Biogas from manure. Biogas from manure: how profitable it is and how to make Biogas from manure with your own hands

Typical design

In recent years, it has become fashionable to use various biogas plants for your own needs, which allow you to obtain energy from waste. As a rule, such a design is a sealed container where, at a given temperature, fermentation of the organic components of wastewater, various wastes, etc. occurs. Do-it-yourself biogas plant is difficult, but doable. The main thing is to know the types of these devices and the principle of their operation, as well as understand the drawings.

Operating principle of the installation

The process of producing biogas from manure or other raw materials is called fermentation, and fermentation is carried out through the activity of special bacteria. In this case, a crust forms on the surface of the raw material, which must be constantly destroyed. This must be done by thoroughly mixing the contents manually or using special devices inside the reactor. As a result of such manipulations, biogas is released.

The resulting biogas, after purification, is collected in a special container - a gas holder, from which it is carried through gas pipes to the place of use. The processed raw materials are turned into biofertilizer. It is unloaded through a special opening, and then can be applied to the soil or used as a feed additive for animals, which depends on the feedstock.

To obtain biogas with your own hands, in addition to observing the oxygen-free regime, several conditions must also be met:

• Availability of nutrients for bacteria.
• Maintaining temperature conditions.
• Choosing the right time for fermentation.
• Maintaining acid and alkaline balance.
• Maintaining the proportions of solid particles in the raw materials and timely mixing.

Types of biogas plants

Note! Today, there are a large number of designs of biogas plants to make the production of biogas not only convenient, but also effective.

They are distinguished by their appearance, as well as by their constituent structural elements and materials used in their creation.

By download type

Depending on the type of raw material loading, there are two types of installation - continuous loading and batch loading.

They differ from each other in the fermentation time of raw materials and the regularity of loading. The most effective from the point of view of producing biogas is a continuous loading installation.

By appearance

The appearance of the device depends on the method of accumulation and storage of biogas. It can be collected in a special gas tank, at the top of the reactor, or under a flexible dome, floating or standing separately from the reactor.

Creating a DIY installation

Building a biogas structure with your own hands is a rather complex and time-consuming process. Such an installation makes the production of biogas an alternative option that allows you to save money on the purchase of fuel and electricity.

What do you need to know?

Generalized scheme

You can make a structure from those materials that are available on the farm, but are not used. For example, a reactor for such an installation can be easily built from old pots, boilings, and basins, but it is better to use cylindrical objects.

Here are some important requirements that a reactor must meet:

• Good thermal insulation.
• Air and water permeability. After all, when biogas and oxygen are mixed, a reaction occurs, and its destructive force can not only break the reactor, but also explode it.
• Reliability and durability, since a huge amount of energy is released during the reaction.

To build a high-quality and efficient biological installation, you must adhere to the following sequence:

• Select a location for installing the future reactor. And be sure to calculate the amount of waste needed for 1 day. This is necessary to determine the dimensions of the structure.
• Prepare the basin, then install the unloading and loading pipes.
• Install and secure the loading hopper and gas outlet pipe as firmly as possible.
• For use, as well as subsequent maintenance and repair of the biogas plant, the manhole cover must be installed.
• Carefully check the reactor for thermal insulation and tightness.

The walls of the future installation should ideally be made of concrete, since the strength of the structure is the key to your safety. In addition, it is very important that the distance from the reactor to the nearest building is at least 500 meters. After all, during fermentation, a poisonous gas is released, which has a detrimental effect on a person and can kill him in a matter of minutes.

To obtain biogas you will need:

The principle of heating a house

• Mix 2 tons of cow manure and about 4.5 tons of humus from rotten waste, tops and leaves.
• Add water to the mixture so that the humidity in the reactor is 70%.
• Unload the resulting mass into the pit and heat it using a heating unit to +40 degrees. After the mixture begins to ferment, its temperature will reach +70 degrees.
• Attach a counterweight to the dome, which should be 2 times heavier than the mixture, so that the dome does not fly off the pit due to the released gas.

It should be remembered that the mass loaded into the reactor should not contain antibiotics, solvents or other synthetic substances. They will not only interfere with the reaction, but even stop it altogether, and will also cause the destruction of the reactor walls.

Equipment options

A homemade installation today is a rare type of alternative energy source on farms. But, given the efficiency and payback of such a design, many farmers began to think about building a biogas plant on their own in order to provide themselves with electricity and heat in this way.

Today there are many options for this type of equipment for producing biogas. Taking into account the climatic conditions of Russia, it is recommended to create the following types of installations.

