Do-it-yourself biogas plant. Biogas plant for the home with your own hands. What can be recycled and how to achieve good results

You can mount small installations at home. To digress, I will say that getting biogas with your own hands is not some kind of new invention. Even in ancient times, biogas at home was actively obtained in China. This country is still the leader in terms of the number of biogas plants. But here how to make a biogas plant with your own hands, what is needed for this, how much it will cost - I will try to tell all this in this and subsequent articles.

Preliminary calculation of biogas plant

Before proceeding with the purchase or self-assembly of a biogas plant, it is necessary to adequately assess the availability of raw materials, their type, quality and the possibility of an uninterrupted supply. Not every raw material is suitable for biogas production. Raw materials that do not fit:

raw materials with a high content of lignin;
raw materials that contain sawdust coniferous trees, (with the presence of resins)
with humidity exceeding 94%
rotting manure, as well as raw materials with mold or synthetic detergents.

If the raw material is suitable for processing, then you can proceed to determine the volume of the bioreactor. The total volume of raw materials for the mesophilic mode (biomass temperature ranges from 25-40 degrees, the most common mode) does not exceed 2/3 of the reactor volume. The daily dose is not more than 10% of the total loaded raw materials.

Any raw material is characterized by three important parameters:

density;
ash content;
humidity.

The last two parameters are determined from statistical tables. The raw material is diluted with water taking into account the achievement of 80-92% humidity. The ratio of the amount of water and raw materials can vary from 1:3 to 2:1. This is done to give the substrate the required fluidity. Those. to ensure the passage of the substrate through the pipes and the possibility of mixing it. For small biogas plants, the density of the substrate can be taken equal to the density of water.

Let's try to determine the volume of the reactor using an example.

Let's say the farm has 10 cattle, 20 pigs and 35 chickens. Excrement comes out per day: 55 kg from 1 cattle, from 1 pig - 4.5 kg and 0.17 kg from chicken. The volume of daily waste will be: 10x55 + 20x4.5 + 0.17x35 = 550 + 90 + 5.95 = 645.95 kg. Round up to 646 kg. The moisture content of pig and cattle excrement is 86%, and that of chicken manure is 75%. To achieve 85% moisture content in chicken manure, add 3.9 liters of water (about 4 kg).

It turns out that the daily dose of loading of raw materials will be about 650 kg. Full load of the reactor: OS=10x0.65=6.5 tons, and reactor volume OP=1.5x6.5=9.75 m³. Those. we need a reactor with a volume of 10 m³.

Biogas yield calculation

Table for calculating the yield of biogas depending on the type of raw material.

Type of raw material	Gas output, m³ per 1 kg of dry matter	Gas output m³ per 1 ton at 85% humidity
Cattle manure	0,25-0,34	38-51,5
Pig manure	0,34-0,58	51,5-88
bird droppings	0,31-0,62	47-94
Horse dung	0,2-0,3	30,3-45,5
sheep manure	0,3-0,62	45,5-94

If we take the same example, then multiplying the weight of each type of raw material by the corresponding tabular data and summing up all three components, we get a biogas yield of approximately 27-36.5 m³ per day.

In order to navigate the required amount of biogas, I will say that an average family of 4 people will need 1.8-3.6 m³ for cooking. To heat a room of 100 m² - 20 m³ of biogas per day.

Installation and fabrication of the reactor

A metal tank, a plastic container can be used as a reactor, or it can be built of brick, concrete. Some sources say that the preferred shape is a cylinder, but in square structures built of stone or brick, cracks form due to the pressure of raw materials. Regardless of the shape, material and installation location, the reactor must:

be water and gas tight. Mixing of air with gas should not take place in the reactor. Between the cover and the body there must be a gasket made of sealed material;
be thermally insulated;
withstand all loads (gas pressure, weight, etc.);
have a hatch for repair work.

The installation and selection of the reactor shape is made for each farm individually.

Fabrication theme do-it-yourself biogas plant very extensive. Therefore, I will focus on this in this article. In the next article, we will talk about the choice of other elements of a biogas plant, prices and where it can be purchased.

Consumption ecology. Farmstead: Is it profitable to produce biofuel at home in small quantities in a personal subsidiary plot? If you have a few metal barrels and other iron junk, as well as an abyss of free time and you do not know how to dispose of it - yes.

Let's assume that natural gas has not been and will not be in your village. And even if there is, it costs money. Although an order of magnitude cheaper than the ruinous heating with electricity and liquid fuel. The nearest workshop for the production of pellets is a couple of hundred kilometers away, it is expensive to carry. It is getting more and more difficult to buy firewood every year, and it is troublesome to heat it. Against this background, it looks very tempting to get free biogas in your own backyard from weeds, chicken manure, manure from your favorite pig or the contents of the master's toilet. It is enough to make a bioreactor! On TV they tell how thrifty German farmers warm themselves with "dung" resources and now they don't need any "Gazprom". This is where the saying “will remove the film from feces” is true. The Internet is replete with articles and videos on the topic "biogas from biomass" and "do-it-yourself biogas plant". But little is known about the practical application of the technology: everyone and everyone is talking about the production of biogas at home, but few people have seen specific examples in the village, just like the legendary Yo-Mobile on the road. Let's try to figure out why this is so and what are the prospects for progressive bioenergy technologies in the countryside.

