Do-it-yourself biogas installation for heating your home. Biogas plants Biogas plants for farmers

The issue of methane production is of interest to those owners of private farms who breed poultry or pigs, and also keep cattle. As a rule, such farms produce a significant amount of organic animal waste, which can bring considerable benefits by becoming a source of cheap fuel. The purpose of this material is to tell you how to produce biogas at home using this same waste.

General information about biogas

Home biogas, obtained from various manures and poultry droppings, mostly consists of methane. There it is from 50 to 80%, depending on whose waste was used for production. The same methane that burns in our stoves and boilers, and for which we sometimes pay a lot of money according to the meter readings.

To give an idea of ​​the amount of fuel that can theoretically be produced when keeping animals at home or in the country, we present a table with data on the yield of biogas and the content of pure methane in it:

As you can see from the table, to effectively produce gas from cow dung and silage waste, a fairly large amount of raw material will be needed. It is more profitable to extract fuel from pig manure and turkey droppings.

The remaining share of substances (25-45%) that make up home biogas is carbon dioxide (up to 43%) and hydrogen sulfide (1%). The fuel also contains nitrogen, ammonia and oxygen, but in small quantities. By the way, it is thanks to the release of hydrogen sulfide and ammonia that the manure heap emits such a familiar “pleasant” smell. As for the energy content, 1 m3 of methane can theoretically release up to 25 MJ (6.95 kW) of thermal energy when burned. The specific heat of combustion of biogas depends on the proportion of methane in its composition.

For reference. In practice, it has been verified that heating an insulated house located in the middle zone requires about 45 m3 of biological fuel per 1 m2 of area during the heating season.

Nature arranges it in such a way that biogas from manure is formed spontaneously and regardless of whether we want to receive it or not. A manure heap rots within a year to a year and a half, simply by being in the open air and even at sub-zero temperatures. All this time it releases biogas, but only in small quantities, since the process is extended over time. The cause is hundreds of types of microorganisms found in animal excrement. That is, nothing is needed to start gas evolution; it will happen on its own. But to optimize the process and speed it up, special equipment will be required, which will be discussed further.

Biogas technology

The essence of effective production is to accelerate the natural process of decomposition of organic raw materials. To do this, the bacteria in it need to create the best conditions for reproduction and waste processing. And the first condition is to place the raw material in a closed container - a reactor, otherwise - a biogas generator. The waste is crushed and mixed in a reactor with a calculated amount of clean water until the initial substrate is obtained.

Note. Clean water is necessary to ensure that substances that adversely affect the life of bacteria do not get into the substrate. As a result, the fermentation process can slow down greatly.

An industrial biogas production plant is equipped with substrate heating, means of mixing and control of the acidity of the environment. Stirring is carried out in order to remove the hard crust from the surface, which occurs during fermentation and interferes with the release of biogas. The duration of the technological process is at least 15 days, during which time the degree of decomposition reaches 25%. It is believed that the maximum fuel yield occurs up to 33% of biomass decomposition.

The technology provides for daily renewal of the substrate, which ensures intensive production of gas from manure; in industrial installations it amounts to hundreds of cubic meters per day. Part of the waste mass, amounting to about 5% of the total volume, is removed from the reactor, and the same amount of fresh biological raw materials is loaded in its place. The waste material is used as organic fertilizer for fields.

Biogas plant diagram

When producing biogas at home, it is impossible to create such favorable conditions for microorganisms as in industrial production. And first of all, this statement concerns the organization of generator heating. As is known, this requires energy expenditure, which leads to a significant increase in the cost of fuel. It is quite possible to control compliance with the slightly alkaline environment inherent in the fermentation process. But how can it be corrected in case of deviations? Costs again.

Owners of private farms who want to produce biogas with their own hands are recommended to make a reactor of a simple design from available materials, and then modernize it according to their capabilities. What need to do:

• hermetically sealed container with a volume of at least 1 m3. Various small tanks and barrels are also suitable, but little fuel will be released from them due to the insufficient amount of raw materials. Such production volumes will not suit you;
• When organizing biogas production at home, you are unlikely to heat the container, but you definitely need to insulate it. Another option is to bury the reactor in the ground, thermally insulating the upper part;
• install a manual stirrer of any design in the reactor, extending the handle through the top cover. The handle passage assembly must be sealed;
• provide pipes for supplying and unloading the substrate, as well as for collecting biogas.

Below is a diagram of a biogas plant located below ground level:

1 – fuel generator (container made of metal, plastic or concrete); 2 - hopper for filling the substrate; 3 – technical hatch; 4 – vessel acting as a water seal; 5 – outlet for unloading waste waste; 6 – biogas sampling pipe.

How to get biogas at home?

The first operation is grinding waste to a fraction whose size is no more than 10 mm. This makes it much easier to prepare the substrate, and it will be easier for bacteria to process the raw materials. The resulting mass is thoroughly mixed with water, its quantity is about 0.7 liters per 1 kg of organic matter. As mentioned above, only clean water should be used. Then a self-made biogas plant is filled with the substrate, after which the reactor is hermetically sealed.

