A DIY biogas plant can be done without much effort. Its use will allow significant savings on energy resources, which today are becoming more and more expensive every time. If you independently decide to build equipment that allows you to obtain biogas from waste, you will be able to consume cheap energy, which will be used for home heating and other needs.

Beneficial use

If during the operation of the installation excess biogas or fertilizers are generated, then it is possible to sell them at the market price, thereby turning what is literally lying under your feet into profit. If you are a large farmer, then you have the opportunity to purchase a ready-made biogas production station. Such factory-produced installations are very expensive, but have a long lifespan.

A do-it-yourself biogas plant can be made from scrap materials, it will not cost very much, and such equipment will work on the same principle. In this case, you can use available tools, as well as parts available in the master’s arsenal.

Principle of biogas formation

If you set out to make a plant that will run on biological gas, then you need to present the technology for the generation of biogas. So, in a special container, which is called a bioreactor, the process of processing biological mass is carried out, and anaerobic bacteria take part in this.

A do-it-yourself biogas plant for home using quail droppings works on the principle of creating conditions that are characterized by the absence of air and fermentation. All this lasts for some time, the duration of which depends on the amount of raw materials used in the process.

Ultimately, a mixture of gases is formed, which contains 60% methane and 35% carbon dioxide. The remaining gaseous components are contained in the mass in an amount of 5%. Among the latter, hydrogen sulfide can be identified in small quantities. The gas thus formed is continuously removed from the reactor, and after undergoing a purification process, it is used for its intended purpose.

Service Features

Waste that has undergone processing becomes high-quality fertilizers, which from time to time must be removed from the bioreactor. They can be laid on the fields. A DIY biogas plant can be done without much effort if you have access to livestock and agricultural facilities. This indicates that the production of biogas will become economically profitable only if there is a source of supply of manure and other organic waste from livestock production.

Features of self-construction of a bioreactor

In order to understand how to make a biogas plant yourself, you need to understand what parts it consists of. You can take as a basis the simplest diagram of equipment that you can build on your own. The design does not provide heating and a mixing device, but there is one of the main parts - a reactor, which is also known as a digester. This component is required for manure processing. In addition, there is a bunker through which raw materials are loaded. It is necessary to equip the structure with an entrance hatch, as well as a water seal. But in order to be able to unload waste raw materials, a pipe will be needed. A similar element will be required in order to realize the possibility of removing biogas.

This is what the diagram of a biogas plant looks like. It is not difficult to make such a design with your own hands. In order to receive free biological fuel, you should choose a place on the site where you can build a reinforced container, which will be based on concrete. This vessel will act as a bioreactor. At its base, it is necessary to provide a hole through which processed raw materials will be removed. This hole must be made in such a way that it can be closed well. This is due to the fact that the system can only operate in sealed conditions.

The dimensions of the concrete compartment can be determined taking into account the amount of organic waste used at a time. You need to find out how much raw material will appear on a farm or private farm every day. But you should not save, since it will be possible to ensure full operation of the bioreactor only if the tank is filled to 2/3 of the available volume. If you make a biogas plant with your own hands from a barrel, it will work according to the following principle: as soon as organic waste enters a well-closed bioreactor container, which is located deep in the soil, it begins to ferment, which leads to the release of biogas.

Features of container manufacturing

A DIY biogas plant can be made taking into account the daily use of a small amount of waste. In this case, it is permissible to replace the reinforced concrete tank with a steel container, which can even be a barrel. If you decide to resort to just such a solution, then you need to choose a metal vessel, guided by certain rules.

First of all, you need to pay attention to the welds, which must be strong enough and airtight. When using a small container, you should not expect to obtain a significant amount of biogas. The yield will depend on the mass of organic waste that is simultaneously processed in the reactor. Thus, in order to generate 100 m 3 of biogas, it is necessary to process a ton of waste.

Reactor heating equipment

A do-it-yourself biogas plant for the home can be made in such a way that its operation can be more efficient. This is ensured by heating. Such manipulations will speed up the process of fermentation of biological mass. If the equipment is installed in the southern regions, then such a need does not arise. The ambient temperature provides natural activation of fermentation. However, if the installation operates in regions with a cold climate, then in winter heating acts as a necessary condition for the operation of biogas production equipment. It must be remembered that the fermentation process begins at a temperature that exceeds 38 o C.

