Small installations can also be installed at home. As an aside, I will say that producing biogas with your own hands is not some kind of new invention. Even in ancient times, biogas was actively produced at home in China. This country is still the leader in the number of biogas installations. But here how to make a biogas plant with your own hands, what is needed for this, how much it will cost - I will try to tell you all this in this and subsequent articles.

Preliminary calculation of a biogas plant

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

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

If the raw material is suitable for processing, then you can begin to determine the volume of the bioreactor. The total volume of raw materials for the mesophilic mode (biomass temperature ranges from 25-40 degrees, the most common mode) does not exceed 2/3 of the reactor volume. The daily dose is no more than 10% of the total loaded raw materials.

Any raw material is characterized by three important parameters:

  • density;
  • ash content;
  • humidity.

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

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

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

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

Biogas yield calculation

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

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

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

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

Reactor installation and fabrication

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

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

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

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

Rising energy prices make us think about the possibility of providing ourselves with them ourselves. One option is a biogas plant. With its help, biogas is obtained from manure, droppings and plant residues, which, after purification, can be used for gas appliances (stoves, boilers), pumped into cylinders and used as fuel for cars or electric generators. In general, processing manure into biogas can meet all the energy needs of a home or farm.

Construction of a biogas plant is a way to independently provide energy resources

General principles

Biogas is a product that is obtained from the decomposition of organic substances. During the process of rotting/fermentation, gases are released, collecting which you can meet the needs of your own household. The equipment in which this process occurs is called a “biogas plant.”

The process of biogas formation occurs due to the vital activity of various kinds of bacteria that are contained in the waste itself. But in order for them to actively “work”, they need to create certain conditions: humidity and temperature. To create them, a biogas plant is being built. This is a complex of devices, the basis of which is a bioreactor, in which waste decomposition occurs, which is accompanied by gas formation.

There are three modes for processing manure into biogas:

  • Psychophilic mode. The temperature in the biogas plant is from +5°C to +20°C. Under such conditions, the decomposition process is slow, much gas is formed, and its quality is low.
  • Mesophilic. The unit enters this mode at temperatures from +30°C to +40°C. In this case, mesophilic bacteria actively reproduce. In this case, more gas is formed, the processing process takes less time - from 10 to 20 days.
  • Thermophilic. These bacteria multiply at temperatures from +50°C. The process goes the fastest (3-5 days), the gas output is the largest (under ideal conditions, with 1 kg of delivery you can get up to 4.5 liters of gas). Most reference tables for gas yield from processing are given specifically for this mode, so when using other modes it is worth making a smaller adjustment.

The most difficult thing to implement in biogas plants is the thermophilic mode. This requires high-quality thermal insulation of the biogas plant, heating and a temperature control system. But at the output we get the maximum amount of biogas. Another feature of thermophilic processing is the impossibility of additional loading. The remaining two modes - psychophilic and mesophilic - allow you to add a fresh portion of prepared raw materials daily. But, in the thermophilic mode, the short processing time makes it possible to divide the bioreactor into zones in which their share of raw materials will be processed with different loading times.

Biogas plant diagram

The basis of a biogas plant is a bioreactor or bunker. The fermentation process occurs in it, and the resulting gas accumulates in it. There is also a loading and unloading hopper; the generated gas is discharged through a pipe inserted into the upper part. Next comes the gas treatment system - cleaning it and increasing the pressure in the gas pipeline to working pressure.

For mesophilic and thermophilic modes, a bioreactor heating system is also required to reach the required modes. For this purpose, gas boilers running on produced fuel are usually used. From it, a pipeline system goes to the bioreactor. Usually these are polymer pipes, since they best withstand being in an aggressive environment.

A biogas plant also needs a system for mixing the substance. During fermentation, a hard crust forms at the top, and heavy particles settle down. All this together worsens the process of gas formation. Mixers are needed to maintain a homogeneous state of the processed mass. They can be mechanical or even manual. They can be started by timer or manually. It all depends on how the biogas plant is made. An automated system is more expensive to install, but requires a minimum of attention during operation.

According to the type of location, a biogas plant can be:

  • Overground.
  • Semi-recessed.
  • Recessed.

Recessed ones are more expensive to install - a large amount of excavation work is required. But when used in our conditions, they are better - it is easier to organize insulation, and the heating costs are lower.

What can be recycled

A biogas plant is essentially omnivorous - any organic matter can be processed. Any manure and urine, plant residues are suitable. Detergents, antibiotics, and chemicals negatively affect the process. It is advisable to minimize their intake, as they kill the flora that processes them.

