Do-it-yourself biogas plant: Internet myths and rural reality. Biogas plant: recycling organic waste with benefits
Rising energy prices are forcing us to look for alternative heating options. Good results can be achieved by self-production of biogas from available organic raw materials. In this article we will talk about the production cycle, the design of the bioreactor and related equipment.
Subject to basic operating rules, a gas reactor is completely safe and is capable of providing fuel and electricity to even a small house or an entire agricultural complex. The result of the bioreactor is not only gas, but also one of the most valuable types of fertilizers, the main component of natural humus.
How to obtain biogas
To produce biogas, organic raw materials are placed in conditions favorable for the development of several types of bacteria, which produce methane during their life processes. Biomass goes through three cycles of transformation, and at each stage different strains of anaerobic organisms take part. Oxygen is not required for their life activity, but has great importance the composition of the raw material and its consistency, as well as temperature and internal pressure. Conditions with a temperature of 40-60 °C and a pressure of up to 0.05 atm are considered optimal. The loaded raw material begins to produce gas after prolonged activation, which takes from several weeks to six months.
The beginning of gas release in the calculated volume indicates that the colonies of bacteria are already quite numerous, therefore, after 1-2 weeks, fresh raw materials are dosed into the reactor, which is almost immediately activated and enters the production cycle.
To maintain optimal conditions, the raw materials are periodically stirred, and part of the heat from gas heating is used to maintain the temperature. The resulting gas contains from 30 to 80% methane, 15-50% carbon dioxide, small admixtures of nitrogen, hydrogen and hydrogen sulfide. For domestic use, gas is enriched by removing carbon dioxide from it, after which the fuel can be used in a wide range of energy equipment: from power plant engines to heating boilers.
What raw materials are suitable for production
Contrary to popular belief, manure is not the best raw material for biogas production. The fuel yield from a ton of pure manure is only 50-70 m 3 with a concentration of 28-30%. However, it is animal waste that contains most of the necessary bacteria to quickly start up and maintain efficient operation of the reactor.
For this reason, manure is mixed with waste from crop production and food industry in a ratio of 1:3. The following are used as plant raw materials:
Raw materials cannot simply be poured into the reactor; certain preparation is required. The initial substrate is crushed to a fraction of 0.4-0.7 mm and diluted with water in an amount of about 25-30% of the dry mass. In larger volumes, the mixture requires more thorough mixing in homogenization devices, after which it is ready to be loaded into the reactor.
Construction of a bioreactor
The requirements for the reactor placement conditions are the same as for a passive septic tank. The main part of the bioreactor is the digester - the container in which the entire fermentation process takes place. To reduce the cost of heating the mass, the reactor is dug into the ground. Thus, the temperature of the medium does not fall below 12-16 °C, and the heat outflow generated during the reaction remains minimal.
Diagram of a biogas plant: 1 - raw material loading bunker; 2 - biogas; 3 - biomass; 4 — compensator tank; 5 — hatch for waste removal; 6 — pressure relief valve; 7 - gas tube; 8 — water seal; 9 - to consumers
For digesters with a volume of up to 3 m 3, it is allowed to use nylon tanks. Since the thickness and material of their walls do not interfere with the outflow of heat, the containers are lined with layers of polystyrene foam or moisture-resistant mineral wool. The bottom of the pit is concreted with a 7-10 cm screed with reinforcement to prevent the reactor from being squeezed out of the ground.
The most suitable material for the construction of large reactors is reinforced expanded clay concrete. It has sufficient strength, low thermal conductivity and a long service life. Before pouring the walls of the chamber, you need to install an inclined pipe to supply the mixture to the reactor. Its diameter is 200-350 mm, the lower end should be 20-30 cm from the bottom.
At the top of the digester there is a gas holder - a dome or cone structure that concentrates gas at the top point. The gas holder can be made of sheet metal, but in small installations the vault is made of brickwork, and then lined with steel mesh and plastered. When constructing a gas tank, it is necessary to provide a sealed passage of two tubes in its upper part: for gas intake and installation of a pressure relief valve. Another pipe with a diameter of 50-70 mm is laid to pump out the waste mass.
The reactor container must be sealed and withstand a pressure of 0.1 atm. To do this, the inner surface of the digester is covered with a continuous layer of coating bitumen waterproofing, and a sealed hatch is mounted on the top of the gas holder.
Gas removal and enrichment
From under the dome of the gas tank, gas is discharged through a pipeline into a container with a water seal. The thickness of the water layer above the tube outlet determines the operating pressure in the reactor and is usually 250-400 mm.
After a water seal, the gas can be used in heating equipment and for cooking. However, internal combustion engines require a higher methane content to operate, so the gas is enriched.
The first stage of enrichment is reducing the concentration of carbon dioxide in the gas. To do this, you can use special equipment that works on the principle of chemical absorption or on semi-permeable membranes. At home, enrichment is also possible by passing gas through a layer of water in which up to half of the CO 2 dissolves. The gas is atomized into small bubbles through tubular aerators, and carbon dioxide-saturated water must be periodically removed and atomized under normal atmosphere conditions. In plant growing complexes, such water is successfully used in hydroponic systems.
At the second stage of enrichment, the gas moisture content is reduced. This feature is present in most factory-made enrichment devices. Homemade dehumidifiers look like a Z-shaped tube filled with silica gel.
Use of biogas: specifics and equipment
Most modern models of heating equipment are designed to work with biogas. Outdated boilers can be relatively easily converted by replacing the burner and the gas-air mixture preparation device.
To obtain gas under operating pressure, a conventional piston compressor with a receiver is used, set to operate at a pressure of 1.2 of the design pressure. Pressure normalization is carried out by a gas reducer, this helps to avoid drops and maintain an even flame.
The productivity of the bioreactor must be at least 50% higher than the consumption. No excess gas is generated in production: when the pressure exceeds 0.05-0.065 atm, the reaction almost completely slows down, and is restored only after part of the gas is pumped out.
10.1. General information about biogas production
In the last decade, much attention has been paid to the development in our country of the use of non-traditional and renewable energy sources due to the shortage of its own fuel and energy resources. One of the non-traditional and renewable energy sources can be energy obtained from biomass. It is the biogas obtained on the farms of the republic and the production of energy from it that will allow saving natural and liquefied gases.
All sources of biomass can be divided into three main groups:
to the first group These include land plants specially grown for energy purposes. Silvicultural energy farms are of the greatest importance for growing various tree species: a fast-growing willow species (developed by Belarusian scientists), ebony, eucalyptus, palm tree, hybrid poplar, etc. One of the promising energy crops is the Jerusalem artichoke, sweet sorghum, and sugar cane.
