The theoretical basis for the production of methane gas from biomass by anaerobic digestion was given.

The role of bacteria in the step-by-step transformation of organic substances was explained, with a description of the necessary conditions for the most intensive production of biogas. In this article, practical implementations of biogas plants will be given, with a description of some improvised designs.

As energy prices rise and many livestock and small farm owners have problems with waste disposal, biogas industrial complexes and small biogas plants for a private home have come on the market. Using search engines, the Internet user can easily find an affordable turnkey solution to match the biogas plant and its price, get in touch with equipment suppliers and agree on the construction of a biogas generator at home or on the farm.

Biogas industrial complex

Bioreactor - the basis of a biogas plant

The container in which the anaerobic decomposition of biomass takes place is called bioreactor, fermenter, or methanetank. Bioreactors are fully sealed, with a fixed or floating dome, with a diving bell design. Bell psychrophilic (not requiring heating) bioreactors have the form of an open reservoir with liquid biomass, in which a container in the form of a cylinder or bell is immersed, where biogas is collected.

The collected biogas exerts pressure on the cylinder, causing it to rise above the tank. Thus, the bell also performs the function of a gas tank - a temporary storage of the resulting gas.

The disadvantage of the bell design of a biogas reactor is the impossibility of mixing the substrate and heating it during the cold periods of the year. Also a negative factor is a strong smell, and unsanitary conditions due to the open surface of part of the substrate.

In addition, part of the resulting gas will escape into the atmosphere, polluting the environment. Therefore, these bioreactors are used only in artisanal biogas plants in poor countries with a hot climate.

In order to prevent environmental pollution and eliminate unpleasant odors, the reactors of biogas plants for home and large industries have a fixed dome design. The shape of the structure in the process of gas formation does not matter much, but when using a cylinder with a dome-shaped roof, significant savings in building materials are achieved. Bioreactors with a fixed dome are equipped with nozzles for adding new portions of biomass and removing the spent substrate.

Main types of biogas plants

Since the fixed dome design is the most acceptable, most ready-made bioreactor solutions are of this type. Depending on the loading method, bioreactors have a different design and are divided into:

• Portion, with a single load of the entire biomass, and with subsequent full unloading after the processing of raw materials. The main disadvantage of this type of bioreactors is the uneven release of gas during the processing of the substrate;
• continuous loading and unloading of raw materials, due to which a uniform release of biogas is achieved. Thanks to the design of the bioreactor, during loading and unloading, biogas production does not stop and there are no leaks, since the nozzles through which the addition and removal of biomass is carried out are made in the form of a water seal that prevents gas from escaping.

Batch biogas reactors can be of any design that prevents gas leakage. So, for example, at one time in Australia, channel methanetanks with an elastic inflatable arch were popular, where a slight overpressure inside the bioreactor inflated a bubble of durable polypropylene. Upon reaching a certain pressure level inside the bioreactor, the compressor was turned on, pumping out the generated biogas.

The type of fermentation in this biogas plant can be mesophilic (with weak heating). Due to the large area of ​​the inflating dome, channel bioreactors can only be installed in heated rooms, or in regions with a hot climate. The advantage of the design is the absence of the need for an intermediate receiver, but the big disadvantage is the vulnerability of the elastic dome to mechanical damage.

Recently, batch bioreactors with dry fermentation of manure without adding water to the substrate are gaining popularity. Since manure has its own moisture, it will be enough for the life of organisms, although the intensity of reactions will decrease.

Dry-type bioreactors look like a sealed garage with tightly closing doors. The biomass is loaded into the reactor using a front loader and remains in this state until the completion of the complete gas generation cycle (about half a year), without the need to add the substrate and mix it.

DIY biogas plant

It should be noted that in most bioreactors, as a rule, only the gas generation zone is sealed, and the liquid biomass at the inlet and outlet is under atmospheric pressure. Overpressure inside the bioreactor displaces part of the liquid substrate into the nozzles, which is why the level of biomass in them is slightly higher than inside the tank.

These designs of home-made bioreactors are popular among folk craftsmen who independently make biogas plants with their own hands for the home, allowing reusable manual loading and unloading of the substrate. In the manufacture of bioreactors with their own hands, many craftsmen experiment with completely sealed containers, using several rubber chambers from the tires of the wheels of large vehicles as a gas holder.

In the video below, an enthusiast of homemade biogas production, using the example of barrels filled with bird droppings, proves the possibility of actually obtaining combustible gas at home, processing poultry waste into useful fertilizer. The only thing that can be added to the design described in this video is that you need to put a pressure gauge and a safety valve on a homemade bioreactor.