What is biogas + a bit of history

Biogas is formed as a result of sequential three-stage decomposition (hydrolysis, acid and methane formation) of biomass by various types of bacteria. A useful combustible component is methane, hydrogen may also be present.

Bacterial decomposition process that produces combustible methane

To a greater or lesser extent, combustible gases are formed during the decomposition of any animal and vegetable residues.

Approximate composition of biogas, specific proportions of components depend on the raw materials and technology used

People have been trying to use this type of natural fuel for a long time, in medieval chronicles there are references to the fact that the inhabitants of the lowlands of present-day Germany a millennium ago received biogas from rotting vegetation, immersing leather furs in marsh slurry. In the dark Middle Ages and even the enlightened centuries, the most talented meteorists, who, thanks to a specially selected diet, were able to start up and set fire to abundant methane flatus in time, aroused the constant delight of the public at fun fair performances. Industrial biogas plants began to be built with varying degrees of success from the middle of the 19th century. In the USSR in the 80s of the last century, a state program for the development of the industry was adopted, but not implemented, although a dozen production facilities were still launched. Abroad, biogas production technology is being improved relatively actively, the total number of operating plants is in the tens of thousands. In developed countries (EEC, USA, Canada, Australia) these are highly automated large complexes, in developing countries (China, India) - semi-handicraft biogas plants for home and small farming.

Percentage of the number of biogas plants in the EU countries. It is clearly seen that the technology is actively developing only in Germany, the reason is solid state subsidies and tax incentives.

What is the use of biogas

It is clear that as fuel, since it burns. Heating of industrial and residential buildings, power generation, cooking. However, not everything is as simple as it is shown in the videos scattered on YouTube. Biogas must burn stably in heat generating plants. To do this, its parameters of the gaseous medium must be brought to fairly stringent standards. The content of methane should not be lower than 65% (optimum 90-95%), there should be no hydrogen, water vapor is removed, carbon dioxide is removed, the remaining components are inert to high temperatures.

It is impossible to use biogas of “dung-animal” origin, which is not freed from malodorous impurities, in residential buildings.

The normalized pressure is 12.5 bar, at a value of less than 8-10 bar, automation in modern models of heating equipment and kitchen equipment stops the gas supply. It is very important that the characteristics of the gas entering the heat generator are stable. In the event of a pressure jump beyond the norm, the valve will work, you will have to turn it back on manually. It is bad if outdated gas appliances are used that are not equipped with a gas control system. In the best case, the burner of the heating boiler may fail. The worst option is that the gas will go out, but its flow will not stop. And this is fraught with tragedy. To summarize what has been said: the characteristics of biogas must be brought to the required parameters, and safety precautions must be strictly observed. Simplified process chain for biogas production. An important stage is separation and gas separation

What raw materials are used to produce biogas

Plant and animal raw materials

Vegetable raw materials are excellent for biogas production: from fresh grass you can get the maximum fuel yield - up to 250 m3 per ton of raw materials, methane content up to 70%. Somewhat less, up to 220 m3 can be obtained from corn silage, up to 180 m3 from beet tops. Any green plants are suitable, algae, hay (100 m3 per ton) are good, but it makes sense to use valuable feed for fuel only if there is a clear excess of it. The output of methane from the pulp, which is formed in the manufacture of juices, oils and biodiesel, is low, but the material is free. The lack of vegetable raw materials is a long production cycle, 1.5-2 months. Biogas can also be obtained from cellulose and other slowly decomposing plant waste, but the efficiency is extremely low, little methane is produced, and the production cycle is very long. In conclusion, we say that vegetable raw materials must be finely ground.
Raw materials of animal origin: traditional horns and hooves, waste from dairies, slaughterhouses and processing plants are also suitable and also in crushed form. The richest "ore" is animal fats, the output of high-quality biogas with a methane concentration of up to 87% reaches 1500 m3 per ton. However, animal raw materials are in short supply and, as a rule, they find other uses for it.

Combustible gas from excrement

Manure is cheap and available in abundance on many farms, but the yield and quality of biogas is much lower than from other types. Cow patties and horse apples can be used in their pure form, fermentation starts immediately, biogas yield is 60 m2 per ton of raw materials with a low methane content (up to 60%). The production cycle is short, 10-15 days. Pig manure and chicken manure are toxic - so that beneficial bacteria can develop, it is mixed with plant waste, silage. Detergent compositions, surfactants, which are used in the cleaning of livestock buildings, present a big problem. Together with antibiotics, which get into the manure in large quantities, they inhibit the bacterial environment and inhibit the formation of methane. It is completely impossible not to use disinfectants, and agricultural enterprises that have invested in the production of gas from manure are forced to find a compromise between hygiene and animal disease control on the one hand and maintaining the productivity of bioreactors on the other.
Human excrement, completely free, is also suitable. But it is unprofitable to use ordinary sewage, the concentration of feces is too low and disinfectants and surfactants are high. Technologists say that they could only be used if “products” only come into the sewer from the toilet, provided that the bowl is flushed with only one liter of water (standard 4/8 l). And no detergents, of course.

Additional requirements for raw materials

A serious problem faced by farms that have installed modern equipment for biogas production is that raw materials should not contain solid inclusions; a stone, nut, piece of wire or board that accidentally gets into the mass will clog the pipeline, disable an expensive fecal pump or mixer. It must be said that the given data on the maximum gas yield from the feedstock correspond to ideal laboratory conditions. In order to approach these figures in real production, it is necessary to observe a number of conditions: maintain the required temperature, periodically mix finely ground raw materials, add additives that activate fermentation, etc. On a makeshift installation, assembled according to the recommendations of articles on “getting biogas with your own hands”, you can barely reach 20% of the maximum level, high-tech installations can achieve values of 60-95%.

