DE102012211781A1 - Treating biomass containing chicken excrement, comprises subjecting biomass to ammonia fermentation, and removing ammonia during fermentation by stripping gas and/or precipitation as magnesium ammonium phosphate, from the biomass - Google Patents

Abstract

Treating biomass containing nitrogen, preferably biomass containing chicken excrement, comprises (a) subjecting the biomass at a dry matter content of less than 70%, preferably less than 50%, to an ammonia fermentation, and (b) removing ammonia during the ammonia fermentation by a stripping gas and/or by precipitation, preferably as magnesium ammonium phosphate, from the biomass. An independent claim is included for an apparatus for treating biomass containing nitrogen, preferably for executing the method, comprising at least one container, which is suspended and/or fixed on a support and/or contains immobilized microorganisms and/or enzymes for ammonia fermentation.

Description

The invention relates to a process for the production of biogas from nitrogen-containing biomass, in particular biomass containing chicken excrement.

In current worldwide practice, ammonia emissions, for example from chicken feces containing uric acid, are suppressed as quickly as possible by drying the feces. The drying process begins immediately after the chicken droppings have been placed on a conveyor belt in the cages. The fresh chicken droppings are finally completely dried to reduce ammonia emission to almost zero. Ammonia is a toxic substance that can damage plant growth around laying hen or broiler stables.

Broilers and laying hens spend between 70 and 200 g of feces per day and animal. The nitrogen content in chicken manure of 3 to 6% in the dry matter is one of the highest of all feces. Chicken droppings emit a strong smell of ammonia. At least 50% of the total nitrogen content, up to 80% in many chicken gut samples, is present as uric acid, which makes the chicken feces a rich source of ammonia.

All previously known measures are aimed at eliminating the emissions of ammonia. The effort involved is substantial and can ultimately only be successful if the chicken droppings are completely dried.

The DE 20 2004 003 883 U1 describes a ventilation device for manure belts in poultry plants. With the aeration device can be carried out a drying of movable Kotbändern over the entire areal extent of the Kotbandes.

The DE 38 39 599 C1 discloses a device for drying chicken droppings. The device has a Kotförderungsband and a circumferentially driven roller body as Kotlockerungsvorrichtung, with which the drying process can be improved.

Furthermore, methods for stripping ammonia from liquid manure are known. That's how it describes DE 41 03 308 A1 a method for manure disposal. The process comprises the enzymatic hydrolysis of the urea to ammonium carbonate with urease preparations, the flocculation of suspended and colloidally dissolved ingredients with organochemical polyelectrolytes, the flotation of the flocs by thermal decomposition of the dissolved ammonium carbonate, the expulsion of the ammonia and its absorption in mineral acid and the feeding of the now nitrogen-poor residual liquid in the denitrification of a sewage treatment plant.

In the DE 10 2010 033 251 A1 is a process for the production of ammonium carbonate, solid fertilizer and industrial / drinking water from manure of livestock or digestate from biogas plants known. In the process liquid manure from livestock or liquid constituents of fermentation residues from biogas fermenters are combined with the enzyme urease.

There are both national and European efforts to reduce nitrogen emissions from poultry farming. The fermentation of ammonia, d. H. the production of ammonia by microorganisms or enzymes can make a significant contribution to the reduction of emissions in animal husbandry, in particular poultry production.

A combination of the ammonia fermentation with the biogas fermentation would be advantageous in the utilization of nitrogen-containing biomass, in particular biomass containing chicken dung. The ammonia fermentation and the biogas fermentation differ in particular by the capabilities of the respective microorganisms. The microorganisms in the Ammoniakfermentation, which belong to a large percentage of the Firmicutes, can live on the degradation products of nitrogen exchange as the sole source of nitrogen and energy, so have a high nitrogen turnover. Firmicutes include aerobic bacteria and anaerobic to aerotolerant clostridia as well as mollicutes.

