WO1997034851A1 - Method and facility for the processing of organic waste, and biogas plant for use in such a facility - Google Patents

Abstract

The invention concerns a facility for the processing of organic waste by a combination of fermentation and composting, the installation being characterized in that it includes a biogas plant (1) for the fermentation of organic waste of simple composition, the biogas plant being connected by a pipe line (2) to a tank (3) containing the fermentation substrate and the tank (3) being connected by a pipe line (4) to a clamp-type composting plant for waste of complex composition (5) and/or to an enclosed composting plant for any contaminated organic waste of complex composition and for waste from a composting reactor (6). The invention also concerns a method of processing waste in such a facility, and a biogas plant (1) for use in the facility.

Description

 Process and plant for recycling organic waste and new biogas plant

description

The invention relates to a plant for the simultaneous recycling of structurally poor and structurally rich organic waste, with which the most varied batches of waste can be processed and which can be flexibly adapted to the quantities and types of waste accumulating.

The invention also relates to a corresponding recycling process and a new biogas plant for the two-stage fermentation of organic waste materials, which is either part of the above plant or can also be used independently of the above-mentioned plant.

Organic waste occurs in different forms and compositions in municipalities and industry, which can be easily collected separately: organic components from the household waste bin, green waste and other tree waste (branches from horticulture, parks and street plants) - clean wood waste such as B. formwork from construction and pallets from the trade, wood waste from construction demolition contaminated by impregnating agents (e.g. tar oils and formaldehyde) and paints, but also from old track systems, Soils, food residues, food waste and vegetable waste from industrial kitchens, slaughterhouses, dairies, wholesale markets as well as other food manufacturing and processing companies or agriculture, sewage sludge contaminated by tar oils, mineral oil hydrocarbons or other organic substances

Fats, organic solvents and other organic residues from chemistry, pharmacy and cosmetics, carcasses that have to be recycled.

The deposition of biodegradable waste in landfills leads to hazards and environmental damage and is therefore increasingly restricted or prevented by laws and regulations; therefore they are increasingly being used biologically.

The biological processes have the advantage that they come very close to the natural decomposition processes and thus cause the slightest changes in the material balance of nature. Lignins and humus substances are preserved. The products of the biological processes can be returned to the food cycle in various forms. Since biological processes have a lower degradation rate than thermal processes, a larger storage or reactor volume is required to implement them. However, the technical effort is generally much lower, which means that the treatment costs are significantly lower than those of thermal processes. Two basic biotechnological operations are used for biological waste recycling, which have their specific effect and their preferred area of application: - Composting

- Anaerobic biomethanization (fermentation). Composting is particularly suitable for converting solid organic waste materials into soil improvers containing humus. It can mainly be used to break down structurally rich, difficult-to-decompose materials such as grass, wood or pruning. The rotting process is very slow. If there is insufficient ventilation or too high humidity, the process tips and the desired humus formation does not occur. There is an odor nuisance. For this reason, composting requires considerable mixing or compression energy for ventilation. On the other hand, the self-heating of the compost in the first rotting phase leads to a hygienization of the waste. There is a large, hardly usable amount of waste heat. The aeration of the compost leads to mass losses, which are caused in particular by the evaporation of the water, but also by the conversion of organic matter into C0 ₂ and water.

Composts are used for soil improvement in agriculture, horticulture, for soil remediation, soil recultivation and landfill cover.

The anaerobic biogas process (fermentation) is particularly suitable for structurally poor, easily degradable, moist waste. With it, the best possible overall utilization of organic matter is achieved. This is predominantly in methane and only to a lesser extent in Converted carbon dioxide. For example, DE-Al-44 46 661 describes a method and a plant for the anaerobic processing of food waste.

The biogas is a valuable, renewable energy source that is adequate for natural gas and is used to generate electrical energy in one

Combined heat and power plant (CHP) is suitable.