Several times during the day you need to visit the container to mix the contents. On the 5th day, you can check for the presence of gas, and if it appears, periodically pump it out with a compressor into a cylinder. If this is not done in time, the pressure inside the reactor will increase and fermentation will slow down, or even stop altogether. After 15 days, it is necessary to unload part of the substrate and add the same amount of new one. You can find out more by watching the video:

Conclusion

It is likely that the simplest biogas installation will not meet all your needs. But, given the current cost of energy resources, this will already be of considerable help in the household, because you do not have to pay for the raw materials. Over time, being closely involved in production, you will be able to grasp all the features and make the necessary improvements to the installation.

The growing popularity of alternative methods for generating heat and electrical energy has led to the desire of many owners of country houses and cottages to gain a certain autonomy from external energy suppliers. Moreover, “purchased” energy shows a constant tendency to increase prices, and the maintenance of a country farm is becoming more and more expensive every day. The biogas plant is an excellent alternative to external energy sources. At a minimum, it can provide the house with flammable gas for the stove, and when the power increases (if there is enough of your own or purchased waste), it can provide both heating and electricity for both the house and the entire household.

Who needs biogas plants

Biogas plants are used to produce combustible gases from biological raw materials. So they are needed wherever flammable gases are required. That is, to obtain thermal and electrical energy.
First of all, biogas plants are necessary for those farms where there is a lot of raw materials in the form of biological waste. In this way, it is possible not only to make production waste-free, but also to significantly increase its profitability - due to independent energy production and the absence of costs for the purchase of both thermal and electrical energy.

Vladimir Rashin, a designer of a biogas plant and a farmer from Perm, has proven from his own experience that agricultural production, which independently disposes of waste using an appropriate device, fully meets its needs for thermal and electrical energy, as well as combustible gas. In his quail farm, biogas is used to heat premises (both residential, utility and industrial), to generate electricity, in kitchen stoves, and also to refuel vehicles - all cars on the Rashin farm run on biogas. In this case, the main raw material for the biogas plant is quail droppings. The output, in addition to biogas, also produces organic fertilizer, which also brings additional income to the farm.

Biogas plants like Vladimir Rashin's can significantly increase the profitability of any agricultural production. Not only manure, but also various waste from wood processing industries (bark, sawdust, etc.), and almost any organic substances can be used as a raw material for producing biogas.

In addition, biogas plants can be used in country houses and cottages, even if such farms do not have a farming focus. The household waste of any farm will be enough to provide raw materials for an individual biogas plant, and if the farm is not fully provided with thermal and electrical energy, then at least reduce the cost of purchasing such energy. In addition, in addition to household waste, any country farm also contains waste from the plot (weeds, branch cuttings, and so on). Well, you can even provide a kitchen stove with flammable gas using a mini-biogas installation in a country house.

Principle of biogas production

Biogas is produced by anaerobic (that is, without oxygen) fermentation of biomass, which is provided by special bacteria. Three types of bacteria are involved in the process: hydrolytic, acid-forming and methane-forming.

A biogas plant consists of several parts (containers). First, the raw material enters a preliminary container, where it is thoroughly mixed and crushed (in the case of the solid fraction) to a homogeneous mass. Then the crushed raw material enters the reactor (a container where the biomass is directly fermented).

The reactor is usually made of reinforced concrete, which is acid-resistant. This container is completely sealed. In order to speed up the fermentation process, the liquid in the container is heated and stirred. Most often, a cogeneration unit is used to heat the reactor - in such an installation it is necessary to cool the heat and power generator, and the removed heat enters the reactor. Heat can also come from a special hot water boiler.

After the fermentation process is completed, the produced gas from the reactor enters the gas holder, where the pressure is equalized, and then the biogas enters the heat and power generator (gas or diesel-gas), as a result of which thermal or electrical energy is produced.

In addition to biogas, a solid fraction—organic fertilizers—settles in the reactor, which can then be used in the fields. Liquid fertilizers are also obtained from the reactor after gas is released. Both liquid and solid fertilizers are concentrated and are actively used in agriculture.

Industrial biogas plants have automatic control. Automation is responsible for the flow of raw materials into the installation, and for mixing, controls the temperature, the operation of the generator, and so on. Also, such installations are equipped with emergency flare devices - in case the engine stops, then the gas is simply burned. In addition, industrial biogas plants are often equipped with a line for packaging liquid fertilizers; in this case, the fertilizers are bottled in small (up to 1 liter) bottles.

Individual biogas plant

The operating principle of an individual biogas plant is the same as that of an industrial one. True, mini-installations are rarely equipped with automatic devices for mixing the substrate and other automation - due to the significant increase in the cost of a household installation with such equipment. Most often, these installations only have devices for controlling temperature, generator operation, and so on, and all maintenance of the mini-biogas plant is carried out manually.