The microorganisms in the methane fermentation, which belong to the archaea, have acetic acid as the main source of methane formation and thus a high acid conversion. The methanogens are summarized in the classes Methanobacteria, Methanococci and Methanomicrobia.

In ammonia fermentation and biogas fermentation, the microorganisms are at the end of the respective degradation product chain and on the one hand deliver reduced nitrogen (NH ₃ ) and, on the other hand, reduced carbon (CH ₄ ). For energetic reasons, the reduction of nitrogen to NH _{3 is} better and occurs before carbon is reduced to CH ₄ . Nitrogen is the better proton acceptor than carbon. Therefore, the ammonia producers can exist better in the digestion than the methanogenic microorganisms in the ammonia fermentation.

The microorganisms of ammonia fermentation and the microorganisms of biogas fermentation have different demands on the respective chemical environment. So will in the Ammonia fermentation, a pH of 8 to 9 is preferred, while in the biogas fermentation, a pH of 7 is preferred. The methanogenic microorganisms can not work properly at a high pH, while the microorganisms in the ammonia fermentation can not work properly at a low pH. The methanogenic microorganisms in the biogas fermentation are inhibited by a low concentration of ammonia, already from 2 g ammonia per liter, even if a certain habituation of the methanogenic microorganisms (up to about 5 g ammonia per liter) can occur.

Either ammonia (NH ₃ ) or the undissociated salt of ammonium bicarbonate (NH ₄ HCO ₃ ) act as inhibitors. It adjusts a pH and temperature-dependent equilibrium according to the formula: ↑ NH ₃ ↔ NH ₄ ⁺ + HCO ₃ ^- ↔ NH ₄ HCO ₃ .

At a high pH, the equilibrium shifts to volatile NH ₃ , at a low pH to the undissociated salt ammonium bicarbonate (NH ₄ HCO ₃ ).

The object of the invention is to provide an improved process for producing biogas from nitrogen-containing biomass, in particular biomass containing chicken excrement, in which the biomass is subjected to both an ammonia fermentation and a biogas fermentation and, in particular, an inhibition of the biogas fermentation by ammonia is reduced.

The object is achieved with the subject matter of claim 1. Advantageous developments emerge from the dependent claims, the description and the figures.

In the method according to the invention for producing biogas from nitrogen-containing biomass, in particular from biomass containing chicken dung, the biomass is subjected to an ammonia fermentation at a dry matter content of less than 70%, in particular a dry matter content of less than 50%. During the ammonia fermentation, ammonia, preferably by means of a stripping gas, in particular air and / or biogas and / or CO ₂ or CO ₂ -containing gas and / or combustion exhaust gas, is removed from the biomass, in particular continuously during the entire duration of the ammonia fermentation. The stripping gas can be passed through and / or over the biomass. In a subsequent step, the biomass depleted in the nitrogen content of the ammonia fermentation is subjected to biogas fermentation.

The nitrogen-containing biomass is depleted in a first step by an ammonia fermentation in the nitrogen content and subjected in a second step of a biogas fermentation. In this way, a generation of biogas from biomass is made possible, which consists exclusively of chicken excrement. Of course, in addition to chicken excrement, the biomass may also contain other biogenic materials, such as sewage sludge, biowaste, manure or manure, especially from cattle and pig farming.

In preferred embodiments, the ammonia fermentation and biogas fermentation may be performed in separate steps, preferably in separate devices. Thus, the ammonia fermentation can be carried out directly on a conveyor belt or in a stirred vessel. The biogas fermentation can be carried out independently in a first or second stirred vessel.

By ammonia fermentation, the nitrogen content of the biomass can be reduced to half to one quarter of the original nitrogen content. In this way, inhibition of the methanogenic microorganisms in the biogas fermentation can be reduced or avoided. In particular, an inhibition threshold concentration of 5 g of ammonia per liter in the biogas plant can be permanently undershot.