Sufficiently objective data on the maximum yield of biogas for various types of raw materials

Biogas plant device

Is biogas production profitable?

We have already mentioned that in developed countries they build large industrial installations, while in developing countries they build mainly small ones, for a small economy. Let's explain why this is so:

Does it make sense to produce biofuels at home?

Is it profitable to produce biofuel at home in small quantities on a personal subsidiary plot? If you have a few metal barrels and other iron junk, as well as an abyss of free time and you do not know how to dispose of it - yes. But the savings, alas, are scanty. And investing in high-tech equipment with small volumes of raw materials and methane production does not make sense in any case.

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Without mixing the raw materials and activating the fermentation process, the methane yield will be no more than 20% of the possible. This means that in the best case, from 100 kg (bunker loading) of selected grass, you can get 5 m3 of gas without taking into account compression. And it will be good if the methane content exceeds 50% and it is not a fact that it will burn in the heat generator. According to the author, the raw material is loaded daily, that is, its production cycle is one day. In fact, the required time is 60 days. The amount of biogas received by the inventor, contained in a 50-liter cylinder, which he managed to fill, in frosty weather for a heating boiler with a power of 15 kW (a residential building of about 150 m2) is enough for 2 minutes.

Those who are interested in the possibility of biogas production are advised to carefully study the problem, especially from a financial point of view, with technical questions refer to professionals with experience in such work. The practical information obtained in those farms where bioenergy technologies have already been used for some time will be very valuable. published

Gas is widely used both for industry, including chemical (for example, raw materials for plastics production) and in everyday life. In domestic conditions, gas is used for heating residential private and apartment buildings, cooking, heating water, as fuel for cars, etc.

From an environmental point of view, gas is one of the cleanest types of fuel. Compared with other types of fuel, the smallest amount of emissions of harmful substances.

But if we talk about gas, then we automatically mean natural gas extracted from the earth's interior.

One day I stumbled upon an article in a newspaper that told how one grandfather assembled a not tricky installation and gets gas from manure. This topic interested me a lot. And I would like to talk about this alternative to natural gas - this is biogas. I find this topic quite interesting and useful ordinary people and especially farmers.

On the farmstead of any peasant farm, you can use not only the energy of wind, the sun, but also biogas.

Biogas- gaseous fuel, a product of anaerobic microbiological decomposition of organic substances. Gas production technology is an environmentally friendly, waste-free method of processing, recycling and disinfection of various organic wastes of plant and animal origin.

The raw material for biogas production is ordinary manure, leaves, grass, in general, any organic debris: tops, food waste, fallen leaves.

The resulting gas - methane - is the result of the vital activity of methane bacteria. From methane - it is also called marsh or firedamp gas, 90-98% consists of natural gas, which is used in everyday life.

The gas plant is very easy to manufacture. We need the main container, you can weld it yourself or use some kind of ready-made one, it can be anything. On the sides of the tank, you need to install thermal insulation, for using the installation in the cold season. From above we make a couple of hatches. From one of them we attach pipes for venting gas. For an intensive fermentation process and gas evolution, the mixture must be periodically stirred. Therefore, you need to install a mixing device. Further, the gas must be collected and stored or used for its intended purpose. To collect gas, you can use an ordinary car chamber, and then, if there is a compressor, compress and pump it into cylinders.

The principle of operation is quite simple: manure is loaded through one hatch. Inside, this biomass is decomposed by special methane bacteria. To make the process more intensive, the contents must be mixed and preferably heated. For heating, you can install pipes inside which hot water should circulate. The methane released as a result of the vital activity of bacteria through the tubes enters the car chambers, and when a sufficient amount of it accumulates, we compress it with a compressor and pump it into cylinders.

In warm weather or when artificial heating is used, the plant can produce a fairly large amount of gas, about 8 m 3 /day.

It is also possible to obtain gas from household waste from landfills, but chemicals used in everyday life are a problem.

Methane bacteria are found in the intestines of animals and therefore in manure. But in order for them to start working, it is necessary to limit their interaction with oxygen, since it depresses their vital activity. That is why it is necessary to create special installations so that bacteria do not come into contact with air.

In the resulting biogas, the concentration of methane is slightly lower than in natural gas, therefore, when it is burned, it will produce slightly less heat. When burning 1 m 3 of natural gas, 7-7.5 Gcal is released, while with biogas - 6-6.5 Gcal.

This gas is suitable both for heating (we still have general information about heating) and for use in household stoves. The cost of biogas is low, and in some cases it is practically zero if everything is made from improvised materials and you keep, for example, a cow.

Waste from gas production is biohumus - an organic fertilizer in which, in the process of decay without access to oxygen, everything from weed seeds rots, and only useful microelements necessary for plants remain.

Abroad, there are even methods for creating artificial gas fields. It looks like this. Since a large proportion of the discarded household waste is organic matter, which can rot and produce biogas. In order for the gas to begin to stand out, it is necessary to deprive the organic matter of interaction with air. Therefore, the waste is rolled up in layers, and the top layer is made of a gas-water-tight material, such as clay. Then wells are drilled and gas is extracted as from natural deposits. And at the same time several problems are being solved, these are waste disposal and energy production.

