly via biogenic gas.

[0031] As a result, large quantities of suitable fermentation substrates are available, which can be produced within the framework of extensive, ecologically beneficial agriculture. The use of fiber-rich plants and plant components also allows the use of plants as fermentation substrates that simultaneously fulfill important ecological functions with regard to soil protection, drinking water and water conservation, and biodiversity conservation.

[0032] Other cellulosic and / or hemicellulose-containing materials can also be used as fermentation substrate, such as waste paper, cardboard, cartons, leaves, plant stems, stalks, grass and straw, production residues from the paper and pulp industry, the pharmaceutical or chemical industry, as well as from grain mills and breweries.

[0033] It has proven particularly advantageous that the process according to the invention provides access to the world's most important renewable raw material (cellulose and hemicelluloses), for which the annual global renewable amount alone is approximately 10 11 tons can be estimated.

[0034] The "process solution," as used herein, refers to an aqueous solution, preferably containing electrolytes. The first and second process solutions preferably have corresponding compositions initially, i.e., prior to contact with one of the biocenoses and the fermentation substrate.

[0035] An advantageous embodiment of the process solution, in particular the first and / or second process solution, can contain, for example, the electrolytes (anions and cations) listed below in optionally demineralized water: 120-210 mmol / l, preferably 140-180 mmol / l, sodium and potassium, whereby the sodium content can be over 100 mmol / l, preferably 120-160 mmol / l; 20-60 mmol / l, preferably 30-50 mmol / l, chloride; 70-130 mmol / l, preferably 80-110 mmol / l hydrogen carbonate; 5-15 mmol / l hydrogen phosphate; 5-15 mmol / l dihydrogen phosphate; 0.3-0.9 mmol / l magnesium; and 0.1-0.4 mmol / l calcium.

[0036] The environmental conditions inside the first and second fermenters require anaerobic conditions for the benefit of the established microbial biocenoses. A small amount of atmospheric oxygen may be acceptable, particularly in the first fermenter. Since some of the microorganism strains forming the microbial biocenosis in the first fermenter are facultative anaerobes, certain amounts of oxygen can be metabolized by them and thus removed from the environment. A redox potential in the range of -400 to -200 mV should preferably be maintained in the first and second fermenters.

[0037] The inner drum provided in the first fermenter enables the mixing of the contents of the first fermenter. Preferably, the drum has an at least partially closed design in the direction of the feed device, in particular adjacent to the first side of the first fermenter.

[0038] The inner drum can be set in rotation by a suitable drive system, e.g., a motor. The rotation speed of the inner drum can be adjusted taking into account certain parameters, such as the nature of the fermentation substrate being fed, the rate of fermentation substrate hydrolysis, and / or The rotation speed of the inner drum is preferably 2 to 30 revolutions per hour, more preferably 3 to 15 revolutions per hour, and particularly preferably 4 to 6 revolutions per hour. The rotation of the inner drum can be continuous or at defined time intervals. The rotation can be clockwise, counterclockwise, or alternating.

[0039] During mixing by the inner drum, fermentation substrate particles whose hydrolysis is more advanced can come into contact with fermentation substrate particles whose hydrolysis is less advanced. This allows for intensive transfer of the microbial biocenosis present in the first fermenter to the fermentation substrate to be hydrolyzed under conditions that are gentle on the biocenosis. Furthermore, the use of the inner drum can achieve intensive mixing of the solid and liquid phases. Due to the high organic dry matter content of many fermentation substrates, mixing and moving the fermentation substrate inside the first fermenter is generally not possible using a conventional agitator, as used in wet fermentation plants. Preferably, the first fermenter does not include an agitator.

[0040] In addition, the inner drum can effectively prevent the formation of floating layers and sinking layers, which can occur if the fermentation substrate is not mixed or only insufficiently mixed. The fermentation substrate generally tends to separate automatically into different phases (sinking layer, mixed layer, floating layer). Fresh fermentation substrate that has only been slightly hydrolyzed tends to separate as a so-called floating layer in the area of ​​the boundary between the liquid and the gaseous phase above it. Gas produced by the ongoing fermentation process inside the fermenter rises through this floating layer and increasingly displaces the liquid phase from the floating layer, which largely stops the continuation of fermentation (hydrolysis) and increases the risk of the fermenter becoming blocked by the fermentation substrate.As the hydrolysis of the fermentation substrate progresses, its particle size decreases and its density increases, which is why the substrate particles tend to become smaller as hydrolysis progresses in the fermenter. to sink and accumulate at the bottom of the tank. The rotational movement of the inner drum, however, effectively prevents the formation of floating layers and sinking layers.

[0041] This allows a homogeneous fermentation substrate mixture to be maintained in the first fermenter. The first biocenosis of microorganisms present in the first fermenter can be gently mixed with the fermentation substrate and the process solution.

[0042] According to a preferred embodiment, the first fermenter comprises a feed device adapted to heat a fermentation substrate and / or a process solution to a temperature of >25°C and to deliver a defined amount of the fermentation substrate and / or the process solution to the first fermenter. The feed device can enable handling and addition of the fermentation substrate and / or the process solution under anaerobic conditions, i.e., essentially under the exclusion of air.

[0043] Before the fermentation substrate is introduced into the first fermenter, the fermentation substrate can be heated in the feed device to the temperature prevailing in the first fermenter of >25°C, for example, 25°C to 60°C, preferably 35°C to 45°C, more preferably 38°C to 42°C, such as 39°C to 41°C and 39.5°C to 40°C. This allows the environmental conditions in the fermenter to be kept constant, particularly with regard to temperature as a relevant process parameter.

[0044] The fermentation substrate can be fed into the first fermenter by means of a conveying device, in particular a screw conveyor or spiral conveyor. The feed device provided with a conveying device, in particular the screw conveyor or spiral conveyor, can be made of stainless steel or plastic, for example. Alternatively, the substrate can also be fed using a solids pump, in particular a rotary lobe pump or eccentric screw pump.