To the second group biomass sources include various organic residues and wastes:
a) biological waste of animals (cattle manure, droppings poultry and etc.);
b) residues from harvesting agricultural crops and by-products of their processing, such as rye and wheat straw, corn cob, cotton stalk, peanut shell, potato waste, rice husks and straw, seed husks, flax husks, etc.;
c) waste from logging, sawmilling and wood processing: bark, sawdust, wood chips, shavings;
d) industrial wastewater (in particular, textile, dairy, and other food processing enterprises);
e) municipal waste (solid and waste water).
Third group– these are aquatic plants, including seaweeds, including giant kelp (brown algae) and water hyacinth. The ocean is seen as the main supplier of large marine brown algae and algae living on the bottom (benthic plants), as well as algae floating in stagnant water. In addition, the possibility of using biomass from the estuary of salt and freshwater marshes is analyzed.
The energy potential of aquatic plants is quite high. For example, fresh seaweed 29.2 t.e./ha/year; water hyacinth -53.6 t.o.e/ha/year, and sugar cane 40.0 t.o.e/ha/year /21/, /26/.
Depending on the humidity and degree of biodegradability, biomass is processed by thermochemical methods (direct combustion, gasification, pyrolysis, liquefaction) or biological methods (anaerobic processing, ethanol fermentation). With their help, various final energy products can be obtained from biomass, including heat, steam, low- and high-calorie gases and various liquid fuels. One of the most widely used methods for processing biomass remains direct combustion to produce heat or electricity. The most promising processes for converting biomass are thermochemical gasification, fermentation and anaerobic processing, which results in synthesis gas (methane). The development of bioenergy based on a renewable energy resource such as wood may be promising for Belarus. This includes the cultivation of fast-growing varieties of wood. In Belarus, research is already underway on growing energy plantations of Canadian willow and Sakhalin knotweed Weirich. These trees are capable of renewing themselves within 25 years, and cutting and fuel collection are carried out after 3 years, and one hectare of plantation can produce an average of 20 m3 of wood. The possibilities of growing and the feasibility of growing Sakhalin bamboo and Sylvia latifolia in our climatic conditions are also being studied. The technology of burning wood pellets is being developed and widely used.
10.2. Producing biogas from anaerobic digestion
One of the ways to produce biogas is the method anaerobic(without oxygen), fermentation or fermentation(overheating) organic matter biological mass of various origins at a temperature of 30÷370 °C, as well as with constant stirring of the loaded raw materials, periodic loading of the raw materials into the fermentation container and unloading of the fermented material /17, pp. 357-364/. The container in which the fermentation process occurs is called digester or reactor. If all the above conditions are met, under the influence of bacteria present in the biomass, organic substances decompose and form a mixture of gases, which is called biogas.To produce biogas, waste from processing agricultural crops can be used - silage, straw, food and other farm waste, manure, bird droppings, sewage and similar raw materials containing organic substances. It is important that the environment of the raw materials is neutral, without substances that interfere with the action of bacteria, such as soap, washing powders, antibiotics / 20/.
Biogas contains 50÷80% methane (CH 4), 50÷20% carbon dioxide (CO 2), 0÷3% hydrogen sulfide (H 2 S), as well as impurities: hydrogen, ammonia and nitrogen oxides. Biogas does not have an unpleasant odor. The heat of combustion of 1 m 3 of biogas reaches 21÷29 MJ, which is approximately equivalent to burning 0.6 liters of gasoline, 0.85 liters of alcohol, 1.7 kg of firewood or using 1.4÷1.6 kWh of electricity. The efficiency of fermentation depends on compliance anaerobic conditions, temperature and duration of fermentation. Fermentation of manure is possible at a temperature of 30÷35 °C ( mesophAndline directorAndmfermentedAndI) and 50÷60°С and above ( thermofAndline directorAndm).
The duration of manure fermentation depends on the type of biomass. For cattle manure and chicken manure, the duration is 20 days, for pig manure - 10 days. The activity of the microbial reaction is largely determined by the ratio of carbon and nitrogen. The most favorable conditions with the ratio C/N== 10:16.
From 1 m 3 of reactor, the biogas yield reaches 2÷3 m 3 of biogas, from bird droppings - 6 m 3 /21/. The following amount of biogas can be obtained per day from one animal: large cattle(weighing 500÷600 kg) -< 1,5 м 3 ; свиньи (массой 80÷100 кг) - 0,2 м 3 ; куры или кролики - 0,015 м 3 .
Data on the specific yield of biogas from various agricultural wastes are given in Table 15.1 /17, p.357/.
The energy obtained from burning biogas can be used for various agricultural needs. Using an electric generator driven by a gas internal combustion engine, electricity can be generated. The disadvantage is that part of the generated energy must be used to operate the biogas plant itself (in some installations up to 50% of the generated energy).
Biogas can be burned as fuel in burners of heating installations, hot water boilers, gas stoves and used in absorption-type refrigeration units, in automotive engines, and in infrared radiation units. A carburetor engine can easily be converted to gas, including biogas. To do this, the carburetor is replaced with a mixer. Converting diesel engines to gas operation is not difficult. When switching from diesel fuel to natural gas, engine power is reduced by 20%, from natural to biogas - by 10%. Biogas consumption is on average 0.65 m 3 /kW h. The gas pressure in front of the engine must be at least 0.4 kPa /17, p. 358/.
In livestock farming for heating water, the need for biogas per animal per year is: dairy cow - 21-30 m 3, pig - 1.4-4.9 m 3. Larger values of these figures refer to small farms, smaller ones - to medium-sized ones.
Table 15.1.
Biogas yield from organic waste
The need for biogas for heating milking parlors is equal to: with the number of cows 40 - 164/327 m 3 /year; with a number of cows of 60 - 212/410 m 3 /year; with a number of cows of 80 - 262/530 m 3 /year. The numerator contains data at an outside air temperature of up to - 10 ° C, and the denominator - at an outside air temperature t below - 10 ° C.
To heat poultry houses at an external temperature of - 10 ° C and an internal temperature of 18 ° C, approximately 1.2 m 3 / h per 1000 birds is required.
The residue (methane mash) can be used as fertilizer.
B And gas installations And (BSU), depending on the characteristics of the technological scheme, are of three types: continuous, periodic and accumulative /17, p.360/.
With a continuous (flow) scheme (Fig. 15.1), fresh substrate is loaded into the fermentation chamber continuously or at certain intervals (from 2 to 10 times a day), removing the same amount of fermented mass. This system allows you to obtain the maximum amount of biogas, but requires more material costs.