Bioreactor Productivity Calculations

The amount of biogas is determined by the mass and quality of the raw materials used. On the Internet, you can find tables that indicate the amount of waste produced by various animals, but the owners, who have to clean manure every day, do not need this theory, because they know the amount and mass of the future substrate through their own practice. Based on the availability of raw materials renewable every day, it is possible to calculate the required volume of the bioreactor and the daily biogas production.

After the calculations have been made and the design of the bioreactor has been approved, you can proceed to its construction. The material can be a reinforced concrete container, poured into the ground, or brickwork, sealed with a special coating that is used to treat pools.

It is also possible to build the main tank of the home biogas plant from iron coated with anti-corrosion material. Small industrial bioreactors are often made from large volume, chemically resistant plastic tanks.

In industrial biogas plants, electronic control systems and various reagents are used to correct the chemical composition of the substrate and its acidity level, and special substances are added to the biomass - enzymes and vitamins that stimulate the reproduction and vital activity of microorganisms inside the bioreactor. In the process of development of microbiology, more and more resistant and effective strains of bacteria methanogens are being created, which can be purchased from companies involved in the production of biogas.

The need for pumping and cleaning biogas

The constant production of gas in a bioreactor of any design leads to the need to pump out biogas. Some primitive biogas plants can burn the resulting gas directly in a burner installed nearby, but the instability of the overpressure in the bioreactor can lead to the disappearance of the flame and subsequent release poisonous gas. The use of such a primitive biogas plant connected to a stove is categorically unacceptable because of the possibility of poisoning with toxic components of raw biogas.

Therefore, almost any scheme of a biogas plant includes gas storage tanks and a gas purification system. As a homemade cleaning complex, you can use a water filter and a homemade container filled with metal shavings, or purchase professional filtration systems. The tank for temporary storage of biogas can be made of chambers from tires, from which the gas is pumped out from time to time by a compressor into standard propane cylinders for storage and subsequent use.

As an alternative to the mandatory use of a gas tank, an improved floating dome bioreactor can be perceived. The improvement consists in the addition of a concentric baffle which forms a water pocket that acts like a water seal and prevents the biomass from coming into contact with air. The pressure inside the floating dome will depend on its weight. By passing the gas through the purification system and reducer, it can be used in a household stove, periodically bled from the bioreactor.

Grinding and mixing of the substrate in the bioreactor

Agitation of the biomass is an important part of the biogas formation process, providing bacteria with access to nutrients that can clump at the bottom of the bioreactor. In order for the biomass particles to be better mixed in the bioreactor, they must be crushed mechanically or manually before being loaded into the methane tank. Currently, in industrial and home-made biogas plants, three methods of mixing the substrate are used:

1. mechanical agitators driven by an electric motor or manually;
2. circulating mixing with a pump or propeller pumping the substrate inside the bioreactor;
3. bubbling mixing by blowing the already existing biogas into the liquid biomass. The disadvantage of this method is the formation of foam on the surface of the substrate.

Mechanical mixing of the substrate inside the bioreactor can be carried out manually or automatically by turning on the electric motor using an electronic timer. Water-jet or bubbling mixing of biomass can only be carried out using electric motors controlled manually or using a software algorithm.

This bioreactor has a mechanical agitator

Substrate heating in mesophilic and thermophilic biogas plants

The optimal temperature for gas formation is the temperature of the substrate in the range of 35-50ºC. To maintain this temperature, various heating systems- water, steam, electric. Temperature control should be carried out using a thermal switch or thermocouples connected to the actuator that regulates the heating of the bioreactor.

You also need to remember that an open flame will overheat the walls of the bioreactor, and inside its biomass will burn. The burnt substrate will reduce heat transfer and the quality of heating, and the hot wall of the bioreactor will quickly collapse. One of the best options is water heating from the return pipe of the home heating system. It is necessary to install a system of electric valves to be able to turn off the heating of the bioreactor or connect the heating of the substrate directly from the boiler if it is too cold.

Heating the substrate in the bioreactor with the help of heating elements will be beneficial only if there is alternative electricity obtained from a wind generator or solar panels. In this case, the heating elements can be connected directly to the generator or battery, which will exclude expensive voltage converters from the circuit. To reduce heat loss and reduce the cost of heating the substrate in the bioreactor, it is necessary to insulate it as much as possible using various heaters.

