How to make methane at home. DIY biogas plant for home

28.08.2023

Many household owners are concerned about how to reduce costs for home heating, cooking and electricity supply. Some of them have already built biogas plants with their own hands and have partially or completely isolated themselves from energy suppliers. It turns out that getting almost free fuel in a private household is not very difficult.

What is biogas and how can it be used?

Owners of homestead farms know: by putting any plant material, bird droppings and manure in a heap, over time you can obtain valuable organic fertilizer. But few of them know that biomass does not decompose on its own, but under the influence of various bacteria.

By processing the biological substrate, these tiny microorganisms release waste products, including a gas mixture. Most of it (about 70%) is methane - the same gas that burns in the burners of household stoves and heating boilers.

The idea of using such eco-fuels for various economic needs is not new. Devices for its extraction were used in ancient China. Soviet innovators also explored the possibility of using biogas in the 60s of the last century. But the technology experienced a real revival in the early 2000s. Currently, biogas plants are actively used in Europe and the USA for heating homes and other needs.

How does a biogas plant work?

The operating principle of the biogas production device is quite simple:

Biomass diluted with water is loaded into a sealed container, where it begins to “ferment” and release gases;
the contents of the tank are regularly updated - the raw materials processed by bacteria are drained and fresh ones are added (on average about 5-10% daily);
The gas accumulated in the upper part of the tank is supplied through a special tube to the gas collector, and then to household appliances.

Diagram of a biogas plant.

What raw materials are suitable for bioreactor?

Installations for producing biogas are profitable only where there is a daily replenishment of fresh organic matter - manure or droppings of livestock and poultry. You can also add chopped grass, tops, leaves and household waste (in particular, vegetable peelings) into the bioreactor.

The efficiency of the installation largely depends on the type of raw material being loaded. It has been proven that, with the same mass, the highest biogas yield is obtained from pig manure and turkey droppings. In turn, cow excrement and silage waste produce less gas for the same load.

Use of bio-raw materials for home heating.

What cannot be used in a biogas plant?

There are factors that can significantly reduce the activity of anaerobic bacteria, or even completely stop the process of biogas production. Raw materials containing:

antibiotics;
mold;
synthetic detergents, solvents and other “chemicals”;
resins (including sawdust from coniferous trees).

It is ineffective to use already rotting manure - only fresh or pre-dried waste can be loaded. Also, the raw materials should not be allowed to become waterlogged - an indicator of 95% is already considered critical. However, a small amount of clean water still needs to be added to the biomass in order to facilitate its loading and speed up the fermentation process. Manure and waste are diluted to the consistency of thin semolina porridge.

Biogas plant for home

Today, industry is already producing installations for producing biogas on an industrial scale. Their acquisition and installation is expensive; such equipment in private households pays for itself no sooner than in 7-10 years, provided that large volumes of organic matter are used for processing. Experience shows that, if desired, a skilled owner can build a small biogas plant for a private home with his own hands, and from the most affordable materials.

Preparing the processing bunker

First of all, you will need a hermetically sealed cylindrical container. You can, of course, use large pots or boils, but their small volume will not allow achieving sufficient gas production. Therefore, for these purposes, plastic barrels with a volume of 1 m³ to 10 m³ are most often used.

You can make one yourself. PVC sheets are commercially available; with sufficient strength and resistance to aggressive environments, they can be easily welded into the structure of the desired configuration. A metal barrel of sufficient volume can also be used as a bunker. True, you will have to carry out anti-corrosion measures - cover it inside and outside with moisture-resistant paint. If the tank is made of stainless steel, this is not necessary.

Gas exhaust system

The gas outlet pipe is mounted in the upper part of the barrel (usually in the lid) - this is where it accumulates, according to the laws of physics. Through a connected pipe, biogas is supplied to the water seal, then to the storage tank (optionally, using a compressor into a cylinder) and to household appliances. It is also recommended to install a release valve next to the gas outlet - if the pressure inside the tank becomes too high, it will release excess gas.

Raw material supply and unloading system

To ensure continuous production of the gas mixture, the bacteria in the substrate must be constantly (daily) “fed”, that is, fresh manure or other organic matter must be added. In turn, already processed raw materials from the bunker must be removed so that they do not take up useful space in the bioreactor.