Methods for biological waste recycling are also known which combine composting and fermentation. In these processes, the composting of the solids follows the biogas production (e.g. HGG process, LINDE-KCA process) or the composting takes place as the first and third stage before and after the biogas production (FIG. 3A -Procedures) (cf. "Working Group for the Utilization of Settlement Waste eV", Issue 29, October 1994, pp. 61-77). However, these processes and systems have the disadvantage that they do not relate to different amounts of waste and Different batches of waste can be adapted, since composting and biogas production cannot be carried out independently of one another and residues are produced which have to be further treated or disposed of.

Another disadvantage of the known two- or three-stage processes, which include both composting and anaerobic treatment, is that some of the substances in the first stage are not optimally treated:

1. The first stage consists of an anaerobic

Biomethanization, the difficult to break down, structurally rich components pass this stage without a significant degradation effect; for them will be additional Reactor space required, which increases the treatment costs. On the other hand, they cause additional difficulties in the process control: formation of a floating blanket or sediment, hinders complete mixing and homogeneous conditions with regard to temperature and concentrations in the anaerobic reactor. This means that more complex reactor designs, increased energy consumption and increasing operating costs for complex cleaning cycles are necessary.

2. If the first stage is composting (aerobic), essential parts of the easily degradable, low-structure organic substance are broken down into carbon dioxide and water and the anaerobic formation of biogas is lost, which reduces the effectiveness of the energetic use. Furthermore, in a strictly aerobic first stage there is the risk that the fatty acids formed here towards the end of the aerobic process with increasing lack of oxygen have an unfavorable composition for methanation, e.g. too high a proportion of lactic acid or propionic acid, which hinder the subsequent methanation and sometimes lead to serious disturbances of the anaerobic process up to its complete cessation. The result is significant odor problems and a reduced amount and quality of biogas.

Furthermore, in the first stage the admixture of substances unsuitable for the respective biological process represents a "dilution" or "contamination" to a certain extent. It is therefore not possible to use intensively working high-performance bioreactors in this configuration in the first stage. The object of the invention was therefore to provide a plant for the recycling of organic waste, with which it is possible to treat different batches of waste, such as food waste, food waste and vegetable waste, e.g. from canteen kitchens, slaughterhouses, dairies, agricultural businesses and food-producing companies, fats, organic solvents and other organic residues from chemistry, pharmacy and cosmetics, carcasses to be recycled, organic components of the bio bin from households, green waste and tree waste, clean and contaminated wood waste as well as contaminated soils for biogas, compost and liquid fertilizer to be processed optimally and effectively in high-performance biological reactors. The plant should be flexibly adaptable to waste quantities and waste batches and, if required, transportable. The high-performance bioreactors used should have the simplest possible reactor designs.

The object of the invention is achieved with a system according to claims 1-7, in which the waste stream for composting and biogas production is carried out in parallel, so that biogas production and composting can be combined and also used independently of one another, thereby making effective use and utilization of energy the waste is guaranteed. A prerequisite for the functioning of the plant according to the invention and the associated method is that the waste which is easily perishable and almost 100% degradable is used in the biogas plant 1. This results in water containing minerals that contains almost no solids. This fermentation substrate is collected in tank 3. The waste, which contains structurally rich and therefore difficult to decompose components, is fed to the composting plants 5 and 6, which are supplied with additional nutrients to accelerate the compost through the drain of the biogas plant from the tank 3.

Structurally rich organic waste, e.g. Cardboard, wood and green waste, which do not pose any problems during composting, can be easily processed into quality compost in an ordinary rental composting plant 5 after appropriate processing, such as shredding and extrusion. Depending on the nitrogen content of the material to be composted, e.g. can vary depending on the green waste, more or less digestate from the tank 3 is fed as a nutrient source and compost accelerator via the pipes 4 and 4a.