Practical experiences that are inevitable when building biogas plants with your own hands

No matter how much literature a novice enthusiast of independent biogas production reads, and no matter how many videos he watches, in practice you will have to learn a lot yourself, and the results, as a rule, will be far from the calculated ones.

Therefore, many novice masters follow the path of independent experiments in obtaining biogas, starting with small containers, determining how much gas from the available raw materials is produced by their small experimental biogas plant. Component prices, methane output and the future costs of building a complete working biogas plant will determine its viability and feasibility.

In the video above, the master demonstrates the capabilities of his biogas plant, noting how much biogas will be produced in one day. In his case, when pumping eight atmospheres into the compressor receiver, the volume of the resulting gas after recalculations, taking into account the volume of the tank 24 l, will be about 0.2 m².

This amount of biogas obtained from a 200 liter barrel is not significant, but, as shown in the following video of this wizard, this amount of gas is enough for an hour of burning one stove burner (15 minutes multiplied by four atmospheres of a cylinder, which is twice the size of the receiver).

In another video below, the master talks about obtaining biogas and biologically pure fertilizers by processing organic waste in a biogas plant. It must be borne in mind that the value of organic fertilizers may exceed the cost of the resulting gas, and then biogas will become a useful by-product of the process of making quality fertilizers. Another useful property of organic raw materials is the ability to store them for a certain period for use at the right time.

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

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

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

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

What is biomethane

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

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

Biomethane is used for the following needs:

• cooking;

• in internal combustion engines of cars;

• for heating a private house.

Biogas releases a lot of heat. 1 cubic meter is equivalent to burning 1.5 kg of coal.

How is biomethane produced?

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

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

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

Under its raw material base fall:

• food industry;

• animal husbandry;

• poultry farming;

• fishing and processing plants;

• dairies;

• production of alcoholic and low-alcohol drinks.

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

Biofuel technology

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

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

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

The temperature regime of the functioning of bacteria

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

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

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

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

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

How to prepare raw materials for pouring into the reactor

For the production of biogas from manure, it is not necessary to specifically add microorganisms to the liquid, because they are already in animal excrement. It is only necessary to maintain the temperature regime and add a new manure solution in time. It must be properly prepared.

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

The next step is to break up the manure solids. The smaller the fraction, the better the bacteria will process the mixture and the more gas will be the output. To do this, in the installations, a stirrer is used, which is constantly working. It reduces the risk of a hard crust forming on the liquid surface.

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

Gas treatment technology

When processing manure into biogas, it turns out:

• 70% methane;

• 30% carbon dioxide;

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

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

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

• It is fed into a water tank where the impurities are dissolved in the liquid.

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

How to reduce moisture content

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

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

What installations are used to produce biogas

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

Private farms build underground tanks as a bioreactor. They are laid out of brick in a prepared pit and coated with cement. Concrete increases the safety of the structure and prevents air from entering. The volume depends on how much raw material is received from pets per day.

Surface systems are also popular in the home. If desired, the installation can be disassembled and moved to another location, unlike a stationary underground reactor. As a tank, plastic, metal or polyvinyl chloride barrels are used.

By type of management there are:

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

• mechanical, where the entire process is controlled manually.

With the help of a pump, it is possible to facilitate the emptying of the tank into which the waste after fermentation enters. Some craftsmen use pumps to pump gas from pillows (for example, car chambers) to a treatment plant.

Scheme of a home-made plant for producing biogas from manure

Before building a biogas plant in your area, you should be familiar with the potential hazard that could blow up the reactor. The main condition is the absence of oxygen.

Methane is an explosive gas and it can ignite, but for this it must be heated above 500 degrees. If the biogas is mixed with air, an overpressure will develop that will rupture the reactor. Concrete may crack and will not be suitable for further use.

Video: Biogas from bird droppings

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

So, in order to make a bioreactor with all the devices on your site, you need:

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

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

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

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

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

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

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

• Equip a hatch for inspection of the reactor. An airtight seal is placed between it.

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

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

Calculation of the amount of gas

About 100 cubic meters of gas can be obtained from one ton of manure. The question is how much litter do pets give per day:

• chicken - 165 g per day;

• cow - 35 kg;

• goat - 1 kg;

• horse - 15 kg;

• sheep - 1 kg;

• pig - 5 kg.

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

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

The highest is in the waste of meat processing plants. If there are such farms nearby, then you can cooperate and install one reactor for all. The payback period of the bioreactor is 1-2 years.