To do this, two holes are made in the barrel - one (for unloading) almost near the bottom, the other (for loading) higher. Pipes with a diameter of at least 300 mm are welded (soldered, glued) into them. The loading pipeline is directed upward and equipped with a funnel, and the drain is arranged so that it is convenient to collect the processed slurry (it can later be used as fertilizer). The joints are sealed.

Heating system

Thermal insulation of the bunker.

If the bioreactor is installed outdoors or in an unheated room (which is necessary for safety reasons), then it must be provided with thermal insulation and heating of the substrate. The first condition is achieved by “wrapping” the barrel with any insulating material or by deepening it into the ground.

As for heating, you can consider a variety of options. Some craftsmen install pipes inside through which water circulates from the heating system and install them along the walls of the barrel in the form of a coil. Others place the reactor in a larger tank with water inside, heated by electric heaters. The first option is more convenient and much more economical.

To optimize the operation of the reactor, it is necessary to maintain the temperature of its contents at a certain level (at least 38⁰C). But if it rises above 55⁰C, then the gas-forming bacteria will simply “cook” and the fermentation process will stop.

Mixing system

As practice shows, in designs, a manual stirrer of any configuration significantly increases the efficiency of the bioreactor. The axis to which the “mixer” blades are welded (screwed) is removed through the barrel lid. The gate handle is then placed on it, and the hole is carefully sealed. However, home craftsmen do not always equip fermenters with such devices.

Biogas production

After the installation is ready, biomass diluted with water in a ratio of approximately 2:3 is loaded into it. Large waste must be crushed - the maximum fraction size should not exceed 10 mm. Then the lid is closed - all you have to do is wait for the mixture to begin to “ferment” and release biogas. Under optimal conditions, the first supply of fuel is observed several days after loading.

The fact that the gas has “started” can be judged by the characteristic gurgling sound in the water seal. At the same time, the barrel should be checked for leaks. This is done using a regular soap solution - it is applied to all joints and observed to see if bubbles appear.

The first update of bio-raw materials should be carried out in about two weeks. After the biomass is poured into the funnel, the same volume of waste organic matter will pour out of the outlet pipe. Then this procedure is performed daily or every two days.

How long does the resulting biogas last?

In a small farm, a biogas plant will not be an absolute alternative to natural gas and other available energy sources. For example, using a device with a capacity of 1 m³, you can only get fuel for a couple of hours of cooking for a small family.

But with a 5 m³ bioreactor it is already possible to heat a room with an area of 50 m², but its operation will need to be maintained by daily loading of raw materials weighing at least 300 kg. To do this, you need to have about ten pigs, five cows and a couple of dozen chickens on the farm.

Craftsmen who have managed to independently make working biogas plants share videos with master classes on the Internet:

Required mandatory materials:

two containers;
connecting pipes;
valves;
gas filter;
means of ensuring tightness (glue, resin, sealant, etc.);

Desirable:

stirrer with electric motor;
temperature sensor;
pressure meter;

The sequence below is suitable for the southern regions. For operation under any conditions, a reactor heating system should be added, which will ensure heating of the vessel to 40 degrees Celsius and increase thermal insulation, for example, by enclosing the structure with a greenhouse. It is advisable to cover the greenhouse with black film. It is also advisable to add a condensate drainage device to the pipeline.

Creating a simple biogas plant:

Create a storage container. We select a tank where the resulting biogas will be stored. The reservoir is fixed with a valve and equipped with a pressure gauge. If gas consumption is constant, then there is no need for a gas tank.
Insulate the structure inside the pit.
Install pipes. Lay pipes into the pit for loading raw materials and unloading compost humus. An inlet and outlet hole are made in the reactor tank. The reactor is placed in a pit. Pipes are connected to the holes. The pipes are tightly secured using glue or other suitable means. Pipe diameters less than 30 cm will contribute to their clogging. The loading location should be chosen on the sunny side.
Install the hatch. The rector, equipped with a hatch, makes repair and maintenance work more convenient. The hatch and reactor vessel should be sealed with rubber. You can also install temperature, pressure and raw material level sensors.
Select a container for the bioreactor. The selected container must be durable - since fermentation releases a large amount of energy; have good thermal insulation; be air and waterproof. Egg-shaped vessels are best suited. If building such a reactor is problematic, then a cylindrical vessel with rounded edges would be a good alternative. Square-shaped containers are less efficient because hardened biomass will accumulate in the corners, making fermentation difficult.
Prepare the pit.
Select a location for mounting the future installation. It is advisable to choose a place far enough from the house and so that you can dig a hole. Placing it inside a pit allows you to significantly save on thermal insulation, using cheap materials like clay.
Check the tightness of the resulting structure.
Start the system.
Add raw materials. We wait about two weeks until all the necessary processes take place. A necessary condition for gas combustion is to get rid of carbon dioxide. A regular filter from a hardware store will do for this. A homemade filter is made from a 30 cm long piece of gas pipe filled with dry wood and metal shavings.

Composition and types

Biogas is a gas obtained as a result of a three-phase biochemical process on biomass, taking place in sealed conditions.

The process of biomass decomposition is sequential: first it is exposed to hydrolytic bacteria, then acid-forming bacteria and finally methane-forming bacteria. The material for microorganisms at each stage is the product of the activity of the previous stage.

At the output, the approximate composition of biogas looks like this:

methane (50 to 70%);
carbon dioxide (30 to 40%);
hydrogen sulfide (~2%);
hydrogen (~1%);
ammonia (~1%);

The accuracy of the proportions is affected by the raw materials used and gas production technology. Methane has the potential for combustion; the higher its percentage, the better.

Ancient cultures dating back more than three thousand years (India, Persia or Assyria) have experience using flammable swamp gas. The scientific basis was formed much later. The chemical formula of methane CH 4 was discovered by scientist John Dalton, and the presence of methane in swamp gas was discovered by Humphry Davy. The Second World War played a major role in the development of the alternative energy industry, requiring the warring parties to have a huge need for energy resources.

The USSR's possession of huge reserves of oil and natural gas led to a lack of demand for other energy production technologies; the study of biogas was mainly a subject of interest to academic science. At the moment, the situation has changed so much that, in addition to the industrial production of various types of fuel, anyone can create a biogas plant for their own purposes.

Installation device

– a set of equipment designed to produce biogas from organic raw materials.

Based on the type of raw material supplied, the following types of biogas plants are distinguished:

with portioned feeding;
with continuous feed;

Biogas plants with a constant supply of raw materials are more efficient.

By type of raw material processing:

No automatic stirring raw materials and maintaining the required temperature - complexes with minimal equipment, suitable for small farms (Diagram 1).
With automatic stirring, but without maintaining the required temperature - also serves small farms, more efficiently than the previous type.
With support for the required temperature, but without automatic mixing.
With automatic mixing of raw materials and temperature support.

Principle of operation

The process of converting organic raw materials into biogas is called fermentation. The raw materials are loaded into a special container that provides reliable protection of the biomass from oxygen. An event that occurs without the intervention of oxygen is called anaerobic.

Under the influence of special bacteria, fermentation begins to occur in an anaerobic environment. As fermentation progresses, the raw material becomes covered with a crust, which must be destroyed regularly. Destruction is carried out by thorough mixing.

It is necessary to mix the contents at least twice a day, without violating the tightness of the process. In addition to removing the crust, stirring allows you to evenly distribute acidity and temperature inside the organic mass. As a result of these manipulations, biogas is produced.

The resulting gas is collected in a gas tank and from there it is delivered to the consumer through pipes. Biofertilizers obtained after processing the feedstock can be used as a food additive for animals or added to the soil. This fertilizer is called compost humus.

The biogas plant includes the following elements:

homogenization tank;
reactor;
stirrers;
storage tank (gas-holder);
heating and water mixing complex;
gas complex;
pump complex;
separator;
control sensors;
Instrumentation and automation with visualization;
safety system;

An example of an industrial-type biogas plant is shown in Diagram 2.

Raw materials used

The decomposition of any animal or plant matter will release flammable gas to varying degrees. Mixtures of various compositions are well suited for raw materials: manure, straw, grass, various wastes, etc. The chemical reaction requires a humidity of 70%, so the raw material must be diluted with water.