[0045] In addition, the fermentation substrate to be fed to the first fermenter can be mixed with a concentration corresponding to the moisture content / water content of the fermentation substrate. The process solution is preferably heated to the temperature existing in the first fermenter or maintained at this temperature. This allows the addition of various fermentation substrates, regardless of their moisture content, while maintaining the volumetric load (dry matter per cubic meter) in the first fermenter at a constant level.

[0046] According to a further preferred embodiment, the inner drum is provided rotatable about a longitudinal axis of the first fermenter and / or adapted to enable movement of the contents of the first fermenter to the second fermenter, preferably wherein the first fermenter has an inner tube extending through the inner drum with a conveyor unit, for example a conveyor screw or spiral.

[0047] The inner drum can be designed in such a way that spatial mixing of the contents of the first fermenter is further improved. For example, devices can be attached to the inner wall of the inner drum that enable continuous, preferably horizontal, propulsion of the fermentation substrate located inside the drum in the direction of the pipeline or in the direction of the second fermenter. In addition, further devices can be attached to the inner wall of the inner drum that enable mixing in a direction substantially perpendicular to the propulsion direction. The simultaneous continuous, preferably horizontal, propulsion and mixing in a direction substantially perpendicular to the propulsion direction can ensure optimal and continuous mixing of the fermentation substrate located inside the first fermenter and optimal conditions for the cultivation of the first anaerobic microorganisms.

[0048] Biogas produced in the first fermenter can leave the fermenter via a first outlet.

[0049] A substrate-specific and calculable process control of the hydraulic retention time of the fermentation substrate can be achieved by continuously or intermittently feeding the fermentation substrate into the fermenter, in combination with the rotation of the Inner drum and a continuous or intervalic removal of incompletely hydrolyzed fermentation substrate and process solution from the first fermenter.

[0050] The hydraulic residence time of the solid fermentation substrate phase can be further influenced by arranging an inner tube along the longitudinal axis of the inner drum, through which a portion of the fermentation substrate can be conveyed by means of a conveying device, preferably a screw conveyor or spiral conveyor, into the fermentation substrate feed area on the opposite side of the cylindrical fermenter vessel. Thus, the inner tube enables the fermentation substrate to be conveyed from the second side to the first side of the first fermenter. This not only enables intensive contact between freshly added and already hydrolyzed fermentation substrate, but also intensive transfer (contamination) of the fresh fermentation substrate with the microbial biocenosis causing the hydrolysis of the fermentation substrate. This allows the hydrolysis of the fermentation substrate to be initiated quickly.

[0051] The average hydraulic residence time of the fermentation substrate (solid phase) in the first fermenter can be between 24 and 120 hours, preferably 48 to 96 hours. The average hydraulic residence time can depend on the material composition and quality of the fermentation substrate. During this period, a significant portion of the cellulose, hemicelluloses, and other components of the fermentation substrate, such as sugar, starch, and protein, can be hydrolyzed and converted into short-chain fatty acids under the anaerobic conditions prevailing in the first fermenter.

[0052] The design of this fermentation system allows the average hydraulic residence time of the solid and liquid phases in the fermenter to be actively and individually influenced, thus adapting it to requirements, for example, the composition of the fermentation substrate. The residence times of the solid and liquid phases, which can be individually controlled using control technology, also allow for targeted control of the hydrolysis process.

[0053] Such targeted manipulation of the residence times of the solid and liquid phases cannot be achieved in wet fermentation processes. In wet fermentation, the solid and liquid phases flow through the fermenter with an identical average hydraulic residence time.

[0054] According to yet another preferred embodiment, the fermenter system comprises a first separation unit between the first and second fermenters, which is adapted to at least partially, preferably substantially completely, remove solids from the fermenter system.

[0055] Downstream of the first fermenter, fermentation substrate emerging from the first fermenter can be separated into a solid and a liquid phase. The first separation unit is arranged between the first and second fermenters and can provide a material stream to the second fermenter, wherein the material stream is depleted of fermentation substrate or essentially lacks it.

[0056] Alternatively, and preferably, the fermentation substrate-depleted material stream or the substantially fermentation substrate-free material stream is provided to a second separation unit, which is described below. The fermenter system may preferably comprise the first separation unit downstream of the first fermenter, the second separation unit downstream of the first separation unit, and the second fermenter downstream of the second separation unit. More preferably, the first and second separation units are arranged on the pipeline or are fluidly connected to each other and to the first and second fermenters by the pipeline.

[0057] The solid phase (the non-hydrolyzed or incompletely hydrolyzed fermentation substrate, as well as the microbial cell mass adhering to it) can be separated with the first separation unit. For this purpose, devices known in the prior art for solid-liquid separation can be used. A sieve-based first separation unit is preferred. The sieve can be made of stainless steel or a plastic. The use of a plastic sieve made of a plastic material which only is colonized by microorganisms to a limited extent or not at all (biofilm formation). A polyamide, for example, can be used for this purpose.

[0058] The pore size of the sieve can be 10 pm up to 2 mm, preferably 50 pm to 1 mm, particularly, more preferably 100 pm to 500 pm.

[0059] The solid-liquid separation provided by the first separation unit also ensures that no solid fermentation substrate particles enter the process solution circuit with the liquid phase (process solution), which could cause a reduction in flow velocity or flow rates due to material separation or blockages.

[0060] Multiple first separation units may be present. Preferably, a first of the first separation units can be adapted to remove larger fermentation substrate particles, for example, with a sieve having a pore size of 5 mm to 2 mm, for example, 2.5 mm to 2 mm. A second of the first separation units, arranged downstream of the first of the first separation units, can be adapted to remove smaller fermentation substrate particles, for example, with a sieve having a pore size of 500 pm to 10 pm, for example, 200 pm to 100 pm. This can increase the throughput of process solution through the first separation unit and thus the throughput of the fermenter system.