Manual loading reactor without stirring

This is the simplest installation for a home, the volume of which can range from 1 to 10 cubic meters. It is capable of processing up to 200 kg of manure per day.

Manual loading option

It consists of a minimum number of parts:

• Bunker for fresh raw materials.
• Reactor.
• Biogas selection device.
• Capacity for unloading fermented raw materials.

This installation can be used for southern regions, since it operates without stirring or heating, and is also designed to operate in psychophilic mode. The used raw materials are removed from the reactor through the unloading pipe during the loading of the next portion of manure. This occurs due to the biogas pressure in the reactor.

When making such a structure with your own hands, it is recommended to follow the following sequence:

• After calculating the daily volume of manure and selecting a reactor of the required size, it is necessary to determine the location of the future structure, as well as prepare materials for installation.
• Then you need to build a loading and unloading pipe, and also make a pit for installation.
• After installing the reactor in the pit, it is necessary to install a loading hopper and a gas outlet, as well as a manhole cover.
• Check the structure for leaks, paint it and insulate it.
• Put into operation.

Manual loading, heating and stirring design

A biogas plant can be constructed with manual loading of raw materials and periodic mixing. At the same time, it will not require large financial investments from the owner. The design is suitable for a small farm, since its capacity is to process up to 200 kg of manure per day. The drawings of such an installation are similar to the drawings of the previous version, and they can be made by contacting a specialist.

This unit can operate in mesophilic and thermophilic modes

For a stable and maximally intensive fermentation process, a special reactor heating system is installed. The biogas plant can operate in two modes. The reactor is heated using a hot water boiler running on the produced biogas. The rest of the biogas can be used to operate household appliances.

The processed raw materials are stored in a special container until applied to the soil or used as a breeding ground for California worms.

Installation with gas holder, pneumatic loading, heating and mixing of raw materials

A similar installation is intended for small and medium-sized farms with the processing of up to 1.5 tons of manure per day into biogas. The raw materials are heated through a heat exchanger with a water heating boiler, which runs on the resulting gas. The mass unloading pipeline is equipped with a special branch for collecting biofertilizer in storage and for loading into vehicles with subsequent removal to the fields.

The design of such a home-made installation involves pneumatic loading of manure into the reactor, as well as mixing with biogas, the selection of which is carried out automatically. Biogas is stored in a special compartment - a gas holder.

Conclusion

Biogas is a relatively new source of energy. Using it, you can forever forget about electricity tariffs and even solve such issues as methane production. Correctly developed drawings and the efforts made in the manufacture of the installation will significantly save money for more than one farmer, which is especially important these days.

Related Posts

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 constant increase in the cost of traditional energy resources is pushing home craftsmen to create homemade equipment that allows them to produce biogas from waste with their own hands. With this approach to farming, it is possible not only to obtain cheap energy for heating the house and other needs, but also to establish the process of recycling organic waste and obtaining free fertilizers for subsequent application to the soil.

Excess produced biogas, like fertilizers, can be sold at market value to interested consumers, turning into money what is literally “lying under your feet.” Large farmers can afford to buy ready-made biogas production stations assembled in factories. The cost of such equipment is quite high. However, the return on its operation corresponds to the investment made. Less powerful installations that work on the same principle can be assembled on your own from available materials and parts.

What is biogas and how is it formed?

As a result of biomass processing, biogas is obtained

Biogas is classified as an environmentally friendly fuel. According to its characteristics, biogas is in many respects similar to natural gas produced on an industrial scale. The technology for producing biogas can be presented as follows:

• in a special container called a bioreactor, the process of processing biomass takes place with the participation of anaerobic bacteria under airless fermentation conditions for a certain period, the duration of which depends on the volume of loaded raw materials;
• as a result, a mixture of gases is released, consisting of 60% methane, 35% carbon dioxide, 5% other gaseous substances, among which there is a small amount of hydrogen sulfide;
• the resulting gas is constantly removed from the bioreactor and, after purification, is sent for its intended use;
• processed waste, which has become high-quality fertilizers, is periodically removed from the bioreactor and transported to the fields.

Visual diagram of the biofuel production process

In order to establish continuous production of biogas at home, you must own or have access to agricultural and livestock enterprises. It is economically profitable to produce biogas only if there is a source of free supply of manure and other organic waste from animal husbandry.

Gas heating remains the most reliable heating method. You can learn more about autonomous gasification in the following material:

Types of bioreactors

Installations for the production of biogas differ in the type of loading of raw materials, collection of the resulting gas, placement of the reactor relative to the surface of the earth, and material of manufacture. Concrete, brick and steel are the most suitable materials for constructing bioreactors.