Under what conditions is biogas produced?

Conditions for obtaining and energy value of biogas

In order to assemble a small-sized plant, it is necessary to know from what raw materials and by what technology biogas can be obtained.

Gas is obtained in the process of decomposition (fermentation) of organic substances without air access (anaerobic process): pet droppings, straw, tops, fallen leaves and other organic waste generated in an individual household. It follows that biogas can be obtained from any household waste that can decompose and ferment in a liquid or wet state.

The process of decomposition (fermentation) takes place in two phases:

Decomposition of biomass (hydration);
Gasification (biogas release).

These processes take place in a fermenter (anaerobic biogas plant).

The sludge obtained after decomposition in biogas plants increases soil fertility and yield increases by 10-50%. Thus, a valuable fertilizer is obtained.

Biogas consists of a mixture of gases:

methane-55-75%;
carbon dioxide-23-33%;
hydrogen sulfide-7%.

Methane fermentation is a complex organic fermentation process - a bacterial process. The main condition for this process to take place is the presence of heat.

In the process of biomass decomposition, heat is generated, which is sufficient for the process to proceed, in order to retain this heat, the fermenter must be thermally insulated. With a decrease in temperature in the fermenter, the intensity of gas evolution decreases, since microbiological processes in the organic mass slow down. Therefore, reliable thermal insulation of a biogas plant (biofermenter) is one of the most important conditions for its normal operation. When loading manure into the fermenter, it must be mixed with hot water at a temperature of 35-40 ° C. This will help ensure the necessary mode of its operation.

When reloading, heat loss should be kept to a minimum. Biogas Engineering Assistance

For better heating of the fermenter, you can use the "greenhouse effect". To do this, a wooden or light metal frame is installed above the dome and covered with plastic wrap. The best results are achieved when the temperature of the fermented material is 30-32°C and the humidity is 90-95%. In the regions of middle and northern lane part of the gas produced must be spent during the cold periods of the year for additional heating of the fermented mass, which complicates the design of biogas plants.

Installations are easy to build in individual farms in the form of special fermenters for fermentation of biomass. The main organic raw material for loading into the fermenter is manure.

At the first loading of cattle manure, the fermentation process should be at least 20 days, pig manure at least 30 days. You can get more gas when loading a mixture of various components compared to loading, for example, cattle manure.

For example, a mixture of cattle manure and poultry manure during processing produces up to 70% of methane in biogas.

After the fermentation process has stabilized, it is necessary to load raw materials every day no more than 10% of the amount of mass processed in the fermenter.

During fermentation, in addition to the production of gas, disinfection of organic substances occurs. Organic waste gets rid of pathogenic microflora, deodorization of unpleasant odors.

The resulting sludge must be periodically unloaded from the fermenter, it is used as a fertilizer.

When the biogas plant is first filled, the gas taken off does not burn, this happens because the first gas received contains a large amount of carbon dioxide, about 60%. Therefore, it must be released into the atmosphere, and after 1-3 days the operation of the biogas plant will stabilize.

Table No. 1 - the amount of gas obtained per day during the fermentation of the excrement of one animal

In terms of the amount of energy released, 1 m 3 of biogas is equivalent to:

1.5 kg of coal;
0.6 kg of kerosene;
2 kWh of electricity;
3.5 kg of firewood;
12 kg of manure briquettes.

Construction of small biogas plants

Figure 1 - Scheme of the simplest biogas plant with a pyramidal dome: 1 - manure pit; 2 - groove - water seal; 3 - bell for collecting gas; 4, 5 - branch pipe for gas removal; 6 - pressure gauge.

According to the dimensions shown in Figure 1, pit 1 and dome 3 are equipped with dimensions. The pit is lined with reinforced concrete slabs 10 cm thick, which are plastered with cement mortar and covered with resin for tightness. A bell 3 m high is welded from roofing iron, in the upper part of which biogas will accumulate. To protect against corrosion, the bell is periodically painted with two layers of oil paint. It is even better to pre-cover the bell from the inside with red lead. In the upper part of the bell, a fitting 4 is installed for biogas removal and a manometer 5 for measuring its pressure. The gas outlet pipe 6 can be made from a rubber hose, plastic or metal pipe.

Around the pit - the fermenter, a concrete groove is arranged - a water seal 2. filled with water, into which the lower side of the bell is immersed by 0.5 m.

Figure 2 - Device for condensate removal: 1 - pipeline for gas removal; 2 - U-shaped pipe for condensate; 3 - condensate.

Gas can be supplied, for example, to the stove through metal, plastic or rubber pipes. To prevent the tubes from freezing due to freezing of condensing water in winter, a simple device shown in Figure 2 is used: U - shaped tube 2 is connected to pipeline 1 at the lowest point. The height of its free part must be greater than the biogas pressure (in mm of water column). Condensate 3 drains through the free end of the tube, and there will be no gas leakage.

Figure 3 - Scheme of the simplest biogas plant with a conical dome: 1 - manure pit; 2 - dome (bell); 3 - extended part of the branch pipe; 4 - pipe for gas removal; 5 - groove - water seal.