The presence of cleaning agents, chlorine, and washing powders in organic biomass is unacceptable, as they interfere with chemical reactions and can damage the reactor. Also not suitable for the reactor are raw materials with sawdust from coniferous trees (containing resins), with a high proportion of lignin and exceeding the moisture threshold of 94%.

Vegetable. Plant raw materials are excellent for biogas production. Fresh grass gives the maximum fuel yield - about 250 m 3 of gas with a methane share of 70% is obtained from a ton of raw material. Corn silage is slightly smaller - 220 m3. Beet tops – 180 m3.

Almost any plant, hay or algae can be used as biomass. The disadvantage of application is the length of the production cycle. The process of obtaining biogas takes up to two months. The raw materials must be finely ground.

Animal. Waste from processing plants, dairy plants, slaughterhouses, etc. Suitable for biogas plant. The maximum fuel yield is provided by animal fats - 1500 m 3 of biogas with a methane share of 87%. The main disadvantage is shortage. Animal raw materials must also be ground.

Excrement. The main advantage of manure is its cheapness and easy availability. Disadvantage – the quantity and quality of biogas is lower than from other types of raw materials. Horse and cow excrement can be processed immediately. The production cycle will take approximately two weeks and will produce an output of 60 m3 with 60% methane content.

Chicken manure and pig manure cannot be used directly because they are toxic. To start the fermentation process, they must be mixed with silage. Human waste products can also be used, but sewage is not suitable since the fecal content is low.

Schemes of work

Scheme 1 – biogas plant without automatic mixing of raw materials:

Scheme 2 – industrial biogas plant:

Finally, here is a list of useful information that will help you avoid additional problems when creating a biogas plant:

Practice says that to heat a living space with an area of 50 m2, it is necessary to consume 3.5 m3 of gas per hour.
It is not advisable to use biogas directly for cooking, because the taste may change.
It is necessary to avoid getting solid objects (nuts, bolts, etc.) into the raw materials, because the equipment may deteriorate.

In order for biogas to burn stably, it must meet certain standards:

methane content at least 65% (optimal content from 90 to 95%);
there should be no water vapor, hydrogen and carbon dioxide;
normal gas supply pressure 12.5 bar;

If the gas goes out due to a pressure surge or for other reasons, and its supply continues, it can lead to tragic consequences. Therefore, modern equipment with gas monitoring sensors should be used.

You can get a cheap source of energy yourself, at home - you just need to assemble a biogas plant. If you understand the principle of its operation and structure, then this is not difficult to do. The mixture it produces contains a large amount of methane (depending on the loaded raw material - up to 70%), so it has a wide range of applications.

Refilling car cylinders running on gas as fuel for heating boilers is not a complete list of all possible options for using the finished product. Our story is about how to install a biogas plant with your own hands.

There are several designs of the unit. When choosing a particular engineering solution, you need to understand how suitable this installation is to local conditions. This is the main criterion for assessing the feasibility of installation. Plus, you have your own capabilities, that is, what type of raw materials and in what volume you can use, what you can do with your own hands.

Biogas is produced by the decomposition of organic matter, but its “yield” (in volumetric terms), and therefore the efficiency of the plant, depends on what exactly is loaded into it. The table provides relevant information (indicative data), which will help determine the choice of a specific engineering solution. Some explanatory graphics would also be useful.

Design options

With manual loading of raw materials, without heating and stirring

For domestic use, this model is considered the most convenient. With a reactor capacity of 1 to 10 m³, approximately 50–220 kg of manure will be needed daily. This is what you need to proceed from when deciding on the size of the container.

The installation is installed in the ground, so it will require a small pit. A location on the site is selected in accordance with its calculated dimensions. The composition and purpose of all elements of the circuit is not difficult to understand.

Installation feature

After installing the reactor on site, it is necessary to check its tightness. Then the metal must be painted (preferably with a frost-resistant composition) and insulated.

