Method for the material and energetic utilization of biogenic residues from potato processing and arrangement for carrying out the method

Abstract

Method for the material and energetic utilization of biogenic residues from potato processing plants by using the residues in a wet fermentation process, by concentrating the total nutrient potential in the form of nitrogen, phosphorus, potassium and sulfur in a fertilizer fraction obtained from the fermentation residues, and by providing the desulfurized biogas for energy utilization, characterized in that that yeast fermentation is used for bioethanol production and / or methane fermentation for biogas production as wet fermentation processes, that the resulting biogenic residues from the processing of starchy root vegetables, such as potatoes, sweet potatoes, cassava, tapioca, and other root vegetables, are obtained in the form of peelings, starchy white waters, residues from the cleaning of input materials, stillage from the upstream ethanol distillation, aqueous media from periodic plant cleaning, and / or sludge. that the available residual materials are subjected to a suspension process, that, by using additives with a dry matter content of at least 25% in the biosuspension, a dry matter content between 12 and 18% is achieved, that the generated biosuspension is subjected to an aerobic hydrolysis process, that the hydrolysate produced from the biosuspension is fed into an anaerobic fermenter system consisting of at least one hydraulically and partially mixed fermenter with an initially introduced and continuously reproducing special culture, that the potential of plant nutrients contained in the utilized input materials is obtained as a mixture of the solid phase of the fermentation residues and the liquid washing media resulting from the removal of inhibitory substances from the biofiltrates with high levels of ammonium and sulfur compounds, and that the desulfurized, dried and compressed biogas is used for the combined generation of electrical and thermal process energy.

Description

Area of ​​application

[0001] The invention relates to a process for the material and energy recovery of biogenic residues from potato processing and a system for implementing the process. Such a technical solution is needed to increase disposal reliability, reduce costs, reduce pollutant emissions, and increase independence from fossil energy supplies in the potato processing industry. State of the art

[0002] Modern production facilities for processing potatoes, cassava, tapioca, cassava, and similar starchy tubers operate worldwide using similar process technology. The greatest potential for organic and thus energy-rich biomass within the entire range of residues from a potato processing plant is the resulting peeling mass. In its dried state, this residue is a well-tolerated, energy-rich, protein-rich, and storable animal feed. However, given rising energy prices, it can hardly compete with alternative protein feeds such as soybean meal or rapeseed cake. In its moist state, the peeling mass is usually used as a feed supplement. However, due to the risk of infection from this excellent breeding ground for microorganisms, it is heavily dependent on the purchasing livestock farmers and on reliably functioning transport logistics.

[0003] Organic residues unsuitable for animal feed must generally be disposed of as waste, even though they also possess considerable energy potential and plant nutrient content. There are known examples where, to avoid dependence on local livestock farmers, the resulting residues are applied to agricultural land as soil improvers. To prevent damage to soil life, the applied residues must be immediately incorporated into the cultivated layer due to the potential for soil surface crusting caused by the starch content. At the same time, potato processing is being significantly impacted by rising energy prices.

[0004] This is also why there is a strong interest among potato processing plant operators due to the competitive pressure in the industry.

[0005] Despite this situation, no example has been reported in industrial practice to date of the predominantly wet biogenic residues from potato processing being recycled for material and energy purposes.

[0006] The resulting residues could be considered to be materially and energetically utilized if, while avoiding thermal drying through wet fermentation, biogas with a calorific value of at least 1,140 kWh / t, including at least 450 kWh / t of electrical energy, were produced from the at least 22% dry biomass in the moist hull masses, while fully preserving the plant nutrients. Known technical solutions are limited to the utilization of biosludge from wastewater treatment through methane fermentation, which utilizes only a comparatively small portion of the actually available potential.Both the virtually continuous generation of waste and the nearly constant energy demand for electrical energy, heat energy, and cooling energy, as well as motor fuels, create almost ideal conditions for the use of methane fermentation processes for energy generation from renewable sources and for the simultaneous utilization of the resulting fermentation residues for fertilizer production. Therefore, there has been no shortage of attempts to further develop the state of the art so that the use of biogenic waste can contribute, in particular, to reducing the fossil energy requirements of a potato processing facility. The special features of biogenic waste from industrial potato processing are their fine grain size and the constant generation of these wastes.The obvious barriers to the use of these residues in biotechnological recycling plants are the considerable contents of proteins and / or crude fibers, which supposedly prevent monofermentation, whether in the context of yeast fermentation for ethanol production or methane fermentation for biogas production.

[0007] DE 3627253 C2 (1986), for example, describes a process for the biological treatment of substrates containing organic substances, wherein the central treatment stage for the solids-depleted phase of a biosubstrate and the solids-rich phases of the biosubstrate liquefied in subsequent treatment steps is a hydrolysis reactor for the aerobic degradation of the organic substances contained in the biosubstrate.

[0008] However, the described solution provides no information on the treatment of the resulting hydrolysis gases, which are known to also contain fatty acid vapors from the aerobic decomposition of selected phases of the biomaterials introduced. Some of the substrates discharged from the hydrolysis reactor are returned to the hydrolysis stage without further pretreatment.

[0009] The remaining solid-rich phases are separated from remaining undissolved components after several intermediate treatments and removed from further fermentative treatment.

[0010] The claimed suitability for the utilization of production residues from potato processing, which are known to be rich in solids, is not given due to the lack of available adapted methane bacteria cultures and the lack of culture-preserving fermentation technology for the disclosed technical solution.

[0011] Furthermore, DE 4000834 C2 (1990) discloses a technical solution for the biomethanation of organic residues from breweries, which could in principle also be applied to residues from potato processing. It involves adding the usual residues from the immediate production process to the resulting wastewater and subjecting the wastewater, now extremely highly contaminated with organic matter, to a multi-stage fermentation process. The disclosed process utilizes cascade-shaped loop reactors that are at least partially filled with packing and thoroughly mixed by compressed process gases. The recognized need for hydrolytic pretreatment in a first fermentation stage is explicitly met by chemical, enzymatic, and optionally aerobic to anaerobic measures.Apparently in the interest of energetically exploiting the predominantly lignocellulose- and protein-containing pulp components, these should preferably be used after comminution to < 1.0 mm. The described process assumes the possibility of extracting pure water from the digestate resulting from the final anaerobic treatment stage using ultrafiltration, which, however, should also serve as a source of additional degassing. A post-digestion stage is to be used for further solids reduction, and an aerobic post-treatment stage is to be used for odor elimination and nitrogen reduction. The theoretical approach of this proposal contradicts widely confirmed practical experience in several respects and, consequently, has not been incorporated into modern potato processing technology.

[0012] For example, it is generally not possible to maintain a sufficiently stable, specialized bacterial culture suitable for the utilization of lignocellulose- and protein-rich feedstocks in fully mixed fermenters. The recognized requirement for pre-hydrolysis of biosuspensions containing potato processing residues, however, can only be met by adding enzymes or by anaerobic treatment if additive costs are not a factor, or if large-scale additional anaerobic systems are available. In the proposed technical solution, the aerobic nitrogen reduction of the digestate after the multi-stage fermentation process serves exclusively to obtain low-contaminated wastewater, accepting the return of the reduced nitrogen load to the atmosphere.In contrast, eluates from individual fermentation stages are to be recycled to other fermentation stages to control optimal CNP ratios in the respective fermentation substrates. This ignores a crucial prerequisite for maintaining a sustainable fermentation process, according to which the removal of nitrogen and sulfur compounds from the closed fermentation system is essential to prevent the formation of toxic concentrations of these compounds in the fermentation substrate. This is particularly significant because protein-rich and thus nitrogen- and sulfur-rich substrates are introduced into the fermentation process in the form of peeling masses from potato processing.

