Method and device for the production of alternative peat fibres from fibre-containing biomass

Abstract

The invention relates to a method for obtaining peat-substitute fibres from fibre-containing biomass, in particular annual plants, wherein the biomass is subjected to hydrothermal digestion in a thermal hydrolysis process, preferably via steam explosion, and then a first separation of the digested biomass into a first fibre fraction and a liquid phase, which is enriched with dissolved organic and inorganic substances and finely suspended solids. According to the invention, before the hydrothermal digestion, the biomass is comminuted, then process water is added to mash the comminuted biomass, and after the hydrothermal digestion, the digested biomass is mashed again, preferably in a further step, and then the first separation is carried out.

Description

[0001] Method and apparatus for the production of alternative peat fibers from fibrous biomass

[0002] The invention relates to a process for obtaining peat substitute fibers from fibrous biomass, in particular annual plants, wherein the biomass is subjected to a hydrothermal digestion in a thermo-pressure hydrolysis, preferably with steam explosion, and subsequently separated in a first separation plant into a cellulose-rich fiber press cake, preferably with a dry matter content of at least 30%, and a liquid phase enriched with organic and inorganic substances dissolved by the digestion as well as finely suspended solids (fines), which is supplied as a fermentation substrate to a biogas plant for the production of biogas, and to a plant for this purpose.

[0003] Peat is extracted from natural bogs, which have formed over thousands of years as organic sediment from incompletely decomposed plant matter. Peat forms during the silting up of bodies of water, with growth rates of 1 to 10 mm / year, primarily from sphagnum mosses, but also from sedges, rushes, and heathers. A nutrient-poor, oxygen-depleted, or anaerobic environment and acidic bog water with pH values ​​typically between 3.4 and 3.7 are characteristic of peat fiber formation.

[0004] Depending on the degree of decomposition, peat has different structures: Younger peat, also called white peat, still shows clearly recognizable plant fibers, while peat with a higher degree of decomposition is referred to as brown or black peat. The color of peat varies with the degree of decomposition, from reddish-brown to dark brown to almost black. Completely decomposed peat is also called pitch peat.

[0005] Peat is defined as extracted fibrous material with a specific dry mass of at least 30% (see also DIN 11540). Typical characteristics include an ash content of 2–20% and a humic acid content of 10–20%. Historically, and until a few years ago, peat bogs were extensively and economically exploited to produce fuel, although its calorific value is inferior compared to other energy sources. Currently, the primary use of peat is as a substrate in horticulture and the plant industry.

[0006] In 2022, 20 million tons of peat were extracted from the world's 271 million hectares of peatlands for the production of growing media for professional and amateur gardeners. Of this, 2.6 million tons were extracted in Germany, 2.3 million tons in Sweden, and 5.4 million tons in Finland. Extraction volumes are trending downward, as it has been recognized that peatlands are important carbon sinks, and their irreversible destruction is incompatible with the goals of carbon neutrality.

[0007] The properties of peat that make it particularly important for use as a planting substrate include its high structural stability (i.e., low degradation) and its high water retention capacity, which is several times its own weight. Furthermore, peat has a high pore volume, is largely homogeneous, acidic (pH 2.5 to 3) and therefore flexible in its processing, low in pollutants and nutrients, and largely sterile.

[0008] Substrates based on wood or bark are among the materials being tested and used as peat substitutes, but they do not achieve the unique combined properties of peat. Other plant-based raw materials, such as mechanically shredded or extruded grasses or other plants, are only suitable to a limited extent because they are usually not structurally stable and exhibit high nitrogen immobilization during decomposition.

[0009] The object of the invention is therefore to provide a method that produces a high-quality peat substitute from plant fibers, i.e., a peat substitute that is similar or close to peat in its essential properties, in an environmentally friendly, energy-saving and economical way.

[0010] This task is solved by the procedure described below.

[0011] According to the invention, fibers from fibrous biomass, in particular annual plants, are processed. The biomass is subjected to hydrothermal digestion in a thermo-pressure hydrolysis, preferably with steam explosion, followed by a first separation of the digested biomass into a first fiber fraction and a liquid phase enriched with dissolved organic and inorganic substances as well as finely suspended solids. Prior to the hydrothermal digestion, the biomass is comminuted, and process water is subsequently added to mash the comminuted biomass. After the hydrothermal digestion, the digested biomass is preferably mashed again in a further step, followed by the first separation.