In the installation shown in Figure 3, pit 1 with a diameter of 4 mm and a depth of 2 m is lined inside with roofing iron, the sheets of which are tightly welded. The inner surface of the welded tank is covered with resin for anti-corrosion protection. On the outer side of the upper edge of the concrete tank, an annular groove 5 up to 1 m deep is arranged, which is filled with water. It freely install the vertical part of the dome 2, closing the tank. Thus, the groove filled with water serves as a water seal. Biogas is collected in the upper part of the dome, from where it is fed through the outlet pipe 3 and further through the pipeline 4 (or hose) to the place of use.

About 12 cubic meters of organic matter (preferably fresh manure) is loaded into the round tank 1, which is filled with the liquid manure fraction (urine) without adding water. A week after filling, the fermenter starts to work. In this installation, the capacity of the fermenter is 12 cubic meters, which makes it possible to build it for 2-3 families whose houses are located nearby. Such an installation can be built in the backyard if the family raises, for example, bulls or contains several cows.

Figure 4 - Schemes of options for the simplest installations: 1 - supply of organic waste; 2 - container for organic waste; 3 - place of gas collection under the dome; 4 - branch pipe for gas removal; 5 - sludge removal; 6 - pressure gauge; 7 - a dome made of polyethylene film; 8 - water seal and; 9 - cargo; 10 - all-glued polyethylene bag.

Structural and technological schemes of the simplest small-sized installations are shown in Figure 4. The arrows indicate the technological movements of the initial organic mass, gas, and sludge. Structurally, the dome can be rigid or made of polyethylene film. A rigid dome can be made with a long cylindrical part for deep immersion into the processed mass, floating (Figure 4, d), or inserted into a hydraulic seal (Figure 4, e). , w. In the latest version, a weight 9 is placed on the film bag so that the bag does not swell too much, and also to form sufficient pressure under the film.

The gas that is collected under the dome or film is supplied through a gas pipeline to the place of use. To avoid a gas explosion, a valve adjusted to a certain pressure can be installed on the outlet pipe. However, the danger of a gas explosion is unlikely, because with a significant increase in gas pressure under the dome, the latter will be raised in the hydraulic seal to a critical height and overturn, releasing gas.

Biogas production can be reduced due to the fact that a crust forms on the surface of organic raw materials in the fermenter during its fermentation. In order for it not to interfere with the release of gas, it is broken by stirring the mass in the fermenter. You can mix not manually, but by attaching a metal fork from below to the dome. The dome rises in a hydraulic seal to a certain height when gas is accumulated and falls as it is used.

Due to the systematic movement of the dome from top to bottom, the forks connected to the dome will break the crust.

High humidity and the presence of hydrogen sulfide (up to 0.5%) contribute to increased corrosion of metal parts of biogas plants. Therefore, the condition of all metal elements of the fermenter is regularly monitored and the damage sites are carefully protected, best of all with red lead in one or two layers, and then painted in two layers with any oil paint.

Figure 5. Scheme of a biogas plant with heating: 1 - fermenter; 2 - wooden shield; 3 - filler neck; 4 - methane tank; 5 - stirrer; 6 - branch pipe for sampling biogas; 7 - heat-insulating layer; 8 - lattice; 9 - drain valve for processed mass; 10 - channel for air supply; 11 - blower.

Biogas plant with heating of the fermented mass with heat , released during the decomposition of manure, in an aerobic fermenter, is shown in Figure 5. It includes a methanetank - a cylindrical metal container with a filler neck 3. a drain valve 9. a mechanical mixer 5 and a branch pipe 6 for sampling biogas.

Fermenter 1 can be made rectangular and 3 wooden materials. To unload the treated manure, the juice walls are made removable. The floor of the fermenter is slatted, air is blown through the technological channel 10 from the blower 11. The top of the fermenter is covered with wooden shields 2. To reduce heat loss, the walls and bottom are made with a heat-insulating layer 7.

The setup works like this. Preliminarily prepared liquid manure with a moisture content of 88-92% is poured into the methane tank 4 through the golovin 3, the liquid level is determined by the lower part of the filler neck. Aerobic fermenter 1 through the upper opening part is filled with litter manure or a mixture of manure with loose dry organic filler (straw, sawdust) with a moisture content of 65-69%. When air is supplied through the technological channel in the fermenter, the organic mass begins to decompose and heat is released. It is enough to heat the contents of the methane tank. As a result, biogas is released. It accumulates in the upper part of the methanetank. Through the branch pipe 6 it is used for domestic needs. In the process of fermentation, the manure in the digester is mixed with a stirrer 5.

Such an installation will pay off in a year only due to the disposal of waste in a personal household. Approximate values for biogas consumption are given in table 2.

Table No. 2 - approximate values \u200b\u200bfor biogas consumption

Note: the unit can operate in any climate zone.

Figure 6 - Scheme of an individual biogas plant IBGU-1: 1 - filler neck; 2 - .mixer; 3 - branch pipe, for gas sampling; 4 - heat-insulating layer; 5 - branch pipe with a crane for unloading the processed mass; 6 - thermometer.

Individual biogas plant (IBGU-1) for a family with 2 to 6 cows or 20-60 pigs or 100-300 poultry (Figure 6). The unit can process from 100 to 300 kg of manure daily and produces 100-300 kg of environmentally friendly organic fertilizers and 3-12 m 3 of biogas.

cited theoretical basis production of methane gas from biomass by anaerobic digestion.

The role of bacteria in the step-by-step transformation of organic substances was explained, with a description of the necessary conditions for the most intensive production of biogas. In this article, practical implementations of biogas plants will be given, with a description of some improvised designs.