[0013] DE 4226087 A1 (1992) describes, among other things, a process for the biological treatment of organic substances, in particular for anaerobic biological hydrolysis for subsequent biomethanation. The disclosed technical proposal attempts to solve the problem of making the processes known from the prior art simpler and more efficient and, in particular, to provide a control concept by which the pH value, the solids concentration, and the solids residence time can be adjusted independently of one another. The essential means of this technical solution consist in the hydrolytic acidification of the predominantly dissolved organic components of a biosuspension in a first anaerobic hydrolysis stage and the hydrolytic acidification of a solids-rich fraction of the biosuspension to be treated in a second anaerobic stage, so that both hydrolysates can be subjected to methanation in a third treatment stage.Even with these proposals, it is not possible for several reasons to conduct the process of material and energy recovery of potato processing residues with the required energy efficiency and stability.

[0014] The proposed procedures cannot sustainably treat the actual and possibly temporally varying waste stream of a potato processing plant due to the required pH control, nor is the solid fraction discharged from the anaerobic process before the methanation stage available for further energy recovery. Furthermore, any prerequisites for limiting the levels of nitrogen and sulfur compounds in the digestate to concentrations below the toxicity threshold are lacking if protein-rich peeling masses from potato processing are to be fed into the system.

[0015] DE 19613397 C2 (1992) describes a process for the biological treatment of wastewater that differs from the state of the art available at the time in that the biosuspension to be treated, in the form of wastewater, is first subjected to phase separation, with only the solids-rich phase being fed directly to the fermenter. The low-solids phase from this process step is to be subjected to ammonia stripping, although in the case of potato peelings, the nitrogen inventory is known to initially be predominantly in protein form, and ammonium is only formed from this during the anaerobic fermentation process. According to the proposed technical solution, the described attempt at nitrogen removal certainly does not serve to prevent nitrogen accumulation to toxic concentrations during the fermentation process.The aerobic hydrolysis of the effluent from the ammonia stripping process therefore has almost no influence on the required dissolution of the lignocellulose composite and on the exploitation of the energy potential of the lignocellulose-containing residues from potato processing introduced with the peeling masses.

[0016] DE 19615551 C2 (1996) describes, among other things, a technical solution for the multi-stage treatment of biomass to produce biogas. The developed process is intended to solve the problem of achieving maximum degradation of the cell contents of biological waste with minimal investment and operating costs. With short residence times of the biomass in the anaerobic environment, an economically viable gas mixture of methane and carbon dioxide must be obtainable, whereby the amount of biogas must be maximized and the amount of fermentation compost requiring subsequent decomposition minimized. To achieve this, the feedstock must first be freed of non-biodegradable accompanying substances by screening and metal separation, and then processed by secondary shredding.

[0017] The onset of acidification will then be intensified by buffering the fermentation substrate to be treated in a pre-hydrolysis tank. To increase the surface area for the microorganisms to attack, it is planned to dissolve the cell structures using ultrasound treatment.

[0018] A biosuspension is then produced by mixing the fermentation substrate with process water containing active biomass in a static mixer. The resulting biosuspension is then subjected to aerobic hydrolysis treatment at temperatures suitable for the mesophilic degradation process with the addition of air.

[0019] Despite the introduction of air, a sink-float separation and the expulsion of hydrogen sulfide are intended to occur. The resulting liquid phase, containing organic acids, is then heated to temperatures suitable for thermophilic cultures and, with the addition of additional process water, fed to the methane reactor. The solid phase evidently produced in the hydrolysis tank is dewatered, fed to a post-composting unit, or hydrolyzed again. Of note is the proposal to design the methanation section so that each individual fermentation tank is only designed to accommodate a daily amount of the resulting feedstock, thus ensuring the postulated residence time by reliably preventing short-circuit currents. Gentle, complete circulation of the fermentation substrate in the fermentation tanks is ensured by recirculated injected biogas, avoiding so-called dead zones.Just as with the hydrolysis tank, the incompletely degraded solids from the methane reactor are removed by a discharge screw, dewatered, and subjected to aerobically decomposed digestion. The aqueous portion of the digestate is decanted, collected in a process water tank, and used from there as heat transfer medium and mashing water for the hydrolysis process or to humidify the post-decomposition unit and the biofilter.

[0020] The proposed process is clearly designed for the disposal of biogenic waste and, for several reasons, is unsuitable for the efficient material and energy recovery of potato processing residues. While a multi-stage aerobic pre-hydrolysis of the suspended biomass is provided, no measures are taken to avoid toxic concentrations of nitrogen and sulfur compounds in the fermentation medium, which are essential for the use of particularly protein-rich residues from potato processing. Furthermore, the initially undissolved fractions of the biomass used, which are particularly typical for potato peelings from potato processing in the form of proteins and / or lignocellulosic fractions of the peelings, are discharged from the individual process stages as settling and / or floating sludge and, after dewatering, are subjected to aerobic decomposition.Aerobic decomposition primarily requires process energy and leads to the loss of significant amounts of the contained inventory of fertilizing nitrogen and sulfur compounds.

[0021] A bacterial culture specifically adapted for the fermentation of lignocellulosic biomass is neither available nor intended for use, and could not be maintained and reproduced in the fully mixed fermentation vessels.

[0022] DE 102004030482 B4 (2004) describes a process for treating wastewater from the processing and treatment of organic waste. This technical solution includes, among other things, the suggestion of adding at least a portion of the organic feedstock to be recycled not to the fermentation stage, but only to the first, preferably mechanical, phase separation of the resulting fermentation residues as a flocculant in the so-called turbid effluent of this process stage, in order to achieve a clear effluent suitable for the planned downstream membrane filtration stages. The proposal also includes the suggestion of adding a liquid phase to the planned reverse osmosis process, which, through the addition of acid, both enables the formation of acidic ammonium compounds and inhibits the release of ammonia.Finally, the actual fermentation process is to be protected from the buildup of toxic ammonium concentrations in the fermentation substrate by adding reverse osmosis permeate as make-up water during the production of a fermentable biosuspension, thereby diluting the concentration of inhibitors for the fermentation process. This technical solution also fails to meet the requirements for the material and energy recovery of residual materials from the potato processing process, especially since the energy-rich solid phases of the organic waste to be recycled are removed from the biotechnological energy production process early and, in some cases, without any fermentation treatment.

[0023] EP 1783195 A2 (2005) discloses a process for producing fuel from grape pomace, particularly in the form of pellets. The integrated proposal to add up to 10% plant-based additives, such as cereal or potato starch, to the pellets to improve combustion properties represents an energy recovery option for the residues generated during potato processing. However, material recycling, particularly regarding the preservation and return of the contained plant nutrient potential to the economic cycle, is almost completely omitted.

[0024] The process described in the magazine Brauerei-Forum, issue 9 / 2006, under the title “Fermenting spent grains to biogas”, involves adding up to about 15% of spent grains to other residues from plant production and the food industry.