[0012] The first fiber fraction is preferably present in the form of a cellulose-rich fiber press cake.

[0013] According to the invention, process steps may be carried out in a different sequence, overlapping or simultaneously, unless explicitly stated otherwise or technically necessary. It may also be provided that further steps are carried out between the specified steps.

[0014] Mashing refers to the addition of liquid and preferably mixing with the liquid.

[0015] Each of the described mixing steps can involve the addition of one or more different liquid phases, either together and / or separately in time and / or space. For example, during a mixing step, at least a portion of the filtrate from the first filtration and a concentrate from a membrane filtration process, which will be discussed in more detail later, can be added. These two liquid phases can be mixed beforehand, for example using a mixing device, or they can be added separately.

[0016] Process water is understood to be a liquid consisting of water, in which other components may also be dissolved or mixed. For example, the process water can be fresh water or an aqueous liquid obtained during the process, such as at least a portion of the liquid phase. Accordingly, the process water may also contain solids.

[0017] Re-mixing after hydrothermal digestion is optional.

[0018] Particularly if sufficient liquid is available, this step can also be omitted. In this sense, a process can also be provided according to the invention in which fibers from fibrous biomass, in particular annual plants, are used, wherein the biomass is subjected to hydrothermal digestion in a thermo-pressure hydrolysis, preferably with steam explosion, and subsequently a first separation of the digested biomass into a first fiber fraction and into a liquid phase enriched with dissolved organic and inorganic substances as well as finely suspended solids takes place, wherein it is provided that the biomass is comminuted before the hydrothermal digestion, and process water is subsequently added to mix the comminuted biomass.

[0019] Milling the mashed biomass is optional, but improves the quality of the first fiber fraction. It can be done together with or as part of the mashing process.

[0020] The starting material preferably comprises mature, lignocellulose-rich plants or plant residues. Preferably, the starting material includes naturally growing or cultivated biomass crops such as reeds, sedges, miscanthus, reed canary grass, giant reed, bamboo, or Napier grass, as well as crop residues such as straw or by-products of cereals and other agricultural crops, and selected fiber-rich agri-industrial residues such as bagasse or EFB.

[0021] Organic waste such as green waste can also be used for the process and be included in the starting material.

[0022] However, the use of plants and plant remains of sweet grasses and sedges, which may be included in the starting material, is particularly preferred.

[0023] Preferably, the material is moistened, whereby this moistening can be carried out in one stage, two stages or in multiple stages.

[0024] In a first step, preferably shredded biomass material, preferably to a size of 10 to 50 mm, particularly preferably 10 to 30 mm, can be adjusted to a predetermined dry matter content, preferably between 20 and 35%, particularly preferably between 25 and 30%, by adding process water, preferably filtrate or wash water recycled from the subsequent process. Preferably, this first step comprises a first substep in which a quantity of process water, preferably defined by weighing, is added to the biomass, preferably in a batch mixer, which may also be designed as a shredder. Preferably, the adjustment of a specific dry matter content of 40 to 50% in the case of two- or multi-stage moistening, or of 20 to 35% in the case of single-stage moistening, is supported by a dry matter measurement, e.g., using NIR technology.

[0025] After sufficient mixing time, typically 5 to 20 minutes, the material, discharged as a partial or complete batch, can be conveyed directly to the hydrothermal digestion process, or preferably transferred to an intermediate tank, designed, for example, as a scraper or moving floor, and stored for a period of at least 30 minutes, advantageously for more than one hour and up to 4 hours. This settling time promotes the absorption of the added process water into the plant structure, which has been fibroused by the comminution process and is beneficial for the subsequent hydrothermal digestion process.

[0026] The intermediate tank can be used to feed a hydrothermal digestion plant for biomass, either discontinuously or continuously.

[0027] If a two-stage humidification process is planned, the second addition of process water takes place in the area where the pre-moistened biomass is fed into the hydrothermal digestion plant.

[0028] The hydrothermal digestion plant can be operated both discontinuously and continuously. Preferably, pre-steaming of the moistened biomass is provided by recirculating process steam and condensation in the substrate. A particularly suitable configuration for this application is disclosed in EP 2 177 280 and EP 2 576 757.