Problematic substances, such as contaminated wood waste and soils, odor-contaminated waste or waste that is difficult to decompose and structurally rich waste from the organic waste bin are, after appropriate pretreatment such as shredding, extrusion in a closed, ventilated compost reactor 6, optionally with the addition of specially grown pollutant-degrading microorganisms and digestate from the Tank 3 cleaned and composted in one process step. The more complex compost reactor 6 is required here in order to generate the conditions necessary for the safe degradation of the pollutants, such as moisture, ventilation, and optimal temperature in the entire material, and to ensure targeted biotechnological process control at high degradation speeds. However, it is alternatively also possible to use the compost reactor 6 for the composting of "clean" structurally rich waste, for example if the system may take up little space due to a lack of space or must be housed due to noise pollution supplied unpolluted wood, via the supply line 27 with cardboard and via the supply line 28 with green waste.

Easily degradable waste and sewage sludge are optionally fermented in a homogenizer 16 in the biogas plant 1 after homogenization. The biogas plant can be constructed in one or more stages, ie in addition to fermentation also include an upstream hydrolysis. The biogas plant preferably contains at least one conventional hydrolysis reactor and one or two biogas reactors. Also one or more sanitation reactors or bioreactors or thermal or chemical reactors in which special substances, e.g. Bones, hair or feathers can be removed beforehand, can be connected upstream of the hydrolysis reactor. A plant known in the prior art can be used as the biogas plant. However, the biogas plant according to the present invention, which is described below, is particularly preferably used.

The resulting biogas can be converted into electrical energy and thermal energy in a combined heat and power plant (CHP). However, it can also be used directly for combustion in heating systems or for driving machines or vehicles with a gas engine, even after a corresponding gas cleaning stage. The mineral-containing water from the tank 3 becomes corresponding partially supplied to composting plants 5 and / or 6 or used as liquid fertilizer in agriculture or horticulture.

Figure 1 shows a plant according to the invention for recycling organic waste. The individual parts of the system, e.g. Homogenizer, shredder and extruder are known from the prior art and are commercially available.

The invention also relates to a process for recycling organic waste with the system described above in accordance with process claims 8 to 16. It is clear that not only biogas, liquid fertilizer and quality compost are produced according to the invention, but also a plant substrate in a process step connected to the composting can be manufactured. For this purpose, the compost obtained in the composting plants 5 and / or 6 is mixed in the mixer 24 with swellable organic polymers and, if appropriate, clay or clay-containing materials to form a finished plant substrate. If necessary, shredded and extruded wood can be added from the extruder 19. Crosslinked acrylamide / acrylic acid polymers are preferably added as polymers. In a particularly preferred embodiment, the planting substrate is mixed in such a way that it consists of 30 to 85% by volume of porous fiber containing cellulose and / or lignin, 3.5 to 30% by volume of polymers in the pre-swollen state, and 12 up to 40 vol.% from compost and 3 to 20 vol.% from clay. If necessary, fertilizer can also be added. This substrate is then used in agriculture or horticulture as a water-storing substrate, in particular for plantings in arid soils. The invention further relates to a new biogas plant according to claim 17, with which the wet fermentation of food waste can be carried out efficiently and stably. With this system, not only food waste but also any low-structure waste material with an organic dry matter content of up to 25% can be fermented, which can also include carcasses.

It was surprisingly found that in the fermentation process, substantial process stability in the hydrolysis and pre-acidification stage is achieved if the hydrolysis reactor (1.7) is continuously aerated by compressed air over the surface of the homogenized material or via devices inside the reactor, the first stage fermentation is therefore not semi-anaerobic, but semi-anaerobic. The aeration rate depends on the fatty acid spectra, which in turn depend on the proportion of different substances in the feed such as fats, sugar, starch, proteins. The fatty acid spectra can be determined in preliminary tests for the particular material to be fed using methods which are conventional per se. In a preferred embodiment, the system is therefore designed such that the hydrolysis reactor 1.7 is connected to a compressor 1.8.