Household biogas plants are used mainly for the production of combustible gas for kitchen needs, if the farm does not have livestock or crop production. However, there is an increasing tendency to use mini-installations to provide country houses and cottages with a complete energy complex, that is, not only “kitchen” gas, but also thermal and electrical energy. Moreover, this no longer depends on the presence of large or small livestock on the farm; raw materials for home biogas plants are simply purchased from the nearest farm. This can be either manure or waste from wood processing industries.

DIY biogas plant

The construction of biogas plants, even mini ones, for domestic needs, is not cheap. And, although the payback period for such equipment is relatively short (5-7 years), not every owner is ready or has the opportunity to invest the required amount. Yes, the advantages are obvious: in a short time, with the help of a mini-biogas plant, you can gain almost complete autonomy from purchased energy sources, transfer your farm to self-sufficiency, and even have free fertilizers as additional bonuses. However, you need to pay money today, and the benefits will only appear in a few years. Therefore, many owners of country houses and cottages are wondering: how to make a biogas plant yourself?

A mini biogas plant is not that complicated, and its construction is quite manageable. This saves a significant amount. In addition, there are projects for biogas plants that use improvised means and materials (for example, with a bell reactor, and the bell can be made of rubber, and so on). That is, homemade installations for the production of biogas mean acquiring the desired bonuses for minimal money.

When building a biogas plant, it is necessary to make an accurate calculation of what its productivity should be. To do this, you should take into account all the desired consumers of biogas (for example, a cooker, automotive equipment, and so on). If biogas is planned to be used to produce electrical and/or thermal energy, then the calculation must include all energy consumers. Based on the calculation, a biogas plant project is created.

Homemade biogas production plants are widely available on the Internet. You can find sample calculations, a drawing of the device, and a detailed description. A huge selection of devices will allow you to create both a complex installation with several chambers and a simplified version (for example, such a simple device as a cesspool covered with a rubber bell with a device for venting gas). Anyone can choose a home-made installation in accordance with their desires, capabilities and skills. Descriptions accompanied by step-by-step photographs or videos are especially useful in this case.

Making a biogas plant with your own hands allows you to save up to 50% of the cost of the device, which significantly speeds up the payback of the equipment. In addition, making the simplest installation to begin with allows you to assess the need for such equipment in the household, as well as invest money gradually, which for many is much easier than paying the entire required amount at once.

How does a biogas plant work?

Ecology of consumption. Estate: Is it profitable to produce biofuel at home in small quantities on a private plot? If you have several metal barrels and other iron junk, as well as a lot of free time and you don’t know how to manage it - yes.

Suppose there was no natural gas in your village and there never will be. And even if there is, it costs money. Although it is an order of magnitude cheaper than costly heating with electricity and liquid fuel. The nearest pellet production workshop is a couple of hundred kilometers away, and transport is expensive. It’s becoming more and more difficult to buy firewood every year, and it’s also troublesome to burn with it. Against this background, the idea of ​​obtaining free biogas in your own backyard from weeds, chicken droppings, manure from your favorite pig or the contents of the owner’s outhouse looks very tempting. All you have to do is make a bioreactor! On TV they talk about how thrifty German farmers keep themselves warm with “manure” resources and now they don’t need any “Gazprom”. This is where the saying “takes the film off feces” is true. The Internet is replete with articles and videos on the topic “biogas from biomass” and “do-it-yourself biogas plant.” But we know little about the practical application of the technology: everyone is talking about the production of biogas at home, but few people have seen concrete examples in the village, as well as 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 rural areas.

What is biogas + a little history

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

The process of bacterial decomposition that produces flammable methane

To a greater or lesser extent, flammable gases are formed during the decomposition of any remains of animal and plant origin.

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

People have long been trying to use this type of natural fuel; medieval chronicles contain references to the fact that residents of the low-lying regions of what is now Germany a millennium ago received biogas from rotting vegetation by immersing leather furs in swamp 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 release and ignite abundant methane flatus in time, aroused the constant delight of the public at cheerful fair performances. Industrial biogas plants began to be built with varying degrees of success in the mid-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 launched. Abroad, the technology for producing biogas is being improved and is being promoted relatively actively; the total number of operating installations 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 homes and small farms.

Percentage of the number of biogas plants in the European Union. It is clearly visible that the technology is actively developing only in Germany, the reason is solid government subsidies and tax incentives

What uses does biogas have?

It is clear that it is used as fuel, since it burns. Heating of industrial and residential buildings, electricity generation, cooking. However, not everything is as simple as they show in the videos scattered on YouTube. Biogas must burn stably in heat-generating installations. To do this, its gas environment parameters must be brought to fairly stringent standards. The methane content must be at least 65% (optimum 90-95%), hydrogen must be absent, water vapor has been removed, carbon dioxide has been removed, the remaining components are inert to high temperatures.