[0029] The hydrothermal digestion preferably takes place in a heated pressure reactor under saturated steam conditions at temperatures between 150°C and 180°C, preferably between 165°C and 175°C, with reactor residence times of up to 120 minutes, typically between 60 and 90 minutes. Heat can be supplied either indirectly by heating the vessel, e.g., via a jacket heater, or by directly adding hot steam, usually saturated steam.

[0030] The hydrothermal breakdown of plant biomass in an aqueous environment, at sufficient treatment temperature, results in the release of hemicelluloses and proteins from the plant structure, among other things.

[0031] This process also washes out nutrients such as nitrogen, which can promote microbial degradation.

[0032] With increasing treatment temperature in hydrothermal digestion, a progressive conversion of oligomeric sugars formed from hemicelluloses occurs, e.g., from xylose to acetic acid. This process effectively lowers the pH value of the medium to values ​​below pH 5.5, and can even reach pH 3.5.

[0033] In this case, the pH reduction is proportional to the degree of digestion, i.e., with increasing treatment temperature and treatment duration, the pH value decreases further.

[0034] During the hydrothermal digestion, the medium typically remains in the system at a temperature of at least 150°C, preferably above 160°C, for a period of at least 60 minutes.

[0035] This kills both germs and viable seeds, e.g. those of weeds such as blackgrass, and creates a sterile substrate.

[0036] The hydrothermal digestion is preferably combined with a shock relaxation step accompanied by a steam explosion.

[0037] This process utilizes the effect that material boiling under increased pressure releases excess thermal energy from the system when the ambient pressure is reduced. This occurs through the evaporation of a corresponding proportion of water in the system, typically between 10 and 15% in the preferred pressure range of 5 to 10 bar absolute.

[0038] If the pressure drop occurs spontaneously, i.e., within a few seconds, microbubbles formed from droplets develop, with a volume expansion factor of approximately 1000. This partial volume expansion of water, located both within and on the outer surfaces of partially dissolved fibrous structures, exerts enormous localized physical forces on the fiber structures, resulting in exceptionally fine fraying of the aggregates. To optimize this effect, a pressure drop of at least 5 bar is required, so—according to the saturated steam curve—a minimum temperature of 160°C, or even better, 170°C, should preferably be set before shock release.

[0039] Hydrothermal pulping with shock relaxation already defines essential characteristics for peat substitute fibers. After treatment, the fibers obtained are highly acidic, finely fibrous, and sterile.

[0040] In a subsequent step, the aqueous fiber suspension with a dry matter content between 20 and 35%, preferably between 25 and 30%, is diluted in a mixing vessel to a concentration between 3 and 12%, preferably between 5 and 10%, and intensively homogenized by using a mechanical mixer.

[0041] Mixers with homogenizing properties are particularly suitable for this purpose, e.g., jet mixers with slotted guide tubes and sufficient horizontal flow component.

[0042] The dilution medium preferably used is filtrate from the subsequent dewatering process. Fresh water is preferably only used to the extent necessary to achieve a sufficiently low dry matter content for washing and the subsequent refining step. The typical filtrate-to-fresh water ratio is between 3:1 and 5:1. To control the fresh water addition, a solids measurement device integrated into the tank or discharge pipes, e.g., a microwave probe, can be used to monitor the amount of fresh water added.

[0043] Setting up a less concentrated fiber suspension is advantageous for washing out diffuse fine particles and essential for the subsequent step of refining the fibers.

[0044] A refiner machine preferably comprises stationary and rotating grinding units, e.g., in disc, cone, or roller form, which, by rotating against each other, selectively introduce compressive and shear forces into the medium. By appropriately profiling the grinding units and by selecting the appropriate flow rate and specific energy input, targeted effects of internal fibrillation through compression and bending or external fibrillation through shearing of the fibers within the grinding unit can be achieved.

[0045] The typical specific energy input is preferably 100 - 200 kWh / ton, depending on the desired degree of fibrillation.

[0046] The refiner is preferably fed by forced feeding.

[0047] The combination of hydrothermal extraction level and mechanical refining level allows for the targeted generation of different fiber structures, similar to the appearance of peat in qualities ranging from white peat to black peat.

[0048] As our own investigations show, for example, extending the cooking time from 60 to 90 minutes at the same maximum temperature and specific refining energy input leads to significantly different fiber length distributions. Similarly, a higher temperature at the same time and grinding energy produces a similar effect. Increasing the grinding energy also results in a corresponding change in the fiber length distribution.