With a periodic (cyclic) scheme (Fig. 15.2), there are two fermentation chambers, which are loaded in turn. In this case, the useful volume of the chambers is used less efficiently than with continuous. In addition, significant supplies of manure or other substrate are needed to fill them.
With an accumulative scheme, the manure storage facility simultaneously serves as a chamber for fermentation and storage of fermented manure until it is unloaded (Fig. 15.3).
Biogas is a gas obtained as a result of fermentation (fermentation) of organic substances (for example: straw; weeds; animal and human feces; garbage; organic waste, domestic and industrial waters, etc.) under anaerobic conditions. Biogas production involves different types of microorganisms with a varied number of catabolic functions.
Composition of biogas.
More than half of biogas consists of methane (CH 4). Methane makes up approximately 60% of biogas. In addition, biogas contains carbon dioxide (CO 2) about 35%, as well as other gases such as water vapor, hydrogen sulfide, carbon monoxide, nitrogen and others. Biogas produced in different conditions, is different in its composition. Thus, biogas from human excrement, manure, and slaughter waste contains up to 70% methane, and from plant residues, as a rule, about 55% methane.
Microbiology of biogas.
Biogas fermentation, depending on the microbial species of bacteria involved, can be divided into three stages:
The first is called the beginning of bacterial fermentation. Various organic bacteria, when multiplying, secrete extracellular enzymes, the main role of which is to destroy complex organic compounds with the hydrolytic formation of simple substances. For example, polysaccharides to monosaccharides; protein into peptides or amino acids; fats into glycerol and fatty acids.
The second stage is called hydrogen. Hydrogen is produced as a result of the activity of acetic acid bacteria. Their main role is the bacterial decomposition of acetic acid to produce carbon dioxide and hydrogen.
The third stage is called methanogenic. It involves a type of bacteria known as methanogens. Their role is to use acetic acid, hydrogen and carbon dioxide to produce methane.
Classification and characteristics of raw materials for biogas fermentation.
Almost all natural organic materials can be used as feedstock for biogas fermentation. The main raw materials for biogas production are wastewater: sewage; food, pharmaceutical and chemical industry. In rural areas, this is waste generated during harvesting. Due to the differences in origin, the formation process is also different, chemical composition and structure of biogas.
Sources of raw materials for biogas depending on origin:
1. Agricultural raw materials.
These raw materials can be divided into raw materials with a high nitrogen content and raw materials with a high carbon content.
Raw materials with high nitrogen content:
human feces, livestock manure, bird droppings. The carbon-nitrogen ratio is 25:1 or less. So raw it was completely overcooked gastrointestinal tract person or animal. As a rule, it contains a large number of low molecular weight compounds. The water in such raw materials was partially transformed and became part of low molecular weight compounds. This raw material is characterized by easy and rapid anaerobic decomposition into biogas. And also a rich methane output.
Raw materials with high carbon content:
straw and husk. The carbon-nitrogen ratio is 40:1. It has a high content of high-molecular compounds: cellulose, hemicellulose, pectin, lignin, vegetable waxes. Anaerobic decomposition occurs quite slowly. In order to increase the rate of gas production, such materials usually require pre-treatment before fermentation.
2. Urban organic water waste.
Includes human waste, sewage, organic waste, organic industrial wastewater, sludge.
3. Aquatic plants.
Includes water hyacinth, other aquatic plants and algae. Estimated planned load production capacity are characterized big addiction from solar energy. They have high profitability. Technological organization requires a more careful approach. Anaerobic decomposition occurs easily. The methane cycle is short. The peculiarity of such raw materials is that without pre-treatment it floats in the reactor. In order to eliminate this, the raw materials must be slightly dried or pre-composted for 2 days.
Sources of raw materials for biogas depending on humidity:
1.Solid raw materials:
straw, organic waste with a relatively high dry matter content. They are processed using the dry fermentation method. Difficulties arise with removing large amounts of solid deposits from the rector. The total amount of raw materials used can be expressed as the sum of the solids content (TS) and volatile substances (VS). Volatiles can be converted to methane. To calculate volatile substances, a sample of raw materials is loaded into a muffle furnace at a temperature of 530-570°C.
2. Liquid raw materials:
fresh feces, manure, droppings. Contains about 20% dry matter. Additionally, they require the addition of water in an amount of 10% for mixing with solid raw materials during dry fermentation.
3. Organic waste of medium humidity:
stillage from alcohol production, wastewater from pulp mills, etc. Such raw materials contain varying amounts of proteins, fats and carbohydrates, and are good raw materials for the production of biogas. For this raw material, devices of the UASB type (Upflow Anaerobic Sludge Blanket - upward anaerobic process) are used.
| Name of fermented waste | average speed biogas flow during normal gas production (m 3 /m 3 /d) | Biogas output, m 3 /Kg/TS | Biogas production (% of total biogas production) | |||
| 0-15d | 25-45 d | 45-75 d | 75-135 d | |||
| Dry manure | 0,20 | 0,12 | 11 | 33,8 | 20,9 | 34,3 |
| Chemical industry water | 0,40 | 0,16 | 83 | 17 | 0 | 0 |
| Rogulnik (chilim, water chestnut) | 0,38 | 0,20 | 23 | 45 | 32 | 0 |
| Water salad | 0,40 | 0,20 | 23 | 62 | 15 | 0 |
| Pig manure | 0,30 | 0,22 | 20 | 31,8 | 26 | 22,2 |
| Dry grass | 0,20 | 0,21 | 13 | 11 | 43 | 33 |
| Straw | 0,35 | 0,23 | 9 | 50 | 16 | 25 |
| Human excrement | 0,53 | 0,31 | 45 | 22 | 27,3 | 5,7 |
Calculation of the process of methane fermentation.
General principles Fermentation engineering calculations are based on increasing the loading of organic raw materials and reducing the duration of the methane cycle.
Calculation of raw materials per cycle.
The loading of raw materials is characterized by: Mass fraction TS (%), mass fraction VS (%), concentration COD (COD - chemical oxygen demand, which means COD - chemical indicator of oxygen) (Kg/m 3). The concentration depends on the type of fermentation devices. For example, modern industrial wastewater reactors are UASB (upstream anaerobic process). For solid raw materials, AF (anaerobic filters) are used - usually the concentration is less than 1%. Industrial waste as a raw material for biogas most often has a high concentration and needs to be diluted.
Download speed calculation.