Ammonia, which is removed during the ammonia fermentation, can be used as a starting material for a variety of different products, such as fertilizers, explosives, resins, detergents and hair dyes, and pharmaceuticals. With the aid of the method according to the invention chicken excrements can be used as monosubstrate in biogas plants. High energy and drying costs for the drying of chicken excrement can be reduced or avoided. In particular, a poisoning of a biogas fermenter can be avoided by ammonia, which could have a failure of the biogas plant of several months result.

The liquid digestate produced during the process can be used directly for the dilution of biomass. Due to the low nitrogen concentration, this eliminates a costly treatment of the digested substances with ultrafiltration or membrane processes. Furthermore, due to the upstream ammonia fermentation, the fermenter space in biogas fermentation can be reduced by up to 50%. Advantageously, the storage space, which must be provided for a storage period of at least 180 days, can be reduced.

By removing ammonia during ammonia fermentation, the equilibrium is shifted towards the production of ammonia. In this way, the depletion of the biomass in the nitrogen content can be increased. The removal of the ammonia preferably takes place by means of a stripping gas, in particular air and / or biogas and / or CO ₂ or CO ₂ -containing gas and / or combustion exhaust gas. Ammonia can then be separated from the stripping gas by a scrubber. Advantageously, exhaust gases from combined heat and power plants and / or exhaust gases, which are incurred in the treatment of biogas to natural gas quality, are used for stripping the ammonia. When biogas is used as the stripping gas, production of biogas during ammonia fermentation can be reduced or avoided by shifting the equilibrium to the educt side. Of course, a combination of the above-mentioned gases can be used as the stripping gas for ammonia.

The biomass may preferably contain chicken excrement and more preferably consist solely of chicken excrement. Further, the biomass may include slaughterhouse waste or wastes incurred in the processing of hides or shellfish. Domestic waste or industrial sludge may also be present in the biomass. By the method according to the invention, a generation of biogas from biomass with a high nitrogen content can be made possible.

Particularly preferably, ammonia is removed continuously throughout the duration of the ammonia fermentation, whereby the depletion of the biomass in the nitrogen content is increased.

With a dry matter content of the biomass greater than 15%, the ammonia fermentation can be carried out as dry fermentation. Advantageously, in the dry fermentation of chicken manure no microorganisms must be supplied from the outside. Preferably, the dry fermentation can be carried out on a conveyor belt. During dry fermentation, ammonia can be removed from the biomass by passing a stripping gas over and / or through the biomass. The biomass can be circulated, in particular continuously circulated.

The stripping gas may preferably be passed over the biomass at a rate of greater than 0.2 m / s and remove about 50% to 80% of the ammonia formed during the ammonia fermentation from the biomass. The dry fermentation can be carried out at a low negative pressure. The negative pressure may help to remove ammonia from the biomass by both vacuum distillation and stripping.

A slight drying of the biomass during the dry fermentation can be accepted. Preferably, however, the stripping gas is humidified to prevent drying out of the biomass during dry fermentation. For moistening the biomass can be advantageously used urine. In particular, the stripping gas has a moisture content of 60% to 100%. Alternatively, or in addition to wetting the stripping gas, the biomass itself may be humidified during the ammonia fermentation. By moistening the biomass and / or the stripping gas, an activity of the microorganisms can be maintained. Furthermore, ammonia can dissolve in the moisture and thus more efficiently be removed from equilibrium by stripping.

The ammonia fermentation can be configured as a wet fermentation. The dry matter content of the biomass can be below 15%, preferably 1 to 5%. The ammonia fermentation can be carried out by means of microorganisms and / or enzymes fixed and / or immobilized on a support. During this embodiment of the ammonia fermentation, ammonia can be removed from the biomass by passing a stripping gas through the biomass, in particular by bubbling it.