[0049] The combination of mechanical refining and the preceding hydrothermal pulping enables particularly fine fibrillation of the fibers, especially with regard to internal fibrillation. This results in a largely homogeneous, cellulose-like, highly interlocking fiber matrix characterized by a high pore volume and the associated water absorption and retention capacity.

[0050] This fulfills other typical characteristics of natural peat, namely homogeneity and high water absorption and retention capacity.

[0051] Following the refining step, the produced fibers are separated and dewatered by a dewatering machine, preferably a screw press, during the initial separation process. The resulting filtrate effectively removes readily biodegradable substances such as dissolved sugars, proteins, and organic acids from the fibers.

[0052] The TDH (thermo-pressure hydrolysis) process and the subsequent leaching of dissolved nutrients also extract significant amounts of plant nutrients such as nitrogen, phosphorus, and potassium from the mostly nutrient-poor plant parts of the raw material, which are then removed with the filtrate. Other soluble salts are also considerably reduced by leaching.

[0053] This fulfills another desired and typical characteristic of natural peat, namely low nutrient and salt content.

[0054] In one possible embodiment of the invention, substances are added to the fibers after hydrothermal digestion that cause a targeted breakdown of the cellulose contained in the fibers, for example enzymes (cellulases) or bacterial strains specializing in cellulose degradation. This can be done both before an initial separation and during a subsequent mashing.

[0055] To optimize the cellulose degradation process, it is advantageous to adjust the environmental conditions favorably, for example, to maintain a pH of around 5 at temperatures between 45 and 55°C. Depending on the additive and its quantity, this process typically takes between 4 and 96 hours, preferably between 10 and 48 hours. After subsequent separation, the pressed material contains fibers with a significantly reduced cellulose content. The filtrate can be reused, for example, as mashing water to recirculate and concentrate active bacteria in the process. The reduction of cellulose in the fibers impairs their biodegradability, thereby improving the resistance of the peat substitute fibers to premature decomposition.This is in line with the product properties, as good biodegradability of the peat substitute substrate is undesirable because microbial degradation removes nutrients, especially nitrogen, from the substrate, making them unavailable for plant growth. This effect is known as nitrogen immobilization and is a crucial, even critical, aspect in assessing the quality of peat substitute fibers.

[0056] In natural peat, the cellulose-rich fibers are protected from rapid microbial degradation by a high natural content of humic and fulvic acids. To achieve this effect in peat substitute substrates, a preferred embodiment of the invention provides for the artificial addition of such humic and fulvic acids to the process in order to replace, as far as possible, the more readily degradable organic acids (e.g., acetic acid) from the hydrothermal digestion process.

[0057] Such humic or fulvic acids (hereinafter also referred to simply as humic substances) can be obtained, for example, from compost leachate or extracted from lignite or biochar.

[0058] The addition of such humic substances can take place in concentrated or diluted aqueous solution as well as in granular form.

[0059] According to this invention, several possibilities for adding humic substances are provided, which can be used individually or in combination:

[0060] 1) Addition during the mixing of dry substrates after the substrate has been crushed or mixing into moist raw materials before thermopressure hydrolysis treatment, or TDH treatment for short.

[0061] This variant artificially lowers the pH value during the pulping reaction, thereby supporting the pulping process and allowing it to proceed at a reduced temperature. Furthermore, more intensive impregnation of the fibers with humic acids is possible during the cooking process at increased pressure and temperature. 2) Addition after the TDH step to enrich the hot, cooked substrate accordingly.

[0062] 3) Addition in the subsequent mashing step of the fiber material, which has already been dewatered at least once in a separation, thereby improving the absorption of humic acids into the pressed fiber cake. The humic-rich filtrate from a subsequent separation is recirculated to achieve the highest possible utilization of the added humic substances.

[0063] Particularly preferred is an addition according to 1), followed by 3), or a combination of 1) and 3).

[0064] The filtrate from the separation of the fiber after a TDH contains dissolved sugars, proteins and organic acids as well as dissolved salts produced by the cooking process.

[0065] The filtrate also contains suspended compounds, essentially small fiber fragments, which contain predominantly lignin or, to a lesser extent, hemicellulose and cellulose.

[0066] In one variant of the invention, these suspended solids are separated from the filtrate and added to the fiber pressing material because these fine particles exhibit useful product properties, particularly when the lignin content of the particles is increased, and thus increase the raw material yield without impairing the product quality of the peat substitutes.