To determine the daily reactor loading amount: concentration COD (Kg/m 3 ·d), TS (Kg/m 3 ·d), VS (Kg/m 3 ·d). These indicators are important indicators for assessing the efficiency of biogas. It is necessary to strive to limit the load and at the same time have a high level of gas production volume.
Calculation of the ratio of reactor volume to gas output.
This indicator is an important indicator for assessing the efficiency of the reactor. Measured in Kg/m 3 ·d.
Biogas yield per unit mass of fermentation.
This indicator characterizes the current state of biogas production. For example, the volume of the gas collector is 3 m 3. 10 Kg/TS is supplied daily. The biogas yield is 3/10 = 0.3 (m 3 /Kg/TS). Depending on the situation, you can use the theoretical gas output or the actual gas output.
The theoretical yield of biogas is determined by the formulas:
Methane production (E):
E = 0.37A + 0.49B + 1.04C.
Carbon dioxide production (D):
D = 0.37A + 0.49B + 0.36C. Where A is carbohydrate content per gram of fermentation material, B is protein, C is fat content
Hydraulic volume.
To increase efficiency, it is necessary to reduce the fermentation period. To a certain extent there is a connection with the loss of fermenting microorganisms. Currently, some efficient reactors have fermentation times of 12 days or even less. The hydraulic volume is calculated by calculating the volume of daily feedstock loading from the day the feedstock loading began and depends on the residence time in the reactor. For example, fermentation is planned at 35°C, feed concentration is 8% (total amount of TS), daily feed volume is 50 m 3, fermentation period in the reactor is 20 days. The hydraulic volume will be: 50·20 = 100 m3.
Removal of organic contaminants.
Biogas production, like any biochemical production, has waste. Biochemical production waste can cause environmental damage in cases of uncontrolled waste disposal. For example, falling into the river next door. Modern large biogas plants produce thousands and even tens of thousands of kilograms of waste per day. The qualitative composition and methods of disposal of waste from large biogas plants are controlled by enterprise laboratories and the state environmental service. Small farm biogas plants do not have such controls for two reasons: 1) since there is little waste, there will be little harm to the environment. 2) Carrying out high-quality analysis of waste requires specific laboratory equipment and highly specialized personnel. Small farmers don’t have this, but government agencies they rightly consider such control to be inappropriate.
An indicator of the level of contamination of biogas reactor waste is COD (chemical indicator of oxygen).
The following mathematical relationship is used: COD of organic loading rate Kg/m 3 ·d= loading concentration of COD (Kg/m 3) / hydraulic shelf life (d).
Gas flow rate in the reactor volume (kg/(m 3 ·d)) = biogas yield (m 3 /kg) / COD of organic loading rate kg/(m 3 ·d).
Advantages of biogas energy plants:
solid and liquid waste have a specific odor that repels flies and rodents;
the ability to produce useful final product- methane, which is a clean and convenient fuel;
during the fermentation process, weed seeds and some of the pathogens die;
during the fermentation process, nitrogen, phosphorus, potassium and other fertilizer ingredients are almost completely preserved, part of the organic nitrogen is converted into ammonia nitrogen, and this increases its value;
the fermentation residue can be used as animal feed;
biogas fermentation does not require the use of oxygen from the air;
anaerobic sludge can be stored for several months without adding nutrients, and then when loading primary raw materials, fermentation can quickly begin again.
Disadvantages of biogas energy plants:
complex device and requires relatively large investments in construction;
requires a high level of construction, management and maintenance;
The initial anaerobic propagation of fermentation occurs slowly.
Features of the methane fermentation process and process control:
1. Temperature of biogas production.
The temperature for biogas production can be in a relatively wide temperature range of 4~65°C. With increasing temperature, the rate of biogas production increases, but not linearly. Temperature 40~55°C is a transition zone for the life activity of various microorganisms: thermophilic and mesophilic bacteria. The highest rate of anaerobic fermentation occurs in a narrow temperature range of 50~55°C. At a fermentation temperature of 10°C, the gas flow rate is 59% in 90 days, but the same flow rate at a fermentation temperature of 30°C occurs in 27 days.
A sudden change in temperature will have a significant impact on biogas production. The design of a biogas plant must necessarily provide for control of such a parameter as temperature. Temperature changes of more than 5°C significantly reduce the productivity of the biogas reactor. For example, if the temperature in the biogas reactor was long time 35°C, and then suddenly dropped to 20°C, then the production of the biogas reactor will almost completely stop.
2. Grafting material.
Methane fermentation typically requires a specific number and type of microorganisms to complete. The sediment rich in methane microbes is called inoculum. Biogas fermentation is widespread in nature and places with grafting material are just as widespread. These are: sewer sludge, silt deposits, bottom sediments of manure pits, various sewage sludges, digestive residues, etc. Due to the abundant organic matter and good anaerobic conditions, they develop rich microbial communities.
Inoculum added for the first time to a new biogas reactor can significantly reduce the stagnation period. In the new biogas reactor, it is necessary to manually fertilize with grafting material. When using industrial waste as raw materials, special attention is paid to this.
3. Anaerobic environment.
The anaerobicity of the environment is determined by the degree of anaerobicity. Typically, the redox potential is usually denoted by the value Eh. Under anaerobic conditions, Eh has a negative value. For anaerobic methane bacteria, Eh lies in the range of -300 ~ -350mV. Some bacteria that produce facultative acids are able to live a normal life at Eh -100 ~ + 100 mV.
In order to ensure anaerobic conditions, it is necessary to ensure that biogas reactors are built tightly closed, ensuring that they are watertight and leak-free. For large industrial biogas reactors, the Eh value is always controlled. For small farm biogas reactors, the problem of controlling this value arises due to the need to purchase expensive and complex equipment.
4. Control of the acidity of the medium (pH) in the biogas reactor.
Methanogens require a pH range within a very narrow range. On average pH=7. Fermentation occurs in the pH range from 6.8 to 7.5. pH control is available for small biogas reactors. To do this, many farmers use disposable litmus indicator paper strips. On large enterprises Electronic pH monitoring devices are often used. Under normal circumstances, the balance of methane fermentation is a natural process, usually without pH adjustment. Only in isolated cases of mismanagement do massive accumulations of volatile acids and a decrease in pH appear.
Measures to mitigate the effects of high acidity pH include:
(1) Partially replace the medium in the biogas reactor, thereby diluting the volatile acid content. This will increase the pH.
(2) Add ash or ammonia to increase pH.
(3) Adjust pH with lime. This measure is especially effective in cases of extremely high acid contents.