[0061] According to a preferred embodiment, the fermenter system comprises a second separation unit between the first and second fermenter, which is adapted to separate a first process solution from a second process solution in such a way that only small molecules can pass from the first process solution into the second process solution, preferably wherein the second separation unit comprises a membrane with a cut-off of 1000 g / 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 can be an osmosis unit with a membrane with a cut-off of 1000 g / mol or less. The mass transfer through the membrane can be based on an alternating hydraulic pressure change. The acid transfer can also be due to a pH gradient between the first and second process solutions. Optionally, the second separation unit can be a reverse osmosis unit or an ultrafiltration unit.

[0062] The second separation unit, or SCFA exchange unit (short chain fatty acid exchange unit), facilitates the transfer of small molecules, e.g., molecules with a molecular weight of 1000 g / mol or less, from the first process solution to the second process solution. For this purpose, a membrane with an exclusion limit of 750 g / mol or less, 500 g / mol or less, more preferably 400 g / mol or less, 300 g / mol or less, 300 g / mol or less, even more preferably 150 g / mol or less, is preferably used.

[0063] The second separation unit can bring the process solution enriched with short-chain fatty acids in the first fermenter as a result of the hydrolysis and acidification taking place there into contact with a process solution from the second fermenter which is depleted in terms of its fatty acid content and thus enable a transfer of fatty acids to the process solution circuit of the second fermenter.

[0064] The process solutions in the process solution circuit of the first fermenter and the second fermenter are in material exchange with each other via the second separation unit. Through the fermentation substrate feed in the first fermenter, both organic and inorganic fermentation substrate components enter the process solution circuit of the first fermenter. The first separation unit described above allows the solid phase to be separated from the liquid phase. While the solid phase consists primarily of incompletely degraded plant biomass, the liquid phase contains, in addition to the short-chain fatty acids formed during fermentation, the water-soluble mineral components of the plant biomass or fermentation substrate, the so-called ash fraction.The ash portion is preferably removed regularly from the first separation unit in order to prevent its accumulation in the process solution circuit of the first fermenter over time and the associated deterioration of the environmental conditions.

[0065] The substrate feed also introduces relevant amounts of water into the first fermenter, depending on the water or moisture content of the fermentation substrate. The water or moisture content of common fermentation substrates, particularly agricultural ones, is typically between 60 and 80 percent. For biomass from aquatic environments, the water content is generally significantly higher than this percentage; for some residual and waste materials, such as paper and cardboard, straw, etc., it can sometimes be significantly lower. To drain such excess water, a discharge from the process solution circuits of the fermenter system is also necessary.

[0066] The SCFA exchange unit can partially separate the process solution circuits of the first fermenter and the second fermenter. This allows the process solution exiting the first fermenter, including the dissolved short-chain fatty acids and electrolytes, to enter the process solution circuit of the second fermenter.

[0067] The transfer of short-chain fatty acids, electrolytes, and excess water from the process solution circuit of the first fermenter to the process solution circuit of the second fermenter can occur through a membrane with limited permeability, possibly using a pressure change. After the mass transfer (fatty acids, electrolytes, excess water) to the process solution circuit of the second fermenter has taken place, the process solution from the first fermenter is preferably removed using a pump from the SCFA exchange unit and returned to the feed device of the first fermenter, if necessary after heating to the temperature prevailing in the first fermenter.

[0068] A plurality of second separation units may be present. For example, a first of the second separation units may have a first membrane with an exclusion limit of 2000 to 1000 g / mol, and a second of the second separation units, which is arranged downstream of the first of the second separation units, may have a second membrane with an exclusion limit of 500 g / mol or less. The plurality of second separation units may be osmosis units. Alternatively or additionally, the plurality of second separation units are designed as ultrafiltration units and / or reverse osmosis units. Osmosis units, ultrafiltration units, and / or reverse osmosis units can be combined as desired. For example, a first of the plurality of second separation units can be an osmosis unit, and a second of the plurality of second separation units can be a reverse osmosis unit. Alternatively or in addition to the series connection of a plurality of second separation units described above, a plurality of second separation units can also be connected in parallel, with the second separation units preferably each having a membrane with the same exclusion limit.

[0069] This allows the throughput of process solution through the second separation unit and thus the throughput of the fermenter system to be increased.

[0070] Larger fermentation substrate particles can be removed with the first separation unit before entering the second separation unit. For this purpose, the first separation unit can, for example, have a sieve, in particular a sieve with a pore size of 2 mm to 0.25 mm, for example 1.5 mm to 0.5 mm, 1.25 mm to 0.75 mm, or 1.0 mm to 0.9 mm. Several first separation units can be present. A second of the first separation units, which is arranged downstream of the first separation unit, can be adapted to remove smaller fermentation substrate particles than the first of the first separation units. This can increase the throughput of process solution. For example, a first of the first separation units can have a sieve with a pore size of 2 mm to 1.5 mm and a second of the first separation units can have a sieve with a pore size of 1.0 mm to 0.9 mm.

[0071] The process solution of the second fermenter's process solution circuit, which is enriched with short-chain fatty acids in the SCFA exchange unit, can be fed back into the second fermenter via a pump.

[0072] In the second fermenter, the quantitatively significant degradation of the short-chain fatty acids formed in the first fermenter by hydrolysis and acidification into methane and carbon dioxide can take place.

[0073] This can be done using the second anaerobic microorganisms, for example with the microorganisms listed below: Methanotrix, Methanosarcina, Methanobrevibacter ruminantium, Methanomicrobium mobile, Syntrophobacter wolnii, Syntrophomonas, Propionibacterium, Chlostridium propionicum and / or Propionigenium modestum.