Methods for equipping a biogas plant with heating

A do-it-yourself biogas plant for your home can be equipped with heating using several methods. The first involves the need to connect the installation to a heating system using a coil type. It must be mounted under the reactor. The second method involves installing an electric heating element at the base of the tank. The third method is characterized by providing direct heating of the tank by using electric heating systems and gas equipment. Activation of biological gas production at home can be supplemented with the function of mixing the mass in the compartment. To do this, you should design a device that resembles a household mixer. It will be driven by a shaft brought out through a hole in the lid; as an alternative solution, it can be placed in the walls of the tank.

Equipment of the installation with an output system

A mini biogas plant, designed with your own hands, cannot operate without a gas exhaust system. To do this, the installation must have a special hole, which must be mounted in the upper part of the lid, the latter must cover the tank well. To eliminate the possibility of gas mixing with air, it is necessary to ensure its removal through a water seal.

Biogas is a mixture of gases that are formed during the decomposition of organic matter by anaerobic bacteria. Biogas is highly flammable and produces a clean flame when burned, so it can be used not only for cooking, but also for internal combustion engines (for example, for generating electricity).

Advantages of a biogas plant at home:
– you can easily obtain biogas at home without the use of expensive equipment;
– an excellent alternative energy for those whose home is located far from civilization, or for those who want to be independent from the state;
– available raw materials (manure, kitchen waste, chopped vegetation, etc.);
– concern for the environment, since in the process of decomposition of organic substances in nature, gas enters the atmosphere, which entails a greenhouse effect, and in this case, biogas will be burned, producing CO2;
– production of fertilizers as a by-product of a biogas plant.

But besides the advantages, biogas plant has its disadvantages:
– bacteria work at a temperature of 18-40 degrees, so you can get biogas in the summer. If you insulate a biogas plant and equip it with heating, you can get biogas in the spring-autumn period, but the costs of insulation and heating may cancel out the benefits received
– it is necessary to constantly introduce new raw materials, and therefore drain fertilizers.

To make a biogas plant with your own hands we will need:
1. Two 200l barrels
2. 30-60l barrel, or large plastic bucket
3. Plastic sewer pipes
4. Gas hose
5. Crane

For clarity, I will give home biogas installation diagram

Operating principle of a biogas plant. Raw materials (manure, kitchen waste, chopped vegetation, etc.) and water are loaded into the reactor. The biogas plant will not start working immediately, but after a few days, when the number of anaerobic bacteria increases to its maximum.

During the life of anaerobic bacteria, biogas is released, which will be collected at the top point of the barrel (a tap should be located in this place). From the reactor, biogas enters the collector through a gas hose.

The collector is a 200 liter barrel of water, and an inverted bucket in it to collect gas, as well as to create the pressure necessary for the operation of a gas furnace. As gas enters, the bucket will float. If the amount of biogas is greater than the plastic bucket can contain, then the gas will simply come out through the water.

For making a reactor You will need a 200 liter sealed barrel. We make several holes in the upper part of the barrel and install:
– Plastic pipe for pouring raw materials. At the end of the pipe it is necessary to install a transition to a large pipe (a kind of watering can, for the convenience of pouring raw materials)
– Plastic pipe for draining fertilizers. Since a biogas plant is not a perpetual motion machine, it is necessary to constantly add raw materials. When introducing new raw materials, the excess (already processed raw materials - fertilizers) will exit through the drain pipe.
– A tap at the highest point of the biogas collection barrel.

When manufacturing a reactor, it is very important that all connections are sealed, otherwise, under the resulting pressure, gas may leak out. The drain pipe must be located below the installation level of the gas tap. The drain and fill pipes should be tightly plugged when not in use.

To make the collector you will need a 200 liter plastic barrel without a lid. Pour 3/4 of the water into the barrel and install another barrel, upside down, smaller in volume. In the bottom of a smaller barrel we cut a fitting for connecting the hose from the reactor, and a tap for connecting the hose going to the gas furnace.

To fill the raw materials, open the inlet and drain holes and fill the raw materials. It is best to use manure diluted in water. It is best to use rainwater or settled water so that the chlorine content from the water supply does not reduce the colonies of bacteria. Also, if you use kitchen scraps, be sure to keep detergents, eggshells, bones, and onion skins away as they may affect the operation of the biogas plant for the worse.

Biogas itself has a very unpleasant odor, but when burned there is no odor. If you burn gas without mixing with air, you will get a yellow flame with soot, which will easily smoke the bottom of the pan.

If you mix biogas with air and then set it on fire, you will get a clean blue flame without soot. So, for example, in factory gas stoves, the instructions say that when switching from mains gas to bottled gas and vice versa, it is necessary to change the jets (which differ in hole diameter), otherwise the burner will smoke. Alternatively, you can use laboratory Bunsen burner.