Cattle manure is considered ideal, since it contains large quantities of microorganisms. If there are no cows on the farm, when loading the bioreactor, it is advisable to add some of the manure to populate the substrate with the required microflora. Plant residues are pre-crushed and diluted with water. Plant materials and excrement are mixed in a bioreactor. This “filling” takes longer to process, but at the end of the day, under the correct mode, we have the highest product yield.

Location determination

To minimize the costs of organizing the process, it makes sense to locate the biogas plant close to the source of waste - near buildings where poultry or animals are kept. It is advisable to develop the design so that loading occurs by gravity. From a barn or pigsty, you can lay a pipeline at a slope through which manure will flow by gravity into the bunker. This greatly simplifies the task of maintaining the reactor, and also removing manure.

It is most advisable to locate the biogas plant so that waste from the farm can flow by gravity

Typically, buildings with animals are located at some distance from a residential building. Therefore, the generated gas will need to be transferred to consumers. But laying one gas pipe is cheaper and easier than organizing a line for transporting and loading manure.

Bioreactor

There are quite strict requirements for manure processing tanks:


All these requirements for the construction of a biogas plant must be met, as they ensure safety and create normal conditions for processing manure into biogas.

What materials can it be made from?

Resistance to aggressive environments is the main requirement for materials from which containers can be made. The substrate in the bioreactor can be acidic or alkaline. Accordingly, the material from which the container is made must tolerate various environments well.

Not many materials meet these requests. The first thing that comes to mind is metal. It is durable and can be used to make containers of any shape. The good thing is that you can use a ready-made container - some old tank. In this case, the construction of a biogas plant will take very little time. The disadvantage of metal is that it reacts with chemically active substances and begins to collapse. To neutralize this disadvantage, the metal is coated with a protective coating.

An excellent option is a bioreactor container made of polymer. Plastic is chemically neutral, does not rot, does not rust. You just need to choose from materials that can withstand freezing and heating to fairly high temperatures. The reactor walls should be thick, preferably glass fiber reinforced. Such containers are not cheap, but they last a long time.

A cheaper option is a biogas plant with a container made of bricks, concrete blocks, or stone. In order for the masonry to withstand high loads, it is necessary to reinforce the masonry (in every 3-5 rows, depending on the thickness of the wall and the material). After completing the wall construction process, to ensure water and gas impermeability, subsequent multi-layer treatment of the walls is necessary both inside and outside. The walls are plastered with a cement-sand composition with additives (additives) that provide the required properties.

Reactor sizing

The reactor volume depends on the selected temperature for processing manure into biogas. Most often, mesophilic is chosen - it is easier to maintain and it allows for the possibility of daily reloading of the reactor. Biogas production after reaching normal mode (about 2 days) is stable, without surges or dips (when normal conditions are created). In this case, it makes sense to calculate the volume of the biogas plant depending on the amount of manure generated on the farm per day. Everything is easily calculated based on average statistical data.

The decomposition of manure at mesophilic temperatures takes from 10 to 20 days. Accordingly, the volume is calculated by multiplying by 10 or 20. When calculating, it is necessary to take into account the amount of water that is necessary to bring the substrate to an ideal state - its humidity should be 85-90%. The found volume is increased by 50%, since the maximum load should not exceed 2/3 of the tank volume - gas should accumulate under the ceiling.

For example, there are 5 cows, 10 pigs and 40 chickens on a farm. The result is 5 * 55 kg + 10 * 4.5 kg + 40 * 0.17 kg = 275 kg + 45 kg + 6.8 kg = 326.8 kg. To bring chicken manure to 85% humidity, you need to add a little more than 5 liters of water (that’s another 5 kg). The total weight is 331.8 kg. For processing in 20 days you need: 331.8 kg * 20 = 6636 kg - about 7 cubic meters only for the substrate. We multiply the found figure by 1.5 (increase by 50%), we get 10.5 cubic meters. This will be the calculated value of the reactor volume of the biogas plant.

Loading and unloading hatches lead directly into the bioreactor tank. In order for the substrate to be evenly distributed over the entire area, they are made at opposite ends of the container.

When installing a biogas plant in-depth, the loading and unloading pipes approach the body at an acute angle. Moreover, the lower end of the pipe should be below the liquid level in the reactor. This prevents air from entering the container. Also, rotary or shut-off valves are installed on the pipes, which are closed in the normal position. They open only during loading or unloading.