Waste biomass after gas production

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

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

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

Full use of biogas plant products

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

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

Video: Biogas in 2 days

The fact is that for the maintenance of a livestock farm, there can be a lot of energy resources received, especially in summer, when there is no need to heat a cowshed or a pigsty.

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

Use as a fertilizer

In addition to generating gas, the bioreactor is useful in that the waste is used as a valuable fertilizer, which retains almost all of the nitrogen and phosphates. When manure is introduced into the soil, 30-40% of nitrogen is irretrievably lost.

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

Potassium and phosphorus after fermentation pass into a chelate form, which is absorbed by plants by 90%. When viewed in general, then 1 ton of fermented manure can replace 70 - 80 tons of ordinary animal excrement.

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

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

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

From 700 to 1,000 kg/l of undiluted fertilizer is needed per hectare. Taking into account that up to 40 kg of fertilizers are obtained from one cubic meter of the reactor area per day, it is possible to provide not only your site, but also the neighbor's site by selling organic matter in a month.

What nutrients can be obtained after working out manure

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

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

In addition to the main ones - nitrogen, potassium and phosphorus - there are trace elements in the biofertilizer. But their number depends on the feedstock - vegetable or animal origin.

Sludge storage methods

It is best to store fermented manure in a dry state. This makes it easier to package and transport. Dry matter loses less useful properties and can be stored closed. Although during the year such fertilizer does not deteriorate at all, it must be closed in a bag or container further.

Liquid forms should be stored in closed containers with tight-fitting lids to prevent nitrogen venting.

The main problem of producers of biofertilizers is marketing in winter, when the plants are at rest. In the world market, the cost of fertilizers of this quality ranges from $130 per ton. If you set up a line for packaging concentrates, then you can pay back your reactor within two years.

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The modern world is built on ever-increasing consumption, which is why mineral and raw material resources are depleted especially quickly. At the same time, millions of tons of stinking manure are accumulated annually on numerous livestock farms, and considerable funds are spent for its disposal. Humans are also not far behind in the production of biological waste. Fortunately, a technology has been developed that allows simultaneously solving these problems: using biowaste (primarily manure) as a raw material, obtaining an environmentally friendly renewable fuel - biogas. The use of such innovative technologies has given rise to a new promising industry - bioenergy.

What is biogas

Biogas is a volatile, colorless, odorless, gaseous substance. It consists of 50-70 percent of methane, up to 30 percent of it is carbon dioxide CO2 and another 1-2 percent - gaseous substances - impurities (when cleaned from them, the purest biomethane is obtained).

Qualitative physico-chemical indicators of this substance are approaching the usual high-quality natural gas. According to scientists, biogas has very high calorific properties: for example, the heat released during the combustion of one cubic meter of this natural fuel is equivalent to the heat from one and a half kilograms of coal.

The release of biogas occurs due to the vital activity of a special type of bacteria - anaerobic, while mesophilic bacteria are activated when the environment is heated to 30-40 degrees Celsius, and thermophilic bacteria multiply at a higher temperature - up to +50 degrees.

Under the action of their enzymes, organic raw materials decompose with the release of biological gas.

Raw materials for biogas

Not all organic waste is suitable for processing into biogas. For example, litter from poultry farms and pig farms in its pure form cannot be used categorically, because they have a high level of toxicity. To obtain biogas from them, it is necessary to add diluting substances to such waste: silage mass, green grass mass, as well as cow manure. The last component is the most suitable raw material for obtaining environmentally friendly fuel, since cows eat only plant foods. However, it must also be controlled for the content of heavy metal impurities, chemical components, surfactants, which in principle should not be in the raw material. A very important point is the control of antibiotics and disinfectants. Their presence in manure can prevent the process of decomposition of the raw mass and the formation of volatile gas.

Additional Information. It is impossible to completely do without disinfectants, because otherwise mold begins to form on the biomass under the influence of high temperatures. It is also necessary to follow and timely clean the manure from mechanical impurities (nails, bolts, stones, etc.), which can quickly damage biogas equipment. Humidity of the raw materials going to obtain biogas should be at least 80-90%.

Mechanism of gas formation

In order for biogas to be released from organic raw materials during airless fermentation (scientifically called anaerobic fermentation), appropriate conditions are necessary: ​​a sealed container and elevated temperature. If done correctly, the produced gas rises to the top where it is selected for use, and what remains is an excellent bio-organic agricultural fertilizer, rich in nitrogen and phosphorus, but free from harmful microorganisms. For the correct and complete flow of processes, the temperature regime is very important.