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

The normalized pressure is 12.5 bar; if the value is less than 8-10 bar, the 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. If the pressure jumps beyond the normal limits, the valve will work and you will have to turn it back on manually. It’s bad if you use outdated gas appliances that are not equipped with a gas control system. At best, the boiler burner may fail. The worst case scenario is that the gas will go out, but its supply will not stop. And this is already fraught with tragedy. Let us summarize what has been said: the characteristics of biogas must be brought to the required parameters, and safety precautions must be strictly observed. Simplified technological 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

• Plant raw materials are excellent for the production of biogas: from fresh grass you can get the maximum fuel yield - up to 250 m3 per ton of raw material, 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 and hay are good (100 m3 per ton), but it makes sense to use valuable feed for fuel only if there is an obvious excess of it. The yield of methane from the pulp formed during the production of juices, oils and biodiesel is low, but the material is also free. The lack of plant raw materials is a long production cycle, 1.5-2 months. It is possible to obtain biogas 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 plant raw materials must be finely chopped.
• 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 yield 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, other uses are found for them.

Flammable gas from excrement

• Manure is cheap and is available in abundance on many farms, but the yield and quality of biogas is significantly lower than from other types. Cow pats and horse apples can be used in their pure form, fermentation begins immediately, biogas yield is 60 m2 per ton of raw material with a low methane content (up to 60%). The production cycle is short, 10-15 days. Pig manure and chicken droppings are toxic - so that beneficial bacteria can develop, it is mixed with plant waste and silage. A big problem is represented by detergent compositions and surfactants, which are used when cleaning livestock buildings. Together with antibiotics, which enter 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 seek a compromise between hygiene and control over animal disease, on the one hand, and maintaining the productivity of bioreactors, on the other.
• Human excrement, completely free, is also suitable. But using ordinary sewage is unprofitable, the concentration of feces is too low and the concentration of disinfectants and surfactants is high. Technologists claim that they could be used only if “products” only flow from the toilet into the sewer system, provided that the bowl is flushed with only one liter of water (standard 4/8 l). And without detergents, of course.

Additional requirements for raw materials

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

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

Biogas plant design

Is it profitable to produce biogas?

We have already mentioned that in developed countries large industrial installations are built, while in developing countries they mainly build small ones for small farms. 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 private plot? If you have several metal barrels and other iron junk, as well as a lot of free time and you don’t know how to manage it - yes. But the savings, alas, are meager. And investing in high-tech equipment with small volumes of raw materials and methane production does not make sense under any circumstances.

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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 one. This means that, in the best case, with 100 kg (hopper 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, raw materials are loaded daily, that is, his production cycle is one day. In fact, the required time is 60 days. The amount of biogas obtained by the inventor, contained in a 50-liter cylinder, which he managed to fill, in frosty weather for a heating boiler with a capacity of 15 kW (a residential building of about 150 m2) is enough for 2 minutes.

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

Anyone who lives outside the city knows well that at present, at current energy prices, it is most profitable to heat a house and cook food using mains gas. But connecting to a pipe with “blue fuel” can cost a pretty penny, even if the pipeline runs along the border with the site. Therefore, homeowners are looking for ways to save money without turning into a stoker or stoker. A team of engineers from Israel offers one solution to the problem of “how to replace bottled gas for a stove.” To achieve this, alternative energy enthusiasts have developed a portable installation for producing biogas at home.

Yair Teller

Our team proposes to use waste food, liquid fertilizers and manure to produce biogas. Of course, the installation capacity with a total volume of about 2 cubic meters. m is not enough to extract enough gas from biomass for a heating system. But, as practice has shown, the gas produced is enough to connect a portable gas stove to the installation and cook food on it.

The installation is a closed container - a reactor with a volume of 1200 liters, filled with water, into which waste is discharged.

The installation is made of flexible, high-strength stretchable material.

A second tank with a volume of 700 liters is mounted on top to collect the resulting gas.

According to the developers, all the user needs is to place organic waste into the installation through a special receiver, and bacteria will do the rest.

Yair Teller

From the organic household waste of the average family, you can get energy - methane gas, which is enough to run a single-burner gas stove for three hours a day. Bacteria in the reactor process organic matter and convert it into biogas and high-quality liquid fertilizers that can be used to grow plants in the garden.

When disassembled, the biogas plant is placed in a box measuring 1000x450x400 mm.

The length of the gas hose can reach 20 meters. This is enough to place the reactor at some distance from the house, because biogas consists of methane, carbon dioxide and unpleasant-smelling hydrogen sulfide.

Installation of the unit takes less than 1 hour.

After assembly, the reactor is filled with clean water, and to quickly “start” the fermentation process, in addition to the biomass raw material, a special set of bacteria is dumped into the installation. After reaching the operating mode, “feeding” with bacteria is no longer required.

Features of organic waste processing in home bio-installations. Processing organic waste without access to oxygen is a highly effective way to obtain high-quality organic fertilizers and an environmentally friendly energy carrier, which is biogas. Moreover, this method of waste processing is absolutely safe for the environment.

Biogas is a gas that is approximately 60% methane and 40% carbon dioxide (CO2). A variety of microbial species metabolize carbon from organic substrates under oxygen-free (anaerobic) conditions (Table 4).