[0025] Such a process should also be suitable for peeling masses due to the qualitative similarity between brewing residues and residues from potato processing. The described process chain does not include process steps to prevent the buildup of so-called inhibitors during the fermentation process. The feedstock mixture is first sanitized for one hour at 70 °C and then hydrolyzed using acidifying bacteria. The resulting hydrolyzate is subsequently treated in methane fermenters. According to the description of the technology used, there is no media recirculation; the resulting fermentation residues are either used untreated for fertilization or processed in a dedicated wastewater treatment plant to produce wastewater suitable for receiving water and a solids-rich composting material.

[0026] DE 102007004135 A1 (2007) describes a process and device for the fermentation of biomass and is expressly intended to be suitable for the utilization of organic residues from the brewing process. If the process is actually suitable, it should also be suitable for the utilization of moist residues from potato processing. The proposed method envisages the use of a storage tank for the resulting digestate, located downstream of the anaerobic digestion system. Membrane technology is used to remove part of the aqueous phase from the digestate, allowing the remaining partially dewatered substance to be recycled into the fermentation process.This proposal contains neither a solution for the use and sustainable reproduction of an adapted culture for the lignocellulosic residues, nor measures to avoid overloading the fermentation stage with nitrogen and sulfur compounds, the formation of which is inevitable when using highly protein-rich residues from the potato processing process. The multiple treatment of at least part of the input solid fraction, envisaged as a helpful measure, fails to achieve the required energy yields due to the lack of targeted hydrolytic treatments.

[0027] US 2009 / 0077863 A1 (2007) discloses a process for the utilization of algae. According to this process, algae with higher fat contents are to be used for oil extraction and the subsequent production of biodiesel, and algae with higher starch contents are to be used for bioethanol production.

[0028] The wide range of achievable qualities of algae, especially microalgae, through selectable cultivation conditions makes it seem possible to have starchy algae without significant protein content. In such a case, the necessary measures for treating the protein load, as contained in any conventional plant-based starch raw material, could be eliminated, so that, in addition to the energy product ethanol, only the broken cell walls would be used for energy production. However, the proposed technical solution does not include any suggestion for this.

[0029] DE 202008014330 U1 (2008) describes a device for supplying energy to a brewery, which, among other things, refers to means for the hydrolysis and fermentation of brewery residues. Due to the similarity of the resulting residues, such a technical solution must be equally suitable for a potato processing plant. However, the problem to be solved by the inventive proposal is to improve the energy supply. This is to be achieved primarily by coupling various technologies for generating electrical and thermal energy from renewable sources. The proposal preferably provides for separate hydrolysis for each of the available feedstocks, without providing any information on the type of hydrolysis. The solid phases are then removed from the aqueous substrates resulting from the hydrolysis stages and kept away from the further biotechnological process.Only the comparatively low-energy, solids-depleted media are to be fed to the fermentation stage, without giving any indication as to how the nitrogen and sulfur compounds dissolved in the fermentation substrates from the use of the protein-rich residues are to be treated before concentration in the fermentation process.

[0030] DE 102008060140 A1 (2008) describes a brewer's spent grain hydrolysis process that, if suitable, should also be suitable for potato processing due to the material similarity of brewer's spent grain to the hull residues from potato processing. It proposes first mixing the available protein- and lignocellulose-rich residues with wastewater and sludge and then subjecting them to an initial hydrolysis process.

[0031] The resulting hydrolysate will then be phase-separated into a high-solids and a low-solids fraction, with the high-solids fraction being subjected to solids digestion using caustic soda. The medium resulting from the caustic soda digestion will then be subjected to another phase-separation, and the resulting high-solids fraction will be subjected to another caustic soda digestion in a second hydrolysis process. After another phase-separation, the low-solids fraction will be fed to a third hydrolysis stage, while the high-solids fraction will be dried, if necessary, with other biogenic residues, and compacted for subsequent incineration. The substrate resulting from the third hydrolysis stage will finally be fed to a fermentation process.A special starter culture, which must preferably be taken from parallel plants or specially cultivated in small-scale facilities, is to be used in the first hydrolysis stage, which should also preferably be operated at 60 °C. Clearly, anaerobic hydrolysis processes are being discussed, in which the active bacterial cultures produce the necessary acidification enzymes themselves. Hydrolytic pretreatment is not required for the fats, proteins, and carbohydrates used with the residues, but at best for the accelerated process in the fermentation stage.

[0032] Regularly neutralizing the more or less acidic hydrolysates from the individual hydrolysis stages by adding alkali does not discernibly result in the lignocellulosic fractions used, particularly with the residues, being digested for the subsequent fermentation process. These energy-rich fractions from the residues used are almost certainly found in the high-solids fraction discharged after the second hydrolysis stage and, with a moisture content well over 70% after energy-intensive drying, contribute little to the energy yield for the potato processing process.Even if a starter culture supporting the hydrolysis process is available, it can hardly effectively support the methanation process in the downstream fermentation stage at the temperatures of 60 °C mentioned, because the microorganisms required there are known to have different compositions, either in the temperature range between 30 and 40 °C as a mesophilic culture or in the temperature range between 48 and 55 °C as a thermophilic culture.

[0033] DE 102010005818 A1 (2010) discloses an energy-optimized process for operating a bioethanol production plant. Such a process is particularly relevant to a specialist because both the stillages from bioethanol production and the peeling masses from potato processing are equally aqueous substrates with predominantly protein and lignocellulose contents. In their initial state, the peeling masses have a higher dry matter content than the ethanol stillages. In accordance with the stated task, the disclosed proposal merely states that the stillages resulting from the bioethanol production process are fed into a methane fermentation process.There, the dissolved organic compounds contained in the stillages would be predominantly converted into biogas, allowing the aqueous phase of the digestate to be used, at least in part, to replace the freshwater required for the mashing process. To avoid additional burdens on the ethanol plant's mashing process, the solids-rich phase of the recycled digestate is to be removed before reuse. An increase in the concentration of dissolved hydrogen sulfide and ammonium in the recycled digestate is to be prevented by appropriate depletion steps. No further information can be found in the above-mentioned proposal. Summary of the known state of the art

[0034] The technical solutions disclosed to date share the common flaw that monofermentation of biogenic residues from potato processing with the required biotechnological stability and without the significant addition of diluents, such as fresh or wastewater, cannot be guaranteed. Furthermore, suitable proposals for the effective preparation of the energy-rich lignocellulosic components of the available residues from potato processing for biogas production have not yet been disclosed. Finally, the sources published to date do not provide any useful information on how to counteract the high protein content of the peeling masses from potato processing and the resulting systemic stresses caused by nitrogen and sulfur compounds that act as inhibitors of the biotechnological process.

[0035] Consequently, none of the proposals announced so far have found their way into industrial potato processing. Object of the invention

[0036] The object of the invention is therefore to overcome the deficiencies of known technical solutions. In particular, the invention is intended to enable technical, logistical, energetic, and ecological improvements in potato processing, which should lead to sustainable cost reductions and improved competitive positions. The desired independence from the fossil energy market on the one hand and the conventional feed market on the other is considered a prerequisite for stable and predictable potato processing. In particular, the exclusive material and energetic utilization of the biogenic residues generated in a potato processing plant should be possible with high energetic and ecological efficiency. High reliability is to be ensured by avoiding disruptive influences on the biotechnological process. Description of the invention

[0037] The object is achieved according to the invention according to the teachings of claims 1 and 11. Advantageous embodiments of the invention are described in the subclaims.