As energy prices rise and many livestock and small farm owners have problems with waste disposal, industrial complexes for the production of biogas and small biogas plants for a private house. Using search engines, the Internet user can easily find an affordable turnkey solution to match the biogas plant and its price, get in touch with equipment suppliers and agree on the construction of a biogas generator at home or on the farm.

Biogas industrial complex

Bioreactor - the basis of a biogas plant

The container in which the anaerobic decomposition of biomass takes place is called bioreactor, fermenter, or methanetank. Bioreactors are fully sealed, with a fixed or floating dome, with a diving bell design. Bell psychrophilic (not requiring heating) bioreactors have the form of an open reservoir with liquid biomass, in which a container in the form of a cylinder or bell is immersed, where biogas is collected.

The collected biogas exerts pressure on the cylinder, causing it to rise above the tank. Thus, the bell also performs the function of a gas tank - a temporary storage of the resulting gas.

Floating Dome Bioreactor

The disadvantage of the bell design of a biogas reactor is the impossibility of mixing the substrate and heating it during the cold periods of the year. Also a negative factor is a strong smell, and unsanitary conditions due to the open surface of part of the substrate.

In addition, part of the resulting gas will escape into the atmosphere, polluting the environment. Therefore, these bioreactors are used only in artisanal biogas plants in poor countries with a hot climate.

Another example of a floating dome bioreactor

To prevent pollution environment and elimination of unpleasant odors biogas reactors for home and large industries have a fixed dome design. The shape of the structure in the process of gassing does not matter much, but when using a cylinder with a domed roof, significant savings are achieved. building materials. Bioreactors with a fixed dome are equipped with nozzles for adding new portions of biomass and removing the spent substrate.

A variation of the fixed dome bioreactor

Main types of biogas plants

Since the fixed dome design is the most acceptable, most ready-made bioreactor solutions are of this type. Depending on the loading method, bioreactors have a different design and are divided into:

Portion, with a single load of the entire biomass, and with subsequent full unloading after the processing of raw materials. The main disadvantage of this type of bioreactors is the uneven release of gas during the processing of the substrate;
continuous loading and unloading of raw materials, due to which a uniform release of biogas is achieved. Thanks to the design of the bioreactor, during loading and unloading, biogas production does not stop and there are no leaks, since the nozzles through which the addition and removal of biomass is carried out are made in the form of a water seal that prevents gas from escaping.

Batch bioreactor example

Batch biogas reactors can be of any design that prevents gas leakage. For example, at one time in Australia, channel methanetanks with an elastic inflatable roof were popular, where a slight overpressure inside the bioreactor inflated a bubble of durable polypropylene. Upon reaching a certain pressure level inside the bioreactor, the compressor was turned on, pumping out the generated biogas.

Channel bioreactors with flexible gas holder

The type of fermentation in this biogas plant can be mesophilic (with weak heating). Due to the large area of the inflating dome, channel bioreactors can only be installed in heated rooms, or in regions with a hot climate. The advantage of the design is the absence of the need for an intermediate receiver, but the big disadvantage is the vulnerability of the elastic dome to mechanical damage.

Large channel bioreactor with flexible gas tank

Recently, batch bioreactors with dry fermentation of manure without adding water to the substrate are gaining popularity. Since manure has its own moisture, it will be enough for the life of organisms, although the intensity of reactions will decrease.

Dry-type bioreactors look like a sealed garage with tightly closing doors. The biomass is loaded into the reactor using a front loader and remains in this state until the completion of the complete gas generation cycle (about half a year), without the need to add the substrate and mix it.

Batch bioreactor loaded through a hermetically sealed door

DIY biogas plant

It should be noted that in most bioreactors, as a rule, only the gas generation zone is sealed, and the liquid biomass at the inlet and outlet is under atmospheric pressure. Overpressure inside the bioreactor displaces part of the liquid substrate into the nozzles, which is why the level of biomass in them is slightly higher than inside the tank.

The red lines in the diagram indicate the difference in levels in the bioreactor and nozzles

These designs of home-made bioreactors are popular among folk craftsmen who independently make biogas plants with their own hands for the home, allowing reusable manual loading and unloading of the substrate. In the manufacture of bioreactors with their own hands, many craftsmen experiment with completely sealed containers, using several rubber chambers from the tires of the wheels of large vehicles as a gas holder.

Drawing of a gas tank made from tractor chambers

In the video below, an enthusiast of homemade biogas production, using the example of barrels filled with bird droppings, proves the possibility of actually obtaining combustible gas at home, processing it in useful fertilizer poultry waste. The only thing that can be added to the design described in this video is that you need to put a pressure gauge and a safety valve on a homemade bioreactor.

Bioreactor Productivity Calculations

The amount of biogas is determined by the mass and quality of the raw materials used. On the Internet, you can find tables that indicate the amount of waste produced by various animals, but the owners, who have to clean manure every day, do not need this theory, because they know the amount and mass of the future substrate through their own practice. Based on the availability of raw materials renewable every day, it is possible to calculate the required volume of the bioreactor and the daily biogas production.

Table of obtaining the amount of manure from some animals with an approximate calculation of the biogas yield

After the calculations have been made and the design of the bioreactor has been approved, you can proceed to its construction. The material can be a reinforced concrete container, poured into the ground, or brickwork, sealed with a special coating that is used to treat pools.