Biogas yield (m3) from one ton of organic matter
Type of organic raw materials	Gas output, m3 per ton of raw material
Cattle manure
Pig manure
Bird droppings
Horse dung
Sheep manure
Corn silage
Grass silage
Fresh grass
Sugar beet leaves
Ensiled sugar beet leaves

This is the process of so-called putrefaction or oxygen-free fermentation.

Methane fermentation is a complex anaerobic process (without air access), which occurs as a result of the vital activity of microorganisms and is accompanied by a number of biochemical reactions. The fermentation temperature is 35°C (mesophilic process) or 50°C (thermophilic process). This method should be assessed as a local environmental protection measure, which at the same time improves the energy balance of the economy, since it is possible to organize a low-waste, energy-saving economy.

During the processing of liquid manure with a moisture content of up to 90-91% in a methane digestion unit, three primary products are obtained: dewatered sludge, biogas, and liquid waste. Dehydrated sludge is odorless, does not contain pathogenic microflora, and the germination of weed seeds is reduced to zero. In general, dewatered sludge is a highly concentrated, disinfected, deodorized organic fertilizer suitable for direct application to the soil. It is also used as a raw material for the production of vermicompost. Methane fermentation improves the quality of the substrate. This occurs due to the fact that during methane fermentation without access to oxygen, ammonia nitrogen is converted into ammonium form, which subsequently, in the process of aerobic fermentation, reduces nitrogen losses. The substrate obtained from fermented manure and litter helps increase crop yields by 15-40%.

Since 1920, biogas has been produced on a large scale from sewage wastewater. In European cities, city truck fleets began to be converted to run on biogas in 1937. During World War II and the post-war era, the production of biogas from organic waste was researched and promoted. Due to the decline in oil prices, the development of biogas technologies ceased in the 60s. In developing countries, simple biogas plants have become widespread. Millions of such “backyard” type installations have already been created in China. About 70 million units have been built in India. In developed countries, after the 1973 crisis, large-volume biogas plants became widespread. It has become possible to quickly ferment sewage in anaerobic filters at a relatively low fermentation temperature.

Among the variety of biogas plants that operate today in many countries around the world, there are plants with reactor volumes from several to several thousand cubic meters. Conventionally, they can be divided into:

Small, or household - reactor volume up to 20 m3;

Farm - 20-200 m3;

Medium - 200-500 m3;

Large - over 500 m3

Advantages of biogas plants:

Agronomic - the ability to obtain highly effective organic fertilizers;

Energy - biogas production;

Environmental - neutralization of the negative impact of waste on the environment;

Social - improving living conditions, which is especially important for residents of rural areas.

Many countries are widely using the potential that this method of waste processing provides. Unfortunately, in Ukraine even now it remains somewhat exotic and is used in practice in isolated cases, in particular for the anaerobic processing of organic waste for fertilizer, which is relevant in the current conditions. Even the energy crisis did not stimulate the development of this energy production technology, while in some countries, such as India and China, national programs for recycling waste in bio-based plants have been operating for a long time. A significant percentage of the energy needs in many European countries are provided by this technology, and in England, even before 1990, it was planned to provide the rural population with gas of “own production.”

Figure 41. Biogas plantFigure 42.Indian

biogas plant in Ethiopia

Without discounting the importance of large-scale plants, it is worth paying close attention to the advantages of small biogas plants. They are cheap, available for construction by individual and industrial methods, simple and safe to maintain, and the products of organic waste processing in them - biogas and high-quality organic fertilizers - can be used directly for the needs of the farm without the cost of transportation.

The advantages of small biogas plants include the availability of local materials for the construction of the plant, the possibility of maintenance by the owner, the absence of the need for accounting, transportation over long distances and preparation for the use of biogas.

Small biogas plants also have certain disadvantages compared to large ones. Here it is more difficult to automate and mechanize the processes of preparing the substrate and the operation of the installations themselves; grinding the substrate, its heating, loading and unloading, storage before and after processing, which predetermines the need for containers for storing fermented waste, is problematic. In addition, in order to bring the substrate to the concentration required for fermentation, you should have another container and a certain amount of water. To reduce water costs, it is worth considering the possibility of its reuse. Problems also arise with dehydration of the fermented mass. Most often, units that are used for mechanization of work (grinding, mixing, heating, feeding processed products, etc.) in large installations are unsuitable for use in small ones due to their technical parameters and high cost.

Homestead plants produce small volumes of biogas, so it is more difficult to organize the processes of its dehydration and purification from impurities of non-combustible components.

The problems of operating small biogas plants include the unevenness of the process of producing biogas at different times of the year. During the summer period of operation, problems arise due to the fact that in the presence of a gas heater, less biogas of own production will be spent on heating the substrate; its commercial quantity will be greater than in the winter. In the summer, when animals are turned out to pasture, the amount of waste, the raw material for the bioreactor, decreases. As part of such installations, it is inappropriate to provide units for significant accumulation of biogas - when more gas is produced than is needed for the economy, it will simply have to be released into the atmosphere.