[0038] The next step is to utilize the biogenic residues from potato processing plants for material and energy recovery by using them in a wet fermentation process to produce biogas. The extensive conversion of the carbon compounds contained in the residues into biogas results in a significant concentration of the nutrient potential, particularly in the form of nitrogen, phosphorus, potassium, and sulfur, in a fertilizer fraction obtained from the fermentation residues. The biogas produced in the fermentation process is available for energy recovery after almost complete removal of entrained hydrogen sulfide and water vapor.

[0039] The biogenic residues arising from potato processing, such as peeling masses, white water, residues from the cleaning of the input materials, aqueous media from periodic plant cleaning and / or sludge from operational wastewater treatment, are subjected to a suspension process in their respective state without further pretreatment and, if necessary, even without intermediate storage.

[0040] By using additives of similar quality with dry matter contents of at least 25%, such as grain cleaning residues and the like and / or process water, the resulting biosuspension achieves a dry matter content of between 12 and 18%. The resulting biosuspension is then subjected to an aerobic hydrolysis process.

[0041] This not only achieves the desired acidification processes, but also at least partial degradation of the lignocellulosic components of the biosuspension. The resulting hydrolysate enters an anaerobic fermentation system, which consists of at least one hydraulically and only partially mixed fermenter. This fermentation system is equipped with a special culture, initially introduced and continuously reproducing.

[0042] The potential plant nutrients contained in the recycled input materials as a mixture of the solid phase of the fermentation residues and the fertilizer concentrates with high contents of ammonium and sulfur compounds obtained in the inhibitor removal station are completely recovered and reintroduced into the economic cycle as organic NPKS fertilizer.

[0043] The biogas produced during the fermentation process is desulfurized, dried, and compressed as needed. At this quality, it is preferably used for the combined generation of electrical and thermal energy.

[0044] The function of the proposed process thus results from the direct coupling of known process steps, such as the production of a biosuspension from the available residues from potato processing in the respective state and in the respective quantities without prior intermediate stacking, the addition of qualitatively similar waste materials from agriculture or the food industry as welcome co-fermentates, pre-treatment of the produced biosuspension in an aerobic hydrolysis which also splits lignocellulose, biological gas desulfurization to obtain a sulfurous bioacid required in the utilization process, as well as from newly developed process steps.

[0045] Such procedural steps consist - in the use of a special methane bacteria mixed culture adapted for the utilization of protein- and lignocellulose-rich biowaste, - in the application of a fermentation technology suitable for the unrestricted maintenance or continuous reproduction of the starter culture used, - in the recycling of part of the fermentation residues to the suspension stage, combined with repeated hydrolytic and fermentative treatment of the biogenic potential contained in the recycled fermentation residues, - in the creation of an additional inhibitor sink to prevent an increase in the concentration of ammonium and hydrogen sulphide in the fermentation substrates to values ​​close to the toxic threshold values ​​and - in the use of the washing liquid from the inhibitor removal station containing the removed inhibitors as a liquid fertilizer concentrate.

[0046] In a preferred embodiment, at least portions of the sour mash produced in the upstream yeast fermentation in the form of solids-rich press cakes or the stillages obtained during the ethanol distillation of the sour mash are added to the biosuspension.

[0047] In another variant, additional biogenic potential is extracted in the form of the sludge fraction from the aerobic and / or anaerobic treatment of the potato processing plant's production wastewater and fed into the suspension process. This not only reduces the potato processing plant's wastewater load, but also leads to a reduction in odor emissions and an increase in the generation of renewable energy from the plant's own biogenic sources.

[0048] Another solution involves stabilizing the entire process by increasing the dry matter content of the biosuspension to values ​​above 14%. To achieve this, additives with a composition similar to the residues from potato processing, such as malt dust, grain chaff, mill dust, and / or brush dust from grain cleaning, are preferably used in the suspension process. In addition to stabilizing the process, the biogenic potential contained in the additives is simultaneously utilized with virtually undiminished efficiency to generate process energy for the potato processing process.

[0049] Advantageously, the biofiltrates obtained during mechanical phase separation of the fermentation residues are recycled as process water into the suspension process as part of the fermentation residues. Due to the comparatively high input rates of proteins contained in the potato processing residues, the biotechnological utilization of these residues is jeopardized by excessive ammonium and hydrogen sulfide levels in the fermentation substrates as soon as a required concentration reduction cannot be ensured. According to the invention, those biofiltrates from the fermentation residues are used for this purpose, from which portions of the nitrogen and sulfur compounds contained were previously removed in an inhibitor removal process. On the one hand, this eliminates any threat to process stability, and on the other hand, the removed inhibitors are used as valuable plant nutrients for fertilization.

[0050] In a further advantageous embodiment of the invention, portions of the dissolved ammonium and / or dissolved hydrogen sulfide are removed from the biofiltrate in an expeller at temperatures elevated to 65 °C and at a pressure in the supernatant vapors of no more than 980 mbar. The ammonia- and / or hydrogen sulfide-containing vapors produced in the expeller are subsequently cooled in an intermediate heat exchanger to temperatures of no more than 45 °C. The cooled ammonia- and / or hydrogen sulfide-containing vapors are then fed to a downstream vapor scrubber in the form of a trickle-bed apparatus, with sulfurous bioacid from biogas desulfurization being used as the scrubbing medium at a maximum temperature of 25 °C and a pH value between 1 and 3.5. In the scrubber sump, the binding of ammonium into the scrubbing medium causes a steady increase in its pH value, which simultaneously reduces scrubbing efficiency. When the selectable upper limit for the permissible pH range is reached, a portion of between 10 and 60% is removed from the scrubber sump and used as a fertilizer concentrate with high nitrogen and sulfur concentrations. The removed scrubbing liquid is then replaced with fresh sulfurous bioacid from the gas desulfurization process.

[0051] The specific hydrolysis process is essential for the desired high energy efficiency of the process according to the invention. In a preferred embodiment, the hydrolysis process is carried out under intensive mixing with ambient air in a stirred tank at temperatures between 50 and 60 °C. Ambient air is added to the hydrolysis process in a quantity between 2 and 10 vol.% of the biogas obtained in the entire fermentation process.

[0052] The dimensions of the hydrolysis tank(s) are chosen so that an average residence time of the biosuspension in the hydrolysis tank of approximately 2 days can be maintained.

[0053] The hydrolytic treatment is effectively supported by adding between 20 and 100% of the sulfurous bioacid produced during the biological desulfurization of the biogas to the hydrolysis process. Because the gaseous conversion products released during hydrolysis remain in the gas system, the ambient air supplied to the hydrolysis process also serves to feed the aerobic sulfur bacteria in the gas desulfurization process. Odor emissions, especially in the form of fatty acid vapors produced during hydrolysis, are reliably eliminated.

[0054] It is possible to compress the resulting hydrolysis gas to at least 30 mbar and feed it into the central raw gas pipeline upstream of the gas desulfurization station.

[0055] In another embodiment, the resulting hydrolysis gas can be compressed to at least 30 mbar in order to then feed it to the corrosion-resistant post-fermentation station.

[0056] In this case, overcoming the pressure loss of the gas desulfurization station does not require any additional gas extraction technology.