5. Mixing the medium in the biogas reactor.
In a typical fermentation tank, the fermentation medium is usually divided into four layers: top crust, supernatant layer, active layer and sediment layer.
Purpose of mixing:
1) relocation of active bacteria to a new portion of primary raw materials, increasing the contact surface of microbes and raw materials to accelerate the rate of biogas production, increasing the efficiency of use of raw materials.
2) avoiding the formation of a thick layer of crust, which creates resistance to the release of biogas. Raw materials such as straw, weeds, leaves, etc. are especially demanding for mixing. In a thick layer of crust, conditions are created for the accumulation of acid, which is unacceptable.
Mixing methods:
1) mechanical mixing with wheels various types installed inside the working space of the biogas reactor.
2) mixing with biogas taken from the upper part of the bioreactor and supplied to the lower part with excess pressure.
3) mixing with a circulating hydraulic pump.
6. Carbon to nitrogen ratio.
Only an optimal ratio of nutrients contributes to effective fermentation. The main indicator is the carbon to nitrogen ratio (C:N). The optimal ratio is 25:1. Numerous studies have proven that the limits of the optimal ratio are 20-30:1, and biogas production is significantly reduced at a ratio of 35:1. Experimental studies have revealed that biogas fermentation is possible with a carbon to nitrogen ratio of 6:1.
7. Pressure.
Methane bacteria can adapt to high hydrostatic pressures (about 40 meters or more). But they are very sensitive to changes in pressure and because of this there is a need for stable pressure (no sudden changes in pressure). Significant changes in pressure can occur in cases of: a significant increase in biogas consumption, relatively fast and large loading of the bioreactor with primary raw materials, or similar unloading of the reactor from sediments (cleaning).
Ways to stabilize pressure:
2) supply fresh primary raw materials and cleaning simultaneously and at the same discharge rate;
3) installing floating covers on a biogas reactor allows you to maintain a relatively stable pressure.
8. Activators and inhibitors.
Some substances, when added in small quantities, improve the performance of a biogas reactor, such substances are known as activators. While other substances added in small quantities lead to significant inhibition of the processes in the biogas reactor, such substances are called inhibitors.
Many types of activators are known, including some enzymes, inorganic salts, organic and inorganic substances. For example, adding a certain amount of the enzyme cellulase greatly facilitates the production of biogas. The addition of 5 mg/Kg of higher oxides (R 2 O 5) can increase gas production by 17%. The biogas yield for primary raw materials from straw and the like can be significantly increased by adding ammonium bicarbonate (NH 4 HCO 3). Activators are also activated carbon or peat. Feeding a bioreactor with hydrogen can dramatically increase methane production.
Inhibitors mainly refer to some of the compounds of metal ions, salts, fungicides.
Classification of fermentation processes.
Methane fermentation is a strictly anaerobic fermentation. Fermentation processes are divided into the following types:
Classification according to fermentation temperature.
Can be divided into "natural" fermentation temperatures (variable temperature fermentation), in which case the fermentation temperature is about 35°C and the process with high temperature fermentation (about 53°C).
Classification by differentialness.
According to the differential nature of fermentation, it can be divided into single-stage fermentation, two-stage fermentation and multi-stage fermentation.
1) Single-stage fermentation.
Refers to the most common type of fermentation. This applies to devices in which acids and methane are simultaneously produced. Single-stage fermentations may be less efficient in terms of BOD (Biological Oxygen Demand) than two- and multi-stage fermentations.
2) Two-stage fermentation.
Based on separate fermentation of acids and methanogenic microorganisms. These two types of microbes have different physiology and nutritional requirements, and there are significant differences in growth, metabolic characteristics and other aspects. Two-stage fermentation can greatly improve the biogas yield and decomposition of volatile fatty acids, shorten the fermentation cycle, bring significant savings in operating costs, and effectively remove organic contaminants from waste.
3) Multi-stage fermentation.
It is used for primary raw materials rich in cellulose in the following sequence:
(1) The cellulose material is hydrolyzed in the presence of acids and alkalis. Glucose is formed.
(2) The grafting material is introduced. This is usually active sludge or wastewater from a biogas reactor.
(3) Create suitable conditions for the production of acidic bacteria (producing volatile acids): pH=5.7 (but not more than 6.0), Eh=-240mV, temperature 22°C. At this stage, the following volatile acids are formed: acetic, propionic, butyric, isobutyric.
(4) Create suitable conditions for the production of methane bacteria: pH=7.4-7.5, Eh=-330mV, temperature 36-37°C
Classification by periodicity.
Fermentation technology is classified into batch fermentation, continuous fermentation, semi-continuous fermentation.
1) Batch fermentation.
Raw materials and grafting material are loaded into the biogas reactor once and subjected to fermentation. This method is used when there are difficulties and inconveniences in loading primary raw materials, as well as unloading waste. For example, not chopped straw or large briquettes of organic waste.
2) Continuous fermentation.
This includes cases when raw materials are routinely loaded into the biorector several times a day and fermentation waste is removed.
3) Semi-continuous fermentation.
This applies to biogas reactors, for which it is normal to add different primary raw materials from time to time in unequal quantities. This technological scheme is most often used by small farms China and is associated with the peculiarities of agricultural management. works Biogas reactors with semi-continuous fermentation can have various design differences. These designs are discussed below.
Scheme No. 1. Biogas reactor with fixed lid.
Design features: combining a fermentation chamber and a biogas storage facility in one structure: raw materials ferment in the lower part; biogas is stored in the upper part.
Operating principle:
Biogas comes out of the liquid and is collected under the lid of the biogas reactor in its dome. The biogas pressure is balanced by the weight of the liquid. The higher the gas pressure, the more liquid leaves the fermentation chamber. The lower the gas pressure, the more liquid enters the fermentation chamber. During the operation of a biogas reactor, there is always liquid and gas inside it. But in different proportions.
Scheme No. 2. Biogas reactor with floating cover.
Scheme No. 3. Biogas reactor with fixed lid and external gas holder.
Design features: 1) instead of a floating cover, it has a separately built gas tank; 2) the biogas pressure at the outlet is constant.
Advantages of Scheme No. 3: 1) ideal for the operation of biogas burners that strictly require a certain pressure rating; 2) with low fermentation activity in a biogas reactor, it is possible to ensure stable and high pressure biogas from the consumer.
Guide to building a domestic biogas reactor.
GB/T 4750-2002 Domestic biogas reactors.
GB/T 4751-2002 Quality acceptance of domestic biogas reactors.
GB/T 4752-2002 Rules for the construction of domestic biogas reactors.