Since manure may contain large fragments (litter elements, grass stems, etc.), small diameter pipes will often become clogged. Therefore, for loading and unloading, they must have a diameter of 20-30 cm. They must be installed before the start of work on insulating the biogas plant, but after the container is installed in place.

The most convenient mode of operation of a biogas plant is with regular loading and unloading of the substrate. This operation can be performed once a day or once every two days. Manure and other components are preliminarily collected in a storage tank, where they are brought to the required state - crushed, if necessary, moistened and mixed. For convenience, this container may have a mechanical stirrer. The prepared substrate is poured into the receiving hatch. If you place the receiving container in the sun, the substrate will be preheated, which will reduce the cost of maintaining the required temperature.

It is advisable to calculate the installation depth of the receiving hopper so that waste flows into it by gravity. The same applies to unloading into the bioreactor. The best case is if the prepared substrate moves by gravity. And a shutter will fence it off during preparation.

To ensure the tightness of the biogas plant, the hatches on the receiving hopper and in the unloading area must have a sealing rubber seal. The less air there is in the container, the cleaner the gas will be at the outlet.

Collection and removal of biogas

Biogas is removed from the reactor through a pipe, one end of which is under the roof, the other is usually lowered into a water seal. This is a container with water into which the resulting biogas is discharged. There is a second pipe in the water seal - it is located above the liquid level. Cleaner biogas comes out into it. A gas shut-off valve is installed at the outlet of their bioreactor. The best option is a ball one.

What materials can be used for the gas transmission system? Galvanized metal pipes and gas pipes made of HDPE or PPR. They must ensure tightness; seams and joints are checked using soap foam. The entire pipeline is assembled from pipes and fittings of the same diameter. No contractions or expansions.

Cleansing from impurities

The approximate composition of the resulting biogas is:

  • methane - up to 60%;
  • carbon dioxide - 35%;
  • other gaseous substances (including hydrogen sulfide, which gives the gas an unpleasant odor) - 5%.

In order for biogas to be odorless and burn well, it is necessary to remove carbon dioxide, hydrogen sulfide, and water vapor from it. Carbon dioxide is removed in a water seal if slaked lime is added to the bottom of the installation. Such a bookmark will have to be changed periodically (as soon as the gas starts to burn worse, it’s time to change it).

Gas drying can be done in two ways - by making water seals in the gas pipeline - by inserting curved sections into the pipe under the water seals, in which condensate will accumulate. The disadvantage of this method is the need to regularly empty the water seal - if there is a large amount of collected water, it can block the passage of gas.

The second way is to install a filter with silica gel. The principle is the same as in a water seal - the gas is supplied to the silica gel, and dried out from under the lid. With this method of drying biogas, the silica gel must be dried periodically. To do this, you need to warm it up in the microwave for some time. It heats up and the moisture evaporates. You can fill it up and use it again.

To remove hydrogen sulfide, a filter loaded with metal shavings is used. You can load old metal scourers into the container. Purification occurs in exactly the same way: gas is supplied to the lower part of the container filled with metal. As it passes, it is cleared of hydrogen sulfide, collected in the upper free part of the filter, from where it is discharged through another pipe/hose.

Gas tank and compressor

The purified biogas enters a storage tank - a gas holder. This can be a sealed plastic bag or plastic container. The main condition is gas tightness; shape and material do not matter. The gas holder stores a supply of biogas. From it, with the help of a compressor, gas under a certain pressure (set by the compressor) is supplied to the consumer - to the gas stove or boiler. This gas can also be used to generate electricity using a generator.

To create stable pressure in the system after the compressor, it is advisable to install a receiver - a small device for leveling pressure surges.

Mixing devices

In order for the biogas plant to operate normally, it is necessary to regularly mix the liquid in the bioreactor. This simple process solves many problems:

  • mixes a fresh portion of the load with a colony of bacteria;
  • promotes the release of produced gas;
  • equalizes the temperature of the liquid, excluding warmer and colder areas;
  • maintains the homogeneity of the substrate, preventing the settling or floating of some components.

Typically, a small homemade biogas plant has mechanical agitators that are driven by muscle power. In large-volume systems, the agitators can be driven by motors that are activated by a timer.

The second method is to stir the liquid by passing some of the generated gas through it. To do this, after exiting the metatank, a tee is installed and part of the gas flows into the lower part of the reactor, where it exits through a tube with holes. This part of the gas cannot be considered a consumption, since it still enters the system again and, as a result, ends up in the gas tank.

The third method of mixing is to use fecal pumps to pump the substrate from the lower part and pour it at the top. The disadvantage of this method is its dependence on the availability of electricity.