Removal of waste occurs naturally - either during the process of adding a new portion, or when there is an excess of gas in the reactor with the valve closed. Therefore, the capacity of the waste collection container should be no less than that of the working one.
Despite the simplicity of the device and the attractiveness for do-it-yourself assembly, due to the fact that mixing and heating of the mass are not provided, this installation option is advisable to operate in regions with a mild climate, that is, mainly in the south of Russia. Although, with high-quality thermal insulation, in conditions where underground water layers are deep, this design is quite suitable for the middle zone.

Without heating, but with stirring

Almost the same thing, only a small modification that significantly increases the performance of the installation.

How to make a mechanism? For someone who assembled it with their own hands, for example, this is not a problem. A shaft with blades will have to be mounted in the reactor. Therefore, it is necessary to install support bearings. It is good to use a chain as a transmission link between the shaft and the lever.

The biogas plant can be operated in almost all regions, with the exception of the northern regions. But unlike the previous model, it requires supervision.

Stirring + heating

The thermal effect on biomass increases the intensity of the decomposition and fermentation processes occurring in it. The biogas unit is more versatile in use, as it can operate in two modes - mesophilic and thermophilic, that is, in the temperature range (approximately) 25 - 65 ºС (see graphs above).

In the above diagram, the boiler runs on the resulting gas, although this is not the only option. Heating of biomass can be done in different ways, depending on how it is more convenient for the owner to organize it.

Automated options

The difference between this scheme is that it is connected to the installation. This allows you to accumulate gas reserves rather than using it immediately for its intended purpose. Ease of use is also due to the fact that almost any temperature regime is suitable for intensive fermentation.

This installation is even more productive. It is capable of processing up to 1.3 tons of raw materials per day with a similar reactor volume. Loading, mixing - pneumatics are responsible for this. The outlet channel allows waste to be removed either into a bunker for short-term storage, or into mobile containers for immediate removal. For example, for fertilizing fields.

These biogas plant options are hardly suitable for domestic use. Installing them, especially with your own hands, is much more difficult. But for a small farm it is a good solution.

Mechanized biogas plant

The difference from previous models is in the additional tank in which preliminary preparation of the raw material mass occurs.

Compressed biogas is fed into the loading hopper and then into the reactor. It is also used for heating.

The only thing that is necessary when assembling any of the installations with your own hands is accurate engineering calculations. You may need to consult a specialist. Otherwise everything is quite simple. If at least one of the readers becomes interested in a biogas unit and installs it themselves, then the author did not work on this article in vain. Good luck!

Farms need fuel for heating systems, generating electricity and other daily needs. Since energy prices are steadily rising year after year, every home or small business owner has at least once thought about how to produce biogas at home.

Biogas plants are increasingly being used on farms, allowing them to save money on heating

A biogas plant for a private home allows you to organize the production of biogas right in your yard, which solves the fuel problem. Since a significant percentage of village residents have skills in working with welding and plumbing tools, the question of self-manufacturing a gas production plant seems logical. This way you can save not only on work, but also on materials if you use improvised means.

What is biogas and how is it formed: obtaining and production

Biogas is a substance formed during the fermentation of organic waste, which contains methane in sufficient quantities to be used as fuel. When burned, biogas releases heat, which is enough to heat a house or refuel a car. the source of energy is manure, which is easily accessible and cheap or even free if we are talking about a livestock enterprise or a large private farm.

Biogas is an environmentally friendly biofuel that you can produce with your own hands; biological gas is related to natural gas. The gas is produced by processing waste by anaerobic bacteria. Fermentation takes place in an airless container called a bioreactor. The rate of biogas production depends on the amount of waste loaded into the biogenerator. Under the influence of bacteria, a mixture of methane and carbon dioxide with some admixtures of other gaseous substances is released from the raw material. The resulting gas is removed from the bioreactor, purified and used for its own needs. The processed raw materials upon completion of the process become fertilizer, which is used to improve soil fertility. Producing biogas is beneficial for livestock enterprises that have access to free manure and other organic waste.

Benefits of burning fuel from manure (farm fertilizer) for heating: electricity from methane

The advantages of biogas as a fuel include:

Efficient and environmentally friendly waste recycling
Availability of raw materials for gas production in rural areas
Possibility to organize a closed cycle of waste-free production of gas and fertilizers from manure
Non-exhaustible, self-replenishing source of raw materials

How to build a bioreactor (installation) with your own hands

Biogas plants that produce gas from manure can be easily assembled with your own hands on your own site. Before assembling a bioreactor for processing manure, it is worth drawing drawings and carefully studying all the nuances, because a container containing a large amount of explosive gas can be a source of great danger if it is used incorrectly or if there are errors in the design of the installation.