In addition, the targeted introduction of air promotes the expulsion of the hydrogen sulfide formed, so that the biogas generated in the plant has a hydrogen sulfide content below the detection limit of 10 ppm. At the same time, the targeted air intake promotes bacterial degradation in the hydrolysis reactor. In addition, the efficiency of the hydrolysis stage can be increased further if the hydrolysis does not occur at ambient temperature (the plant is generally outdoors in summer and winter), but at at least 20 ° C. and at most 40 ° C., that is to say under mesophilic conditions ¬ is performed. For this purpose, the hydrolysis reactor 1.7 is equipped in a preferred embodiment with a conventional temperature controller which regulates the temperature to at least 20 ° C. and at most 40 ° C. This leads to greater operational safety, since a larger number of microorganisms have their optimum in this temperature range.

In order to further improve the described method with regard to faster throughput and operational reliability, it has proven to be extremely effective to connect at least two settling tanks, which work alternately and with a minimal rest period, in both one and two methanation reactors Ensure at least 6 hours, better 12 hours. This significantly accelerates the concentration of the biomass in the process water.

Furthermore, it has been shown that it is essential with regard to process stability and effectiveness, not the biomass as described in DE 44 46 661, but process water containing biomass in relation to the amount of waste supplied, preferably from 2: 1 to 1: 2 for seeding in the hydrolysis reactor 1.7 and, if necessary, in the methanization reactor III (see piping system 1.15). The process water containing biomass can be recycled into the methanation reactor 1.11 in a ratio of 1: 5 to 1:10 to the amount of hydrolyzed material leaving the hydrolysis reactor 1.7. This eliminates the agile separation of the biomass, the process water concentrated with biomass is in each case returned, which has accumulated in the respective settling tank after at least 6 hours in the lower part.

According to the invention, about 40-60% of the process water is returned, which on the one hand guarantees seeding and on the other hand simultaneously ensures a dilution of the material in the hydrolysis reactor of about 2: 1 to 1: 2. This dilution, which is excluded in the process described, has a significant advantage in terms of process stability.

Furthermore, complete mixing of the reactors 1.7, 1.11.1 and 1.11.2 is ensured, for which purpose these e.g. can be equipped with agitators. Pumping around the reactor contents or blowing in biogas are also possible.

For hygienization, if required by law or other regulations, the hydrolysis reactor 1.7 can be preceded by a hygienization tank 1.3, into which the shredded material is introduced from the homogenizer 16 by means of a pump 1.2 and then e.g. is heated at 70 to 90 ° C for half an hour. Others, e.g. Hygiene units that work with ozone are conceivable. Furthermore, an aerobic or semi-anaerobic bioreactor or thermal or chemical reactor for the digestion of components that are difficult to decompose, e.g. Bones or feathers upstream.

Depending on the material to be fermented, the units can

16, 1.3 and 1.5 available or not available or arranged in a different order. If, for example, If sludges are to be fermented, there is no need for homogenization, so that the homogenization unit 16 can be dispensed with. Storage 1.5 and hygienizer 1.3 are also not necessary in every case. In the event that they are necessary, a memory with an integrated homogenizer is used in a preferred variant of the invention. Hygienization tank 1.3 and storage 1.5 may or may not be stirred, depending on the optimal process design in accordance with the starting material.

If materials with a high mineral content are fermented, the solids must first be separated in the settling tank 1.13 and if necessary transferred into a solid tank to be connected, only then can the process water concentrated with the biomass be returned to the hydrolysis and methanation stage.

With the continuously operating system according to the invention, it is possible to fully automatically, reliably and effectively ferment any waste with an oTS content of maximum 25%. It is a hygienically closed system. 90% of the organic matter is broken down. The biogas produced is of high quality and contains 65-75%, preferably 70-75%, methane.