The full cycle of converting manure into ecological fuel is from 12 days to a month, it depends on the composition of the raw material. About two liters of biogas are obtained from one liter of useful volume of the reactor. If more advanced modernized installations are used, then the biofuel production process is accelerated to 3 days, and biogas production increases to 4.5-5 liters.

People began to study and use the technology of extracting biofuels from organic natural sources since the end of the 18th century, and in the former USSR, the first device for producing biogas was developed back in the 40s of the last century. Nowadays, these technologies are becoming increasingly important and popular.

Advantages and disadvantages of biogas

Biogas as an energy source has undeniable advantages:

• it serves to improve the ecological situation in those areas where it is widely used, since, along with a reduction in the use of polluting fuel, there is a very effective destruction of biowaste and disinfection of effluents, i.e. biogas equipment acts as a cleaning station;
• the raw materials for the production of this fossil fuel are renewable and practically free - as long as the animals on farms are fed, they will produce biomass, and, therefore, fuel for biogas plants;
• the purchase and use of equipment is economically beneficial - once purchased, a biogas plant will no longer require any investments, and it is easy and cheap to maintain; for example, a biogas plant for use in a farm begins to pay off already three years after launch; there is no need to build engineering communications and power transmission lines, the cost of launching a biostation is reduced by 20 percent;
• there is no need to bring such engineering communications as power lines and gas pipelines;
• biogas production at the station using local organic raw materials is a non-waste enterprise, as opposed to enterprises using traditional energy carriers (gas pipelines, boiler houses, etc.), waste does not pollute the environment and does not require a place for its storage;
• when using biogas, a certain amount of carbon dioxide, as well as sulfur, is released into the atmosphere, however, these amounts are minimal compared to the same natural gas and are assimilated by green spaces during breathing, so the contribution of bioethanol to the greenhouse effect is minimal;
• compared to other alternative energy sources, biogas production is always stable, the activity and productivity of biogas production plants can be controlled by a person (unlike, for example, solar batteries), by assembling several plants into one or, conversely, splitting them into separate sections to reduce risk accidents;
• in exhaust gases when using biofuels, the content of carbon monoxide is reduced by 25 percent, and nitrogen oxides - by 15;
• in addition to manure, some types of plants can be used to obtain biomass for fuel, for example, sorghum will help improve soil conditions;
• when bioethanol is added to gasoline, its octane number increases, and the fuel itself becomes more knock-resistant, its auto-ignition temperature is significantly reduced.

Biogas– not an ideal fuel, it and the technology for its production are also not without drawbacks:

• the rate of processing of organic raw materials in biogas production equipment is a weak point in technology compared to traditional energy sources;
• bioethanol has a lower calorific value than fuel from oil - 30 percent less energy is released;
• the process is rather unstable, it requires a large amount of enzymes of a certain quality to maintain it (for example, a change in the diet of cows greatly affects the quality of manure raw materials);
• unscrupulous producers of biomass for processing stations can significantly deplete the soil with increased sowing, this violates the ecological balance of the territory;
• pipes and tanks with biogas can depressurize, which will lead to a sharp decrease in the quality of biofuel.

Where is biogas used?

First of all, this ecological biofuel is used to meet the household needs of the population, as a replacement for natural gas, for heating and cooking. Enterprises can use biogas to start a closed production cycle: its use is especially effective in gas turbines. With proper adjustment and full combination of such a turbine with a biofuel plant, its cost competes with the cheapest nuclear energy.

The efficiency of using biogas is very easy to calculate. For example, from one unit of cattle, you can get up to 40 kilograms of manure, from which one and a half cubic meters of biogas is produced, sufficient to generate 3 kilowatts / hours of electricity.

By determining the farm's electricity needs, it is possible to determine which type of biogas plant to use. With a small number of cows, it is best to produce biogas at home using a simple low-capacity biogas plant.

If the farm is very large, and a large amount of biowaste is constantly generated on it, it is advantageous to install an automated industrial-type biogas system.

Note! When designing and commissioning, the help of qualified specialists will be required here.

Construction of a biogas plant

Any bioinstallation consists of the following main parts:

• bioreactor, where the biodegradation of the manure mixture takes place;
• organic fuel supply system;
• unit for mixing biological masses;
• devices for creating and maintaining the desired temperature level;
• tanks for placing the resulting biogas in them (gas holders);

• containers for placing the formed solid fractions there.

This is a complete list of elements for industrial automated plants, while a biogas plant for a private house is much more simply designed.