[0074] The conversion of simultaneously formed hydrogen and carbon dioxide to methane and water can be carried out, for example, using the methanogens described here.

[0075] The second processing solution may have the composition described above. The second processing solution preferably has a nearly neutral to slightly alkaline pH, preferably in a range of 6.8 to 8.0, more preferably in a range of 7.0 to 7.5. The temperature of the second processing solution is preferably 35°C to 41°C, preferably 37°C to 40.5°C, such as 38°C to 40°C.

[0076] The biogas produced in the second fermenter can leave the fermenter via a second outlet.

[0077] According to another preferred embodiment, the second fermenter comprises a feed device adapted to uniformly distribute a process solution in the second fermenter. For this purpose, the process solution provided by the first fermenter can be introduced into the second fermenter via a pipeline or pipelines provided with a plurality of bores, preferably after passing through the first and / or second separation unit.

[0078] For example, the process solution enriched with short-chain fatty acids in the second separation unit or SCFA exchange unit can be pumped into the bottom of the fermenter by means of a pump and distributed evenly over an inlet area by means of an installed piping system. For this purpose, a structure consisting of several pipes running parallel along the longitudinal axis of the horizontally arranged second fermenter can be arranged in the bottom of the second fermenter. The pipes have, for example, a diameter of approximately 1.75 cm to approximately 5 cm, preferably 1.875 cm to 4.25 cm, more preferably 2.4 cm to 2.6 cm, such as 2.5 cm. The pipes can be attached adjacent to each other or at a specific distance from an inner wall of the second fermenter. The number, diameter, and spacing of the parallel pipes can correlate with the amount of process solution fed into the fermenter daily. This amount of process solution can, for example, be up to twice the fermenter volume.

[0079] The piping can have holes through which the process solution enters the second fermenter. The spacing and diameter of the holes can correlate with the amount of process solution to be fed into the fermenter daily.

[0080] The perforated pipelines ensure gentle delivery of the second process solution to the microbial biocenosis contained in the second fermenter. This prevents any unintentional detachment of the second microorganisms immobilized in the second fermenter, at least partially and, if necessary, completely. Furthermore, by allowing the process solution to flow into the second fermenter at multiple points, a reduction in the pH value can be prevented. Thus, the pH value of the process solution in the bottom of the fermenter is only insignificantly affected, despite the fatty acid load flowing into this area. The environmental conditions thus maintained promote the conversion rate at which the biocenosis established in the second fermenter can convert the short-chain fatty acids contained in the supplied process solution into biogas.The buffering effect of the hydrogen carbonate, hydrogen phosphate and dihydrogen phosphate ions contained in the process solution can also have an advantageous effect.

[0081] According to yet another preferred embodiment, the second fermenter has a mesh structure adapted to provide a settlement area for anaerobic microorganisms, preferably wherein the mesh structure has packing elements fixed in the mesh structure. The packing elements can be incorporated into the mesh structure in such a way that floating or sinking of the packing elements in the second fermenter is prevented. Alternatively, the packing elements can be attached to the mesh structure, optionally in a movable manner.

[0082] The mesh structure can be a two- or three-dimensional mesh secured in the second fermenter. The process solution can flow vertically through the second, preferably horizontally arranged, fermenter, counter to the direction of the gravity vector. The mesh structure is arranged above the feed device. Preferably, the mesh structure occupies approximately the same area as the feed device. More preferably, the mesh structure extends over substantially the entire horizontal cross-section of the horizontally arranged second fermenter.

[0083] The mesh structure can comprise a plurality of packing elements, which provide the biocenosis established in the second fermenter with a settlement area for the formation of a biofilm. These packing elements can comprise Pall rings or other structurally comparable packing elements, e.g., cylindrical rings, saddles, or grid-like structures, and are preferably made of polypropylene or polyethylene. To prevent the packing elements from floating or sinking within the second fermenter, they are, for example, integrated into the mesh structure. The meshes of the mesh structure can be smaller than the packing elements, so that the packing elements are held within the mesh structure.

[0084] Preferably, polypropylene Pall rings in nominal size 25 (length 25 mm; diameter 25 mm) are used as packing. The mesh structure can have rectangular meshes with an edge length of < 25 mm, e.g., 20 mm.

[0085] The process solution passing through the mesh structure and exiting above it, whose fatty acid content has been reduced by the biocenosis as a result of microbial degradation within the mesh structure, can then be removed from the second fermenter via a removal device. The removal device can be designed as a pipe with holes, which is located in the upper area of ​​the horizontally arranged second fermenter, i.e. above the mesh structure.

[0086] The pipe provided with bores is preferably constructed according to the feed device.

[0087] For example, and preferably, the process solution is fed into the second fermenter via a first piping system arranged below the network structure. The first piping system can have 10 to 20 first pipes with a pipe spacing of 10 to 20 cm. The length of each of the first pipes can be 5 to 10 m. Each of the first pipes can have an inner diameter of 1.5 to 3.5 cm. Each of the first pipes can have first bores at a spacing of 10 to 50 cm. The number of first bores can be 10 to 100. The first bores can independently have a diameter of 0.3 to 0.5 cm.

[0088] For example, and preferably, the collection or removal of the process solution from the second fermenter takes place via a second piping system arranged above the network structure. The second piping system can have 1 to 10 second pipes with a pipe spacing of 2 to 10 cm. The length of each of the second pipes can be 5 to 10 m. Each of the second pipes can have an inner diameter of 2 to 10 cm. Each of the second pipes can have second bores at a spacing of 10 to 100 cm. The number of second bores can be 10 to 30. The second bores can independently have a diameter of 1 to 2 cm.

[0089] The process solution can be removed from the second fermenter using a pump, which can be designed as a magnetically coupled centrifugal pump.

[0090] The exiting process solution stream can be fed into two pipelines, which can be selectively controlled and / or closed via one or more valves. The valve can be an electrically controlled solenoid valve, preferably a pneumatic valve controlled via a pilot valve.