Based on the type of loading, a distinction is made between bio-installations, into which a given portion of raw materials is loaded and goes through a processing cycle, and then completely unloaded. Gas production in these installations is unstable, but any type of raw material can be loaded into them. As a rule, they are vertical and take up little space.

A portion of organic waste is loaded into the system of the second type daily and an equal portion of ready-made fermented fertilizers is unloaded. The working mixture always remains in the reactor. The so-called continuous feeding plant consistently produces more biogas and is very popular among farmers. Basically, these reactors are located horizontally and are convenient if there is free space on the site.

The selected type of biogas collection determines the design features of the reactor.

• balloon systems consist of a rubber or plastic heat-resistant cylinder in which a reactor and a gas holder are combined. The advantages of this type of reactor are simplicity of design, loading and unloading of raw materials, ease of cleaning and transportation, and low cost. The disadvantages include a short service life, 2-5 years, and the possibility of damage as a result of external influences. Balloon reactors also include channel-type units, which are widely used in Europe for processing liquid waste and wastewater. This rubber top is effective at high ambient temperatures and there is no risk of damage to the cylinder. The fixed dome design has a completely enclosed reactor and a compensating tank for slurry discharge. Gas accumulates in the dome; when loading the next portion of raw materials, the processed mass is pushed into the compensation tank.
• Biosystems with a floating dome consist of a monolithic bioreactor located underground and a movable gas holder, which floats in a special water pocket or directly in the raw material and rises under the influence of gas pressure. The advantage of a floating dome is ease of operation and the ability to determine gas pressure by the height of the dome. This is an excellent solution for a large farm.
• When choosing an underground or above-surface installation location, you need to take into account the slope of the terrain, which makes it easier to load and unload raw materials, enhanced thermal insulation of underground structures, which protects the biomass from daily temperature fluctuations and makes the fermentation process more stable.

The design can be equipped with additional devices for heating and mixing raw materials.

Is it profitable to make a reactor and use biogas?

The construction of a biogas plant has the following goals:

• production of cheap energy;
• production of easily digestible fertilizers;
• savings on connecting to expensive sewerage;
• recycling of farm waste;
• possible profit from gas sales;
• reducing the intensity of unpleasant odors and improving the environmental situation in the area.

Profitability chart for biogas production and use

To assess the benefits of building a bioreactor, a prudent owner should consider the following aspects:

• the cost of a bio-plant is a long-term investment;
• homemade biogas equipment and installation of a reactor without the involvement of third-party specialists will cost much less, but its efficiency is also lower than that of an expensive factory one;
• To maintain stable gas pressure, the farmer must have access to livestock waste in sufficient quantity and for a long period of time. In the case of high prices for electricity and natural gas or the lack of possibility of gasification, the use of the installation becomes not only profitable, but also necessary;
• for large farms with their own raw material base, a profitable solution would be to include a bioreactor in the system of greenhouses and cattle farms;
• For small farms, efficiency can be increased by installing several small reactors and loading raw materials at different time intervals. This will avoid interruptions in gas supply due to a lack of feedstock.

How to build a bioreactor on your own

The decision to build has been made, now you need to design the installation and calculate the necessary materials, tools and equipment.

Important! Resistance to aggressive acidic and alkaline environments is the main requirement for bioreactor material.

If a metal tank is available, it can be used provided it has a protective coating against corrosion. When choosing a metal container, pay attention to the presence of welds and their strength.

A durable and convenient option is a polymer container. This material does not rot or rust. A barrel with thick hard walls or reinforced will withstand the load perfectly.

The cheapest way is to lay out a container made of brick or stone or concrete blocks. To increase strength, the walls are reinforced and covered inside and outside with a multi-layer waterproofing and gas-tight coating. The plaster must contain additives that provide the specified properties. The best shape to withstand all pressure loads is oval or cylindrical.

At the base of this container there is a hole through which waste raw materials will be removed. This hole must be tightly closed, because the system only works effectively in sealed conditions.

Calculation of necessary tools and materials

To lay out a brick container and install the entire system, you will need the following tools and materials:

• container for mixing cement mortar or concrete mixer;
• drill with mixer attachment;
• crushed stone and sand for constructing a drainage cushion;
• shovel, tape measure, trowel, spatula;
• brick, cement, water, fine sand, reinforcement, plasticizer and other necessary additives;
• welding machine and fasteners for installation of metal pipes and components;
• a water filter and a container with metal shavings for gas purification;
• tire cylinders or standard propane cylinders for gas storage.

