Biogas plant for a private home: we extract energy resources with our own hands. Do-it-yourself biogas installation for home heating Methane gas generator using food waste

A biogas plant is a special unit that allows you to process agricultural and food industry waste into biological fertilizers and biological gas.

The use of such an installation allows you to quickly get rid of various types of manure (including bird droppings), process plant residues (overwintered silage, tops of food crops, etc.) and efficiently dispose of organic waste from slaughterhouses and poultry farms. The time for obtaining biological waste and gas depends on the density of the processed materials and their quantity.

Such installations are most widespread in countries such as Germany and Holland. In recent years, a huge number of Chinese farms and food production plants have also been equipped with biogas plants of their own production.

Construction of a biogas plant. It should be said that biogas plants have a very simple design. Modern models of such installations have a sufficient degree of automation and require minimal human control. So, a modern biogas plant consists of:

A transition container into which raw materials enter at the very beginning of processing for heating.
Mixers for grinding large particles of grass and manure.
A gas container (gas holder), in which the resulting gas is stored, is necessary to maintain reserves and pressure in the system.
The bioreactor is the most important part of the biogas plant, in which the fermentation of raw materials occurs and gas is produced.
Gas system, a set of pipes and hoses for supplying and discharging the resulting gas.
Separators sort processed raw materials into solid and liquid fertilizers.
Pumps for pumping raw materials and water.
Devices for measuring and monitoring the pressure in the reactor and the temperature of the heating liquid.
A cogeneration station serves to distribute the resulting gas.
Emergency burners for bleeding excess gas from the reactor and gas tank are necessary to maintain a given pressure.

At first glance, it seems that the design of a biogas plant is too complex and confusing, and it includes expensive units and components. However, in reality this is far from the case. Most of the components have menacing names, but in fact they are based on everyday objects. In any case, similar designs have been used by people all over the world for many years, which means that the principle of operation of the installation can be understood without any difficulty.

Operating principle of a biogas plant. Before moving on to a detailed examination of the operating principle of a biogas plant, it should be said that this device appeared solely due to the processes of fermentation and decomposition. As you know, any organic substance (over time and under appropriate conditions) breaks down into simple chemical substances, one of which is biogas. It is on the principles of fermentation and decay that any biogas plant is created, and additional components and assemblies have auxiliary or controlling functions.

Stages of operation of a biogas plant.

1. Delivery of processed products and waste to the installation. If the waste is liquid, it is advisable to deliver it to the reactor using specialized pumps. More solid waste can be delivered to the reactor manually or by means of a conveyor belt. In some cases, it is advisable to heat the waste in order to increase its rate of fermentation and decay in the bioreactor. To heat the waste, a transition tank is used, in which the processed products are brought to the required temperature.
2. Processing in a reactor. After the transition tank, the prepared (and heated!) waste enters the reactor. A high-quality bioreactor is a hermetic structure made of especially strong steel or concrete with a special anti-acid coating. Without fail, the reactor must have ideal thermal and gas insulation. Even the slightest entry of air or decrease in temperature will stop the process of fermentation and decay. The reactor is heated using hot water tubes. The system is autonomous. The water is heated using the produced biogas. The reactor operates without access to oxygen, in a completely closed environment. Several times a day, using a pump, you can add new portions of the processed substance to it. The optimal temperature regime for the reactor is about 40 degrees Celsius. If the temperature is lower, the fermentation process will slow down significantly. If you increase the temperature, rapid evaporation of water will occur, which will not allow the waste to completely disintegrate. In order to speed up the fermentation process, a special mixer is used. This device mixes the substance in the reactor after a certain period of time.
3. Output of the finished product. After a certain time (from several hours to several days), the first results of fermentation appear. These are biogas and biological fertilizers. As a result, the resulting biogas ends up in a gas holder (gas storage tank). The gas pressure in the gas tanks is regulated using valves. In case of excessive pressure, emergency burners will be activated, which will simply burn off excess gas, thereby stabilizing the pressure. The resulting biogas needs to be dried. Only after this can it be used like ordinary natural gas. Separately, it should be said that to maintain the operation of a biogas plant, about 15% of the gas produced is required. In turn, biological fertilizers end up in a specially prepared tank with a separator. There is a division into solid (vermicompost) and liquid fertilizers. Vermicompost makes up only about 5% of the total amount of fertilizer received. Actually, fertilizers can immediately be used for their intended purpose. They do not require additional processing. Moreover, in Europe there are entire production lines that package the resulting biological fertilizers in plastic containers. Trading such fertilizers is a fairly profitable business. The operation of the biogas plant is continuous. To put it simply, new portions of processed material are constantly entering the reactor, and gas and biological fertilizers are also constantly entering the gas holder and separator tank.