[0067] The separation of the suspended solids is carried out, for example, by single- or multi-stage microfiltration, in particular vibrating sieves or a centrifuge or a combination of both methods.

[0068] The collected filtrates, whether or not suspended solids have been removed, are advantageously fed into a biogas plant. This plant uses the organic components to produce biogas or biomethane through anaerobic digestion, which is then used to cover the plant's energy needs, particularly the thermal energy requirements of the TDH treatment, as far as possible. This is achieved, for example, by burning the biogas in a gas burner and heating thermal oil with the resulting hot exhaust gas. So-called "high-rate reactors," including UASB, EGSB, fixed-bed, and sludge-bed reactors, are particularly suitable for the anaerobic treatment of the filtrates.

[0069] Sludge bed reactors exhibit a high tolerance to particulate substances, which is advantageous for the process, and are particularly suitable for arrangements without filtrate removal.

[0070] Fixed-bed reactors with biomass immobilized on static or mobile support structures are particularly suitable for depleted filtrates, primarily due to a significantly lower requirement for dissolved macronutrients such as nitrogen and phosphorus for the fermentative conversion of the substrate. Nitrogen and phosphorus are typically present only in small amounts in the raw materials used, potentially necessitating the addition of these nutrients for biogas production.

[0071] The fermentation residues from the anaerobic fermentation of the filtrate contain, in addition to cell remains of the biocenosis, organic residues that could not be broken down in the anaerobic environment.

[0072] One way to utilize these digestate residues is to use them as agricultural fertilizer, either after nutrient concentration through membrane processes or evaporation, or directly without further treatment.

[0073] One variant of this invention provides for subjecting the liquid digestate to aerobic treatment in a further treatment stage after anaerobic fermentation. This can be implemented as a so-called activated sludge process, preferably with an ultrafiltration system to retain the active biomass (so-called MBR process - membrane bioreactor). Aerobic-biological processes with submerged stationary (fixed bed) or mobile (MBBR - moving bed bioreactor) growth surfaces are also suitable.

[0074] The goal of this treatment is the further breakdown of organic components.

[0075] In this process, some of the organic substances are converted into non-biodegradable organic compounds, primarily humic substances. These humic substances are selectively recycled back into the process and, as previously described, added either before or after the TDH process as a component of recirculated process water.

[0076] In one embodiment of the invention, this can also be achieved after selective separation and preferably concentration, e.g., by a suitable membrane system that does not retain dissolved salts or mineral fertilizer components (nutrients) in the humic substance-rich concentrate. Selective separation preferably refers to at least size-selective separation. This allows larger molecules such as humic substances to be retained, while smaller molecules such as salts are carried away with the filtrate. Preferably, ultrafiltration membranes and / or nanofiltration membranes are used for membrane filtration.

[0077] With this preferred variant, a peat substitute can be produced from fibrous plant raw materials, impregnated with humic substances produced in-house and thus more resistant to microbial degradation.

[0078] In summary, the described invention makes it possible to produce a peat substitute from fibrous plant raw materials, which in the best case

[0079] - has a homogeneous fiber structure, is strongly acidic, sterile, low in nutrients, has a high water absorption and water retention capacity, and exhibits good resistance to nitrogen immobilization.

[0080] By selecting the intensity of the digestion in the TDH (thermal digestion process) as well as in the mechanical post-treatment, different fiber qualities can be specifically produced, and peat qualities from white to black peat can be specifically replicated.

[0081] By selecting different plants as raw materials, whether as mono- or mixed substrates, products or mixtures with specific properties can be created. Preferably, mature harvest by-products (straw from various plants) as well as biomass plants from dry, normal, and wet soils (also known as paludiculture) are used.

[0082] In principle, suitable plants include sweet grasses (cereals and other grasses), sedges, maize, fiber plants, various bamboo varieties and oilseeds, as well as fibrous by-products from the agricultural industry (e.g. bagasse, EFB, tea residues, hop vines).

[0083] The product or fiber yield, when calculated on dry matter, is typically 50-80%, preferably 60-70%, based on the starting material.

[0084] The invention will now be explained in more detail with reference to a non-limiting embodiment shown in the figure. It shows:

[0085] Fig. 1 shows a method in an embodiment according to the invention in a block diagram.