[0091] One of the two pipelines can be connected to the SCFA exchange unit. This pipeline can be equipped with a pump. If this pipeline is controlled by a valve, the fatty acid content within the second The process solution depleted in the fermenter is fed to the SCFA exchange unit in order to be enriched again with fatty acids formed in the fermenter.

[0092] Process solution can be withdrawn from the fermenter system's process solution circuit via the other pipe by actuating a valve accordingly. This allows water added to the fermenter system with the fermentation substrate to be removed from the fermentation process, and the amount of water circulating in the fermenter system to be adjusted to a suitable level.

[0093] This excess process solution, removed from the fermentation process, contains, among other things, electrolytes and microbial cell mass. This liquid can be processed, for example, into plant fertilizer. Depending on the ingredients, sterilization processes to ensure microbiological safety as well as processes to increase the concentration of solutions, such as reverse osmosis, can be advantageously used.

[0094] According to a preferred embodiment, the second fermenter has a removal device and optionally a return line which fluidly connects the second fermenter and the first fermenter, preferably wherein the removal device is arranged on the return line.

[0095] According to a further preferred embodiment, the process according to (iii) comprises a step (iiia): substantially removing solids from the fermenter system. This can be carried out with the first separation unit.

[0096] According to a further preferred embodiment, the method according to (iii) comprises a step (iiib): contacting the first process solution and the second process solution such that substances substantially dissolved in the first process solution, in particular short-chain fatty acids, are at least partially transferred into the second process solution. This can be carried out using the second separation unit.

[0097] Preferably, steps (iii), (iiia) and (iiib) are carried out in this order.

[0098] According to yet another preferred embodiment, the fermentation substrate and the process solution are heated to the substantially constant temperature before step (i); and / or the first and / or second process solution is / are adjusted to a substantially constant pH value.

[0099] According to yet another embodiment, impurities contained in the biogenic gases, preferably oxygen, hydrogen sulfide, and / or ammonia, are removed. Preferably, the biogenic gases are fed to a utilization facility, e.g., a combined heat and power plant, and / or a separation facility for separating the biogenic gases into a hydrocarbon-containing fraction and a carbon dioxide-containing fraction. The removal of such impurities is familiar to those skilled in the art.

[0100] According to a preferred embodiment, the first anaerobic microorganisms comprise species of the genera Fibrobacter succinogenes, Ruminococcus albus, Butyrivibro fibrisolvens, Clostridium lockheadii, Ruminococcus flavefaciens, or Bacteroides succinogenes, protozoa, for example of the genera Isotricha, Dasytricha, Eutodinium, or Diplodinium, and / or fungi, for example of the species Neocallimastix, Piromonas, or Sphaermonas; and / or wherein a stomach content of a forestomach system, in particular the rumen, of a ruminant, for example of a cattle, sheep, and / or goat, is used as the first anaerobic microorganisms. The first anaerobic microorganisms form a first biocenosis.

[0101] The hydrolysis of the cellulose and hemicellulose portion of the fermentation substrate can be carried out by the cellulolytically active first anaerobic microorganisms (cellulase-producing microorganisms) listed above. The end products of the microbial metabolism of the first anaerobic microorganisms listed above are short-chain fatty acids, including acetate, formate, propionate, butyrate, lactate, succinate, as well as hydrogen and carbon dioxide. Hydrogen and carbon dioxide can, in turn, be converted into methane and water by certain microorganisms (archaea).

[0102] Alternatively or additionally, the stomach contents of the forestomach system of ruminants (Ruminantia), particularly those of ruminants relevant for human consumption (cattle (Bovini), sheep (Ovis), goats (Capra)), can be utilized. The contents of the rumen (rumen) of ruminants, which, for example, accrue in slaughterhouses, can advantageously be used as starting inoculum. If additional fermentation substrate is added to such a starting inoculum in the fermenter and the starting inoculum is mixed with fresh fermentation substrate, a continuously fermenting biocenosis builds up throughout the fermenter, which hydrolyzes cellulose and hemicelluloses in particular into their monomers and converts these monomers (intermediate products) into short-chain fatty acids.

[0103] Monomers formed by hydrolysis of the cell wall components and structural substances of the plant fermentation substrate can be converted to pyruvate by anaerobic glycolysis (Embden-Meyerhof pathway) and in the pentose phosphate cycle. Pyruvate is the central intermediate product of microbial carbohydrate metabolism, which is rapidly converted into short-chain fatty acids, particularly acetic acid, propionic acid, and butyric acid.

[0104] Environmental conditions in the first fermenter usually require a pH value in a slightly acidic to slightly alkaline range, for example from 5.5 to 7.5, preferably 6.0 to 7.0, more preferably 6.5 to 6.8, for the benefit of the microbial biocenosis established therein.

[0105] Due to its specific microbial composition, the microbial biocenosis established in the first fermenter can enable a particularly rapid hydrolysis of the cellulose and hemicelluloses contained in the fermentation substrate as well as other fermentation substrate ingredients degradable under anaerobic conditions, forming a mixture of short-chain fatty acids, in particular acetic acid, propionic acid and butyric acid as well as valeric acid and isovaleric acid.

[0106] The rate of hydrolysis and acid formation (acidification) is so high that the environmental conditions within the first fermenter would change significantly negatively due to the rapidly falling pH value.

[0107] Preferably, the process solution enriched with short-chain fatty acids is removed from the first fermenter quickly, e.g., within the retention times listed above, to avoid any acidosis that may occur, and replaced with fresh process solution. This can be achieved, in particular, by continuously operating the fermenter system, which includes the second separation unit.

[0108] By means of a suitable process control technology, it can be ensured that the process solution on the one hand and the solid fermentation substrate phase on the other hand have an individual residence time adapted to the fermentation substrate type and quality by means of a synchronized control of the substrate feed quantity, the process solution feed, the rotation of the inner drum, the internal substrate return and the substrate removal.