A subject of the invention is furthermore a method for producing biogas from nitrogen-containing biomass, in particular biomass containing chicken dung, having the features a) and c) of claim 1 and the further feature that the ammonia fermentation is immobilized by means of microorganisms fixed and / or immobilized on a support and / or or enzymes is performed, d. H. a method in which this feature replaces the feature b) of claim 1. However, the further subject of the invention can advantageously be supplemented by feature b) of claim 1 of the present application. The further subject of the invention is thus:

• a) die Biomasse bei einem Trockenmassegehalt von weniger als 70 %, insbesondere einem Trockenmassegehalt von weniger als 50 %, einer Ammoniakfermentation unterzogen wird,
• b) die Ammoniakfermentation mittels auf einem Träger fixierter und/oder immobilisierter Mikroorganismen und/oder Enzyme durchgeführt wird und
• c) die durch die Ammoniakfermentation im Stickstoffgehalt abgereicherte Biomasse in einem sich anschließenden Schritt einer Biogasfermentation unterzogen wird;
• d) wobei optional Ammoniak während der Ammoniakfermentation, bevorzugt mittels eines Strippgases, insbesondere Luft und/oder Biogas und/oder CO₂ oder CO₂-haltigen Gas und/oder Verbrennungsabgas, aus der Biomasse entfernt wird, insbesondere kontinuierlich während der gesamten Dauer der Ammoniakfermentation entfernt wird.

Process for the production of biogas from nitrogen-containing biomass, in particular from biomass containing chicken excrement, in which

• (a) the biomass is subjected to ammonia fermentation at a dry matter content of less than 70%, in particular a dry matter content of less than 50%;
• b) the ammonia fermentation is carried out by means of carriers and / or immobilized microorganisms and / or enzymes, and
• c) the biomass depleted in nitrogen content by the ammonia fermentation is subjected to a biogas fermentation in a subsequent step;
• d) wherein optionally ammonia during the ammonia fermentation, preferably by means of a Stripping, in particular air and / or biogas and / or CO ₂ or CO ₂ -containing gas and / or combustion exhaust gas is removed from the biomass, in particular continuously during the entire duration of the ammonia fermentation is removed.

This further subject of the invention is advantageously further developed by each of the further features disclosed herein, individually and in each combination of features, wherein further features concerning the stripping can assume the above feature d).

The enzyme fixed and / or immobilized on a carrier can be in particular urease or uricase. Optionally, other enzymes, such as coenzymes, can be fixed on a carrier and / or immobilized. Furthermore, cofactors or coferments can be fixed and / or immobilized on the support. In particular, the enzymes may be involved in urea degradation or uric acid degradation. The enzymes can be used as organic material in high purity or as a largely purified material, ie, in technical purity present material. The enzymes can be recovered from dead organic material, such as by drying and milling, a bacterial mixture. In particular, the enzymes can be obtained by mechanical disruption of a bacterial mixture. In ammonia fermentation, however, the enzymes can also act in living organisms by fixing and / or immobilizing microorganisms on a support without being fixed to surfaces. Through the use of microorganisms and / or enzymes fixed and / or immobilized on a support, an ammonia yield can be achieved which exceeds the ammonia yield of a mere stripping.

The ammonia fermentation by means of microorganisms and / or enzymes immobilized on a support and / or immobilized can be carried out in particular in a stirred vessel. In preferred embodiments, the carrier can comprise inert material, in particular plastic or alginate, and / or be porous. The carrier can be formed by a stationary carrier, in particular a fixed bed. Furthermore, the carrier may be formed by the biomass itself. This applies in particular to an ammonia fermentation as dry fermentation. Alternatively or additionally, a carrier which is suspended in the biomass and separated from the biomass after the ammonia fermentation, in particular by means of gravity separation, can be used.

The fixation and / or immobilization of the microorganisms and / or enzymes can take place on inner and / or outer surfaces of the carrier. Before the wet fermentation, the biomass can be freed of suspended matter, in particular by means of a press screw separator. The ammonia fermentation can then be carried out on a biomass consisting essentially of urine. In this case, an ammonia fermentation by means of carrier-fixed and / or immobilized microorganisms is particularly advantageous when the carrier is suspended in the biomass.