It is also possible to build the main tank of the home biogas plant from iron coated with anti-corrosion material. Small industrial bioreactors are often made from large volume, chemically resistant plastic tanks.

Construction of a masonry bioreactor

In industrial biogas plants, electronic systems control and various reagents for correction chemical composition substrate and its acidity level, as well as special substances are added to the biomass - enzymes and vitamins that stimulate the reproduction and vital activity of microorganisms inside the bioreactor. In the process of development of microbiology, more and more resistant and effective strains of bacteria methanogens are being created, which can be purchased from companies involved in the production of biogas.

The graph shows that with the use of enzymes, the maximum biogas yield occurs twice as fast.

The need for pumping and cleaning biogas

The constant production of gas in a bioreactor of any design leads to the need to pump out biogas. Some primitive biogas plants can burn the resulting gas directly in a burner installed nearby, but the instability of the overpressure in the bioreactor can lead to the disappearance of the flame and subsequent release poisonous gas. The use of such a primitive biogas plant connected to a stove is categorically unacceptable because of the possibility of poisoning with toxic components of raw biogas.

The burner flame when burning biogas must be clean, even and stable

Therefore, almost any scheme of a biogas plant includes gas storage tanks and a gas purification system. As a home-made cleaning complex, you can use a water filter and a home-made container filled with metal shavings, or purchase professional systems filtration. The tank for temporary storage of biogas can be made of chambers from tires, from which the gas is pumped out from time to time by a compressor into standard propane cylinders for storage and subsequent use.

In some African countries, inflatable gas holders in the form of a pillow are used to store and transport biogas.

As an alternative to the mandatory use of a gas tank, an improved floating dome bioreactor can be perceived. The improvement consists in the addition of a concentric baffle which forms a water pocket that acts like a water seal and prevents the biomass from coming into contact with air. The pressure inside the floating dome will depend on its weight. By passing the gas through the purification system and reducer, it can be used in a household stove, periodically bled from the bioreactor.

Bioreactor with floating dome and water pocket

Grinding and mixing of the substrate in the bioreactor

Agitation of the biomass is an important part of the biogas formation process, providing bacteria with access to nutrients that can clump at the bottom of the bioreactor. In order for the biomass particles to be better mixed in the bioreactor, they must be crushed mechanically or manually before being loaded into the methane tank. Currently, in industrial and home-made biogas plants, three methods of mixing the substrate are used:

mechanical agitators driven by an electric motor or manually;
circulating mixing with a pump or propeller pumping the substrate inside the bioreactor;
bubbling mixing by blowing the already existing biogas into the liquid biomass. disadvantage this method is the formation of foam on the surface of the substrate.

The arrow indicates the mixing circulation screw in a homemade bioreactor

Mechanical mixing of the substrate inside the bioreactor can be carried out manually or automatically by turning on the electric motor using an electronic timer. Water-jet or bubbling mixing of biomass can only be carried out using electric motors controlled manually or using a software algorithm.

This bioreactor has a mechanical agitator

Substrate heating in mesophilic and thermophilic biogas plants

The optimal temperature for gas formation is the temperature of the substrate in the range of 35-50ºC. To maintain this temperature, various heating systems- water, steam, electric. Temperature control should be carried out using a thermal switch or thermocouples connected to the actuator that regulates the heating of the bioreactor.

You also need to remember that an open flame will overheat the walls of the bioreactor, and inside its biomass will burn. The burnt substrate will reduce heat transfer and the quality of heating, and the hot wall of the bioreactor will quickly collapse. One of the best options is water heating from the return pipe of the house heating system. It is necessary to install a system of electric valves to be able to turn off the heating of the bioreactor or connect the heating of the substrate directly from the boiler if it is too cold.

Electric and water heating system of the bioreactor

Heating the substrate in the bioreactor with the help of heating elements will be beneficial only if there is alternative electricity obtained from a wind generator or solar panels. In this case, the heating elements can be connected directly to the generator or battery, which will exclude expensive voltage converters from the circuit. To reduce heat loss and reduce the cost of heating the substrate in the bioreactor, it is necessary to insulate it as much as possible using various heaters.

Insulation of the bioreactor with thermal insulation material

Practical experiences that are inevitable when building biogas plants with your own hands

No matter how much literature a novice enthusiast of independent biogas production reads, and no matter how many videos he watches, in practice you will have to learn a lot yourself, and the results, as a rule, will be far from the calculated ones.

Therefore, many novice masters follow the path of independent experiments in obtaining biogas, starting with small containers, determining how much gas from the available raw materials is produced by their small experimental biogas plant. Component prices, methane output and the future costs of building a complete working biogas plant will determine its viability and feasibility.

In the video above, the master demonstrates the capabilities of his biogas plant, noting how much biogas will be produced in one day. In his case, when pumping eight atmospheres into the compressor receiver, the volume of the resulting gas after recalculations, taking into account the volume of the tank 24 l, will be about 0.2 m².

This amount of biogas obtained from a 200 liter barrel is not significant, but, as shown in the following video of this wizard, this amount of gas is enough for an hour of burning one stove burner (15 minutes multiplied by four atmospheres of a cylinder, which is twice the size of the receiver).

In another video below, the master talks about obtaining biogas and biologically pure fertilizers by processing organic waste in a biogas plant. It must be borne in mind that the value of organic fertilizers may exceed the cost of the resulting gas, and then biogas will become a useful by-product of the process of making quality fertilizers. Another useful property of organic raw materials is the ability to store them for a certain period for use at the right time.