[0109] By specifically controlling the residence time of the solid phase (fermentation substrate), the extent of substrate degradation (conversion of biomass into biogas) can be optimized. While a short residence time can result in suboptimal substrate degradation because a significant portion of the plant biomass fed into the fermentation process is not degraded and is removed from the first fermenter as solid digestate, a longer residence time carries the risk of suboptimal use of the available fermenter volume. As the residence time increases, components of the fermentation substrate that are difficult to degrade or cannot be degraded under anaerobic conditions increasingly accumulate in the fermenter. This applies in particular to lignin, which is regularly present in the plant biomass of terrestrial plants and is not degradable under the anaerobic conditions prevailing in fermenters.

[0110] According to another preferred embodiment, the second anaerobic microorganisms comprise methanogens, in particular Methanobacterium, Methanobrevibacter, in particular M. ruminantium, Methanococcus, Methanomicrobium, in particular M. mobile, Methanogenium, Methanospirillium, Methanoplanus, Methanocorpusculum, Methanoculleus and / or Methanosarcina, Methanotrix, Syntrophobacter wolnii, Syntrophomonas, Propionibacterium, Clostridium propionicum and / or Propionigenium modestum; and / or wherein actively degrading sludge from wastewater treatment plants or digesters from biogas plants are used as the second anaerobic microorganisms. The second anaerobic microorganisms, usually Archaea, enable the conversion of hydrogen and carbon dioxide into methane and water. The second anaerobic microorganisms form a second biocenosis.

[0111] The second anaerobic microorganisms can be cultivated at a pH of 6.8 to 8.0, preferably 7.0 to 7.5.

[0112] Microbial biocenoses, such as those found in the sediments of water bodies, the actively degrading sludge of wastewater treatment plants or in the fermenters of biogas plants, can be used as starting inoculum.

[0113] In order to establish a biocenosis capable of converting even a larger load of short-chain fatty acids into biomethane and biocarbon dioxide at a rate sufficiently high to prevent the accumulation of such acids in the process solution and, in particular, a reduction in the pH of the process solution resulting from such accumulation, it has proven advantageous to create an enrichment culture containing a high population density of fatty acid-converting microorganisms. Such an enrichment culture can be created by adding a defined mixture of short-chain fatty acids to a fermenter within a closed process solution cycle, after adding a starting inoculum of second anaerobic microorganisms, under constant pH control.As a result of this specific substrate supply, those microorganisms that are capable of materially utilizing the short-chain fatty acids supplied to the fermenter accumulate in the biocenosis, while at the same time those microorganism populations that are not capable of doing so are increasingly displaced.

[0114] To pump the process solution, the fermenter system can have 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 impeller housing or the drive shaft connected to the drive motor is required. Potential leaks that could arise due to corrosion on the drive shafts and drive seals can thus be effectively prevented. The one or more pumps preferably have a pump housing made of plastic, in particular polyethylene or polypropylene. This eliminates corrosion or other damage to the drive shafts and seals caused by the process solution, in particular the electrolytes contained therein.Magnetically coupled centrifugal pumps with a housing made of a plastic, in particular polyethylene or polypropylene, have proven to be particularly advantageous.

[0115] Biogas exiting the first fermenter via the first outlet and the second fermenter via the second outlet can be fed into a common central gas pipeline. Measuring devices for continuous measurement of the gas quantity and composition can be integrated into this collection line.

[0116] The biogas exiting or extracted from the fermenter system primarily consists of methane and carbon dioxide and may also contain small amounts of oxygen, hydrogen sulfide, ammonia, and other trace gases. Furthermore, the biogas may contain a moisture content, particularly water, that largely depends on the temperature prevailing in the fermenters.

[0117] Before the biogas is used for energy or material purposes, the oxygen, hydrogen sulfide, and / or ammonia content, preferably hydrogen sulfide and ammonia, can be removed. This can be done using any method known in the art.

[0118] For example, ammonia can be added to the gas mixture using an acidic solution, for example diluted sulfuric acid (1 to 25%), forming Ammonium sulfate can be essentially removed, which in turn can be used as fertilizer, for example.

[0119] This process step can be followed by a substantially quantitative removal of the hydrogen sulfide from the gas mixture. For example, an acidic solution of a water-soluble lead salt, such as lead chloride, lead acetate, or lead nitrate, can be used. Since lead sulfide has a low solubility product even in an acidic aqueous solution, the hydrogen sulfide contained in the gas stream can be effectively removed. The resulting lead sulfide can be recycled in the lead processing industry.

[0120] The remaining biogas, which consists primarily of methane and carbon dioxide, can be fed, preferably after prior drying, into a power plant, such as a combined heat and power plant, to generate electricity and / or heat. Direct use for heat generation is also possible.

[0121] Other optional uses of biogas may require additional gas treatment processes. These can be used to separate the methane and / or carbon dioxide. This can be achieved, for example, using adsorption processes known in the art, such as pressure swing scrubbing; absorption processes, such as amine scrubbing; membrane processes, in which the gases are separated using membranes with a suitable exclusion limit, e.g., made of metal, ceramic, or plastic; and cryogenic processes, in which the gases contained in the mixture are successively liquefied by reducing the temperature.

[0122] After purification, the resulting methane or carbon dioxide can be readily used. For example, methane can be fed into the natural gas grid.

[0123] Digestates can be sterilized. Sterilized or unsterilized fermentation residues can be separated into fiber components and proteins, for example. Fiber components can be further used industrially. Proteins can be added to animal feed, for example.

[0124] The liquid extracted from the second fermenter can be sterilized and used, for example, as fertilizer. Alternatively, the extracted liquid can be sterilized and separated, for example, using reverse osmosis, to produce concentrated liquid fertilizer and water.