Operation and installation of a biogas plant. Installation of a biogas plant is strictly individual. You can’t just bring and assemble all the components. It is necessary to carry out a whole series of preparatory work, dig several large pits, and carry out high-quality insulation of the reactor. It is necessary to take into account all the individual characteristics of a farm or enterprise, and make the biogas plant relevant for specific tasks. One person can monitor the biogas plant, since the processing process is fully automated. Operation of the installation does not require large expenses. With good care and timely maintenance, the annual cost of maintaining such an installation will not exceed 5% of its original cost.

Advantages of using a biogas plant. A biogas plant is a truly magical device that allows you to obtain truly necessary things from industrial waste and manure. In particular, you can get:

Biogas
Biological fertilizers
Electrical and thermal energy
Fuel for cars.

In order to convert biogas into electrical and thermal energy, it is necessary to equip the installation with additional units. This increases the cost of the installation itself, but allows you to achieve significant autonomy from utilities and significantly reduce bills. If the car is equipped with gas equipment, then it can be refueled with gas produced by a biogas plant. Naturally, biological gas will require additional purification, which will filter out carbon dioxide. After this, the car will be able to drive on gas produced by the biogas plant. This helps to save significantly on the purchase of gasoline, which is very profitable at current fuel prices.

Who needs a biogas plant?

As mentioned above, a biogas plant is a technically complex device that requires professional installation and timely maintenance.

Therefore, a small farmer whose farm consists of a dozen cows and several hectares of land definitely does not need such equipment. He simply does not have enough manure and other fertilizers to make the biogas plant work around the clock and generate significant income. And it’s a completely different matter if we talk about a large farm, poultry farm or meat processing plant. These industries generate hundreds of kilograms of various waste every day, which simply has nowhere to go. For them, purchasing a biogas plant is almost the only way to solve the problem of waste disposal, and at the same time receive free gas, electricity and biological fertilizers.

As practice shows, such biogas systems begin to pay for themselves within 2 years after installation. Considering that the average service life of an installation is 25 years, it is not difficult to calculate the profit that such equipment will bring.

Biogas, biogas plants- these words are found more and more often in the media, in the conversations of enterprising people. The reason is obvious - rising fuel prices
Biogas is a mixture of methane and carbon dioxide formed during the process of anaerobic digestion in special reactors - methane tanks, designed and controlled in such a way as to ensure maximum methane release. The energy obtained by burning biogas can reach from 60 to 90% of that of the source material. Another advantage of the biomass recycling process is that its waste contains significantly fewer pathogens than the original material.

produce biogas by controlled digestion of biomass under anaerobic conditions.
Biogas can be produced in biogas plants of various sizes. These can be small treatment plants and installations for providing the enterprise with their own energy and giant centralized energy parks for supplying gas and electricity to the network.
Most waste from the food industry and agriculture, as well as specially grown energy plants, are suitable for biogas production. Biogas plants can operate on both mono-raw materials and mixtures.
Biogas plants are construction projects consisting of sealed reactors equipped with a complex of raw material supply, heating, mixing, sewage, air gas and electrical systems.

Biogas - benefits

Biogas plant- This is the most active cleaning system. Any other cleaning systems consume energy rather than produce it.

In addition to the environment, the main benefits are the production of biogas and biofertilizers.

Additional benefits of a biogas plant: generation of electricity and heat, production of biomethane, savings on capital costs for treatment plants when building new enterprises.

Biogas production helps prevent the release of methane into the atmosphere. Capturing it is the best way to prevent global warming.

Operating principle of a biogas plant

The biogas plant produces biogas and biofertilizers through anoxic fermentation from biowaste and energy crops.