But no matter what, anaerobic processing of organic waste is a highly effective and profitable way to obtain high-quality organic fertilizers and environmentally friendly energy carriers. Small household biogas-humus plants with a reactor of up to 20 m3 can be recommended for installation in almost every rural yard where organic waste accumulates.

Among the main modern trends in the development of biogas technologies are the following:

Fermentation of multicomponent substrates;

The use of “dry” type of anaerobic fermentation for the production of biogas from energy plant crops;

Creation of centralized biogas stations with high productivity and the like.

There are four main types of implementation of anaerobic digestion technology, namely: covered lagoons and digesters operating in the mode of a mixing reactor and a reactor with a biomass carrier. The technical and economic feasibility of using one type or another depends mainly on the moisture content of the substrates and climatic conditions in the area where the biogas plant is located. The type of bioreactor used affects the total duration of the methanization process.

Indoor lagoons are advisable to use in warm and temperate climates - for liquid manure waste that does not contain inclusions with significant hydraulic coarseness. Such reactors are not specially heated, and therefore they are considered not intensive. The duration of decay of organic matter to stabilize waste significantly exceeds that in reactors with intensive fermentation mode.

Reactors with intensive fermentation mode include heated reactors of various types. There are two fundamental differences between the designs of such reactors, which depend on the characteristics of the fermented substrates. In reactors of the first type, substrates with a predominance of liquid manure waste are fermented. The most common type of such reactors are cylindrical concrete or steel with a central column, covered with an elastic membrane, which serves to seal the structure and accumulate the generated biogas. Such reactors operate on the principle of complete mixing, when each fresh portion of the mixture of initial substrates is mixed with the entire fermentable mass of the reactor. The basic design of such reactors is shown in Figure 43.

Fig.43 . Vertical type digester

2 - substrate overflow;

3 - air supply pump;

4 - thermal insulation of the methane tank;

5 - central column, which supports the gas tank membrane from falling;

6 - mixing device;

7 - drive of the mixing device;

8 - service area;

9 - gas tank membrane;

10 - methane tank filling level;

11 - height of raising of the gas tank membrane;

12 - heating pipelines

Another type of reactor for liquid substrates is the horizontal type, operating on the displacement principle. In such structures, the initial substrate mixture is supplied from one side and removed from the other. In this case, organic matter undergoes successive transformations due to a consortium of microorganisms already present in the original substrate. Such reactors can be considered less efficient in terms of the intensity of the process, however, in them, due to the spatial separation of the entry points of fresh substrates and the exit points of fermented ones, it is possible to minimize the risk of the release of an unfermented portion of fresh substrates along with the fermented substrate (which is removed from the methane tank). It is advisable to use reactors of this type for small volumes of fermented substrates.

The following type of reactors are designed for the methanization of dry organic mixtures, in which cosubstrates from energy plant crops predominate. Reactors of this type are becoming widespread along with the spread of technologies for “dry” fermentation of energy plant crops. A characteristic feature of such methane tanks is that they are designed as full displacement reactors.

From a technological point of view, the process of producing biogas from organic matter is multi-stage. It consists of the process of preparing substrates for fermentation, the process of biological decomposition of the substance, post-fermentation (optional), processing of the fermented substrate and extracted biogas, preparing them for use or disposal on site. Figure 2 shows a schematic flow diagram of a typical farm biogas station for co-digestion of manure waste and organic co-substrates.

Rice. 44. Schematic diagram of a typical farm biogas station

Preparing the substrate for fermentation involves collecting and homogenizing (mixing) the substrate. To collect the substrate, depending on its design quantity, a storage tank is built, equipped with a special mixing device and a pump, which will subsequently supply the prepared substrate to the reactor (methane tank). Depending on the types of substrates, the substance preparation system can be complicated by modules for grinding or sterilizing cosubstrates (if necessary).

After preliminary preparation, a pre-calculated amount of substrate is pumped using pumps through a pipeline system to the reactor. In a reactor (methane tank), the substrate is subject to destruction with the participation of microbiocenosis over a calculated period of time, depending on the selected temperature regime. The digester tank is equipped with a system of heating pipelines, a mixing device (to eliminate the possibility of stratification of the medium and the formation of a crust, uniform division of substances nutritious for the microbiological environment and leveling the temperature of the substrate), systems for removing the extracted biogas and discharging the fermented substrate. In addition, the digester tank is equipped with an air supply system, a small amount of which is needed to purify biogas from hydrogen sulfide by biochemical precipitation.

The degree of decomposition of organic matter at the time of completion of active gas formation approaches 70-80%. In this state, the fermented organic mass can be fed to a separation system to be divided into solid and liquid parts in a special separator.

There are several schemes for utilization of extracted biogas, the main one of which is the combustion of biogas in a cogeneration plant directly on site, with the production of electricity and heat, which are used for the own needs of the farm and the biogas station. In addition, part of the electrical energy is transmitted to the power grid.

The main substrate for anaerobic digestion, as a rule, is animal and poultry manure, as well as slaughterhouse waste. Substrates of this origin contain the most microorganisms necessary for the organization and progress of the methane fermentation process, since they are already present in the stomach of animals.