GB 175 -1999 Portland cement, ordinary Portland cement.
GB 134-1999 Portland slag cement, tuff cement and fly ash cement.
GB 50203-1998 Masonry construction and acceptance.
JGJ52-1992 Quality Standard for Ordinary Sand Concrete. Test methods.
JGJ53- 1992 Quality standard for ordinary crushed stone or gravel concrete. Test methods.
JGJ81 -1985 Mechanical properties of ordinary concrete. Test method.
JGJ/T 23-1992 Technical specification for testing the compressive strength of concrete by the rebound method.
JGJ70 -90 Mortar. Test method for basic characteristics.
GB 5101-1998 Bricks.
GB 50164-92 Quality control of concrete.
Air tightness.
The design of the biogas reactor provides an internal pressure of 8000 (or 4000 Pa). The leak rate after 24 hours is less than 3%.
Unit of biogas production per reactor volume.
For satisfactory conditions for biogas production, it is considered normal when 0.20-0.40 m 3 of biogas is produced per cubic meter of reactor volume.
The normal volume of gas storage is 50% of the daily biogas production.
Safety factor is not less than K=2.65.
Normal service life is at least 20 years.
Live load 2 kN/m2.
The bearing capacity of the foundation structure is at least 50 kPa.
Gas tanks are designed for a pressure of no more than 8000 Pa, and with a floating lid for a pressure of no more than 4000 Pa.
The maximum pressure limit for the pool is not more than 12000 Pa.
The minimum thickness of the arched vault of the reactor is at least 250 mm.
The maximum reactor load is 90% of its volume.
The design of the reactor provides for the presence of space under the reactor lid for gas flotation, amounting to 50% of the daily biogas production.
The reactor volume is 6 m 3, gas flow rate is 0.20 m 3 /m 3 /d.
It is possible to build reactors with a volume of 4 m3, 8 m3, 10 m3 according to these drawings. To do this, it is necessary to use the correction dimensional values indicated in the table on the drawings.
Preparation for the construction of a biogas reactor.
The choice of biogas reactor type depends on the quantity and characteristics of the fermented raw material. In addition, the choice depends on local hydrogeological and climatic conditions and the level of construction technology.
A household biogas reactor should be located near toilets and premises with livestock at a distance of no more than 25 meters. The location of the biogas reactor should be on the leeward and sunny side on solid ground with low level groundwater.
Use flow tables to select biogas reactor design building materials given below.
| Reactor volume, m 3 | |||||
| 4 | 6 | 8 | 10 | ||
| Volume, m 3 | 1,828 | 2,148 | 2,508 | 2,956 | |
| Cement, kg | 523 | 614 | 717 | 845 | |
| Sand, m 3 | 0,725 | 0,852 | 0,995 | 1,172 | |
| Gravel, m 3 | 1,579 | 1,856 | 2,167 | 2,553 | |
| Volume, m 3 | 0,393 | 0,489 | 0,551 | 0,658 | |
| Cement, kg | 158 | 197 | 222 | 265 | |
| Sand, m 3 | 0,371 | 0,461 | 0,519 | 0,620 | |
| Cement paste | Cement, kg | 78 | 93 | 103 | 120 |
| Total amount of material | Cement, kg | 759 | 904 | 1042 | 1230 |
| Sand, m 3 | 1,096 | 1,313 | 1,514 | 1,792 | |
| Gravel, m 3 | 1,579 | 1,856 | 2,167 | 2,553 | |
| Reactor volume, m 3 | |||||
| 4 | 6 | 8 | 10 | ||
| Volume, m 3 | 1,540 | 1,840 | 2,104 | 2,384 | |
| Cement, kg | 471 | 561 | 691 | 789 | |
| Sand, m 3 | 0,863 | 0,990 | 1,120 | 1,260 | |
| Gravel, m 3 | 1,413 | 1,690 | 1,900 | 2,170 | |
| Plastering the prefabricated building | Volume, m 3 | 0,393 | 0,489 | 0,551 | 0,658 |
| Cement, kg | 158 | 197 | 222 | 265 | |
| Sand, m 3 | 0,371 | 0,461 | 0,519 | 0,620 | |
| Cement paste | Cement, kg | 78 | 93 | 103 | 120 |
| Total amount of material | Cement, kg | 707 | 851 | 1016 | 1174 |
| Sand, m 3 | 1,234 | 1,451 | 1,639 | 1,880 | |
| Gravel, m 3 | 1,413 | 1,690 | 1,900 | 2,170 | |
| Steel materials | Steel rod diameter 12 mm, kg | 14 | 18,98 | 20,98 | 23,00 |
| Steel reinforcement diameter 6.5 mm, kg | 10 | 13,55 | 14,00 | 15,00 | |
| Reactor volume, m 3 | |||||
| 4 | 6 | 8 | 10 | ||
| Volume, m 3 | 1,257 | 1,635 | 2,017 | 2,239 | |
| Cement, kg | 350 | 455 | 561 | 623 | |
| Sand, m 3 | 0,622 | 0,809 | 0,997 | 1,107 | |
| Gravel, m 3 | 0,959 | 1,250 | 1,510 | 1,710 | |
| Plastering the prefabricated building | Volume, m 3 | 0,277 | 0,347 | 0,400 | 0,508 |
| Cement, kg | 113 | 142 | 163 | 208 | |
| Sand, m 3 | 0,259 | 0,324 | 0,374 | 0,475 | |
| Cement paste | Cement, kg | 6 | 7 | 9 | 11 |
| Total amount of material | Cement, kg | 469 | 604 | 733 | 842 |
| Sand, m 3 | 0,881 | 1,133 | 1,371 | 1,582 | |
| Gravel, m 3 | 0,959 | 1,250 | 1,540 | 1,710 | |
| Description | Designation on drawings |
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| Link to detail drawing. The top number indicates the part number. The bottom number indicates the drawing number with a detailed description of the part. If a “-” sign is indicated instead of the bottom digit, this indicates that detailed description details are shown in this drawing. | |
| Section of the part. Bold lines indicate the plane of the cut and the direction of view, and the numbers indicate the identification number of the cut. | |
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Designs of biogas reactors.
Peculiarities:
Type of design feature of the main pool.
The bottom slopes from the inlet port to the outlet port. This ensures the formation of a constant moving flow. Drawings No. 1-9 indicate three types of biogas reactor structures: type A, type B, type C.
Biogas reactor type A: The most simple design. Removal of the liquid substance is provided only through the outlet window by the force of biogas pressure inside the fermentation chamber.