An industrial biogas station is a construction project in which the share of equipment is 70-80%. These are closed reactors (digesters) made of monolithic reinforced concrete or coated steel. The design is modular with a diameter of 24 m and a height of 6 m. As the power increases, the number of reactors increases.

Liquid biowaste is pumped to the biogas plant by fecal pumps through a pipeline. They fall into a preliminary container, where the mass is mixed, diluted to the required humidity and heated to the required temperature.

Biogas outputs

Biogas plant equipment

Biogas reactor

The biogas reactor consists of panels made of steel with high-quality coating using high-temperature sintering technology “elamel”. This coating is durable, chemical, corrosion and impact resistant. The design allows for quick assembly and disassembly.

The advantage of biogas reactors made of coated steel compared to concrete ones is durability, no need for formwork, reduced time, and the possibility of year-round construction. Stainless steel hatches, reinforced cutouts for mixers, inspection windows - everything is designed taking into account the features of biogas technology.

An important advantage of a metal reactor compared to reinforced concrete. is that it can be easily dismantled and is recognized by banks as the best collateral.

Loader for biogas plant

Silage or other solid raw materials are fed directly into the biogas reactor by a screw feeder. The bunker is equipped with two turbo augers, which have a soft start system, which saves energy and guarantees reliable operation of the drive 24 hours a day.

Particularly durable alloy steel construction with acid-resistant coating allows the units to operate under heavy loads. The use of special scrapers with adjustable knives increases productivity. A drive with reliable planetary gearboxes guarantees stable operation at maximum loads and torques, and hydraulic damper control ensures cleaning of the turbo auger and conveyor.

Inclined mixer for biogas plant

Inclined mixers are specially designed to work in the aggressive conditions inside a biogas reactor. The propellers are manufactured using special equipment that ensures millimeter precision in the inclination of the blades.

The electrically driven stirrer is designed to operate in Class 1 and Class 2 explosive atmospheres. All parts of the stirrer, including the insulating membrane for the drive tube, are protected from ultraviolet radiation. The screw mixer is mounted on the outside of the fermenter wall.

The mixer is supported by two upper slats or optionally on a rack and pinion gear, which allows you to set any angle of inclination. The propeller shaft, screw, and plate are made of stainless steel.

Submersible mixer

Electrically driven submersible mixers for biogas stations are designed to operate in explosive and at the same time aggressive environments.

The mixer is mounted on a mast using a motor mount to adjust the height of the device. Thanks to the roller guides, the stirrer can be lowered and raised smoothly without friction, even if the cable is pulled at a slight angle.

The gear motor is made of nodular cast iron and painted on top. The propeller is galvanized and the motor mount is made of stainless steel. The submersible mixer is made in the form of a waterproof monoblock driving a three-blade propeller.

Biogas station heating station

A fixed temperature for microorganisms is maintained inside the biogas reactor. The temperature in the reactor is mesophilic, about +37°C. The reactor is heated by a coolant. The coolant temperature at the reactor inlet is +80°C. The carrier temperature after the reactor is about +55°C.

The heating system consists of boilers, pumps, heat exchangers, combs. A network of heating tubes is located inside the reactor wall or on its inner surface. If the biogas plant is equipped with a cogeneration plant, then the coolant from the generator cooling is used to heat the reactor.

Sources of heat supply for biogas plant structures can be gas boilers that operate on biogas, natural gas and mixtures, as well as electric boilers.

Gas holder bag

The material of the gas holder is resistant to ignition by live electrical wires, fireworks, as well as to breakthrough by metal rods, even red-hot ones.

Mounted in a special ventilated hangar. The design of the gas tank allows you to accumulate and maintain biogas pressure under the film from 0.005-0.01 Bar.

Biogas is supplied to the gas tank through special pipes equipped with safety valves to prevent overflow.

Gas holder of a biogas plant

Gas holder is a biogas storage facility. It is hermetically attached to the top of the reactor. The gas holder system has a two-layer design. The outer dome cover is resistant to ultraviolet radiation and precipitation.

The inner dome is stretched under the action of the produced biogas.

Air is pumped between the outer and inner domes to create pressure on the lower dome and also to give shape to the outer one. The biogas pressure inside the gas tank ranges from 200 to 500 Pa. Gas holder reserve for 2-3 hours of biogas storage.