The microorganisms and / or enzymes fixed and / or immobilized on a carrier can be separated after the ammonia fermentation, in particular by means of gravity separation, for example in a settler, and fed again to a nitrogen-containing biomass. The ammonia fermentation by means of microorganisms and / or enzymes fixed and / or immobilized on a carrier is particularly suitable for the ammonia fermentation of urine. The enzyme urease is particularly preferably used.

As described above, the ammonia fermentation may be formed as dry fermentation or wet fermentation. The fermentation can be aerobic or anaerobic.

Preferably, no other fermentation process takes place during the ammonia fermentation. In particular, the ammonia fermentation has a duration of 10 minutes to 48 hours, preferably from one hour to five hours. The duration of the ammonia fermentation can be adjusted in particular so that a loss of organic to biodegradable mass is as low as possible.

The ammonia fermentation can be carried out under mesophilic or thermophilic conditions. In particular, the ammonia fermentation at a temperature of 30 ° C to 75 ° C, preferably from 35 ° C to 60 ° C, are performed.

The ammonia fermentation may preferably be carried out at a pH of 7 to 9, in particular a pH of 8.0 to 8.5. An addition of chemicals such as calcium sulfate or alkalis is not required.

In particular, not all ammoniacal nitrogen (GAS-N) is converted to ammonia during ammonia fermentation. In preferred embodiments, between 20 and 80% of the total ammoniacal nitrogen is converted to ammonia. Advantageously, a portion of the total ammoniacal nitrogen may be left in the substrate to adjust a particular carbon / nitrogen ratio. In particular, the ammonia fermentation can increase the carbon content compared to the nitrogen content. In this way, in particular Low-carbon urine can be depleted in nitrogen content and then used for biogas fermentation.

Another subject of the invention is a method for producing biogas from biomass, in which the biomass is heated by means of a warm biogas stream, in particular preheated. The process does not have to include ammonia fermentation, but can advantageously be supplemented by ammonia fermentation. This further subject of the invention is further developed by each of the further features disclosed herein, individually and in any combination of features.

At least part of the biogas produced in the biogas fermentation can be used to heat the biomass. The heating of the biomass can be carried out directly by means of flowing or circulating or overflowing the biomass with a warm biogas stream and / or indirectly, in particular by means of at least one heat exchanger for indirect heat exchange. Biogas from a fermenter is usually saturated with moisture. When warm biogas comes into contact with the colder biomass, for example as stripping gas for stripping ammonia, the condensation of water vapor releases energy. This energy can be used to heat the colder biomass.

Furthermore, can be dispensed with a dehumidification of the biogas by cooling, such as with a Kompressionskälteaggregat. Dehumidification of biogas by cooling is usually required to prevent condensation in pipelines. Furthermore, dehumidification by cooling may be necessary to provide a biogas for charging cogeneration plants, which has a reduced moisture content of 50 to 80%. The elimination of a compression refrigeration unit, the own power consumption of a biogas plant can be significantly reduced. In addition, an amount of heat available for sale of the biogas plant can be increased.

In a preferred embodiment, a warm, moisture-saturated biogas stream may be passed through a biomass in a gas-liquid heat exchanger. Advantageously, a gas-liquid heat exchanger is more efficient than a gas-gas heat exchanger. In this way, the biomass can be preheated for further processing. In particular, the cooled biogas stream can then be passed to a second heat exchanger.

The second heat exchanger may preferably be formed as an indirect gas-liquid heat exchanger. The second heat exchanger can heat the cooled biogas stream, which can then be further processed as a reheated biogas stream. In this case, the moisture content of the cooled biogas stream can be reduced. As a heat source for heating the cooled biogas stream can be used warm ausgefaultes substrate. Alternatively, the return water of a combined heat and power plant can be used as a heat source for heating the cooled biogas stream.