Of course, do-it-yourself biogas is not for everyone. First, you must be the owner of a private house. A home-made installation has dimensions and installation options in which the conditions of the apartment are categorically not suitable. Secondly, at home it is possible only if there is a large amount of organic waste. And thirdly, perhaps most importantly, knowledge is needed.

It makes no sense to come up with an installation - everything has already been invented a long time ago. But in order to implement a ready-made idea according to ready-made drawings, this must be understood. A tool, ingenuity, understanding and awareness of the scheme of the device, and also a desire that will allow you not to deviate from the intended goal - this is all very important.

To summarize:

Place. Only private courtyards, where there are plots up to 10 m2 free from buildings and trees. It is also worth considering such options when, in the future, it is possible to construct a building of an economic or even residential type above the installation itself.
Material. Stainless steel, brick, concrete, pipes (metal and/or plastic) are the most basic. Let's add tools to this list: welding equipment, concrete mixers, metal-cutting tools.
Raw material. The main source of biogas can only be organic matter - manure, waste of plant origin, waste from the slaughterhouse. Each type of raw material gives its own amount of biogas of a certain quality. In any case, there should be enough raw materials to increase profitability.
Understanding and comprehension of the idea. You can do without it: invited, paid, received - why understanding? But even the most primitive and designed for small biogas production is expensive, and the whole point is to get everything you need, based on your own strength. So here you have to be the bearer of the unspoken title of "craftsman".

Many European farmers have long switched to this alternative fuel. The payback of a biogenerator is 3-5 years, it all depends on the scale of consumption. For example, Danish owners of mini-farms with only 50-100 head of livestock manage to obtain biogas with their own installations, which fully meets the needs of both a residential building and the farm itself. The comfort at home and on the farm, thanks to their own biogas production, is perceived by them as already something ordinary.

How it works

In the entire biological installation, almost every element is the main one:

Tank - a container in which the fermentation of biomass occurs due to the action of bacteria. Different sizes and from different materials, the tank serves as a kind of pan. It would be more correct to call it a bioreactor. This complex structure must not only contain the biomass for fermentation, but also have such qualities as reliability and durability. The biogas plant is not a reusable building. You need to do it once and only improve the design, otherwise the profitability will fall below zero.
Connecting elements that must not poison the gas. Methane is an explosive gas and an accidental spark can lead to disastrous consequences.
Raw material mass mixing system. In artisanal conditions, it is quite difficult to make, but it is highly desirable. Regular mixing improves productivity.
Reactor insulation system. Reliable and high-quality insulation allows maintaining the required temperature inside the reactor. Bacteria are able to survive at low temperatures, but they are not viable. And although the temperature inside will always be above zero, it must be able to maintain and control it.
Gas holder - a container for temporary (until consumption) storage of gas. In artisanal conditions, it is represented by a steel tank.
Filtration system or filtration system. It is desirable to clean the gas obtained as a result of fermentation from CO2.

The raw material, entering the bioreactor, begins to ferment. The emitted gas is not clean. It contains the proportion of methane (up to 80-90%), carbon dioxide (up to 20-30%), hydrogen (up to 5-10%). Intermittent agitation promotes the frequency of outgassing. Gas enters the gas tank, then to the filtration system, and then to the consumed unit (boiler, furnace, etc.).

Basic moments

Biogas at home can be obtained in different volumes and different qualities. Several factors influence this:

The amount of raw materials. For continuous operation of the bioreactor, biomass must be periodically fed inward. The feeding frequency depends on the dimensions of the reactor. High performance is achieved by filling the tank by 75%. A lower value reduces the efficiency of production, as well as a load of more than 75%.
Origin of raw materials. Manure or corn mass - the difference is significant. Usually they start from the presence of one or another type of raw material. For example, a huge amount of high quality methane can be obtained from animal fats - up to 1500 m3 per ton of raw materials. At the same time, the methane content will also be the maximum possible - up to 90%. The production of biogas from algae has lower indicators - up to 250-300 m3 per ton.
Feed frequency. Fermentation must be completed almost completely, the released water must be drained, unfermented residues disposed of, and only then a new supply of a certain amount is possible. In artisanal conditions, this process is quite difficult to control. Industrial installations are more progressive and the whole process is controlled by automation.
Combination of raw materials. Some types of biomass can complement each other, acting as catalysts for chemical processes inside the reactor. Some, on the contrary, are able to slow down the course of the reaction. For example, grain stillage in combination with manure gives good results as a result of the combination. Whereas fats are not combined with almost any other type of raw material.

The table shows the volume of gas produced (in m3) from one ton of raw materials:

How to use

Biogas at home can be used based on its quantity and quality. Usually this is the heating of outbuildings or a residential building. With small volumes of gas, it can only be enough to heat water, but in this case, the profitability of the installation needs to be reconsidered. Some craftsmen have brought their designs to enormous performance levels and completely forgot about the consumption of state-owned electricity and natural gas.

In any case, by means of a biogas plant, several positive aspects are realized both for the gas consumer and for all mankind as a whole:

transition to low-cost production,
savings,
partial waste disposal,
prevention of global warming.

Mankind has made a giant leap forward, having learned to control nature and life. Biogas, as an alternative fuel and type of energy, has now become possible to obtain at home. Of course, the high cost of equipment is somewhat scary, but payback calculations show that a bioreactor at home is a profitable and expedient solution.