Biogas station separator

The separator is designed to separate the fermented mass into solid and liquid fractions and is included in the basic package of the biogas production plant. The separator parts are made of corrosion- and wear-resistant steel. The mixture is supplied randomly or supplied using a pump through the mixture supply pipe into the loading chamber. From the loading chamber, using a variable pitch screw made of wear-resistant steel, the mixture is fed into the separation chamber.

The separation chamber is a cylindrical sieve, also made of wear-resistant steel. In the separation chamber, liquid and solid fractions are separated by pressing. The liquid fraction is drained through a drain pipe into a storage tank. The solid fraction leaves the separator through the unloading device and accumulates in the storage container.

Biogas plant torch

The flare unit is designed for temporary or periodic complete combustion of biogas produced by biogas plants or solid waste landfills in the absence of the possibility of its beneficial use as an energy carrier.

The combustion system consists of a burner and additional components.

The burner is designed on the principle of injection combustion and consists of a nozzle, an injector with an air supply control system, a flame protection pipe, a fitting and a burner control system.

The biogas combustion system is made of stainless steel. The supporting structure holds the burner and the vertically mounted fitting.

The burner control system is installed in a cabinet, which is mounted on the supporting structure of the combustion system, and contains all the elements for monitoring and controlling the ignition and flame.

Biogas plant options

Cogeneration

The production of electrical and thermal energy in installations based on an internal combustion engine is the most common way to benefit from a biogas plant. Electricity can be used year-round both for own needs and for supply to the network at an unregulated or feed-in tariff.

From 1 m3 of biogas, 2.4 kWh of electrical + 2.5 kWh of thermal energy is produced simultaneously.

Advantages of cogeneration plants compared to analogues:
— oil changes not 500, but 2000 engine hours,
- high el. Efficiency up to 40%, total efficiency electric + heat up to 90%,
- highest reliability.

The power plant is the main part of a biogas plant and has the most moving parts. Revenue directly depends on this unit and this is something you should not save on.

Purification to methane

This system allows for purification (enrichment) of biogas to the state of biomethane. Biomethane is a complete analogue of Gost natural gas with a methane concentration in the range of 95-99%. After the purification system, the gas can be used as motor fuel for refueling cars, can be supplied to the general gas supply system in a medium or low pressure pipe, or used for technological needs to completely replace natural gas.

A regenerative water biogas enrichment system is proposed. Its operating principle is based on the different solubilities of gases in liquids. When biogas is passed through cold water, carbon dioxide dissolves in it, and when heated, it is released.

The advantage of a water biogas enrichment system compared to PSA or carbon absorption systems is the low cost of gas purification. Thanks to the use of water as the main component of this process, the process does not require any reagents or high costs for

Fertilizer drying

Drying biofertilizers allows you to more fully use the potential of a biogas station and significantly increase its profitability. Dried biofertilizers have a higher selling price compared to simply separated biomass. In dried granular form, fertilizers can be transported at low cost to any distance and stored for a long time. Two by-products of a biogas plant - heat and raw biofertilizers - can be used to produce a sought-after product. Dried biofertilizers are comparable to guano.

The low temperature conveyor dryer works with a highly efficient method to dry biomass using low temperature. Low emissions and a high-quality end product with low consumption are the advantages of the technology. Adjusting the product feed rate guarantees constant moisture content of the dried product and optimal use of additional thermal energy.

Every year on our planet energy resources become less and less. It is because of this that we have to constantly look for new, alternative sources of energy. Definitely, after some time our planet will run out of oil and gas deposits, and then the world will have to seriously think about the extraction (collection) and use of biogases as the main source of energy.

What is biogas? Principles of biogas production

As already mentioned, biogas is an alternative source of energy. It is released during the fermentation of various household wastes, as well as waste excreted by animals (manure).

This method has been used since ancient times in China, but later, centuries later, it was unclaimed and as a result was forgotten.

Do-it-yourself biogas production at home

Step 1: Selecting a Barrel

First we need to choose a suitable barrel in which we will store the “energy source”, that is, as you understand, food waste and manure.

Step 2: Making the holes

We make holes at the inlet and outlet of the barrel. It can be done using a drill, but in this case, the hole is made using a heated metal pipe.

Step 3: Installation of pipes

We install pipes at the inlet and outlet into the holes we made earlier. We insert and glue the pipes.