The quality of the biogas enables the operator of the plant to make sensible use. For example, the following are possible direct thermal utilization, electricity and heat generation via cogeneration or feeding into the regional natural gas network.

Each functional unit of the plant (storage, hydrolysis reactor, bioreactor) has its own control system a microcontroller module which controls the process parameters according to a dynamically adaptable program.

A preferred embodiment of the biogas plant 1 according to the invention is shown in FIG. 2 below. All parts of the technical system as well as the automatic control and the piping system can be designed as modules, so that the processing capacity can be further increased by additional modules. It is preferred according to the invention that all units are of the same type and size. The system according to the invention can also be accommodated in a portable container.

Reference list

Fig. 1

Biogas plant 12 feed

Feed fermentation substrate 13 feed

3 tank for the 13a separation plant for fermentation substrate waste from the bio-bin feeder

14 Feeder a feeder

15 Feeder b Feeder

16 Homogenizer rental composting plant for composting 17 shredders of structurally rich organic waste 18 shredders closed composting 19 extruder plant for composting possibly 20 extruders contaminated structurally rich organic 21 sieve waste

22 feeder feeder

23 feeder feeder

24 Mixing system feed

25 Feeder a unpacking plant for food waste 26 Feeder 0 feeder 27 Feeder 1 feeder 28 Feeder Continuation of the list of reference symbols