Biogas reactor type B: The main pool is equipped with a vertical pipe in the center, through which during operation it is possible to supply or remove a liquid substance, depending on the need. In addition, to form a flow of substance through a vertical pipe, this type of biogas reactor has a reflective (deflector) partition at the bottom of the main pool.
Biogas reactor type C: It has a similar design to the type B reactor. However, it is equipped with a manual piston pump of a simple design installed in a central vertical pipe, as well as other reflective baffles at the bottom of the main basin. These design features make it possible to effectively control the parameters of the main technological processes in the main pool due to the simplicity of express samples. And also use a biogas reactor as a donor of biogas bacteria. In a reactor of this type, diffusion (mixing) of the substrate occurs more completely, which in turn increases the yield of biogas.
Fermentation characteristics:
The process consists of selecting grafting material; preparation of primary raw materials (finishing density with water, adjusting acidity, adding grafting material); fermentation (control of substrate mixing and temperature).
Human feces, livestock manure, and bird droppings are used as fermentation materials. With a continuous fermentation process, relatively stable conditions for the effective operation of a biogas reactor are created.
Design principles.
Compliance with the “triple” system (biogas, toilet, barn). The biogas reactor is a vertical cylindrical tank. Height of the cylindrical part H=1 m. The upper part of the tank has an arched vault. The ratio of the height of the arch to the diameter of the cylindrical part is f 1 /D=1/5. The bottom slopes from the inlet port to the outlet port. Tilt angle 5 degrees.
The design of the tank ensures satisfactory fermentation conditions. The movement of the substrate occurs by gravity. The system operates when the tank is fully loaded and controls itself based on the residence time of the raw materials by increasing biogas production. Biogas reactors of types B and C have additional devices for processing the substrate.
The tank may not be fully loaded with raw materials. This reduces gas output without sacrificing efficiency.
Low cost, ease of management, widespread popular use.
Description of building materials.
The material of the walls, bottom, and roof of the biogas reactor is concrete.
Square parts such as the loading channel can be made of brick. Concrete structures can be made by pouring a concrete mixture, but can also be made from precast concrete elements (such as: inlet port cover, bacteria tank, center pipe). The bacteria tank is round in cross section and consists of a bat eggshells, placed in a braid.
Sequence of construction operations.
The formwork pouring method is as follows. The outline of the future biogas reactor is marked on the ground. The soil is removed. First the bottom is filled. Formwork is installed at the bottom to pour concrete in a ring. The walls are poured using formwork and then the arched vault. Steel, wood or brick can be used for formwork. Pouring is done symmetrically and tamping devices are used for strength. Excess flowable concrete is removed with a spatula.
Construction drawings.
Construction is carried out according to drawings No. 1-9.
Drawing 1. Biogas reactor 6 m 3. Type A:
Drawing 2. Biogas reactor 6 m 3. Type A:
The construction of biogas reactors from precast concrete slabs is a more advanced construction technology. This technology is more advanced due to the ease of implementation of maintaining dimensional accuracy, reducing construction time and costs. Main feature construction is that the main elements of the reactor (arched vault, walls, channels, covers) are manufactured away from the installation site, then they are transported to the installation site and assembled on site in a large pit. When assembling such a reactor, the main attention is paid to the accuracy of the installation horizontally and vertically, as well as the density of the butt joints.
Drawing 13. Biogas reactor 6 m 3. Details of the biogas reactor made of reinforced concrete slabs:
Drawing 14. Biogas reactor 6 m 3. Biogas reactor assembly elements:
Drawing 15. Biogas reactor 6 m 3. Assembly elements of a reinforced concrete reactor:
new installations. The Alemans, who inhabited the wetlands of the Elbe basin, imagined Dragons in driftwood in the swamp. They believed that the flammable gas accumulating in the pits in the swamps was the foul-smelling breath of the Dragon. To appease the Dragon, sacrifices and leftover food were thrown into the swamp. People believed that the Dragon comes at night and his breath remains in the pits. The Alemans came up with the idea of sewing awnings from leather, covering the swamp with them, diverting the gas through leather pipes to their home and burning it for cooking. This is understandable, because dry firewood was difficult to find, and swamp gas (biogas) perfectly solved the problem. Humanity learned to use biogas a long time ago. In China, its history goes back 5 thousand years, in India – 2 thousand years.
The nature of the biological process of decomposition of organic substances with the formation of methane has not changed over the past millennia. But modern science and technology have created equipment and systems to make these “ancient” technologies cost-effective and with a wide range of applications.
Biogas- gas produced by methane fermentation of biomass. Biomass decomposition occurs under the influence of three types of bacteria.
Biogas plant– installation for the production of biogas and other valuable by-products by processing waste from agricultural production, food industry, and municipal services.
Producing biogas from organic waste has the following positive features:
- sanitary treatment of wastewater is carried out (especially livestock and municipal wastewater), the content of organic substances is reduced up to 10 times;
- anaerobic processing of livestock waste, crop waste and activated sludge makes it possible to obtain ready-to-use mineral fertilizers with a high content of nitrogen and phosphorus components (unlike traditional ways preparation of organic fertilizers using composting methods, during which up to 30-40% of nitrogen is lost);
- with methane fermentation, there is a high (80-90%) efficiency of converting the energy of organic substances into biogas;
- Biogas can be used with high efficiency to generate heat and electricity, as well as fuel for internal combustion engines;
- biogas plants can be located in any region of the country and do not require the construction of expensive gas pipelines and complex infrastructure;
- biogas plants can partially or completely replace outdated regional boiler houses and provide electricity and heat to nearby villages, towns, and small towns.
Benefits received by the owner of a biogas plant
Direct
- biogas (methane) production
- electricity and heat production
- production of environmentally friendly fertilizers
Indirect
- independence from centralized networks, tariffs natural monopolies, complete self-sufficiency of electricity and heat
- everyone's solution environmental problems enterprises
- significant reduction in costs for burial, removal, and disposal of waste
- possibility of own production of motor fuel
- reduction in personnel costs
Biogas production helps prevent methane emissions into the atmosphere. Methane has a greenhouse effect 21 times greater than CO2 and remains in the atmosphere for 12 years. Capturing methane is the best short-term way to prevent global warming.
Processed manure, stillage and other waste are used as fertilizer in agriculture. This reduces the use of chemical fertilizers and reduces the load on groundwater.
Biogas is used as a fuel for the production of electricity, heat or steam, or as a vehicle fuel.