If you don’t have a laboratory burner, you can easily make one from a piece of pipe by drilling holes at the base. Thus, the gas, passing through the pipe, will mix with air, and at the exit of the tube we will get a mixed gas.

You can experiment with pieces of wood as jets, sharpening them to resemble a pencil and drilling holes of different diameters in them. In this way, the optimal torch size can be obtained.

For the experiment, an old barbecue was used as a stove, a hole was cut in the bottom and a Bunsen burner was installed. And subsequently, the barbecue was replaced with a single-burner stove.

To create gas pressure, a weight is placed on the manifold (a small barrel for collecting gas). For example, if you set a load of 5 kg, then 1 liter of water can be boiled in 15 minutes. If you set a load of 10 kg, then 1 liter of water will boil in 10 minutes.

To summarize, it should be noted that homemade biogas plant produces biogas for 30 minutes of burner operation per day, if the raw material is manure. If you use kitchen scraps as raw materials, the productivity is only 15 minutes per day.

The gas released is not that much, but you will agree that the biogas plant is not that big either. Therefore, if you want to increase the amount of gas produced, you will need to increase the volumes of the reactor and collector.

The dimensions of the collector do not need to be increased if you timely pump the biogas into another container (for example, into a cylinder). Most simply, this can be done using a compressor from a refrigerator, which has one input and one output. We connect the input to the manifold, and the output to the cylinder.

The compressor can be equipped with automation, for example, when the manifold is filled with gas, the barrel rises, closes the contacts, thereby turning on the compressor. And the compressor, in turn, turned off when the barrel dropped to the minimum level.

The reactor of a biogas plant must be made of plastic, but in no case made of metal, since due to oxidative processes the metal will quickly rust. As an option, you can use large-volume plastic barrels (for example, a Eurocube). And so that large volumes of barrels do not take up much space in the yard, they can be buried.

Nov 19, 2016 Gennady

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:

1. Create a storage container. We select a tank where the resulting biogas will be stored. The tank 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.
2. Insulate the structure inside the pit.
3. 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.
4. 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.
5. 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.
6. Prepare the pit.
7. 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.
8. Check the tightness of the resulting structure.
9. Start the system.
10. 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:

1. No automatic stirring raw materials and maintaining the required temperature - complexes with minimal equipment, suitable for small farms (diagram 1).
2. With automatic stirring, but without maintaining the required temperature - also serves small farms, more efficiently than the previous type.
3. With support of the required temperature, but without automatic mixing.
4. 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:

One of the problems that has to be solved in agriculture is the disposal of manure and plant waste. And this is a rather serious problem that requires constant attention. Recycling takes not only time and effort, but also considerable amounts. Today there is at least one way to turn this headache into an income source: processing manure into biogas. The technology is based on the natural process of decomposition of manure and plant residues due to the bacteria they contain. The whole task is to create special conditions for the most complete decomposition. These conditions are the absence of oxygen access and optimal temperature (40-50 o C).

Everyone knows how manure is most often disposed of: they put it in heaps, then, after fermentation, they take it out to the fields. In this case, the resulting gas is released into the atmosphere, and 40% of the nitrogen contained in the initial substance and most of the phosphorus also escape there. The resulting fertilizer is far from ideal.

To obtain biogas, it is necessary that the process of decomposition of manure takes place without access to oxygen, in a closed volume. In this case, both nitrogen and phosphorus remain in the residual product, and the gas accumulates in the upper part of the container, from where it can be easily pumped out. There are two sources of profit: gas itself and effective fertilizer. Moreover, the fertilizer is of the highest quality and 99% safe: most of the pathogenic microorganisms and helminth eggs die, and the weed seeds contained in the manure lose their viability. There are even lines for packaging this residue.

The second prerequisite for the process of processing manure into biogas is maintaining an optimal temperature. The bacteria contained in the biomass are inactive at low temperatures. They begin to act at an ambient temperature of +30 o C. Moreover, manure contains two types of bacteria:

Thermophilic plants with temperatures from +43 o C to +52 o C are the most effective: in them, manure is processed for 3 days, and the output from 1 liter of useful bioreactor area is up to 4.5 liters of biogas (this is the maximum output). But maintaining a temperature of +50 o C requires significant energy expenditure, which is not profitable in every climate. Therefore, biogas plants often operate at mesophilic temperatures. In this case, the processing time can be 12-30 days, the yield is approximately 2 liters of biogas per 1 liter of bioreactor volume.