Fiα. 2

16 homogenizer

1.2 pump

1.3 Hygiene device

1.4 pump

1.5 storage or pre-treatment reactor

1.6 pump

1.7 hydrolysis reactor

1.8 compressor

1.9 Exhaust filter

1.10 pump

1.11.1 Methanation reactor

1.11.2 Methanation reactor l.12 pump

1.13.1 settling tanks

1.13.2 settling tanks

1.14 pump

1.15 Process water return

1.16 Gas storage

1.17 gas torch

1.18 combined heat and power plant

2 Feeding fermentation substrate

Claims

claims 1. Plant for the recovery of organic waste by combining fermentation and composting, characterized in that it includes a biogas plant (1) for the fermentation of low-structure organic waste, which is connected via a pipe (2) to a tank for the fermentation substrate (3) is, and this tank (3) by means of a Pipeline (4) is connected to a rent composting plant for composting structurally rich organic waste (5) and / or a closed composting plant for composting any contaminated structurally rich organic waste and waste from the bio-bin (6). 2. Plant according to claim 1, characterized in that the biogas plant (1) is a homogenizer (16) is connected upstream, which is connected on the input side to the feeds (8) and / or (9). 3. Plant according to claim 1 or 2, characterized in that the rent composting plant (5) is preceded by a shredder (17) and / or an extruder (19), the shredder (17) is connected on the input side to the feed (10) and the extruder (19) is connected on the input side to the feeds (10) and (11). 4. Plant according to one of claims 1 to 3, characterized in that the closed composting plant (6) is preceded by a shredder (18) and / or an extruder (20) and / or a sieve (21), the shredder (18 ) is connected on the inlet side to the feeds (13) and / or (14), the extruder (20) is connected on the inlet side to the feeders (25) and / or (27) and the screen (21) is connected to the inlet (15) connected is. 5. Plant according to one of claims 1 to 4, characterized in that the rent composting system (5) by means of a discharge (22) and / or the closed composting system (6) by means of a discharge (23) are connected to a mixing system (24). 6. Plant according to one of claims 1 to 5, characterized in that the feed (26) connects the extruder (19) and the mixing plant (24). 7. Plant according to one of claims 1 to 6, characterized in that the biogas plant (1) is connected directly to the feed (7), the rental composting plant (5) directly to the Feeder (12) and the closed composting plant (6) directly with the feeder (28). 8. Process for recycling organic waste by means of a combined composting and fermentation process, characterized in that by means of a plant according to claims 1 to 6 low-structure and liquid organic waste are fermented in a biogas plant (1), the remaining fermentation substrate as a nutrient source from the Tank (3) is fed via the pipeline (4a) to a rental composting plant (5) which is used for composting structurally rich organic waste, and / or is fed via the pipeline (4b) to a closed composting plant (6) which is used for composting of possibly contaminated structurally rich organic waste and waste from the bio-bin, and thus a complete degradation of the organic waste to biogas, liquid fertilizer and compost takes place, the Then compost if necessary via the Feeders (22) and (23) in a mixing plant (24) transported and there with aggregates and possibly via the feed (26) shredded and extruded wood from the extruder (19) is added so that a plant substrate is obtained. 9. The method according to claim 8, characterized in that the low-structure and liquid organic waste, which are fermented in the biogas plant (l), food waste, Food waste, fruit and vegetable waste, carcasses, fats, waste water, sewage sludge and chemical, pharmaceutical and cosmetic waste. 10. The method according to claim 8, characterized in that the structurally rich organic waste, which are composted in the rental composting system (5) or in the closed rental composting system (6), are unpolluted waste such as wood, wood chips, cardboard and green waste. 11. The method according to claim 8, characterized in that the contaminated structurally rich organic waste in the closed Composting plant (6) can be composted, problem wastes are like contaminated soils, contaminated wood waste and odor-contaminated waste. 12. The method according to claim 8, characterized in that swellable organic polymers and optionally clay- or clay-containing materials are added as additives in the mixing plant (24). 13. The method according to claim 8 and 9, characterized in that the biogas plant (1) via the feed (7) the low-structure and liquid organic waste from chemistry, pharmacy and Cosmetics and the waste water are fed in and the food waste, fruit and vegetable waste and carcasses are fed in via the feed (8) and the food waste, which may be unpacked in Appendix 9a, is fed in via the feed (8), the food waste, food waste, fruit waste and vegetable waste and carcasses before entry into the Biogas plant (l) may be homogenized in the homogenizer (16). 14. The method according to claim 8 and 10, characterized in that the rent composting system (5) on the feed (10) wood, on the feed (11) cardboard and the feed (12) green waste are fed, the wood being shredded (17) and / or extruded in the extruder (19) and also the cardboard before the entry into the rent composting system (5) Entry in the rent composting system (5) is optionally extruded in the extruder (19). 15. The method according to claim 8 and 11, characterized in that the closed composting plant (6) the structurally rich waste from the bio-bin via the feeder (13), optionally after sifting, sorting and separating in the system 13a, are fed in the feed (14) contaminated wood and via the feed (15) the problem waste including the contaminated soils are fed in, the contaminated wood possibly being shredded and / or shredded (18) before being fed into the closed composting plant (6) is extruded in the extruder (20) and the problem wastes are passed through a sieve (21) before being fed into the closed composting (6). 16. The method according to claim 8 and 10, characterized in that the closed composting plant (6) are supplied with unpolluted waste, wherein wood is fed in via the feed (14), cardboard via the feed (27) and green waste via the feed (28), the wood being shredded in the shredder (18) and / or before being fed into the plant (6), and / or or is extruded in the extruder (20) and the cardboard is optionally extruded in the extruder (20) before being fed into the system (6). 17. Biogas plant for the two-stage fermentation of organic waste materials with a maximum organic dry matter content of 25%, comprising a hydrolysis reactor (1.7) for hydrolysis and pre-acidification of the organic material, to which at least one, preferably two, methanation reactors ( 1.11) for the thermophilic fermentation of the hydrolyzed and pre-acidified material, characterized in that the hydrolysis reactor (1.7) can be aerated by compressed air, that at least two parallel settling tanks (1.13 .1, 1.13.2) to concentrate the resulting biomass in the process water, which are operated alternately and that the settling tanks (1.13.1, 1.13.2) via the pump (1.14) and via the pipeline (1.15) for process water return with the Hydrolysis reactor (1.7) and optionally connected to the methanization reactor (l.ll).