Biogas production scheme

The capacity of the bioreactor is calculated based on the amount of raw material that is used to produce methane. In order for operating conditions to be optimal, the reactor capacity is filled with waste to at least two-thirds. For these purposes, a deep pit is used. To ensure high tightness, the walls of the pit are reinforced with concrete or reinforced with plastic, and sometimes concrete rings are installed in the pit. The surface of the walls is treated with moisture-proofing solutions. Tightness is a necessary condition for efficient operation of the installation. The better the container is insulated, the higher the quality and quantity. In addition, waste breakdown products are poisonous and, if leaked, can be harmful to health.

A stirrer is installed in the waste container. It is responsible for mixing waste during fermentation, preventing uneven distribution of raw materials and the formation of a crust. Following the mixer, a drainage structure is installed in the manure, which facilitates the removal of gas into the storage tank and prevents leakage. It is necessary to remove the gas for safety reasons, as well as to improve the quality of the fertilizers remaining in the reactor after processing. A hole is made in the bottom of the reactor for. The hole is equipped with a tight lid so that the equipment remains sealed.

How to ensure active fermentation of biomass at home using a generator and other equipment: waste processing, composition and extraction

In order for the processing process in a bioreactor to proceed faster, heating is necessary. The ambient temperature is sufficient for manure processing to occur without outside help. But under unfavorable weather conditions, in the winter, a mini-biogas plant needs an additional heat source, otherwise gas production becomes impossible. For bacteria to convert waste into gas, the temperature in the reactor must be above 38 degrees Celsius. It is not difficult to obtain biogas with your own hands; the main thing is to know certain manufacturing rules.

The container is heated using a coil, which is located under the reactor, or by installing electric heaters to directly heat the reservoir. , which process waste into gas, are already in the raw material. To activate microorganisms and start the process of biogas production, the temperature in the container must be sufficient for fermentation. To make it easier to control compliance with temperature conditions, automatic heating is connected to the reactor. It heats the container when fuel is loaded into it to the desired temperature and turns off the heating when the desired mark on the thermometer is reached. A temperature control device for, which is easy to find in a gas equipment store, can handle the role of an automatic heater.

Temperature control module. It can be purchased at any hardware store

Correct gas removal from a bioreactor: drawings, use of technology

To easily remove the formed gas from the tank, biogas plants are equipped with a number of devices:

Vertically arranged plastic pipes with a large number of holes to facilitate the separation of gas from the raw material. The top of the pipe should protrude above the waste mass, allowing gas to escape freely.
A film laid over the container and creating a kind of greenhouse effect. It maintains the desired temperature inside the container and also prevents gas from mixing with air.

Sometimes the container is covered with a dome made of concrete or other material. To prevent such a dome from flying away under the pressure of the resulting gas, it is carefully attached to the structure and tied with cables.
A gas exhaust pipe is placed at the top of the reactor. The pipe is equipped with a tight locking mechanism so as not to violate the tightness of the structure. The newly released biogas, entering the outlet pipe, is saturated with water vapor and contains many impurities. occurs by condensation: when cooled to ambient temperature, water settles in the form of condensation on the walls of the pipe. To avoid corrosion, the discharge pipe is installed in such a way as to facilitate the removal of condensate through the separator.
To remove hydrogen sulfide impurities from biogas, a filter made of specially treated activated carbon is installed on its way to the storage facility, in which the mixture is oxidized into sulfur and deposited in the sorbent.

WATCH THE VIDEO

A self-assembled biogas plant, processing manure into biogas at home, significantly reduces heating and electricity costs. Such an installation will reduce the cost of providing a private home with heat, reduce the cost of farm products, thereby increasing the profitability of the farm. – the ability to turn waste into a source of energy and an alternative to natural gas. Biogas is environmentally friendly and modern.

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 quantity.

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 manufacturer’s 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.