As the experience of Germany shows, most installations operate on a mixture of cosubstrates with different proportions. The country implemented a special program to collect data from more than 60 representative operating biogas plants and analyzed them. There are quite a lot of stations (about 45%), where manure is used as the main substrate in a volume of 75-100% of the total volume of the mixture. However, there are also many stations where the slurry content is less than 50%. This indicates that biogas plants in Germany largely utilize the potential not only of manure waste, but also of a variety of additional co-substrates when producing biogas.

Analysis of data on biogas production at these stations showed that with an increase in cosubstrate particles in the mixture, the specific yield of methane increases. The most common type of cosubstrate is corn silage. It is purchased from farmers in crushed form, ready for loading into reactors, and stored in open fenced areas. In addition to corn silage, grass silage, grain chaff, fat waste, grass clippings, whey, food and vegetable waste, and the like are also widely used.

In the minds of the Ukrainian farmer, a biogas plant is strongly associated exclusively with the processing of waste from large farms. The main incentive for the construction of biogas plants in Ukraine, which is often not very effective, remains the need for wastewater treatment. The possibility of obtaining high-quality organic fertilizers is also interesting for the farmer. The energy aspects of biogas production remain underutilized due to low tariffs for electricity and heat, resulting in very low return on investment for biogas plants through energy sales.

Of course, in order for biogas technologies to begin to actively develop, it is necessary to legalize the system of “green” tariffs for all types of renewable electrical and thermal energy, as has already happened in many countries of the world, and not only in developed ones.

Another way to increase the efficiency of biogas plants is to actively use additional substrates for fermentation, such as corn silage. An excellent example of an effective biogas plant is the BGU of the German company Envitek Biogas. The company's standard BGU is equipped with a 2500 m3 reactor and a cogeneration unit with an electrical power of 500 kW. The basic supplier of raw materials for such an installation could be a typical German pig farm with a population of 5,000 pigs. An increase in biogas yield is achieved by adding corn silage. For continuous operation of the installation throughout the year, 6000 tons of silage are needed, or 300 hectares of land with a silage yield of 20 t/ha.

Brief technical characteristics of biogas company LLC					Biodieseldnepr"
Installation brand	Reactor volume, m 3	Installed power		Biogas output	Electricity production, kW	Production heat, kW	Biogasoline

Liquid waste is a disinfected, deodorized liquid that contains up to 1% of suspended substances and contains fertilizing elements. Centrate is an excellent organic feed for agricultural crops, the use of which is convenient both for watering and irrigation. After post-treatment, liquid waste can even be used as process water.

Biogas is used to produce electrical and thermal energy. By burning 1 m3 of biogas, you can get 2.5-3 kW/hour of electricity and 4-5 kW of thermal energy. At the same time, 40-60% of biogas is used for the technological needs of the installation. Biogas under pressure 200-220 atm. can be used to refuel vehicles.

In addition to producing energy and fertilizers during waste fermentation, biogas plants act as treatment facilities - they reduce chemical and bacteriological pollution of soil, water, air and convert organic waste into neutral mineralized products. Compared to the energy of small rivers, wind and solar energy, where installations use environmentally friendly energy sources (passively clean plants), bioenergy plants (BES) are actively clean, which eliminates the environmental hazards of the products that are their raw materials.

There are many types of biogas plants in use around the world. They contain devices for receiving plant manure, metatanks and energy power units.

Methane tanks differ from each other in the design of devices for mixing the mass during fermentation. The most frequent mixing is carried out using a shaft with blades, which ensures layer-by-layer mixing of the fermented mass. In addition, they are mixed by hydraulic and mechanical devices, which ensure that the mass is taken from the lower layers of the digester and fed to the upper part. Biogas plants that operate in intensive mode have aerobic (oxygen) fermentation chambers, where the mass is prepared for fermentation, and anaerobic (methane) fermentation. There are also devices for mixing the mass, made in the form of a shaft with blades, located along the vertical axis of the housing and attached to the top of the floating gas cap. Mixing of the mass in the reactor occurs due to the rotation of the shaft with blades and the movement of the floating floor. Some devices only provide breaking of the crust that forms on the surface of the mass of the workpiece. Mixing is also achieved by using partitions and a double-acting siphon, which ensures alternate pouring of mass from the lower zone of one section to the upper zone of the second and, vice versa, by regulating the gas pressure. Sometimes the methane tank is designed in the form of a sphere or cylinder, which must be able to rotate around its geometric axis.

In Ukraine, due to the sharp rise in price of natural gas and the depletion of its resources, interest in biogas technologies has increased. Today, small biogas plants are not yet used in homesteads and small farms in the country. At the same time, for example, in China and India, millions of small methane tanks have been built and are successfully operating. In Germany, out of 3,711 operating biogas plants, about 400 are farm biogas plants, in Austria there are more than 100 of them.