Heating system and thermal insulation

Without heating the processed liquid, psychophilic bacteria will multiply. The processing process in this case will take 30 days, and the gas output will be small. In the summer, if there is thermal insulation and preheating of the load, it is possible to reach temperatures of up to 40 degrees, when the development of mesophilic bacteria begins, but in winter such an installation is practically inoperative - the processes proceed very sluggishly. At temperatures below +5°C they practically freeze.

What to heat and where to place it

For best results, use heating. The most rational is water heating from a boiler. The boiler can run on electricity, solid or liquid fuel, and you can also run it on the produced biogas. The maximum temperature to which water needs to be heated is +60°C. Hotter pipes can cause particles to stick to the surface, reducing heating efficiency.

You can also use direct heating - insert heating elements, but firstly, it is difficult to organize mixing, secondly, the substrate will stick to the surface, reducing heat transfer, the heating elements will quickly burn out

A biogas plant can be heated using standard heating radiators, simply pipes twisted into a coil, or welded registers. It is better to use polymer pipes - metal-plastic or polypropylene. Corrugated stainless steel pipes are also suitable; they are easier to install, especially in cylindrical vertical bioreactors, but the corrugated surface provokes sediment sticking, which is not very good for heat transfer.

To reduce the possibility of particles settling on the heating elements, they are located in the stirrer area. Only in this case everything must be designed so that the mixer cannot touch the pipes. It often seems that it is better to place the heaters at the bottom, but practice has shown that due to sediment on the bottom, such heating is ineffective. So it is more rational to place heaters on the walls of the metatank of a biogas plant.

Water heating methods

Depending on the method of pipe arrangement, heating can be external or internal. When installed internally, heating is effective, but repair and maintenance of heaters is impossible without stopping and pumping out the system. Therefore, special attention is paid to the selection of materials and the quality of connections.

Heating increases the productivity of the biogas plant and reduces the processing time of raw materials

When the heaters are located externally, more heat is required (the cost of heating the contents of a biogas plant is much higher), since a lot of heat is spent heating the walls. But the system is always available for repair, and heating is more uniform, since the environment is heated from the walls. Another advantage of this solution is that stirrers cannot damage the heating system.

How to insulate

First, a leveling layer of sand is poured onto the bottom of the pit, then a heat-insulating layer. It can be clay mixed with straw and expanded clay, slag. All these components can be mixed and poured in separate layers. They are leveled to the horizon and the capacity of the biogas plant is installed.

The sides of the bioreactor can be insulated with modern materials or with classic old-fashioned methods. One of the old-fashioned methods is coating with clay and straw. Apply in several layers.

Modern materials include high-density extruded polystyrene foam, low-density aerated concrete blocks, etc. The most technologically advanced in this case is polyurethane foam (PPU), but the services for its application are not cheap. But the result is seamless thermal insulation, which minimizes heating costs. There is another heat-insulating material - foam glass. It is very expensive in slabs, but its chips or crumbs cost very little, and in terms of characteristics it is almost ideal: it does not absorb moisture, is not afraid of freezing, tolerates static loads well, and has low thermal conductivity.

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

General information about biogas

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

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

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

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

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

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

Biogas technology

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

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

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

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

Biogas plant diagram

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

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

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

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

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

How to get biogas at home?

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

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

Conclusion

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

The production of biogas (methane) is important for owners of livestock and poultry breeding farms. On farms with poultry and cattle, the issue of waste disposal is always acute. In order to get rid of litter and manure, you need to take care of collection, removal, disinfection and processing. All these procedures require certain material expenditures, time and effort.

In order for the process of manure recycling to begin to bring profit rather than losses, it is advisable to think about processing manure into biogas. Homemade biogas from bird and animal droppings consists of 50-80% methane. This is the same gas that burns in boilers, stoves and is used for cars. Methane is released from manure randomly, on its own. If you leave droppings to rot in the sun for a year, it will begin to “ferment” and release biogas. You just need to optimize this process to increase the amount of methane released and speed up its production time.

To increase the efficiency of biogas production, it is necessary to accelerate the process of decomposition and fermentation of raw materials. To do this, you need to create the most favorable conditions for the proliferation of the necessary bacteria. To do this, you will need to place the manure in a special container - a reactor. The container must be closed - in such conditions bacteria will multiply more actively. Already in the reactor, the manure is crushed and then mixed with water. The water must be clean. Otherwise, foreign microbes will enter the substrate, which can slow down the fermentation process.