[0086] The process shown in the block diagram begins with a pretreatment 1 of the provided fibrous biomass. During this pretreatment, the biomass, and in particular the fibers within it, are shredded. A mill, a crusher, a shredder, and / or another suitable tool may be used for this purpose.

[0087] Pretreatment 1 also includes mashing the biomass after it has been shredded. Process water is added to the biomass in the form of a filtrate. This filtrate is later recovered in the process, for example, as indicated by the arrows, through steps 6 and / or 16, which will be explained in more detail later. It may also contain solids.

[0088] This mashing process takes place in two or more stages, whereby in a first stage the dry matter content of the biomass is adjusted to about 45% and in a second stage this mixture is stored in an intermediate container for about 2.5 hours.

[0089] Pretreatment 1 further includes pre-steaming after the second stage of mashing. Following pretreatment 1, the shredded biomass undergoes thermo-pressure hydrolysis (TDH) 2, during which the biomass is heated to 170°C for, for example, 65 minutes. This is followed by a sudden pressure reduction, resulting in a steam explosion 3, which further reduces the size of the fibers.

[0090] This is followed by a renewed mashing process 4, preferably in a pulper, in which the dry matter content is adjusted to approximately 5% by adding process water.

[0091] The biomass is then milled 5, preferably in a refiner. After milling 5, a first separation 6 takes place, preferably in a separation unit such as a filter device, centrifuge or similar device, yielding on the one hand a first fiber fraction 7 and on the other hand a liquid fraction 11, for example in the form of a filtrate.

[0092] Similarly, the addition of cellulose-degrading enzymes or bacterial cultures is possible. Under suitable environmental conditions, for example at 50°C and pH 5.5, these selectively degrade the cellulose in the fibers over a period of, for example, 10 hours in the mash tank or pulper, or even in a separate reaction vessel, thereby reducing the cellulose content in the fibers. In principle, these additives can be used at any point after hydrothermal pulping; however, addition after refining (5) is particularly advantageous, either before separation (6) or afterward during a second mashing (8) followed by separation (9).

[0093] When using cellulose-degrading bacterial cultures, the filtrates from such a separation are preferably recirculated for re-mixing in order to enrich these bacterial cultures in the system.

[0094] The first fiber fraction 7, or a portion thereof, can then be subjected to a third (further) mashing step 8, whereby, as in the previously discussed mashing steps, an enrichment of humic acid can be achieved by adding humic substances. This mixture can be subjected to a second separation step 9, yielding a second fiber fraction 10 and a second liquid phase. The liquid phase 11 can be subjected to microfiltration 12. The solid phase obtained from microfiltration can then be thickened 13 and used for the third mashing step 8. The microfiltration 12 can be carried out, for example, using a single-stage or multi-stage vibrating screen.

[0095] The filtrate from microfiltration 12 and / or the filtrate from the second separation 9 can be subjected to fermentation 14, preferably biogas fermentation 15 in a biogas digester, thereby producing biogas. This biogas can be used to operate the process, particularly preferably for the thermal pressure hydrolysis 2 (indicated by the arrows). After biogas fermentation 15, the filtrate can be subjected to aerobic treatment 15, for example, using a wastewater treatment plant, and subsequently to further filtration 16, preferably membrane filtration. From this, the retained phase, preferably in the form of a humic acid-rich concentrate, can be recycled to steps 1, 4, or 8, and high-quality water can be obtained for removal.This keeps environmental impact as low as possible while simultaneously using valuable resources efficiently.

Claims

PATENT CLAIMS 1. A process for obtaining peat substitute fibers from fibrous biomass, in particular annual plants, wherein the biomass is subjected to a hydrothermal digestion in a thermo-pressure hydrolysis, preferably with steam explosion, and subsequently a first separation of the digested biomass into a first fiber fraction and into a liquid phase enriched with dissolved organic and inorganic substances as well as finely suspended solids takes place, characterized in that the biomass is comminuted before the hydrothermal digestion, process water is subsequently added to mash the comminuted biomass, and preferably that after the hydrothermal digestion, the digested biomass is mashed again in a further step and then the first separation takes place.

2. Method according to claim 1, characterized in that the biomass is reduced to a size of 10 to 50 mm, preferably to 10 to 30 mm, during the comminution process.

3. Method according to claim 1 or 2, characterized in that the mashed biomass has a dry matter content of 20% to 35%, preferably between 25% and 30%, prior to hydrothermal digestion.