The bioreactor must be completely sealed, i.e. oxygen access is not allowed. It can be a metal container in the form of a cylinder, installed on the surface of the soil; former fuel tanks with a capacity of 50 cubic meters are well suited for these purposes. Ready collapsible bioreactors are quickly mounted / dismantled and easily moved to a new location.

If a small biogas plant is expected, then it is advisable to place the reactor underground and make it in the form of a brick or concrete tank, as well as metal or PVC barrels. It is possible to place such a bioenergy reactor indoors, however, it is necessary to ensure constant ventilation of the air.

Bunkers for the preparation of biological raw materials are a necessary element of the system, because before getting into the reactor, it must be prepared: crushed into particles up to 0.7 millimeters and soaked in water to bring the moisture content of the raw material to 90 percent.

Raw material supply systems consist of a raw material receiver, a water pipeline and a pump for supplying the prepared mass to the reactor.

If the bioreactor is made underground, the raw material container is placed on the surface so that the prepared substrate flows into the reactor on its own under the action of gravity. It is also possible to place the raw material receiver at the top of the hopper, in which case a pump is required.

The waste outlet is located closer to the bottom, opposite the raw material inlet. The receiver for solid fractions is made in the form of a rectangular box, where the outlet tube leads. When a new portion of the prepared bio-substrate enters the bioreactor, the batch of solid waste of the same volume is fed into the receiver. In the future, they are used on farms as excellent biofertilizers.

The resulting biogas is stored in gas holders, which are placed, as a rule, on top of the reactor and have a conical or domed shape. Gas holders are made of iron and painted over with oil paint in several layers (this helps to avoid corrosive destruction). In large industrial bio-installations, biogas tanks are made in the form of separate tanks connected to the reactor.

To give the resulting gas combustible properties, it is necessary to rid it of water vapor. The biofuel is wired through a pipe through a water tank (hydraulic lock), after which it can be fed through plastic pipes directly for consumption.

Sometimes you can find special bag-shaped PVC gas holders. They are located in close proximity to the installation. As the bags are filled with biogas, they open, their volume increases enough to receive all the produced gas.

For the efficient flow of biofermentation processes, constant mixing of the substrate is necessary. To prevent the formation of a crust on the surface of the biomass and slow down the fermentation processes, it is necessary to constantly actively mix it. To do this, submersible or inclined stirrers in the form of a mixer for mechanical mixing of the mass are mounted on the side of the reactor. For small stations, they are manual, for industrial ones - with automatic control.

The temperature required for the vital activity of anaerobic bacteria is maintained using automated heating systems (for stationary reactors), they start heating when the heat drops below the norm and automatically turn off when the normal temperature is reached. You can also use boiler plants, electric heaters, or install a special heater in the bottom of the container with raw materials. At the same time, it is necessary to reduce heat losses from the bioreactor, for this it is wrapped with a layer of glass wool or other thermal insulation is carried out, for example, from expanded polystyrene.

Biogas do it yourself

For private houses, the use of biogas is now very relevant - from almost free manure, you can get gas for domestic needs and heating houses and farms. Having your own biogas plant is a guarantee against power outages and rising gas prices, as well as a great way to dispose of biowaste, as well as unnecessary paper.

For construction for the first time, it is most logical to use simple schemes, such structures will be more reliable and last longer. In the future, the installation can be supplemented with more complex details. For a house of 50 square meters, a sufficient amount of gas is obtained with a fermentation tank volume of 5 cubic meters. To ensure a constant temperature regime, necessary for proper fermentation, a heating pipe can be used.

At the first stage of construction, they dig a trench for the bioreactor, the walls of which must be reinforced and sealed with plastic, concrete mix or polymer rings (preferably with a blank bottom - they will have to be replaced periodically as they are used).

The second stage consists in the installation of gas drainage in the form of polymer pipes with numerous holes. During installation, it should be taken into account that the tops of the pipes must exceed the planned filling depth of the reactor. The diameter of the outlet pipes should be no more than 7-8 centimeters.

The next step is isolation. After that, it is possible to fill the reactor with the prepared substrate, after which it is wrapped in a film to increase the pressure.

At the fourth stage, the domes and the outlet pipe are mounted, which is placed at the highest point of the dome and connects the reactor to the gas holder. The gas tank can be overlaid with bricks, a stainless steel mesh is mounted on top and covered with plaster.

A hatch is placed in the upper part of the gas tank, which closes hermetically, a gas pipe with a valve for pressure equalization is taken out of it.