The composition of the gas varies depending on the raw materials and processing conditions, but it is approximately as follows: methane - 50-70%, carbon dioxide - 30-50%, and also contains a small amount of hydrogen sulfide (less than 1%) and very small amounts of ammonia, hydrogen and nitrogen compounds. Depending on the design of the plant, biogas may contain a significant amount of water vapor, which will require drying (otherwise it simply will not burn). What an industrial installation looks like is demonstrated in the video.

This can be said to be an entire gas production plant. But for a private farmstead or small farm such volumes are useless. The simplest biogas plant is easy to make with your own hands. But the question is: “Where should the biogas be sent next?” The heat of combustion of the resulting gas is from 5340 kcal/m3 to 6230 kcal/m3 (6.21 - 7.24 kWh/m3). Therefore, it can be supplied to a gas boiler to generate heat (heating and hot water), or to an electricity generation installation, to a gas stove, etc. This is how Vladimir Rashin, a biogas plant designer, uses manure from his quail farm.

It turns out that if you have at least a decent amount of livestock and poultry, you can fully meet your farm’s needs for heat, gas and electricity. And if you install gas installations on cars, then it will also provide fuel for the fleet. Considering that the share of energy resources in the cost of production is 70-80%, you can only save on a bioreactor, and then earn a lot of money. Below is a screenshot of an economic calculation of the profitability of a biogas plant for a small farm (as of September 2014). The farm cannot be called small, but it is definitely not large either. We apologize for the terminology - this is the author's style.

This is an approximate breakdown of the required costs and possible income Schemes for homemade biogas plants

Schemes of homemade biogas plants

The simplest scheme of a biogas plant is a sealed container - a bioreactor, into which the prepared slurry is poured. Accordingly, there is a hatch for loading manure and a hatch for unloading processed raw materials.

The simplest scheme of a biogas plant without any bells and whistles

The container is not completely filled with the substrate: 10-15% of the volume should remain free to collect gas. A gas outlet pipe is built into the tank lid. Since the resulting gas contains a fairly large amount of water vapor, it will not burn in this form. Therefore, it is necessary to pass it through a water seal to dry it. In this simple device, most of the water vapor will condense, and the gas will burn well. Then it is advisable to clean the gas from non-flammable hydrogen sulfide and only then can it be supplied to a gas holder - a container for collecting gas. And from there it can be distributed to consumers: fed to a boiler or gas oven. Watch the video to see how to make filters for a biogas plant with your own hands.

Large industrial installations are placed on the surface. And this, in principle, is understandable - the volume of land work is too large. But on small farms the bunker bowl is buried in the ground. This, firstly, allows you to reduce the cost of maintaining the required temperature, and secondly, in a private backyard there are already enough all kinds of devices.

The container can be taken ready-made, or made from brick, concrete, etc. in a dug pit. But in this case, you will have to take care of the tightness and impermeability of air: the process is anaerobic - without air access, therefore it is necessary to create a layer impenetrable to oxygen. The structure turns out to be multi-layered and the production of such a bunker is a long and expensive process. Therefore, it is cheaper and easier to bury a ready-made container. Previously, these were necessarily metal barrels, often made of stainless steel. Today, with the advent of PVC containers on the market, you can use them. They are chemically neutral, have low thermal conductivity, a long service life, and are several times cheaper than stainless steel.

But the biogas plant described above will have low productivity. To activate the processing process, active mixing of the mass located in the hopper is necessary. Otherwise, a crust forms on the surface or in the thickness of the substrate, which slows down the decomposition process, and less gas is produced at the outlet. Mixing is carried out in any available way. For example, as demonstrated in the video. In this case, any drive can be made.

There is another way to mix the layers, but it is non-mechanical - barbitation: the generated gas is fed under pressure into the lower part of the container with manure. Rising upward, gas bubbles will break the crust. Since the same biogas is supplied, there will be no changes in processing conditions. Also, this gas cannot be considered a consumption - it will again end up in the gas tank.

As mentioned above, good performance requires elevated temperatures. In order not to spend too much money on maintaining this temperature, you need to take care of insulation. What type of heat insulator to choose, of course, is up to you, but today the most optimal one is polystyrene foam. It is not afraid of water, is not affected by fungi and rodents, has a long service life and excellent thermal insulation performance.

The shape of the bioreactor can be different, but the most common is cylindrical. It is not ideal from the point of view of the complexity of mixing the substrate, but it is used more often because people have accumulated a lot of experience in building such containers. And if such a cylinder is divided by a partition, then they can be used as two separate tanks in which the process is shifted in time. In this case, a heating element can be built into the partition, thus solving the problem of maintaining temperature in two chambers at once.