[0057] The hydrogen and carbon monoxide contained in the hydrolysis gas, as well as the expected fatty acid vapors, are incorporated into the biogas production either in the anaerobic digestate storage facility and / or in the post-fermentation station. The mixed population of methane bacteria, initially used as a starter culture for the fermentation process, is cultivated in a culture station for mesophilic or thermophilic mixed cultures by adding predominantly lignocellulosic feedstocks. In the event of a so-called "overturn" of the fermentation process, which is only conceivable in the case of extreme violations of the specified operating regulations, the culture station can be used to restart the fermentation process and continue without any noticeable reduction in yield.

[0058] The proposed arrangement for carrying out the method according to the invention consists of at least - a suspension station, - a fermentation station for methane fermentation, - a phase separation station for the digestate, - a biofiltrate storage tank and - a gas desulfurization station.

[0059] According to the invention, the suspension station is connected to a storage and dosing system for additives rich in dry matter. Furthermore, an inhibitor removal station is arranged between the biofiltrate storage tank and the suspension station. For gas desulfurization, a gas scrubber, preferably in the form of a trickle-bed system, is arranged.

[0060] To store the sulfurous bioacid obtained in the gas desulfurization station, a bioacid storage tank is arranged between the gas desulfurization station and the inhibitor removal station and / or the hydrolysis station. Finally, a hydrolysis station is arranged between the suspension station and the fermenter station. It is essential to the invention that the fermentation station consists of at least one main fermenter and at least one downstream secondary fermenter. This arrangement of the plant components ensures that a stable material and energy recovery process for the residual materials from potato processing can be maintained without special comminution, storage, dosing, and mandatory continuous supply processes for external media, such as chemical and / or biotechnological additives and / or dilution media for the suspension process.By dividing the fermentation process into a main and a secondary fermentation station, an important objective can be addressed in a simple manner. This is because the inevitably varying composition of the residues from potato processing is first treated with a comparatively robust mesophilic culture after hydrolysis in the main fermentation station. The further fermentation of the fermentation substrates leaving the main fermentation station can then be carried out with significantly smaller quality differences in the main parameters using the more efficient but less robust thermophilic cultures. For the long-term preservation of the starting culture used, which is particularly suitable for the protein- and lignocellulose-rich residues from potato processing, it is essential to the invention that at least the main fermenter(s) are hydraulically mixed and not completely mixed apparatuses. Advantages of the invention

[0061] The advantages of the invention, based on its economic impact, primarily lie in the reduction of process energy costs for potato processing plants. If the thermal process energy demand is largely covered by the operation of combined heat and power (CHP) technology for the energetic utilization of the recoverable biogas, additional revenue can be generated by selling surplus electrical energy. In any case, partial or complete independence of the operation of potato processing plants from price developments on the market for process energy from fossil sources is achieved.

[0062] The logistical and contractual dependence on the animal producers who utilize the resulting hulling masses is completely avoided due to the practically impossible storage of these nutrient-rich and therefore extremely infection-prone feeds.

[0063] The solid fermentation residues resulting from the phase separation can be sold as nutrient-rich organic NPKS (nitrogen-phosphorus-potassium-sulfur) fertilizers to generate additional revenue.

[0064] The avoidable disposal of waste, such as sludge from industrial wastewater treatment or loaded filter aids, leads to a noticeable reduction in costs in the potato processing process.

[0065] In the case of the sale of certificates from the saved emissions of CO2 equivalents, additional revenue is generated.

[0066] Plant-related freight traffic, which is relevant for emissions control regulations, will be significantly reduced. Furthermore, cross-traffic between feed and waste transports on the one hand and food transports on the other can be safely avoided.

[0067] The odor emissions resulting from the intermediate storage and transport of feed and biogenic waste can be safely avoided.

[0068] The wastewater load, which is often a limiting factor for potential production expansion, can be reduced by discharging it into public wastewater treatment plants.

[0069] Finally, the use of so-called “green” energy can be marketed in a way that is effective in increasing the acceptance of the products produced. Example

[0070] The invention will be explained in more detail below with exemplary embodiments. The accompanying drawings show: Fig. 1 the process scheme of the technical solution according to the invention; Fig. 2 the process scheme of the technical solution according to the invention with an upstream bioethanol production plant for the utilization of the carbohydrates contained in the residues; Fig. 3 the block diagram showing the interaction of the plant components when the resulting peeling masses are fed directly into the suspending station; Fig. 4 the block diagram showing the interaction of the plant components when using the solid phase from the phase separation of the resulting peeling masses in the suspending station; List of reference symbols 1 starter culture 2 potato processing plants (supplier of ethanol distillers, peelings, white water, residues from the cleaning of feedstocks, organically contaminated cleaning agents) 3 storage areas for suspension additives (malt dust, grain chaff, thick sour mash, mill by-products) 4 operational wastewater treatment plant (supplier of wastewater sludge) 5 Inhibitor removal station 6 Suspension station 7 Hydrolysis station 8 main fermenters 9 post-fermenters 10- Digestate storage 11 Phase separation station 12 Biofiltrate storage tank 13 fertilizer storage 14 Gas desulfurization station 15 Bioacid storage tank 16 gas storage facilities 17 energy gas utilization complex Example 1:

[0071] According to the Fig. 1 and Fig. 3, the available biogenic residues from a potato processing plant 2, in particular the peeling masses, the white water and the sludge from the operational wastewater treatment plant 4, are fed to a suspension station 6 according to their occurrence in the potato processing process, predominantly by means of pipeline transport. In the example, 1 part by mass of peeling mass with 22% dry matter content and 94% organic content of the dry matter, 0.012 parts by mass of sediment from the so-called white waters with 15% dry matter content and 98% organic content of the dry matter, 0.015 parts by mass of sludge from the operational wastewater treatment with 28% dry matter content and 65% organic content of the dry matter and 0.21 parts by mass of thickened sludge from the flotation of the resulting biofiltrates with 10.1% dry matter content and 96% organic content of the dry matter, a total of 1.648 parts by mass of biosuspension with 15% dry matter content and 93.7% organic content of the dry matter were obtained using recycled biofiltrate.

[0072] In a storage facility for suspension additives 3, additives such as malt dust, hop dust, and / or grain cleaning residues with an average dry matter content of at least 85% and at least 80% organic content of the dry matter are stored. In the event of increased production of residue fractions from potato processing plant 2 with lower dry matter contents, the preferred dry matter concentration in the batch-produced biosuspension is adjusted to between 12 and 18 mass% by admixing these additives. The produced biosuspension is then pumped into hydrolysis station 7 and subjected to aerobic hydrolytic treatment. Ambient air is fed into the hydrolysis tank at a rate of approximately 10%, based on the volume of biogas to be desulfurized. Additional heat energy is supplied to the hydrolysis tank via heating surfaces integrated into the tank wall.Through the effect of the exothermic hydrolytic reactions and the heat energy indirectly supplied to the hydrolysate via heating water, a temperature between 55 and 60 °C is maintained in hydrolysis station 7. The average residence time of the biosuspension in hydrolysis station 7 is at least 2 days. The added ambient air is injected into the hydrolysis tank above the tank bottom in the form of fine bubbles. The hydrolysis tank also features a centrally positioned propeller agitator, which not only maintains intensive, degassing turbulence in the upper area of ​​the hydrolysis tank, but also repeatedly brings the escaping oxygen-containing gases into contact with the biosuspension via the resulting vortex.The acidification process effected in the hydrolysis tank, which leads to a reduction of the pH of the biosuspension from approximately 7.5 to less than 4 for the hydrolysate leaving hydrolysis station 7, is supported by the addition of the available bioacid.