Step 4: Creating and installing a “gas tank” holder

We took a 20-liter paint bucket; this tank will contain the gas we extract. The tank is secured with a valve that plumbers use.

Step 5: Add Cow Manure

Mix cow dung (5 kg per 50 liters) and add water. Place it in the tank.

Step 6: Almost done

You will not receive gas for the first 10-15 days, as this time is necessary for all the necessary processes to go through.

Step 7: Get Rid of Carbon Dioxide

In order for this gas to burn, it is necessary to get rid of carbon dioxide. This can be achieved by using a regular filter, of which there are many in various hardware stores.

Step 8: Done!

You will notice how the “fuel tank” will rise as chemical reactions occur. Then it is necessary to open the valve and obtain biogas.

Biogas can be used for different purposes. It is not recommended to use biogas for cooking, as it can negatively affect the taste (if the flavors are not removed).

Video Lesson: Biogas production at home

Small installations can also be installed at home. As an aside, I will say that producing biogas with your own hands is not some kind of new invention. Even in ancient times, biogas was actively produced at home in China. This country is still the leader in the number of biogas installations. 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 you all this in this and subsequent articles.

Preliminary calculation of a biogas plant

Before you start purchasing or independently assembling a biogas plant, you must adequately assess the availability of raw materials, their type, quality and the possibility of uninterrupted supply. Not every raw material is suitable for producing biogas. Raw materials that are not suitable:

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

If the raw material is suitable for processing, then you can begin 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 no 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 to achieve 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 a farm has 10 heads of cattle, 20 pigs and 35 chickens. The following excrement is produced per day: 55 kg from 1 cattle, 4.5 kg from 1 pig 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. Let's round up to 646 kg. The moisture content of pig and cattle excrement is 86%, and that of chicken droppings is 75%. To achieve 85% moisture in chicken manure, you need to add 3.9 liters of water (about 4 kg).

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

Biogas yield calculation

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

Raw material type	Gas output, m³ per 1 kg of dry matter	Gas output m³ per 1 ton at humidity 85%
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 obtain a biogas yield of approximately 27-36.5 m³ per day.

In order to get an idea of the required amount of biogas, I will say that the 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.

Reactor installation and fabrication

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

be water- and gas-tight. Mixing of air and gas should not occur in the reactor. There must be a gasket made of sealed material between the cover and the body;
be thermally insulated;
withstand all loads (gas pressure, weight, etc.);
have a hatch for carrying out repair work.

Installation and selection of the reactor shape is carried out individually for each farm.

Manufacturing theme DIY biogas plant very extensive. Therefore, in this article I will focus on this. In the next article we will talk about choosing the remaining elements of a biogas plant, prices and where it can be purchased.

Among the important components of our lives, energy resources are of great importance, prices for which are rising almost every month. Every winter season makes a hole in family budgets, forcing them to incur heating costs, and therefore, fuel for stoves and heating boilers. But what to do, after all, electricity, gas, coal or firewood cost money, and the more remote our homes are from major energy highways, the more expensive heating will cost... Meanwhile, alternative heating, independent of any suppliers and tariffs, can be built on biogas, the production of which does not require geological exploration, well drilling, or expensive pumping equipment.

Biogas can be obtained in almost home conditions, while incurring minimal, quickly recouping costs - most of the answers on this issue are contained in this article.

Biogas heating - history

Interest in flammable gas formed in swamps during the warm season of the year arose among our distant ancestors - advanced cultures of India, China, Persia and Assyria experimented with biogas over 3 thousand years ago. In the same ancient times, in tribal Europe, the Alemanni Swabians noticed that the gas released in the swamps burned well - they used it to heat their huts, supplying gas to them through leather pipes and burning them in the hearths. The Swabians considered biogas to be the “breath of dragons,” which they believed lived in swamps.

Centuries and millennia later, biogas experienced its second discovery - in the 17th and 18th centuries, two European scientists immediately paid attention to it. The famous chemist of his time, Jan Baptista van Helmont, established that the decomposition of any biomass produces a flammable gas, and the famous physicist and chemist Alessandro Volta established a direct relationship between the amount of biomass in which decomposition processes take place and the amount of biogas released. In 1804, the English chemist John Dalton discovered the formula for methane, and four years later the Englishman Humphry Davy discovered it as part of swamp gas. Interest in the practical use of biogas arose with the development of gas street lighting - at the end of the 19th century, the streets of one district of the English city of Exeter were illuminated gas obtained from the wastewater collector.