In the simplest version, homemade biogas plants are a rectangular pit, the walls of which are made of concrete, and for tightness they are treated with a layer of fiberglass and polyester resin. This container is equipped with a lid. It is extremely inconvenient to use: heating, mixing and removal of the fermented mass is difficult to implement, and it is impossible to achieve complete processing and high efficiency.

The situation is a little better with trench biogas manure processing plants. They have beveled edges, making it easier to load fresh manure. If you make the bottom at a slope, then the fermented mass will shift to one side by gravity and it will be easier to select it. In such installations, it is necessary to provide thermal insulation not only for the walls, but also for the lid. It is not difficult to implement such a biogas plant with your own hands. But complete processing and the maximum amount of gas cannot be achieved in it. Even with heating.

The basic technical issues have been dealt with, and you now know several ways to build a plant for producing biogas from manure. There are still technological nuances.

What can be recycled and how to achieve good results

The manure of any animal contains the organisms necessary for its processing. It has been discovered that more than a thousand different microorganisms are involved in the fermentation process and gas production. Methane-forming substances play the most important role. It is also believed that all these microorganisms are found in optimal proportions in cattle manure. In any case, when processing this type of waste in combination with plant matter, the largest amount of biogas is released. The table shows average data for the most common types of agricultural waste. Please note that this amount of gas output can be obtained under ideal conditions.

For good productivity it is necessary to maintain a certain substrate humidity: 85-90%. But water must be used that does not contain foreign chemicals. Solvents, antibiotics, detergents, etc. have a negative effect on processes. Also, for the process to proceed normally, the liquid should not contain large fragments. Maximum fragment sizes: 1*2 cm, smaller ones are better. Therefore, if you plan to add herbal ingredients, you need to grind them.

It is important for normal processing in the substrate to maintain an optimal pH level: within 6.7-7.6. Usually the environment has normal acidity, and only occasionally acid-forming bacteria develop faster than methane-forming bacteria. Then the environment becomes acidic, gas production decreases. To achieve the optimal value, add regular lime or soda to the substrate.

Now a little about the time it takes to process manure. In general, the time depends on the conditions created, but the first gas can begin to flow already on the third day after the start of fermentation. The most active gas formation occurs when manure decomposes by 30-33%. To give you a sense of time, let’s say that after two weeks the substrate decomposes by 20-25%. That is, optimally the processing should last a month. In this case, the fertilizer is of the highest quality.

Calculation of bin volume for processing

For small farms, the optimal installation is a constant one - this is when fresh manure is supplied in small portions daily and removed in the same portions. In order for the process not to be disrupted, the share of the daily load should not exceed 5% of the processed volume.

Homemade installations for processing manure into biogas are not the pinnacle of perfection, but are quite effective

Based on this, you can easily determine the required tank volume for a homemade biogas plant. You need to multiply the daily volume of manure from your farm (already in a diluted state with a humidity of 85-90%) by 20 (this is for mesophilic temperatures, for thermophilic temperatures you will have to multiply by 30). To the resulting figure you need to add another 15-20% - free space for collecting biogas under the dome. You know the main parameter. All further costs and system parameters depend on which biogas plant scheme is chosen for implementation and how you will do everything. It is quite possible to make do with improvised materials, or you can order a turnkey installation. Factory developments will cost from 1.5 million euros, installations from the Kulibins will be cheaper.

Legal registration

The installation will have to be coordinated with the SES, gas inspectorate and firefighters. You will need:

• Technological diagram of the installation.
• Layout plan for equipment and components with reference to the installation itself, the installation location of the thermal unit, the location of pipelines and energy mains, and pump connections. The diagram should indicate the lightning rod and access roads.
• If the installation will be located indoors, then a ventilation plan will also be required, which will provide at least an eightfold exchange of all the air in the room.

As we see, we cannot do without bureaucracy here.

Finally, a little about the performance of the installation. On average, per day a biogas plant produces a volume of gas twice the useful volume of the reservoir. That is, 40 m 3 of slurry will produce 80 m 3 of gas per day. Approximately 30% will be spent on ensuring the process itself (the main expense item is heating). Those. at the output you will receive 56 m 3 of biogas per day. According to statistics, to cover the needs of a family of three and to heat an average-sized house, 10 m 3 is required. In net balance you have 46 m3 per day. And this is with a small installation.

Results

By investing a certain amount of money in setting up a biogas plant (with your own hands or on a turnkey basis), you will not only meet your own needs and needs for heat and gas, but will also be able to sell gas, as well as high-quality fertilizers resulting from processing.