[0073] The resulting oxygen-containing hydrolysis gas is captured at the top of the hydrolysis tank, compressed to approximately 50 mbar using a booster fan, and pumped into the raw gas line. By incorporating oxygen-containing ambient air into the hydrolysis process, any anaerobic bacteria introduced into the biosuspension are sustainably damaged, ensuring that the mixed culture of methane bacteria active in the 8 main fermenters remains safely protected from displacement.

[0074] The hydrolysate produced in the hydrolysis station 7 is removed from the hydrolysis tank by the dosing pump station and fed to the main fermenter station 8.

[0075] The hydrolysis tank thus also serves to decouple the process between the batch production of the biosuspension in suspension station 6 and the quasi-continuous feeding of the main fermenters 8. The hydrolysis tank also serves as a pump reservoir for the dosing pump station. The dosing pump station is used to feed the individual main fermenters 8 of the main fermenter station.

[0076] At four-hour intervals, each fermenter 8 of the main fermentation station is fed one-sixth of the intended daily dose of hydrolysate. During the commissioning of the recycling plant for the biogenic residues of the potato processing plant, the main fermentation station was filled with biomass containing a mesophilic starter culture 1 from an existing recycling plant for potato processing residues or from an active fermentation plant for the biotechnological recycling of predominantly lignocellulosic feedstocks, such as grain cleaning residues, oilseed cleaning residues, brewery waste, ethanol distillers' slurry, and / or pulp from starch production.

[0077] The two main fermenters 8 used in the main fermenter station are hydraulically mixed devices operated according to the push-through principle. They contain three zones with different demands on the biomass used. A first zone is flow-mixed at regular and selectable intervals. A central, unmixed zone is designed as a plug to prevent short-circuits and serves to ensure undisturbed reproduction of the biomass used as starter culture 1. A third zone is located above the so-called plug zone and comprises the portion of the fermentation substrate in main fermenter 8 that is located directly at the fermenter outlet. After the full mixing pressure is reached, the biogas produced in the first zone also flows into this zone, leading to intensive and turbulent mixing of the largely degassed fermentation substrate.At the same time, the fermentation substrate at the outlet is fluidized so effectively that the formation of floating layers, which could impede gas release and / or the drainage of the fermentation residue, is reliably prevented. The dosed hydrolysate batch enters the first fermenter section.

[0078] There, after the dosing process is completed, the fermentation substrate is briefly equalized between the gas space above the flow-mixed fermenter zone (maximum 490 mbar) and the unmixed plug zone at the fermenter outlet (maximum 50 mbar), resulting in a circular flow due to the resulting mixing impulse. At the same time, a portion of the mesophilic biomass growing in the unmixed plug under ideal conditions is returned to the flow-mixed fermenter zone. This allows even particularly low-germ biomass, such as the peelings from a potato processing plant, to be brought into contact with an active and already adapted methane bacteria mixed culture early in the fermentation process.During the dosing of a hydrolysate batch into the first fermenter section, an adequate volume of fermentation substrate, reduced by the mass of biogas released into the fermenter station since the previous dosing, is discharged via the fermenter outlet. This ensures virtually no significant change in the fermenter's fill volume throughout its entire service life. The fermentation substrate outlet from the two main fermenters 8, which are alternately fed with hydrolysate, now enters the secondary fermenter 9 of the secondary fermenter station for post-treatment. The secondary fermenter 9 is constructed similarly to the main fermenter 8.

[0079] However, it has two special features: First, it operates at a maximum mixing pressure of 420 mbar, which reduces the mixing energy available for flow mixing in the first fermenter section in the secondary fermenter 9 by approximately 15%. This is unproblematic considering the reduction in the dry matter content of the fermentation substrate already achieved in the main fermenter station. However, this allows the fermentation substrate effluent from the main fermenters 8 to reach the secondary fermenter 9 at virtually any time. Second, after passing through the main fermentation station, the fermentation substrate is sufficiently homogenized in terms of its biogenic content that the secondary fermenter 9 can be operated stably with an adapted thermophilic bacterial culture without overwhelming the less robust thermophilic bacteria due to the strongly fluctuating qualities of the fermentation substrate. This arrangement of consecutive anaerobic treatment steps using mesophilic and thermophilic bacterial cultures accommodates the changing composition of the biogenic residues generated in potato processing plant 2 without risking overloading the biotechnological system.

[0080] At the same time, due to the minimum residence time of the fermentation substrate in the post-fermentation station at temperatures suitable for thermophilic bacterial cultures, the requirements for effective sanitation of biogenic waste materials are met if they are to be placed on the market, for example as organic fertilizers, after biotechnological treatment.

[0081] A digestate storage tank 10 is located downstream of the post-fermentation station, primarily serving to decouple the nine process stages of fermentation and phase separation. The digestate storage tank 10 is covered with a double-membrane gas storage system to additionally capture any residual gas escaping from the digestate. The phase separation station 11, located downstream of the digestate storage tank 10, is used to extract a high-solids fraction from the digestate, which is then fed directly to the fertilizer storage tank 13 as a nutrient-rich organic NPKS fertilizer. The biofiltrate, which is produced in parallel as a low-solids fraction, enters the biofiltrate storage tank 12, which also serves to decouple the phase separation and inhibitor removal process stages.The biofiltrate can initially be withdrawn from the biofiltrate storage tank 12 either as organic NPKS liquid fertilizer for use in agriculture or as a liquid component for producing a suitable biosuspension in the suspension station 6.

[0082] Furthermore, it is possible to use biofiltrates depleted of nitrogen and sulfur compounds in the suspension station 6 if this is necessary to prevent the accumulation of toxic concentrations of ammonium and / or hydrogen sulfide in the fermentation substrate. In this case, the biofiltrate removed from the biofiltrate storage tank 12 only returns to the biotechnological treatment process after passing through the inhibitor removal station 5.

[0083] Alternatively, a flotation station is fed from the biofiltrate storage tank 12 as part of the biofiltrate treatment process, up to the receiving water quality. Finally, the biofiltrate storage tank 12 also serves as a storage tank for the biofiltrate pumping station.

[0084] The biogases escaping from fermenters 8 and 9, at the inherent pressure of the gases in the fermenters, enter the raw gas line via pressure-reducing valves. The raw gas line operates at an absolute pressure of approximately 1,050 mbar. The hydrolysis gas generated in hydrolysis station 7 also enters this raw gas line. This gas contains not only the ambient air supplied there to stimulate the aerobic hydrolysis process, but also the gases from the aerobic treatment of the biosuspension used, as well as vapors from the resulting short-chain fatty acids.