The invention will be explained in more detail with reference to figures. The features which become apparent on the figures form each individually and in each combination of features, the objects of the claims advantageously continue. Show it:

1 in a schematic representation of a container for carrying out the ammonia fermentation as dry fermentation,

2 in a schematic representation of a stirred kettle for carrying out the ammonia fermentation as a wet fermentation,

3 in a schematic representation of a container with a mixing device for carrying out the ammonia fermentation as a wet fermentation,

4 in a schematic representation of a container with a trickling filter for carrying out the ammonia fermentation as a wet fermentation,

5 in a diagram the influence of the pH value and the temperature on the ammonia fermentation, and

6 in a schematic representation of a device for heating biomass by warm biogas.

In the 1 is schematically a container 1 shown in which nitrogenous biomass 3 an ammonia fermentation is subjected to dry fermentation. In the container 1 is a conveyor belt 5 arranged on which the biomass 3 is encouraged. The biomass 3 is formed here by chicken excrement and has a dry matter content of more than 15%.

The container 1 has a stripping gas inlet 7 and a stripping gas outlet 9 on. During ammonia fermentation, stripping gas is passed through and over the biomass 3 directed to remove ammonia from the biomass, as in the 1 by means of the arrows 11 illustrated. The speed of the stripping gas can be in particular higher than 0.2 m / s.

Further, in the container 1 a circulating device 18 provided with the biomass 3 circulated during the ammonia fermentation, in particular continuously circulated. Preferably, during the ammonia fermentation in the container 1 a slight negative pressure can be applied to ammonia from the biomass 3 both by stripping and by vacuum distillation to remove.

After ammonia fermentation, the nitrogen depleted biomass becomes 3 transferred in a container, not shown here, in which the biomass 3 is subjected to a biogas fermentation. The by means of the stripping gas from the biomass 3 Removed ammonia can be separated from the stripping gas by a scrubber. The ammonia thus obtained can be used as a starting material for a variety of different products.

The 2 shows a stirred kettle 13 in which the biomass 15 an ammonia fermentation is subjected to wet fermentation. The stirred kettle 13 has a stirrer 17 on, with which the biomass 15 can be stirred continuously. In wet fermentation, the dry matter content of the biomass 15 below 15%, preferably about 5%. At the bottom of the stirred kettle 13 are stripping gas inlets 19 intended. At the upper end, the stirred kettle 13 Strippgasauslässe 21 on. Like in the 2 Illustratively, stripping gas is continuously passed through the biomass during wet fermentation 15 guided or bubbled.

In the biomass 15 are on a carrier 22 suspended and / or immobilized microorganisms and / or enzymes suspended. The carrier 22 may be a filler of inert material, in particular plastic or alginate.

After the ammonia fermentation, the carrier 22 in particular by means of gravity separation from the biomass 15 be separated. The nitrogen depleted biomass 15 can be transferred to a container in which the biomass 15 is subjected to a biogas fermentation.

The 3 shows a container 23 in which the biomass 15 an ammonia fermentation is subjected to wet fermentation, according to a further embodiment. In the container 23 is a mixing device 25 arranged. Through the mixing device 25 Stripping gas is passed. In this way, the biomass 15 circulated by means of the stripping gas and mixed.

Another embodiment of a container 27 in which the biomass 15 is subjected to an ammonia fermentation as wet fermentation, is in the 4 shown. The container 27 has a trickling filter 29 on. The trickling filter 29 can be formed by disks or paddles. During ammonia fermentation, the trickling filter 29 at least partially into the biomass 15 plunge. In particular, the trickling filter can 29 during ammonia fermentation. On the trickling filter 29 can a movie from the biomass 15 be formed, which can be contacted by the stripping gas. The trickling filter 29 may be designed as a carrier for fixation and / or immobilization of microorganisms and / or enzymes.

In the 5 the influence of pH and temperature on the ammonia fermentation is shown in a diagram. The pH is plotted on the X-axis and the ratio of ammonia to total ammoniacal nitrogen (NH ₃ / GAS-N) is plotted on the Y-axis. The diagram shows a temperature range from 5 ° C to 60 ° C. The ratio NH ₃ / GAS-N is preferably between 0.2 and 0.8. As indicated by the dashed line in the 3 indicated, the ammonia fermentation can thus be preferably carried out at a pH of 8 to 9 and a temperature of 35 ° C to 60 ° C.