The technology is not new. It began to develop back in the 18th century, when Jan Helmont, a chemist, discovered that manure emits gases that are flammable.

His research was continued by Alessandro Volta and Humphrey Davy, who found methane in the gas mixture. At the end of the 19th century in England, biogas from manure was used in street lamps. In the mid-20th century, bacteria were discovered that produce methane and its precursors.

The fact is that three groups of microorganisms alternately work in manure, feeding on the waste products of previous bacteria. The first to start working are acetogenic bacteria, which dissolve carbohydrates, proteins and fats in the slurry.

After processing the nutrient supply by anaerobic microorganisms, methane, water and carbon dioxide are formed. Due to the presence of water, biogas at this stage is not able to burn - it needs purification, so it is passed through treatment facilities.

What is biomethane

The gas obtained as a result of the decomposition of manure biomass is an analogue of natural gas. It is almost 2 times lighter than air, so it always rises. This explains the artificial production technology: free space is left at the top so that the substance can be released and accumulate, from where it is then pumped out for use for one’s own needs.

Methane greatly influences the greenhouse effect - much more than carbon dioxide - 21 times. Therefore, manure processing technology is not only an economical, but also an environmentally friendly way to dispose of animal waste.

Biomethane is used for the following needs:

• cooking;

• in internal combustion engines of automobiles;

• for heating a private house.

Biogas produces a large amount of heat. 1 cubic meter is equivalent to burning 1.5 kg of coal.

How is biomethane produced?

It can be obtained not only from manure, but also algae, plant matter, fat and other animal waste, and residues from the processing of raw materials from fish shops. Depending on the quality of the source material and its energy capacity, the final yield of the gas mixture depends.

The minimum amount of gas obtained is 50 cubic meters per ton of cattle manure. Maximum - 1,300 cubic meters after processing animal fat. The methane content is up to 90%.

One type of biological gas is landfill gas. It is formed during the decomposition of garbage in suburban landfills. The West already has equipment that processes waste from the population and turns it into fuel. As a type of business, it has unlimited resources.

Its raw material base includes:

• food industry;

• livestock farming;

• poultry farming;

• fisheries and processing plants;

• dairies;

• production of alcoholic and low-alcohol drinks.

Any industry is forced to dispose of its waste - it is expensive and unprofitable. At home, with the help of a small homemade installation, you can solve several problems at once: free heating of the house, fertilizing the land with high-quality nutrients left over from manure processing, freeing up space and eliminating odors.

Biofuel production technology

All bacteria that take part in the formation of biogas are anaerobic, that is, they do not need oxygen to function. To do this, completely sealed fermentation containers are constructed, the outlet pipes of which also do not allow air from the outside to pass through.

After pouring the raw liquid into the tank and raising the temperature to the required value, the bacteria begin to work. Methane begins to be released, which rises from the surface of the slurry. It is sent to special pillows or tanks, after which it is filtered and ends up in gas cylinders.

The liquid waste from bacteria accumulates at the bottom, from where it is periodically pumped out and also sent for storage. After this, a new portion of manure is pumped into the tank.

Temperature regime of bacteria functioning

To process manure into biogas, it is necessary to create suitable conditions for bacteria to work. some of them are activated at temperatures above 30 degrees - mesophilic. At the same time, the process is slower and the first product can be obtained after 2 weeks.

Thermophilic bacteria work at temperatures from 50 to 70 degrees. The time required to obtain biogas from manure is reduced to 3 days. In this case, the waste is a fermented sludge that is used in the fields as fertilizer for agricultural crops. There are no pathogenic microorganisms, helminths and weeds in the sludge, as they die when exposed to high temperatures.

There is a special type of thermophilic bacteria that can survive in an environment heated to 90 degrees. They are added to raw materials to speed up the fermentation process.

A decrease in temperature leads to a decrease in the activity of thermophilic or mesophilic bacteria. In private households, mesophylls are more often used, since they do not require special heating of the liquid and gas production is cheaper. Subsequently, when the first batch of gas is received, it can be used to heat the reactor with thermophilic microorganisms.

Important! Methanogens do not tolerate sudden changes in temperature, so in winter they must be kept warm at all times.

How to prepare raw materials for pouring into the reactor

To produce biogas from manure, there is no need to specially introduce microorganisms into the liquid, because they are already found in animal excrement. You just need to maintain the temperature and add a new manure solution in time. It must be prepared correctly.