Important! The resulting gas must be removed and consumed constantly, since its long-term storage in the free part of the bioreactor can provoke an explosion from high pressure. It is necessary to provide a water seal so that the biogas does not mix with air.

To heat the biomass, you can install a coil coming from the heating system of the house - this is much more economically profitable than using electric heaters. External heating can be provided with the help of steam, this will exclude overheating of raw materials above the norm.

In general, a do-it-yourself biogas plant is not such a complex structure, but when arranging it, you need to pay attention to the smallest details in order to avoid fires and destruction.

Additional Information. The construction of even the simplest biological installation must be formalized with the relevant documents, it is necessary to have a technological scheme and equipment installation map, and it is necessary to obtain the approval of the Sanitary and Epidemiological Station, fire and gas services.

Nowadays, the use of alternative energy sources is gaining momentum. Among them, a very promising sub-sector of bioenergy is the production of biogas from organic waste such as manure and silage. Biogas production stations (industrial or small home) are able to solve the problems of waste disposal, obtaining ecological fuel and heat, as well as high-quality agricultural fertilizers.

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Biogas plants for farms, the price depends on the number of components, various parameters characteristic of such devices, varies within 170 thousand rubles.

They work to obtain, as a result of the processing of the final product, environmentally friendly fuel, fertilizers, which are produced in the unit, which includes technical structures, devices, combined in a single technological cycle.

Biogas plants for the home may one day completely replace expensive energy sources for the rural dweller. Economic cataclysms require developers of equipment for agriculture to produce analogues of natural resources in the form of improvised raw materials to reduce the cost of maintaining a private farmstead, farming.

The goals of farmers are different - some get cheap energy for others, it is important to process waste with the help of a small mini installation:

• cattle

As a result of the work, biofertilizers and their own energy source are obtained. In addition, farms have to get rid of various accumulations of household garbage; a convenient, universal structure helps them in this, which gives useful products instead of unnecessary.

Who operates the equipment

Small biogas plants will be useful in modern rural farms. Larger devices are used by serious pastoralists, where it is impossible to exist without units that produce the necessary energy species.

The justification for installation in the courtyard of a private house or a large farm is the accumulation of organic matter, since any equipment needs power to work.

The world is fighting for the ecology of the environment, the most acceptable means for this are the construction of biogas facilities, they release pure substances and consume alternative fuels. On this basis, the devices have received demand in the farms of our country and abroad.

Standard equipment

Engineers complete mechanisms of different sizes. Production depends on the required power, which is to be processed by the unit and issued in exchange. The standard view installation consists of the following components:

• storage tank, it receives material for mining
• mixers, mills structurally different from each other, they grind large raw fragments
• gas tank, hermetically sealed, gas accumulates here
• a reactor in the form of a tank where biofuel is formed
• devices that feed raw materials into a container
• installations that transfer the received fuel from one point to another for subsequent conversion
  automatic systems that protect and control the production process

The work of the technological cycle has been worked out to the smallest detail in order to make it easier for a person to maintain the unit during the processing period.

How it works

The performance of the aggregates is based on the principle of the impact of bacterial formations of various nature on organic matter, causing fermentation. These processes take place inside the reactor. From the decomposition of some products, another substance is obtained, it consists of:

• methane
• carbon dioxide
• impurities of ammonia, hydrogen sulfide, nitrogen

The principle of operation consists of the following actions:

• raw materials are fed into the storage tank
• the material is broken up, pumps, conveyors move to the acid tank, in this tank the biomass is subjected to additional heating
• durable, acid-resistant, tightly closed reactor accepts prepared raw materials to create biogas

Devices are installed in the reactor to provide additional heating, within +40 degrees, of mixing substances, create suitable conditions for them, accelerating the processes of decomposition and fermentation, from which the final product is formed. The recycling rate depends on the capacity of the facility and the type of waste.

In the process:

• gas accumulation is carried out in gas tanks, they are mounted as a separate element or connected together with the body
• the reactor capacity collects, after the completion of the decomposition procedure, it transfers for use
• sufficient pressure is created in the gas holder tank to move the gas into the purification system, in this form it will be used by the consumer in various fields of activity
• intended use acquire substances for fertilizers after their separation into components in liquid or solid form, and transfer to the storage part

The decision to start construction should be accompanied by consideration of the conditions under which biogas plants operate with the required efficiency.