The 6 shows a device for heating biomass by warm biogas. The device has a first heat exchanger 35 and a second heat exchanger 37 on. The first heat exchanger 35 is designed in particular as a direct gas-liquid heat exchanger. In the first heat exchanger 35 becomes a warm, moisture-saturated biogas stream 31 through the biomass 3 directed. The biomass 3 is thus preheated for further processing. The cooled biogas stream 33 then becomes the second heat exchanger 37 directed.

The second heat exchanger 37 can be designed in particular as an indirect gas-liquid heat exchanger. The second heat exchanger 37 can cool the biogas stream 33 heat, which subsequently as a reheated biogas stream 41 can be further processed. In this case, the moisture content of the cooled biogas stream 33 be reduced.

As a heat source for heating the cooled biogas stream 33 can warm decomposed substrate 39 be used. Alternatively, as a heat source for heating the cooled biogas stream 33 the return water of a combined heat and power plant can be used.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 202004003883 U1 [0005]
• DE 3839599 C1 [0006]
• DE 4103308 A1 [0007]
• DE 102010033251 A1 [0008]

Claims (12)

Process for the production of biogas from nitrogen-containing biomass ( 3 ; 15 ), in particular biomass containing chicken excrement, in which a) the biomass ( 3 ; 15 ) is subjected to an ammonia fermentation at a dry matter content of less than 70%, in particular a dry matter content of less than 50%, b) ammonia during the ammonia fermentation, preferably by means of a stripping gas, in particular air and / or biogas and / or CO ₂ or CO ₂ -containing gas and / or combustion exhaust gas, from the biomass ( 3 ; 15 ) is removed, in particular continuously removed during the entire duration of the ammonia fermentation, and c) the biomass depleted in the nitrogen content by the ammonia fermentation ( 3 ; 15 ) is subjected in a subsequent step of a biogas fermentation. A method according to claim 1, characterized in that the stripping gas is moistened, in particular a moisture content of 60% to 100%, and / or the biomass ( 3 ) is humidified during the ammonia fermentation. Method according to one of claims 1 or 2, characterized in that the ammonia fermentation at a temperature of 30 ° C to 75 ° C, in particular from 35 ° C to 60 ° C, is performed. Method according to one of claims 1 to 3, characterized in that the ammonia fermentation has a duration of 10 minutes to 48 hours, in particular from 1 hour to 5 hours. Method according to one of the preceding claims, characterized in that the ammonia fermentation by means of on a support ( 22 ; 29 ) fixed and / or immobilized microorganisms and / or enzymes is performed. Method according to claim 5, characterized in that the carrier ( 22 ; 29 ) comprises inert material, in particular plastic or alginate, and / or is porous. Method according to claim 5 or 6, characterized in that the carrier ( 29 ) is formed by a stationary support, in particular a fixed bed. Method according to claim 5 or 6, characterized in that the carrier ( 22 ) in the biomass ( 15 ) and preferably after the ammonia fermentation of the biomass ( 15 ), in particular by means of gravity separation, is separated. Method according to one of the preceding claims, characterized in that the ammonia fermentation at a pH of 7 to 9, in particular a pH of 8.0 to 8.5, is performed. Method according to one of the preceding claims, characterized in that at least part of the biogas produced in the biogas fermentation for heating the biomass ( 3 ; 15 ) is used. Method according to one of the preceding claims, characterized in that the heating of the biomass ( 3 ; 15 ) directly by passing or flowing through the biomass ( 3 ; 15 ) with a warm biogas stream ( 31 ), preferably from the biogas fermentation of step c), and / or indirectly by means of at least one heat exchanger ( 35 ) for indirect heat transfer takes place. Method according to one of the preceding claims, characterized in that the dry matter content in the formed as a wet fermentation ammonia fermentation under 15%, in particular 1% to 5%.

Images