In the 20th century, energy demands caused by World War II forced Europeans to look for alternative energy sources. Biogas plants, in which gas was produced from manure, spread in Germany and France, and partly in Eastern Europe. However, after the victory of the countries of the anti-Hitler coalition, biogas was forgotten - electricity, natural gas and petroleum products completely covered the needs of industries and the population.

Today, the attitude towards alternative energy sources has changed dramatically - they have become interesting, since the cost of conventional energy resources increases from year to year. At its core, biogas is a real way to avoid tariffs and costs for classical energy sources, to get your own source of fuel, for any purpose and in sufficient quantities.

The largest number of biogas plants have been created and operated in China: 40 million plants of medium and low power, the volume of methane produced is about 27 billion m3 per year.

Biogas - what is it

This is a gas mixture consisting mainly of methane (content from 50 to 85%), carbon dioxide (content from 15 to 50%) and other gases in much smaller percentages. Biogas is produced by a team of three types of bacteria that feed on biomass - hydrolysis bacteria, which produce food for acid-forming bacteria, which in turn provide food for methane-producing bacteria, which form biogas.

Fermentation of the original organic material (for example, manure), the product of which will be biogas, takes place without access to an external atmosphere and is called anaerobic. Another product of such fermentation, called compost humus, is well known to rural residents who use it to fertilize fields and vegetable gardens, but the biogas and thermal energy produced in compost heaps are usually not used - and in vain!

What factors determine the yield of biogas with a higher methane content?

First of all, it depends on the temperature. The higher the temperature of their environment, the higher the activity of bacteria fermenting organic matter; at sub-zero temperatures, fermentation slows down or stops completely. For this reason, biogas production is most common in countries in Africa and Asia, located in the subtropics and tropics. In the Russian climate, the production of biogas and a complete transition to it as an alternative fuel will require thermal insulation of the bioreactor and the introduction of warm water into the mass of organic matter when the temperature of the external atmosphere drops below zero. The organic material placed in the bioreactor must be biodegradable, it is required to introduce it contains a significant amount of water - up to 90% of the mass of organic matter. An important point will be the neutrality of the organic environment, the absence in its composition of components that prevent the development of bacteria, such as cleaning and detergents, and any antibiotics. Biogas can be obtained from almost any waste of economic and plant origin, wastewater, manure, etc.

The process of anaerobic fermentation of organic matter works best when the pH value is in the range of 6.8-8.0 - high acidity will slow down the formation of biogas, because the bacteria will be busy consuming acids and producing carbon dioxide, which neutralizes the acidity.

The ratio of nitrogen and carbon in the bioreactor must be calculated as 1 to 30 - in this case, the bacteria will receive the amount of carbon dioxide they need, and the methane content in the biogas will be the highest.

The best yield of biogas with a sufficiently high methane content is achieved if the temperature in the fermentable organic matter is in the range of 32-35 ° C; at lower and higher temperatures, the content of carbon dioxide in the biogas increases and its quality decreases. Bacteria that produce methane are divided into three groups: psychrophilic, effective at temperatures from +5 to +20 ° C; mesophilic, their temperature range is from +30 to +42 °C; thermophilic, operating in the mode from +54 to +56 °C. For the biogas consumer, mesophilic and thermophilic bacteria, which ferment organic matter with a higher gas yield, are of greatest interest.

Mesophilic fermentation is less sensitive to changes in temperature by a couple of degrees from the optimal temperature range and requires less energy to heat organic material in the bioreactor. Its disadvantages, compared to thermophilic fermentation, are lower gas output, a longer period of complete processing of the organic substrate (about 25 days), and the resulting decomposed organic material may contain harmful flora, because the low temperature in the bioreactor does not ensure 100% sterility.

Raising and maintaining the intra-reactor temperature at a level acceptable for thermophilic bacteria will ensure the greatest yield of biogas, complete fermentation of organic matter will take place in 12 days, the decomposition products of the organic substrate are completely sterile. Negative characteristics: a change in temperature by 2 degrees outside the range acceptable for thermophilic bacteria will reduce gas yield; high need for heating, as a result - significant energy costs.