In industrial conditions, it is equipped with a reactor heating system, an acidity controller and special blades for mixing the substrate. Mixing manure allows you to get rid of the formation of a hard crust, which blocks the flow of oxygen from the outside and the release of methane from the inside. The period for producing methane under industrial conditions is at least fifteen days. During this time, manure can decompose up to 25%. The maximum outflow of methane occurs at a degree of decomposition of 33%.

It should be taken into account that rotten sludge forms at the bottom of the reactor. It is discharged using a special tube, which takes it to a separate sludge tank. The sludge is subsequently cleaned out and removed. The methane rising up the tank is purified by a steam bath, and then sent to the gas collector.

Industrial methane production involves daily injection of fresh substrate, which is mixed with what has already begun to ferment. You can add 5% fresh manure per day instead of 5% used manure. Manure removed from the reactor can be used as soil fertilizer. This way you will have a waste-free production, where you can get both biogas and fertilizers.

Creating a biogas plant from manure at home

To design a plant for processing manure into biogas you will need:

  • a hermetically sealed container (made of metal, concrete, plastic) with a volume of at least one cubic meter;
  • cover for the reactor with a sealed passage for the stirrer handle;
  • material for thermal insulation of the bottom (plays the role of a heating system);
  • a hand mixer made from scrap materials (you can use a shovel or a screw auger);
  • pipes for feeding/extracting substrate and for removing biogas.

During the construction process, you may need additional materials: pipes, filters, valves. All this can be found at a hardware store. The design is quite simple, and you can improve it as you build it.

As an experiment, you can try making an installation from an ordinary plastic barrel. They are available in volumes from 100 to 200 liters. The barrel will serve as a reactor. Make two holes in it for the inlet and outlet of the pipes. The inlet hole is made closer to the bottom, and the outlet hole is made from above. The diameter of the holes depends on the diameter of the pipes used. Plastic pipes can be purchased at a hardware store. We insert them into the holes and securely insulate them. A curved pipe (with a connector) is suitable for the inlet, and a short straight pipe for the outlet.

The role of a reservoir for the resulting biogas is given to a container of a smaller volume. For example, you can take a bucket with a volume of 20 liters or more. The bucket is fixed using a plumbing valve. We take the tube from it to a metal holder with a valve, from where the gas will be released.

Don't forget about the thermal insulation of the barrel. It can be wrapped with mineral wool, polyethylene foam or any other material. It is best to place the barrel in the sun to increase the temperature inside the reactor. We pour raw materials inside in a ratio of 0.7 liters of water per 1 kg of manure. We put any suitable container for removing sludge, place a bucket on top and wait for fermentation. We are waiting about three weeks for the first batch of our home biogas. Remember that methane must be stripped of carbon dioxide before use. A special filter, which is sold in the store as a “filter for purifying compressed air, carbon dioxide and steam,” will cope with this task.

Do-it-yourself biogas from manure: building an underground installation

Another easy way to build your own manure-to-biogas plant is to build an underground system. First you need to dig a hole with a volume of at least one cubic meter. Its walls and bottom are filled with expanded clay concrete. From opposite walls there is one pipe for supplying biomass and removing sludge. The outlet pipe should be located closer to the bottom, and the input pipe should be 50 cm above the bottom. The end of the outlet pipe is connected to a waste container. The end of the inlet pipe should be located in such a way that it is convenient for you to pump new raw materials through it.

The upper part of this “bunker” is a dome- or cone-shaped gas holder. It is easiest to make from metal sheets or brickwork. A sealed hatch and a gas pipe with a water seal are mounted on the top of the gas holder. We advise you to provide such an important detail as a pressure relief valve. It will ensure safety when working with the installation and will maintain optimal pressure inside the reactor.

Mixing of the substrate in such an installation occurs according to the bubbling principle. To do this, take several plastic pipes and make as many holes in them as possible. After this, secure the pipes inside the reactor in a vertical position. When the gas rises, it will emit bubbles, which will begin to bubble in the substrate, thereby mixing it.

Biogas from manure is a profitable investment

For those who are not ready to make such a camera, there is always another option - you can buy a ready-made one. Construction of the installation will still require a small investment from you. If you are not confident in your abilities or do not have all the materials, it is advisable to simply buy a PVC installation. As a result, you will still organize your own home production for processing manure and producing biogas.

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

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

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

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

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

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

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

Stages of operation of a biogas plant.

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

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

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

  • Biogas
  • Biological fertilizers
  • Electrical and thermal energy
  • Fuel for cars.

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

Who needs a biogas plant?

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

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

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