[0085] This so-called hydrolysis gas is extracted from the hydrolysis reactor and compressed to an absolute pressure of at least 1,050 mbar before being introduced into the raw gas line. This procedure allows the fermenters 8 and 9 of the main and secondary fermenter stations to be used as sheet steel structures made of unpreserved structural steel. The oxygen-containing mixed gas in the raw gas line first flows through the gas desulfurization station 14, designed as a trickle-bed apparatus, which, during normal operation, has a pressure drop of approximately 40 mbar. From the gas desulfurization station, the biogas finally reaches the double-membrane gas storage tank 16 downstream of the gas desulfurization station 14, which is operated with an absolute support pressure of the weather protection membrane of 1,008 mbar. The desulfurized gas is supplied to the gas desulphurization station at a pressure of 1,008 mbar if required.008 mbar is taken from the gas storage 16, compressed after passing through a gas drying station, and fed to an energetic gas utilization complex 17, in the exemplary embodiment a combined heat and power plant. The nutrient solution used in the gas desulfurization station for the sulfur bacteria colonized on the trickle-bed filters is continuously pumped back to the top of the trickle-bed filter apparatus as a bottom product and, as it passes through the trickle-bed filter packing, experiences a steady reduction in pH to values ​​below pH = 2.0. Portions of the nutrient solution are removed from the apparatus bottom in batches when the pH has reached a value between 1.5 and 2.0. The removed batch enters the bioacid storage tank 15 as bioacid, where it is available as scrubbing liquid for the vapor scrubber of the inhibitor removal station 5. Additional supplies of bioacid are supplied to hydrolysis station 7 to promote the acidification of the biosuspension used there.

[0086] In the exemplary embodiment, biogas with an energy content of 665 kWh is obtained from the produced biosuspension per ton of pulp used. Example 2:

[0087] According to the Fig. 2 and Fig. 4 there is an arrangement for the material and energetic utilization of biogenic residues from a potato processing plant 2 for the production of energy-rich biogas with a heating capacity of 9 MW th. from an upstream bioethanol plant, with the help of which a bioethanol quantity of at least 80,000 m 3 / a. The decision to prioritize bioethanol production from the available starch-containing residues was made in light of the assessment of current market prices for the various forms of energy used: Pos. Form of energy used Market price Useful energy content kWh / ME specific energy value € / MWh 1. Animal feed (feed barley) 140 € / t 4.000 40,- 2. Thermal energy (WE) (natural gas) 0,70 € / m 3 11 kWh / m 3 63,- 3. Cooling energy (KE) (absorption cooling) Heat energy + 10% 12.1 kWh / m 3 69,- 4. Combined heat and power using CHP (diesel fuel) 1,30 € / l 5 kWh WE / l + 4 kWh EE 144,- 5. Electrical energy (RE) on average 0.15 € / kWh Direct application 1 150,- 6. Engine fuel energy on average 1.35 € / l at 45% efficiency 5.4 kWh / l 250,-

[0088] For energetic, ecological, and economic reasons, a variant with the highest proportion of high-quality energy is chosen in this example, as shown in the table above. The preferred variant also proves to be the variant with the highest economic yield. A cassava processing plant for the production of chips and French fries produces approximately 100,000 tons of hulls annually. Starch-rich white water is extracted from the production wastewater after the feedstocks have been cleaned. Both material streams are used as feedstocks for an ethanol production plant, which, unlike conventional distilleries, does not contain the following plant components: - raw material warehouse, - Crushing station, - Station for the production of a raw mash, - Warehouse for the intermediate storage of stillages and white waters, - Transfer facilities for the distribution or disposal of stillages and white water.

[0089] In the distillery, a total of about 80,000 m 3 Bioethanol is extracted. The resulting stillages are then separated into a thick phase and a thin phase as part of the potato processing plant's material and energy recycling system.

[0090] In the example, 1 part by mass of thick stillage with 14.7% dry matter content and 88% organic content of the dry matter, 0.0185 parts by mass of sludge from industrial wastewater treatment with 28% dry matter content and 65% organic content of the dry matter and 0.283 parts by mass of thickened sludge from the flotation of the resulting biofiltrates with 10.1% dry matter content and 96% organic content of the total dry matter using recycled biofiltrate 1.3 parts by mass of biosuspension with 13.9% dry matter content and 88.5% organic content of the dry matter were obtained.

[0091] The thin phase obtained during the phase separation of the ethanol stillages produced in the upstream ethanol distillery is fed into the downstream treatment plant for the excess biofiltrates from the fermentation residues of the methane fermentation plant.

[0092] From the operational wastewater treatment plant 4, wastewater sludge with a dry matter content of approximately 28% in the amount of 4.1 t is conveyed daily without intermediate buffering by means of a screw conveyor to the suspension station 6.

[0093] From the thick stillage produced daily, approximately 225 t of press cake from the phase separation of the thick stillage with a dry matter content of 14.7% are fed to suspension station 6. In addition, 63.5 t of thickened flotate sludge with a dry matter content of 10.1% from the removal of suspended matter from the excess biofiltrate by dissolved air flotation are fed into suspension station 6 daily. From this, a total biosuspension quantity of 292.5 t / d with an average dry matter content of 13.9% is produced in suspension station 6.

[0094] The suspension station 6 consists of a reinforced concrete mixing tank with a useful volume of 600 m 3 , which can reach up to 300 m daily 3Biosuspension is removed and fed to hydrolysis station 7. Hydrolysis station 7 consists of a ventilated stainless steel stirred tank, to which selectable amounts of ambient air are added depending on the gas production during fermentation 8, 9. The usable capacity of hydrolysis station 7 is 800 m 3 .

[0095] Hydrolysis station 7 receives hydrolysate quantities of up to 280 m 3 removed and alternately fed to two parallel operated main fermenters 8 of the main fermenter station.

[0096] The main fermenters 8 are partially and hydraulically mixed devices with useful volumes of 8,000 m each 3 , which are made of unpreserved sheet steel.

[0097] Before the start of operation, a mesophilic starter culture 1 from an existing fermentation plant was introduced into the main fermenters 8 for the material and energy recovery of predominantly lignocellulosic feedstocks.

[0098] When hydrolysate is metered from the hydrolysis station 7 into the two main fermenters 8, fermentation substrate quantities are discharged from each of the main fermenters 8. These fermentation substrate quantities are directly fed into the secondary fermenter 9 of the secondary fermenter station. The secondary fermenter 9 is constructed like the main fermenters 8 and also has a usable volume of 8,000 m 3and has heating surfaces integrated into the tank wall, which can maintain media temperatures between 52 and 57 °C in the secondary fermenter 9. With each feeding of the secondary fermenter 9, fermentation residue from the secondary fermenter 9 is discharged into the digestate storage 10. The digestate storage 10 is an unheated, open stirred tank made of sheet steel with a usable volume of 6,000 m 3 . This is covered by a gas storage 16, which also has a maximum storage capacity of 6,000 m 3This ensures process decoupling while maintaining an average fill level in the gas storage facility 16, bridging disruptions in the downstream gas processing and the energy-generating gas utilization complex 17 of up to two hours. The safety device in the form of the flare system with a thermal output of 9 MW does not yet need to be used. The digestate storage facility 10 serves both for the residual degassing of the fermentation residues discharged from the fermenters 8 and 9 of the main and secondary fermentation stations and for the decoupling of the fermentation station and the digestate processing.

[0099] To obtain a nutrient-rich fertilizer fraction, digestate is removed from digestate storage 10 and fed to a phase separation station 11. There, screw press separators and decanters separate the fermentation residues into press cake with an average dry matter content of 30% and biofiltrate. While the press cake is fed as high-quality fertilizer into fertilizer storage 13 with a bulk material capacity of 2,000 m 3 for approximately 20 days of intermediate storage, the resulting biofiltrate is fed into the closed biofiltrate storage tank 12 made of reinforced concrete with a usable volume of 1,000 m 3 .