The humidity of the solution should be 90% (the consistency of liquid sour cream), Therefore, dry types of excrement are first filled with water - rabbit droppings, horse droppings, sheep droppings, goat droppings. Pig manure in its pure form does not need to be diluted, as it contains a lot of urine.

The next step is to break down the manure solids. The finer the fraction, the better the bacteria will process the mixture and the more gas will be released. For this purpose, the installations use a stirrer that is constantly running. It reduces the risk of a hard crust forming on the surface of the liquid.

Those types of manure that have the highest acidity are suitable for biogas production. They are also called cold - pork and cow. A decrease in acidity stops the activity of microorganisms, so it is necessary to monitor at the beginning how long it takes for them to completely process the volume of the tank. Then add the next dose.

Gas purification technology

When processing manure into biogas, the following is obtained:

• 70% methane;

• 30% carbon dioxide;

• 1% impurities of hydrogen sulfide and other volatile compounds.

In order for biogas to become suitable for use on the farm, it must be cleaned of impurities. To remove hydrogen sulfide, special filters are used. The fact is that volatile hydrogen sulfide compounds, dissolving in water, form acid. It contributes to the appearance of rust on the walls of pipes or tanks if they are made of metal.

• The resulting gas is compressed under a pressure of 9–11 atmospheres.

• It is fed into a reservoir of water, where impurities are dissolved in the liquid.

On an industrial scale, lime or activated carbon, as well as special filters, are used for cleaning.

How to reduce moisture content

There are several ways to get rid of water impurities in gas yourself. One of them is the principle of a moonshine still. The cold pipe directs the gas upward. The liquid condenses and flows down. To do this, the pipe is laid underground, where the temperature naturally decreases. As it rises, the temperature also rises, and the dried gas enters the storage facility.

The second option is a water seal. After exiting, the gas enters a container with water and is cleaned of impurities there. This method is called one-stage, when biogas is immediately cleaned from all volatile substances and moisture using water.

Water seal principle

What installations are used to produce biogas?

If the installation is planned to be located near a farm, then the best option would be a collapsible structure that can be easily transported to another location. The main element of the installation is a bioreactor into which raw materials are poured and the fermentation process occurs. Large enterprises use tanks volume 50 cubic meters.

In private farms, underground reservoirs are built as a bioreactor. They are laid out of brick in a prepared pit and coated with cement. Concrete increases the safety of the structure and prevents air from entering. The volume depends on how much raw material is obtained from domestic animals per day.

Surface systems are also popular at home. If desired, the installation can be disassembled and moved to another location, unlike a stationary underground reactor. Plastic, metal or polyvinyl chloride barrels are used as tanks.

By type of control there are:

• automatic stations in which the filling and pumping out of waste raw materials is carried out without human intervention;

• mechanical, where the entire process is controlled manually.

Using a pump, you can facilitate the emptying of the tank into which the waste after fermentation falls. Some craftsmen use pumps to pump gas from cushions (for example, car inner tubes) into a treatment facility.

Scheme of a homemade installation for producing biogas from manure

Before constructing a biogas plant on your site, you need to become familiar with the potential hazards that could cause the reactor to explode. The main condition is the absence of oxygen.

Methane is an explosive gas and can ignite, but to do so it must be heated above 500 degrees. If biogas mixes with air, overpressure will arise, which will rupture the reactor. Concrete may crack and will not be suitable for further use.

Video: Biogas from bird droppings

To prevent the pressure from tearing off the lid, use a counterweight, a protective gasket between the lid and the tank. The container is not completely filled - there should be at least 10% volume for gas release. Better – 20%.

So, to make a bioreactor with all the accessories on your site, you need to:

• It is good to choose a place so that it is located away from housing (you never know).

• Calculate the estimated amount of manure that animals produce daily. How to count - read below.

• Decide where to lay the loading and unloading pipes, as well as a pipe for condensing moisture in the resulting gas.

• Decide on the location of the waste tank (fertilizer by default).

• Dig a pit based on calculations of the amount of raw materials.

• Select a container that will serve as a reservoir for manure and install it in the pit. If a concrete reactor is planned, then the bottom of the pit is filled with concrete, the walls are lined with bricks and plastered with concrete mortar. After this, you need to give it time to dry.

• The connections between the reactor and the pipes are also sealed at the stage of laying the tank.

• Equip a hatch for inspection of the reactor. A sealed gasket is placed between it.

If the climate is cold, then before concreting or installing a plastic tank, consider ways to heat it. These can be heating devices or tape used in “warm floor” technology.

At the end of the work, check the reactor for leaks.

Gas quantity calculation

From one ton of manure you can get approximately 100 cubic meters of gas. Question: How much litter do pets produce per day?