Fig.45.German biogas plant (farm)

Fig.46 Diagram of a biogas plant for a farm:

1 - collections for pus (schematically); 2 - biomass loading system; 3- reactor 4 fermentation reactor; 5 - substrate; 6 - heating system; 7 - power plant; 8 - automation and control system; 9 - gas pipeline system.

Fig.47 Diagram of a biogas plant for a farm

According to the testimony of veterans of the Great Patriotic War, during the liberation of Romania, they saw in many peasant households small primitive biogas installations that produced biogas used for domestic needs.

Among the small biogas plants, the ones developed by Biodieseldnepr LLC (Dnepropetrovsk) should be mentioned. They are intended for processing by anaerobic digestion (without access of oxygen) of organic waste from household plots and farms. Such installations make it possible to process 200-4000 kg of waste daily in a continuous mode or 1000-20000 kg in a cyclic mode for five days. At the same time, it is ensured that at least 3 m3 of biogas is obtained per 1 m3 of reactor volume, which can be used in installations to generate heat or electricity necessary to cover the energy needs of the installation; for gas supply systems (room lighting, cooking), heating and hot water supply for households; in plants for the synthesis of bioethanol and biodiesel fuel, as well as an appropriate amount of high-quality organic fertilizer, ready to be applied to the soil.

The industrial and commercial company "Dnepr-Desna" (Dnepropetrovsk) has developed a small bioenergy plant "Biogas-6MGS 2", intended for private households (3-4 cows, 10-12 pigs, 20-30 poultry). The productivity of this installation is approximately 11 m 3 of biogas per day.This amount of gas covers the heating needs of a 100 m 2 room and hot water for a family of five people.

The experience of introducing a small biogas plant in the village of Leski, Kenyan district, Odessa region, deserves attention. The biogas plant was developed and manufactured by a private company in Dnepropetrovsk.

The installation was installed within the framework of the project “Model for the disposal of livestock waste in the Danube Delta region”, developed by a group of Odessa non-governmental organizations within the framework of the program of small environmental projects with the financial support of the British Environment Fund for Europe and with the assistance of the Ministry of Environment and Food and British Agriculture and British Council.

Under normal loading and operation, a biogas plant with a reactor volume of 3 m3 will be able to produce up to 3 m3 of biogas per day by processing waste from 100 poultry, or 10 pigs, or 4 cows. These are the minimum requirements for the operation of the installation.

The reactor is installed on the surface of the earth. This is due, firstly, to the design of the reactor. Biological raw materials are loaded into it from below, through an extruder, and waste material is drained through the top, which distinguishes this design from others, in which loading occurs from above and selection from below. The second reason for the above-ground placement is the high level of soil water in the village - at a depth of 50 cm. In winter, heating of manure in the reactor is carried out using electricity, and in summer, solar energy is sufficient.

The resulting gas is used primarily for cooking - the gas pipeline is connected to the summer kitchen. It is necessary to maintain a temperature in the reactor of 30-35°C and monitor the production of biogas. Manure processed in a bioreactor must be unloaded in a timely manner.

As already noted, in Western Europe, biogas plants are being widely implemented on livestock farms. A feature of such installations is the introduction of power units, where biogas is converted into electricity, and the use of plant mass, in addition to manure.

It is advisable to use small feeders to feed plant mass into methane tanks. The capacity of the receiving hopper of such a feeder is 4 m3, the total length of the conveyor is 6 m; drive power - 7.5 kW.

The S-BOKH50 mini-power unit can be effectively used to complete farm biogas plants. The electrical power of such a power unit ranges from 25 to 48 kW; thermal power - from 49 to 97 kW.

Germany offers small compact biogas plants with a power of 30 and 100 kW, which are designed for the use of manure and corn silage. The 30 kW installation includes a storage loader for 5 m3 of solid organic matter, a concrete fermenter for 315 m3 and a USH gas motor with a power of 30 kW of electrical energy and 46 kW of thermal energy. To ensure the operation of a 30 kW biogas plant when using a mixture of 50% manure and 50% silage, it is necessary to have 5-7 hectares of corn. The 100 kW installation has a corn silage receiver-feeder with a capacity of up to 20 m3, a fermenter with a capacity of 1200 m3 and a gas engine with a power of 100 kW of electrical energy and 108 kW of thermal energy. When used to ensure the operation of a 100 kW biogas plant, a mixture of 50% manure and 50 % corn silage you need to have 30 hectares of corn.

It should be noted that when introducing biogas plants, foreign companies take an individual approach to each farmer. For a specific farm, after an appropriate examination of the available types and resources of biomass and determining the main purposes of using the installation, the appropriate technology (technological mode) is developed or selected, on the basis of which the installation (process line) is designed. The configuration depends on the selected technology. Most companies develop and install biogas plants on a turnkey basis. When using biogas plants, much attention is paid to technologies for preparing biomass for fermentation, since energy indicators depend on the quality of the raw materials. To effectively manage a biogas plant, it is advisable to use measuring and control technology.

The most effective technology is considered to be fermentation, which converts biogas energy into electrical and thermal energy.