[0125] Information marked with the term "substantially" may include deviations of +10% and / or -10%. For example, the term "substantially perpendicular" includes an angle of 81° to 99°. For example, the term "substantially completely" includes a distance of 90% to 100%.

[0126] Preferably, the first fermenter and / or the second fermenter do not have an agitator. More preferably, the fermenter system does not have an agitator. Agitators or stirrers within the scope of the present disclosure have one or more axles or shafts, which are typically provided with blades and / or vanes.

[0127] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0128] The invention will now be explained in more detail using examples. The features mentioned therein are considered part of the invention not only in relation to the specific example, but also in isolated form. Reference is made to the accompanying figures.

[0129] The figures show

[0130] Fig. 1 is a schematic representation of an exemplary fermenter system according to the present invention; and

[0131] Fig. 2a-c a schematic representation of the utilization of the fermentation products obtained by the exemplary fermenter system. Implementation examples

[0132] Figure 1 shows a schematic representation 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 each other via a pipeline 4, 6 equipped with a pump. The first fermenter 1 and the second fermenter 2 are designed as cylindrical containers arranged horizontally.

[0133] The first fermenter 1 has, on a first circular side thereof, a feed device 3 with a motor 24, via which a first process solution and fermentation substrate, e.g. plant residues, can be added to the first fermenter 1, wherein in the first fermenter 1 a first biocenosis of anaerobic first microorganisms is present in the first process solution.

[0134] The first fermenter 1 is provided with an inner drum 8 arranged therein, mixing devices 9, 10 and an inner pipe 11 provided with a conveyor screw in order to enable a uniform, spatial mixing of the fermentation substrate, the first process solution and the biocenosis of anaerobic first microorganisms along the flow directions 26, 27 shown schematically by arrows, and their transport to a second circular side of the first fermenter 1.

[0135] As part of the uniform, spatial mixing of the fermentation substrate, the first process solution, and the biocenosis of anaerobic first microorganisms, the fermentation substrate is degraded or fermented to form short-chain fatty acids. A mixture of partially degraded fermentation substrate or digestate and the first process solution, containing the short-chain fatty acids present therein, exits the first fermenter 1 and enters a first separation unit 13, which enables the separation of the digestate from the first process solution, containing the short-chain fatty acids present therein. The first separation unit can, for example, comprise a screw or spiral adapted to lift solid components upwards out of the liquid phase, leaving the liquid phase essentially behind. The first separation unit can further comprise a sieve. After the liquid phase passes through a sieve, it can be removed, for example, using a pump.

[0136] The digestate can be removed from the fermenter system 100, for example, using a motor 25 and can be subjected to a utilization shown schematically in Fig. 2a.

[0137] The first process solution containing the short-chain fatty acids present therein is supplied to a second separation unit 14 via pipeline 4 provided with a pump. The second separation unit 14, designed as a reverse osmosis unit, has a membrane 15 with an exclusion limit of <150 g / mol. Using the membrane 15, the first process solution containing the short-chain fatty acids present therein can be separated from a second process solution. The membrane 15 enables the transfer of small molecules, particularly short-chain fatty acids and electrolytes, into the second process solution. Molecules with a molecular weight of >150 g / mol remain in the first process solution.

[0138] The first process solution depleted of short-chain molecules can be fed back to the feed device 3 via a pipeline 5 provided with a pump.

[0139] The second process solution containing the short-chain fatty acids is introduced into the second fermenter 2 via a pump-driven pipeline 6 of a feed device 17. The second fermenter 2 contains a second process solution and a second biocenosis of anaerobic second microorganisms. The biocenosis is partially immobilized on the packing elements formed as Pall rings on a mesh structure 18 inside the second fermenter 2. The mesh structure 18 extends across the entire (horizontal) cross-section of the horizontally arranged second fermenter 2.

[0140] The second process solution flowing from the feed device 17 into the second fermenter 2 with the short-chain fatty acids present therein flows essentially over the entire cross section of the network structure 18 in such a way that the anaerobic second Microorganisms essentially degrade the short-chain fatty acids present in the second process solution into carbon dioxide and biomethane. A removal device 19 located in the second fermenter 2 enables the second process solution, the biomethane, and carbon dioxide to exit the second fermenter 2.

[0141] The feed device 17 and the removal device 19 are formed on opposite sides of the network structure 18 and each have pipes with a plurality of bores in order to enable a uniform process solution flow along the flow direction 28 shown schematically by an arrow over the entire cross section of the network structure 18.

[0142] Liquid exiting the second fermenter 2 at the withdrawal device 19 can be supplied to a liquid withdrawal point 23 via a pipeline 7 provided with a pump and a valve 21, and can be withdrawn from the fermenter system 100 at this point. Alternatively or additionally, the exiting liquid can be returned to the second separation unit 14 via a pipeline 22 provided with a pump and a valve 20. The liquid withdrawn from the fermenter system 100 can be subjected to a recycling process as shown schematically in Fig. 2c.

[0143] The first and second fermenters 1, 2 are also provided with a first outlet 12 and a second outlet 16 in order to subject the resulting (bio)gas to a utilization shown schematically in Fig. 2b.

[0144] The process parameters, including a constant temperature of the process solutions, the pH value in the first and second fermenters 1, 2, etc., are controlled by a control unit (not shown) in such a way that the two biocenoses are cultivated under the respective optimal conditions.

[0145] Figures 2a-c show a schematic representation of the utilization of the fermentation products obtained by the exemplary fermenter system 100.

[0146] As can be seen from Fig. 2a, the digestate removed from the first fermenter 1 can be sterilized and separated from each other. The resulting fiber components can be reused industrially, for example. The protein obtained can be added to animal feed, for example.