• chicken – 165 g per day;

• cow – 35 kg;

• goat – 1 kg;

• horse – 15 kg;

• sheep – 1 kg;

• pig – 5 kg.

Multiply these figures by the number of heads and you get the daily dose of excrement to be processed.

More gas comes from cows and pigs. If you add energetically powerful plants such as corn, beet tops, and millet to the mixture, the amount of biogas will increase. Marsh plants and algae have great potential.

The highest is for waste from meat processing plants. If there are such farms nearby, then we can cooperate and install one reactor for everyone. The payback period for a bioreactor is 1–2 years.

Biomass waste after gas production

After processing manure in a reactor, the by-product is biosludge. During anaerobic processing of waste, bacteria dissolve about 30% of organic matter. The rest is released unchanged.

The liquid substance is also a by-product of methane fermentation and is also used in agriculture for root feeding.

Carbon dioxide is a waste fraction that biogas producers strive to remove. But if you dissolve it in water, then this liquid can also be beneficial.

Full utilization of biogas plant products

In order to completely utilize the products obtained after processing manure, it is necessary to maintain a greenhouse. Firstly, organic fertilizer can be used for year-round cultivation of vegetables, the yield of which will be stable.

Secondly, carbon dioxide is used as fertilizing - root or foliar, and its output is about 30%. Plants absorb carbon dioxide from the air and at the same time grow better and gain green mass. If you consult with experts in this field, they will help you install equipment that converts carbon dioxide from liquid form into a volatile substance.

Video: Biogas in 2 days

The fact is that to maintain a livestock farm, the energy resources obtained can be a lot, especially in the summer, when heating the barn or pigsty is not needed.

Therefore, it is recommended to engage in another profitable activity - an environmentally friendly greenhouse. Remaining products can be stored in refrigerated rooms - using the same energy. Refrigeration or any other equipment can run on electricity generated by a gas battery.

Use as fertilizer

In addition to producing gas, the bioreactor is useful because the waste is used as a valuable fertilizer, which retains almost all nitrogen and phosphates. When manure is added to the soil, 30–40% of nitrogen is irretrievably lost.

To reduce the loss of nitrogen substances, fresh excrement is added to the soil, but then the released methane damages the root system of plants. After processing the manure, the methane is used for its own needs, and all nutrients are preserved.

After fermentation, potassium and phosphorus pass into a chelated form, which is absorbed by plants by 90%. If you look at it in general, then 1 ton of fermented manure can replace 70 - 80 tons of ordinary animal excrement.

Anaerobic processing preserves all the nitrogen present in manure, converting it into ammonium form, which increases the yield of any crop by 20%.

This substance is not dangerous for the root system and can be applied 2 weeks before planting crops in open ground, so that the organic matter has time to be processed by soil aerobic microorganisms.

Before use, the biofertilizer is diluted with water. in a ratio of 1:60. Both dry and liquid fractions are suitable for this, which after fermentation also goes into the waste raw material tank.

Per hectare you need from 700 to 1,000 kg/l of undiluted fertilizer. Considering that from one cubic meter of reactor area up to 40 kg of fertilizers are obtained per day, in a month you can provide not only your own plot, but also your neighbor’s, by selling organic matter.

What nutrients can be obtained after manure processing?

The main value of fermented manure as a fertilizer is the presence of humic acids, which, like a shell, retain potassium and phosphorus ions. Oxidizing in air during long-term storage, microelements lose their beneficial qualities, but during anaerobic processing, on the contrary, they gain.

Humates have a positive effect on the physical and chemical composition of the soil. As a result of adding organic matter, even the heaviest soils become more permeable to moisture. In addition, organic matter provides food for soil bacteria. They further process the residues that are “not eaten” by anaerobes and release humic acids. As a result of this process, plants receive nutrients that are completely absorbed.

In addition to the main ones - nitrogen, potassium and phosphorus - the biofertilizer contains microelements. But their quantity depends on the source material - plant or animal origin.

Sludge storage methods

It is best to store fermented manure dry. This makes it more convenient to pack and transport. The dry substance loses less useful properties and can be stored closed. Although such fertilizer does not deteriorate at all over the course of a year, it must then be sealed in a bag or container.

Liquid forms must be stored in closed containers with a tight-fitting lid to prevent nitrogen from escaping.

The main problem of biofertilizer producers is marketing in winter, when plants are dormant. On the world market, the cost of fertilizers of this quality fluctuates around $130 per ton. If you set up a line for packaging concentrates, you can pay for your reactor within two years.

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