The contents of the bioreactor must be stirred twice a day, otherwise a crust will form on its surface, creating a barrier to biogas. In addition to eliminating it, stirring allows you to equalize the temperature and acidity level inside the organic mass. In continuous-cycle bioreactors, the highest biogas yield occurs with the simultaneous unloading of organic matter that has undergone fermentation and the loading of a volume of new organic matter in an amount equal to the unloaded volume. In small-volume bioreactors, the kind that are usually used in dacha farms, every day it is necessary to extract and introduce organic matter in a volume approximately equal to 5% of the internal volume of the fermentation chamber.

The yield of biogas directly depends on the type of organic substrate placed in the bioreactor (the average data per kg of dry substrate weight is given below):

horse manure produces 0.27 m3 of biogas, methane content 57%;
cattle manure produces 0.3 m3 of biogas, methane content 65%;
fresh cattle manure produces 0.05 m3 of biogas with 68% methane content;
chicken manure - 0.5 m3, the methane content in it will be 60%;
pork manure - 0.57 m3, the share of methane will be 70%;
sheep manure - 0.6 m3 with a methane content of 70%;
wheat straw - 0.27 m3, with 58% methane content;
corn straw - 0.45 m3, methane content 58%;
grass - 0.55 m3, with 70% methane content;
wood foliage - 0.27 m3, methane share 58%;
fat - 1.3 m3, methane content 88%.

Biogas plants

These devices consist of the following main elements - a reactor, an organic loading hopper, a biogas outlet, and a fermented organic matter unloading hopper.

According to the type of design, biogas plants are of the following types:

without heating and without stirring the fermented organic matter in the reactor;
without heating, but with stirring of the organic mass;
with heating and stirring;
with heating, with stirring and with devices that allow you to control and manage the fermentation process.

The first type of biogas plant is suitable for a small farm and is designed for psychrophilic bacteria: the internal volume of the bioreactor is 1-10 m3 (processing 50-200 kg of manure per day), minimal equipment, the resulting biogas is not stored - it immediately goes to the household appliances that consume it. This installation can only be used in southern regions; it is designed for an internal temperature of 5-20 ° C.

Removal of fermented (fermented) organic matter is carried out simultaneously with the loading of a new batch; the shipment is carried out into a container, the volume of which must be equal to or greater than the internal volume of the bioreactor. The contents of the container are stored in it until introduced into the fertilized soil. The design of the second type is also designed for small farms; its productivity is slightly higher than the biogas plants of the first type - it is equipped with a mixing device with a manual or mechanical drive.

The third type of biogas plants is equipped, in addition to the mixing device, with forced heating of the bioreactor; the hot water boiler runs on alternative fuel produced by the biogas plant. Methane production in such installations is carried out by mesophilic and thermophilic bacteria, depending on the heating intensity and temperature level in the reactor.

The last type of biogas plants is the most complex and is designed for several consumers of biogas; the design of the plants includes an electric contact pressure gauge, a safety valve, a hot water boiler, a compressor (pneumatic mixing of organic matter), a receiver, a gas tank, a gas reducer, and an outlet for loading biogas into transport. These installations operate continuously, allow the setting of any of three temperature conditions thanks to precisely adjustable heating, and biogas selection is carried out automatically.

DIY biogas plant

The calorific value of biogas produced in biogas plants is approximately 5,500 kcal/m3, which is slightly lower than the calorific value of natural gas (7,000 kcal/m3). To heat 50 m2 of a residential building and use a four-burner gas stove for an hour, an average of 4 m3 of biogas will be required.

Industrial biogas production plants offered on the Russian market cost from 200,000 rubles. - despite their apparently high cost, it is worth noting that these installations are precisely calculated according to the volume of loaded organic substrate and are covered by manufacturers’ warranties.

If you prefer to create a biogas plant yourself, then further information is for you!