Biogas plants can be installed as wastewater treatment plants on farms, poultry farms, distilleries, sugar factories, and meat processing plants. A biogas plant can replace a veterinary and sanitary plant, i.e. carrion can be recycled into biogas instead of producing meat and bone meal.
Among industrial developed countries The leading place in the production and use of biogas in relative terms belongs to Denmark - biogas occupies up to 18% in its total energy balance. In absolute terms, Germany occupies the leading place in the number of medium and large installations - 8,000 thousand units. IN Western Europe at least half of all poultry farms are heated with biogas.
In India, Vietnam, Nepal and other countries, small (single-family) biogas plants are being built. The gas produced in them is used for cooking.
The largest number of small biogas plants are located in China - more than 10 million (at the end of the 1990s). They produce about 7 billion m³ of biogas per year, which provides fuel for approximately 60 million farmers. At the end of 2006, there were already about 18 million biogas plants operating in China. Their use makes it possible to replace 10.9 million tons of fuel equivalent.
Volvo and Scania produce buses with biogas engines. Such buses are actively used in the cities of Switzerland: Bern, Basel, Geneva, Lucerne and Lausanne. According to forecasts of the Swiss Gas Industry Association, by 2010 10% of Swiss vehicles will run on biogas.
At the beginning of 2009, the Oslo Municipality switched 80 city buses to biogas. The cost of biogas is €0.4 - €0.5 per liter in gasoline equivalent. Upon successful completion of the tests, 400 buses will be converted to biogas.
Potential
Russia annually accumulates up to 300 million tons of dry equivalent organic waste: 250 million tons in agricultural production, 50 million tons in the form of household waste. These wastes can be used as raw materials for biogas production. The potential volume of biogas produced annually could be 90 billion m³.
There are approximately 8.5 million cows raised in the United States. The biogas produced from their manure will be enough to fuel 1 million cars.
The potential of the German biogas industry is estimated at 100 billion kWh of energy by 2030, which will account for about 10% of the country's energy consumption.
As of February 1, 2009, in Ukraine there are 8 agro-industrial complex facilities for the production of biogas in operation and at the commissioning stage. Another 15 biogas plant projects are at the development stage. In particular, in 2009-2010. it is planned to introduce biogas production at 10 distilleries, which will allow enterprises to reduce consumption natural gas by 40%.
Based on materials
Good day everyone! This post continues the theme of alternative energy for yours. In it I will tell you about biogas and its use for heating the home and cooking. This topic is most interesting to farmers who have access to a variety of raw materials to obtain this type of fuel. Let's first understand what biogas is and where it comes from.
Where does biogas come from and what does it consist of?
Biogas is a flammable gas that arises as a product of the vital activity of microorganisms in a nutrient medium. This nutrient medium can be manure or silage, which is placed in a special bunker. In this bunker, called a reactor, biogas is formed. The inside of the reactor will be arranged as follows:
To speed up the fermentation process of biomass, it needs to be heated. For this, a heating element or a heat exchanger connected to any heating boiler can be used. We must not forget about good thermal insulation in order to avoid unnecessary energy costs for heating. In addition to heating, the fermenting mass must be stirred. Without this, the efficiency of the installation can be significantly reduced. Mixing can be manual or mechanical. It all depends on the budget or available technical means. The most important thing in a reactor is volume! A small reactor is simply physically unable to produce a large amount of gas.
The chemical composition of the gas strongly depends on what processes take place in the reactor. Most often, the process of methane fermentation occurs there, which results in the formation of gas with a high percentage of methane. But instead of methane fermentation, a process with the formation of hydrogen may well occur. But in my opinion, hydrogen is not necessary for the average consumer, and may even be dangerous. Just remember the death of the Hindenburg airship. Now let's figure out what biogas can be obtained from.
What can you get biogas from?
Gas can be produced from various types of biomass. Let's list them in list form:
- Food production waste - this can be waste from slaughtering or dairy production. Suitable waste from the production of sunflower or cottonseed oil. This is not a complete list, but it is enough to convey the essence. This type of raw material produces the highest methane content in the gas (up to 85%).
- Agricultural crops - in some cases grown to produce gas special types plants. For example, silage corn or seaweed are suitable for this. The percentage of methane content in gas is around 70%.
- Manure is most often used on large livestock farms. The percentage of methane in the gas, when using manure as a raw material, usually does not exceed 60%, and the rest will be carbon dioxide and quite a bit of hydrogen sulfide and ammonia.
Block diagram of a biogas installation.
In order to best understand how a biogas plant works, let's look at the following figure:
The design of the bioreactor was discussed above, so we will not talk about it. Let's look at other components of the installation:
- A waste receiver is a kind of container into which raw materials fall at the first stage. In it, raw materials can be mixed with water and crushed.
- The pump (after the waste receiver) is a fecal pump, with the help of which biomass is pumped inside the reactor.
- Boiler is a heating boiler using any fuel, designed to heat biomass inside the reactor.
- The pump (next to the boiler) is a circulation pump.
- “Fertilizer” is a container into which fermented sludge falls. It, as is clear from the context, can be used as fertilizer.
- A filter is a device in which biogas is brought to condition. The filter removes excess gases and moisture.
- Compressor - compresses the gas.
- Gas storage is a sealed tank in which ready-to-use gas can be stored for as long as desired.
Biogas for a private home.
Many owners of small farms are thinking about using biogas for internal needs. But having found out in more detail about how it all works, most abandon this idea. This is due to the fact that equipment for processing manure or silage costs a lot of money, and the gas output (depending on the raw material) can be small. This in turn makes installation of equipment unprofitable. Typically, farmers install primitive installations that run on manure for private homes. Most often, they are only able to provide gas for the kitchen and a low-power wall-mounted gas boiler. At the same time technological process you will have to spend a lot of energy on heating, pumping, and operating the compressor. Expensive filters also cannot be excluded from view.
In general, the moral here is this: the larger the installation itself, the more profitable its operation. But for home conditions this is almost always impossible. But this does not mean that no one does home installations. I suggest you watch the following video to see what it looks like using scrap materials:
Summary.
Biogas — great way useful processing organic waste. The output is fuel and useful fertilizer in the form of fermented sludge. This technology works the more efficiently the greater the volume of raw materials processed. Modern technologies make it possible to significantly increase gas production through the use of special catalysts and microorganisms. The main disadvantage of all this is high price one cubic meter. For ordinary people, it will often be much cheaper to buy gas in cylinders than to build a waste treatment plant. But, of course, there are exceptions to all rules, so before deciding to switch to biogas, it is worth calculating the price per cubic meter and the payback period. That's all for now, write questions in the comments