The size of the concrete tank is determined from the amount of organic waste that appears daily in a private farmstead or farm. Full operation of the bioreactor is possible if it is filled to two-thirds of the available volume.

Let us determine the volume of the reactor for a small private farm: if there are 5 cows, 10 pigs and 40 chickens, then per day of their life activity a litter of 5 x 55 kg + 10 x 4.5 kg + 40 x 0.17 kg = 275 kg + is formed 45 kg + 6.8 kg = 326.8 kg. To bring chicken manure to the required humidity of 85%, you need to add 5 liters of water. Total weight = 331.8 kg. For processing in 20 days you need: 331.8 kg x 20 = 6636 kg - about 7 cubic meters only for the substrate. This is two thirds of the required volume. To get the result, you need 7x1.5 = 10.5 cubic meters. The resulting value is the required volume of the bioreactor.

Remember that it will not be possible to produce large amounts of biogas in small containers. The yield directly depends on the mass of organic waste processed in the reactor. So, to get 100 cubic meters of biogas, you need to process a ton of organic waste.

Preparing a site for a bioreactor

The organic mixture loaded into the reactor should not contain antiseptics, detergents, chemicals that are harmful to the life of bacteria and slow down the production of biogas.

Important! Biogas is flammable and explosive.

For proper operation of the bioreactor, the same rules must be followed as for any gas installations. If the equipment is sealed and biogas is discharged into the gas tank in a timely manner, then there will be no problems.

If the gas pressure exceeds the norm or poisons if the seal is broken, there is a risk of explosion, so it is recommended to install temperature and pressure sensors in the reactor. Inhaling biogas is also dangerous to human health.

How to ensure biomass activity

You can speed up the fermentation process of biomass by heating it. As a rule, this problem does not arise in the southern regions. The ambient temperature is sufficient for the natural activation of fermentation processes. In regions with harsh climatic conditions in winter, it is generally impossible to operate a biogas production plant without heating. After all, the fermentation process starts at a temperature exceeding 38 degrees Celsius.

There are several ways to organize heating of a biomass tank:

• connect the coil located under the reactor to the heating system;
• install electric heating elements at the base of the container;
• provide direct heating of the tank through the use of electric heating devices.

Bacteria that influence methane production are dormant in the raw materials themselves. Their activity increases at a certain temperature level. The installation of an automated heating system will ensure the normal course of the process. The automation will turn on the heating equipment when the next cold batch enters the bioreactor, and then turn it off when the biomass warms up to the specified temperature level.

Similar temperature control systems are installed in hot water boilers, so they can be purchased in stores specializing in the sale of gas equipment.

The diagram shows the entire cycle, starting from the loading of solid and liquid raw materials, and ending with the removal of biogas to consumers

It is important to note that you can activate biogas production at home by mixing biomass in a reactor. For this purpose, a device is made that is structurally similar to a household mixer. The device can be set in motion by a shaft that is output through a hole located in the lid or walls of the tank.

What special permits are required for the installation and use of biogas

In order to build and operate a bioreactor, as well as use the resulting gas, you need to take care of obtaining the necessary permits at the design stage. Coordination must be completed with the gas service, firefighters and Rostechnadzor. In general, the rules for installation and operation are similar to the rules for using conventional gas equipment. Construction must be carried out strictly in accordance with SNIPs, all pipelines must be yellow and have appropriate markings. Ready-made systems manufactured at the factory cost several times more, but have all the accompanying documents and meet all technical requirements. Manufacturers provide a warranty on equipment and provide maintenance and repair of their products.

A home-made installation for producing biogas can allow you to save on energy costs, which occupy a large share in determining the cost of agricultural products. Reducing production costs will affect the increase in profitability of a farm or private farmstead. Now that you know how to obtain biogas from existing waste, all that remains is to put the idea into practice. Many farmers have long learned to make money from manure.

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

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

Biogas heating - history

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

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

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

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

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

Biogas - what is it

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

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

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

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

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

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

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

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

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

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

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

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

Biogas plants

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

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

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

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

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

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

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

DIY biogas plant

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

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

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

Bioreactor form

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

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

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

Bioreactor location

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

Bioreactor equipment

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

Bioreactor thermal insulation

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

Loading and unloading organic substrate

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

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

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

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 reservoir is fixed with a valve and equipped with a pressure gauge. If gas consumption is constant, then there is no need for a gas tank.
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 for 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:

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

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

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

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

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