Bioreactor form

The best shape for it would be oval (egg-shaped), but building such a reactor is extremely difficult. A cylindrical bioreactor, the upper and lower parts of which are made in the form of a cone or semicircle, will be easier to design. Square or rectangular reactors made of brick or concrete will be ineffective because... Over time, cracks will form in the corners in them, caused by the pressure of the substrate; hardened fragments of organic matter will accumulate in the corners, interfering with the fermentation process. Steel tanks of bioreactors are airtight, resistant to high pressure, and they are not so difficult to build. Their disadvantage is their poor resistance to rust; they require a protective coating, for example, resin, to be applied to the inner walls. The outside of the steel bioreactor must be thoroughly cleaned and painted in two layers.

Bioreactor containers made of concrete, brick or stone must be carefully coated on the inside with a layer of resin that can ensure their effective water and gas impermeability, withstand temperatures of about 60 ° C, and the aggression of hydrogen sulfide and organic acids. In addition to resin, to protect the internal surfaces of the reactor, you can use paraffin, diluted with 4% motor oil (new) or kerosene and heated to 120-150 ° C - the surfaces of the bioreactor must be heated with a burner before applying a paraffin layer to them.

When creating a bioreactor, you can use plastic containers that are not susceptible to rust, but only hard plastic with sufficiently strong walls. Soft plastic can only be used in the warm season, because... With the onset of cold weather, it will be difficult to attach insulation to it, and its walls are not strong enough. Plastic bioreactors can only be used for psychrophilic fermentation of organic matter.

Bioreactor location

Its placement is planned depending on the available space on a given site, sufficient distance from residential buildings, distance from the waste disposal site, from animal placement sites, etc. Planning a ground-based, fully or partially submerged bioreactor depends on the groundwater level, the convenience of introducing and removing the organic substrate into the reactor tank. It would be optimal to place the reactor vessel below ground level - savings are achieved on equipment for introducing an organic substrate into the reactor tank, thermal insulation is significantly increased, for which inexpensive materials (straw, clay) can be used.

Bioreactor equipment

The reactor tank must be equipped with a hatch, which can be used to carry out repair and maintenance work. It is necessary to lay a rubber gasket or a layer of sealant between the bioreactor body and the hatch cover. It is optional, but extremely convenient, to equip the bioreactor with a sensor for temperature, internal pressure and organic substrate level.

Bioreactor thermal insulation

Its absence will not allow the biogas plant to be operated all year round, only during the warmer months. To insulate a buried or semi-buried bioreactor, clay, straw, dry manure and slag are used. The insulation is laid in layers - when installing a buried reactor, the pit is covered with a layer of PVC film, which prevents direct contact of the heat-insulating material with the soil. Before installing the bioreactor, straw is poured onto the bottom of the pit with a PVC film laid, a layer of clay is placed on top of it, then the bioreactor is placed. After this, all free areas between the reactor tank and the foundation pit lined with PVC film are filled with straw almost to the end of the tank, and a layer of clay mixed with slag is poured on top of a 300 mm layer.

Loading and unloading organic substrate

The diameter of the pipes for loading into and unloading from the bioreactor must be at least 300 mm, otherwise they will clog. In order to maintain anaerobic conditions inside the reactor, each of these pipes should be equipped with screw or half-turn valves. The volume of the bunker for supplying organic matter, depending on the type of biogas plant, should be equal to the daily volume of input raw materials. The feed hopper should be located on the sunny side of the bioreactor, because this will help to increase the temperature in the introduced organic substrate, accelerating the fermentation processes. If the biogas plant is connected directly to the farm, then the bunker should be placed under its structure so that the organic substrate enters it under the influence of gravity.

The pipelines for loading and unloading the organic substrate should be located on opposite sides of the bioreactor - in this case, the input raw materials will be distributed evenly, and the fermented organic matter will be easily removed under the influence of gravitational forces and the mass of the fresh substrate. Holes and installation of the pipeline for loading and unloading organic matter should be completed before installing the bioreactor at the installation site and before placing layers of thermal insulation on it. The tightness of the internal volume of the bioreactor is achieved by the fact that the inputs of the substrate loading and unloading pipes are located at an acute angle, while the liquid level inside the reactor is higher than the pipe entry points - a hydraulic seal blocks the access of air.

It is easiest to introduce new and remove fermented organic material using the overflow principle, i.e. a rise in the level of organic matter inside the reactor when a new portion is introduced will remove the substrate through the unloading pipe in a volume equal to the volume of the introduced material.