[0147] Figure 2b shows the utilization of the (bio)gas extracted from the first and second fermenters 1, 2. The (bio)gas can be depleted of impurities, particularly hydrogen sulfide and ammonia, and then, after drying, converted into electricity and heat in a combined heat and power (CHP) plant. Furthermore, methane and carbon dioxide can be separated and subsequently liquefied and / or compressed.

[0148] Figure 2c shows the utilization of the liquid extracted from the second fermenter 2. This can be sterilized and applied, for example, as fertilizer. Alternatively, the extracted liquid can be sterilized and separated, for example, using reverse osmosis, to produce concentrated liquid fertilizer and water.

Claims

Patent claims 1. Fermenter system (100) for producing biogenic gases and optionally useful products, in particular fatty acids and / or proteins, comprising a first fermenter (1), a second fermenter (2), and a pipeline (4, 6) which fluidly connects the first fermenter (1) and second fermenter (2), a heating unit which is designed to provide a temperature of > 25°C in the first and second fermenters (1, 2) and the pipeline (4, 6), wherein the fermenter system (100) is designed for an anaerobic process, and wherein the first fermenter (1) has an inner drum (8) which is provided so as to be rotatable in the first fermenter.

2. Fermenter system (100) according to claim 1, wherein the first fermenter (1) has a feed device (3) which is adapted to heat a fermentation substrate and / or a process solution to the temperature of > 25°C and to provide a defined discharge amount of fermentation substrate and / or the process solution into the first fermenter (1).

3. Fermenter system (100) according to one of the preceding claims, wherein the inner drum is provided rotatably about a longitudinal axis of the first fermenter and / or adapted to enable movement of the contents of the first fermenter (1) in the direction of the second fermenter (2), preferably wherein the first fermenter has an inner tube extending through the inner drum with a conveying unit.

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

5. Fermenter system (100) according to one of the preceding claims, wherein the fermenter system (100) comprises a second separation unit (14) between the first and second fermenters (1, 2), which is adapted to separate a first process solution from a second process solution such that only small molecules can pass from the first process solution into the second process solution, preferably wherein the second separation unit (14) comprises a membrane (15) with an exclusion limit of 1000 g / mol or less.

6. Fermenter system (100) according to one of the preceding claims, wherein the second fermenter (2) comprises a feed device (17) adapted to evenly distribute a process solution in the second fermenter (2).

7. Fermenter system (100) according to one of the preceding claims, wherein the second fermenter (2) has a mesh structure (18) adapted to provide a settlement area for anaerobic microorganisms, preferably wherein the mesh structure (18) has packing bodies fixed in the mesh structure (18).

8. Fermenter system (100) according to one of the preceding claims, wherein the second fermenter (2) has a removal device (19) and optionally a return line which fluidly connects the second fermenter (2) and the first fermenter (1), preferably wherein the removal device (19) is arranged on the return line.

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

10. A method for producing biogenic gases and useful products, in particular fatty acids and / or proteins, with a fermenter system (100) comprising a first fermenter (1), a second fermenter (2), a pipeline (4, 6) which fluidly connects the first fermenter (1) and second fermenter (2), wherein the first fermenter (1) has an inner drum (8) which is rotatably provided in the first fermenter (1), the method comprising the steps: (i) providing the first fermenter (1) with first anaerobic microorganisms and a first process solution and the second fermenter (2) with second anaerobic microorganisms and a second process solution; (ii) feeding a fermentation substrate comprising cellulose and / or hemicellulose and the first process solution into the first fermenter (1); (iii) conveying the first process solution into the second fermenter (2); and (iv) removing biogenic gases from the first and second fermenters (1, 2) and removing the fermentation substrate from the first fermenter (1); wherein the first and second fermenters (1, 2) and the pipeline (4, 6) have a temperature of > 25°C; wherein the first anaerobic microorganisms, the fermentation substrate and the first process solution are mixed; and wherein the first anaerobic microorganisms are adapted to degrade the fermentation substrate to short-chain fatty acids with the formation of intermediate products, and the second anaerobic microorganisms are adapted to degrade the short-chain fatty acids to biogas.

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

12. The method according to claim 10 or 11, comprising after (iii) a step (iiib) contacting the first process solution and the second process solution such that substances substantially dissolved in the first process solution, in particular short-chain fatty acids, are at least partially transferred into the second process solution.

13. The method according to any one of claims 10 to 12, wherein the fermentation substrate and the process solution are heated to the substantially constant temperature before (i); and / or wherein the first and / or second process solution is adjusted to a substantially constant pH; and / or comprising removing impurities contained in the biogenic gases, preferably oxygen, hydrogen sulfide and / or ammonia, preferably feeding the biogenic gases to a utilization facility, e.g. a combined heat and power plant, and / or a separation facility for separating the biogenic gases 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 microorganisms comprise species of the genera Fibrobacter succinogenes, Ruminococcus albus, Butyrivibro fibrisolvens, Clostridium lockheadii, Ruminococcus flavefaciens, or Bacteroides succinogenes, protozoa, for example of the genera Isotricha, Dasytricha, Eutodinium, or Diplodinium, and / or fungi, for example of the species Neocallimastix, Piromonas, or Sphaermonas; and / or wherein a stomach content of a forestomach system, in particular rumen, of a ruminant, for example of a cattle, a sheep, and / or a goat, is used as the first anaerobic microorganisms.

15. The method according to any one of claims 10 to 14, wherein the second anaerobic microorganisms are methanogens, in particular Methanobacterium, Methanobrevibacter, in particular M. ruminantium, Methanococcus, Methanomicrobium, in particular M. mobile, Methanogenium, Methanospirillium, Methanopianus, Methanocorpusculum, Methanoculleus and / or Methanosarcina, Methanotrix, Syntrophobacterwolnii, Syntrophomonas, Propionibacterium, Clostridium propionicum and / or Propionigenium modestum; and / or wherein actively degrading sludge from wastewater treatment plants or fermenters from biogas plants are used as the second anaerobic microorganisms.

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