4. A method according to any one of claims 1 to 3, characterized in that the mashing of the biomass is carried out in two stages, wherein first a dry matter content of the mashed biomass of 40% to 50% is achieved by adding process water, and then preferably storage in an intermediate container with a resting time of at least 30 minutes, particularly preferably between 1 and 4 hours, takes place before the thermo-pressure hydrolysis is carried out with the mashed biomass.

5. Method according to one of claims 1 to 4, characterized in that, in addition, after mashing the crushed biomass, a pre-steaming of the mashed biomass takes place before the thermo-pressure hydrolysis is carried out with the mashed biomass.

6. A method according to any one of claims 1 to 5, characterized in that the mashed biomass is subjected to hydrothermal digestion in a heated pressure reactor under saturated steam conditions at temperatures between 150°C and 180°C, preferably between 165°C and 175°C, for reactor residence times of up to a maximum of 120 minutes, preferably 60 to 90 minutes.

7. Method according to any one of claims 1 to 6, characterized in that the decongested biomass is diluted to a dry matter content between 3 and 12%, preferably between 5% and 10%, during the re-mashing process, preferably in a mashing container, and homogenized by using a mechanical mixer.

8. Method according to any one of claims 1 to 7, characterized in that, after hydrothermal digestion and preferably after re-mashing, the digested biomass is subjected to milling before the first separation.

9. Method according to claim 8, characterized in that the decongested biomass is ground in a refiner with an energy input of 100 to 200 kWh / t during the grinding process.

10. Method according to one of claims 8 or 9, characterized in that following the grinding, preferably directly after the grinding, at least one separation of the decongested and ground biomass from a liquid phase takes place.

11. Method according to one of claims 1 to 10, characterized in that after the first separation a further mixing step is carried out, followed by at least a second separation step in which a second fiber fraction is separated from a liquid phase.

12. Method according to one of claims 1 to 11, characterized in that the addition of cellulose-degrading enzymes or bacterial cultures takes place during the mashing process after the hydrothermal digestion.

13. Method according to claim 12, characterized in that a filtrate produced by separation is recirculated for re-mashing to enrich degradation-active ingredients such as bacteria.

14. Method according to one of claims 1 to 13, characterized in that humic substances are added during the mashing process prior to the hydrothermal digestion and / or during the re-mashing process after the hydrothermal digestion prior to the at least one separation and / or after the at least one separation in a further mashing step, to which at least one further separation step follows.

15. Method according to one of claims 1 to 14, characterized in that the filtrates obtained from the at least one separation are supplied to a biogas plant.

16. Method according to any one of claims 1 to 15, characterized in that the filtrates obtained from the at least one first separation are subjected to microfiltration.

17. Method according to claim 16, characterized in that the filtrate obtained from microfiltration is supplied to a biogas plant.

18. Method according to claim 16 or 17, characterized in that the solid phase obtained from microfiltration is thickened and then at least partially mixed with the first fiber fraction obtained from the first separation, and subsequently a second fiber fraction is separated in the further, second separation step.

19. Method according to claim 18, characterized in that humic substances are added during the mashing of the first fiber fraction.

20. Method according to one of claims 13 to 20, characterized in that the filtrate from the second separation step is supplied to a biogas plant.

21. Method according to claim one of claims 8 to 19, characterized in that the filtrate from the second separation step is used in the renewed mashing step before milling.

22. Method according to any one of claims 1 to 21, characterized in that mature, lignocellulose-rich plants or plant residues, such as reeds, sedges, miscanthus, reed canary grass, giant reed, bamboo or Napier grass, crop residues such as straw or by-products of cereals and other agricultural crops, fiber-rich agri-industrial residues such as bagasse, tea residues, hop vines or waste from palm oil production (EFB) and / or biowaste such as green waste, are used as biomass.

23. Method according to one of claims 1 to 22, characterized in that the hydrothermal digestion is carried out at least partially in a heated pressure reactor under saturated steam conditions.

24. Method according to one of claims 1 to 23, characterized in that at least a part of at least one filtrate, preferably after being fed to a biogas plant, is subjected to at least one aerobic treatment, preferably one clarification.

25. Method according to one of claims 1 to 24, characterized in that at least a part of at least one filtrate, preferably after aerobic treatment, is subjected to filtration, preferably membrane filtration, wherein preferably at least a part of a retained phase is returned to the biomass, preferably during at least one mashing step. 2025 11 21 HA

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