[0100] The biofiltrate quantities not required for reuse in the fermentation process are treated into pre-floodable wastewater using a process combination of flotation, UASB fermentation, nitrification, and denitrification. The thin stillage from the phase separation of the stillages generated in the upstream ethanol distillery is fed into the downstream process upstream of the UASB fermentation station.

[0101] The gas / acid vapor mixture produced in hydrolysis station 7 is compressed to approximately 50 mbar overpressure and fed into the raw gas line. The gas produced from the fermenters 8 and 9 of the main and secondary fermentation stations also enters the raw gas line under its own pressure. Between the raw gas line and gas storage 16, the gas desulfurization station 14 is located for a raw gas flow of approximately 1,100 m 3 / h arranged.

[0102] The used bottom product of the gas desulphurisation station 14, which is designed as a trickle-bed system, is discharged as bioacid and stored in the bioacid storage tank 15 with a useful volume of 100 m 3 temporarily stored. The bioacid is primarily used to supply the inhibitor removal station 5 with liquid for the vapor scrubber and also to support the hydrolytic treatment of the biosuspension in the hydrolysis station 7.

[0103] The plant for the utilization of biogenic residues from a cassava processing plant, shown in the example, serves to produce 80,000 m 3 Bioethanol, which is primarily used as motor fuel, and for the production of 8.9 million m 3 Biogas with an average methane content of 65%.

[0104] This amount of methane corresponds to about 108 m 3 Biogas per ton of thick stillage used.

[0105] From the biogas produced, 28,600 MWh of electrical energy and 33,600 MWh of thermal energy are generated annually using combined heat and power (CHP) technology.

Claims

[1] Process for the material and energetic utilization of biogenic residues from potato processing plants by using the residues in a wet fermentation, by concentrating the entire nutrient potential in the form of nitrogen, phosphorus, potassium and sulfur in a fertilizer fraction obtained from the fermentation residues, and by providing the desulphurized biogas for energetic utilization, characterized by , that yeast fermentation for bioethanol production and / or methane fermentation for biogas production are used as wet fermentation, that the biogenic residues arising from the processing of starchy root crops, such as potatoes, sweet potatoes, manioc, tapioca, cassava, are recovered in the form of peeling masses, starchy white water, residues from the cleaning of the input materials, stillages from the upstream ethanol distillation, aqueous media from the periodic plant cleaning and / or sludge, that the available residues are subjected to a suspension process, that by using additives with dry matter contents of at least 25% in the biosuspension, a dry matter content of between 12 and 18% is achieved, that the produced biosuspension is subjected to an aerobic hydrolysis process, that the hydrolysate produced from the biosuspension is fed into an anaerobic fermentation system consisting of at least one hydraulically and partially mixed fermenter with an initially introduced and continuously reproducing special culture, that the potential plant nutrients contained in the recycled feedstocks are obtained as a mixture of the solid phase of the fermentation residues and the liquid washing media with high contents of ammonium and sulphur compounds resulting from the removal of inhibitors from the biofiltrates, and that the desulfurized, dried and compressed biogas is used for the coupled production of electrical and thermal process energy. [2] Method according to claim 1, characterized by that at least parts of the sour mash produced during yeast fermentation are added to the biosuspension in the form of solids-rich press cake. [3] Method according to one of claims 1 and 2, characterized bythat a sludge fraction is obtained as an additional biogenic residue fraction from the production wastewater of the starch production plant before or after aerobic and / or anaerobic treatment. [4] Method according to one of claims 1 and 3, characterized by that grain chaff, mill dust and / or brush dust from grain cleaning are preferably used as additives in the suspension process. [5] Method according to one of claims 1 to 4, characterized by that biofiltrates from the mechanical phase separation of the resulting fermentation residues are used as process water in the suspension process. [6] Method according to claim 5, characterized by that ammonium and / or hydrogen sulphide are removed from the biofiltrates before use in the suspension process in order to avoid concentrations of toxic ingredients that inhibit the fermentation process. [7] Method according to one of claims 5 and 6, characterized by , that parts of the dissolved ammonium and / or dissolved hydrogen sulphide are removed from the biofiltrate in an expeller at temperatures raised to 65 °C and at an absolute pressure in the supernatant vapors of not more than 980 mbar, that the ammonia- and / or hydrogen sulphide-containing vapors from the expeller are cooled in an intermediate heat exchanger to temperatures of not more than 45 °C, that the cooled vapors containing ammonia and / or hydrogen sulphide are fed to a downstream vapor scrubber in the form of a trickle-bed apparatus, whereby sulphurous bioacid from the biogas desulphurisation with a maximum temperature of 25 °C and a pH value between 1 and 3.5 is used as the scrubbing medium and that when the upper pH limit is reached, between 10 and 60 mass% of the fertilizer concentrate with high nitrogen and / or sulphur concentrations is removed from the scrubber sump and replaced by fresh sulphurous bioacid. [8] Method according to one of claims 1 to 7, characterized by , that the hydrolysis process is carried out under intensive mixing with ambient air in a stirred tank at temperatures between 50 and 60 °C, that ambient air is added to the hydrolysis process in a quantity between 2 and 10 vol.% of the biogas obtained in the entire fermentation process, that an average residence time of the biosuspension in the hydrolysis tank of about 2 days is maintained and that between 20 and 100% of the sulphurous bioacid produced during the biological desulfurization of the biogas is added to the hydrolysis process. [9] Method according to one of claims 1 to 8, characterized by that the resulting hydrolysis gas is compressed to at least 30 mbar and fed into the central raw gas line before the gas desulphurisation station or that the resulting hydrolysis gas is compressed to at least 30 mbar and fed into the corrosion-resistant post-fermentation station. [10] Method according to one of claims 1 to 8, characterized by that the special culture is used as a starter culture for the fermentation process and is obtained by adding predominantly lignocellulosic feedstocks in a breeding station for mesophilic or thermophilic mixed cultures. [11] Arrangement for carrying out the process according to claim 1, consisting of at least one suspension station (6), a fermentation station for the methane fermentation (8, 9), a phase separation station (11) for the fermentation residues, a biofiltrate storage tank (12), a gas desulphurisation station (14), characterized by , that the suspension station (6) is connected to a storage and dosing system for additives rich in dry matter, that an inhibitor removal station (5) is arranged between the biofiltrate storage tank (12) and the suspension station (6), that a gas scrubber is preferably arranged in the form of a trickle-bed apparatus as the gas desulphurisation station (14), that a bioacid storage tank (15) is arranged between the gas desulphurisation station (14) and the inhibitor removal station (5) and / or the hydrolysis station (7) for storing the sulphurous bioacid obtained in the gas desulphurisation station (14), that a hydrolysis station (7) is arranged between the suspension station (6) and the fermenter station (8,9) and that the fermenter station (8,9) consists of at least one main fermenter (8) and at least one downstream secondary fermenter (9). [12] Arrangement according to claim 11, characterized by that the plant components are preceded by a plant for bioethanol production from the carbohydrate inventory contained in the peeling masses and / or the starchy sediments of the white waters. [13] Arrangement according to claim 11, characterized by that at least the main fermenter(s) (8) are hydraulically mixed, but not completely mixed, apparatuses. [14] Arrangement according to one of claims 11 and 12, characterized by , that the secondary fermenters (9) are designed as batch-operated and heated stirred tanks. [15] Arrangement according to claim 11, characterized by that different methane bacteria mixed cultures are used in the main fermenters (8) and in the downstream secondary fermenters (9),

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