Basic options for selection

Poor device functionality is due to poor planning. Errors can be noticed immediately or after a while. A thorough and comprehensive study is made to exclude equipment failure. The procedure begins after determining the availability of raw material and how much is needed for the normal existence of energy resources.

The reactor and its dimensions are affected by:

• amount of processing
• material quality
• raw material
• temperature regime
• fermentation period

In practice, in a particular farm, attention should be paid to the following points:

• daily loading of materials in relation to the reactor size
• the volume of the container in which waste is processed
• calculate the output
• the possibility of balancing between the result and actual consumption

Before installing the equipment, you have to make a choice:

• the best place to install
• models suitable for design features

The main criteria on which the constructive choice is based are the place and the definition of an underground or surface structure. In addition, when arranging the structure at the top, one should decide how to install the reactor in a vertical or horizontal position.

Biofertilizers are stored in buildings on the site or in pits, metal barrels. Costs will reduce the finished parts of the installation, if they are on the farm. The accumulation of materials determines the size and shape of the tanks in which they are mixed, as well as what kind of reactor is needed, devices for heating substances, crushing and mixing them.

The selected reactor design must comply with:

• practicality
• ease of maintenance
• gas- and water-tight to eliminate leaks and keep the gas in full

A prerequisite for effective performance is the presence of high-quality thermal insulation. It is possible to reduce construction costs and heat losses with minimal surface areas.

The structure must be stable, withstand pressure loads:

• raw materials

Installations are equipped in the following most optimal forms:

• egg-shaped
• cylindrical
• conical
• semicircular

It is not recommended to equip square forms of concrete or brick. The raw material exerts pressure on the corners, causing cracks to appear, disrupt the processes occurring inside, solid accumulating fragments. Materials roam better, dried surfaces do not appear in structures with internal partitions.

The best building materials are:

• Steel - in these containers you can achieve absolute tightness, they are easy to manufacture, they withstand loads. The problem is increased susceptibility to corrosion. Surfaces are treated to prevent rust. If the farm has a metal tank, its quality should be checked from all sides. Get rid of imperfections.
• Plastic - tanks made of this material are produced soft and hard. The first option is less suitable, since damage is easily caused, it is difficult to insulate. Hard plastic tanks are stable and will not rust.
• Concrete is used by some developing countries. They have no restrictions in terms of operation, special coatings can eliminate the appearance of cracks.
• Brick is used by India and China. For this, only well-burnt products are used or walls made of concrete blocks or stone are laid.

When installing equipment made of concrete, brick or stone, it is necessary to take care of the internal refractory finish that is resistant to organic matter and hydrogen sulfide.

The location of the structure should be taken with particular seriousness, to provide factors:

• vacant areas
• distance from housing
• warehousing
• location of barns, pigsties, poultry houses
• ground water
• convenient loading and unloading of materials

Reactors host:

• on the surface with foundation
• buried in the ground
• installed inside the farm

Devices operating with the help of a chemical, biological reaction are equipped with hatches through which periodic repairs are carried out. The rubber gasket provides a seal when the lid is closed. Thermal insulation is necessary to carry out work regardless of the season.
The building is insulated with improvised materials with layer-by-layer processing of internal surfaces.

You can mount small installations at home. To digress, I will say that getting biogas with your own hands is not some kind of new invention. Even in ancient times, biogas at home was actively obtained in China. This country is still the leader in terms of the number of biogas plants. 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 all this in this and subsequent articles.

Preliminary calculation of biogas plant

Before proceeding with the purchase or self-assembly of a biogas plant, it is necessary to adequately assess the availability of raw materials, their type, quality and the possibility of uninterrupted supply. Not every raw material is suitable for biogas production. Raw materials that do not fit:

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

If the raw material is suitable for processing, then you can proceed 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 not 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 taking into account the achievement of 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 the farm has 10 cattle, 20 pigs and 35 chickens. Excrement comes out per day: 55 kg from 1 cattle, from 1 pig - 4.5 kg 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. Round up to 646 kg. The moisture content of pig and cattle excrement is 86%, and that of chicken manure is 75%. To achieve 85% moisture content in chicken manure, add 3.9 liters of water (about 4 kg).

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

Biogas yield calculation

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

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 get a biogas yield of approximately 27-36.5 m³ per day.

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

Installation and fabrication of the reactor

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

• be water and gas tight. Mixing of air with gas should not take place in the reactor. Between the cover and the body there must be a gasket made of sealed material;
• be thermally insulated;
• withstand all loads (gas pressure, weight, etc.);
• have a hatch for repair work.

The installation and selection of the reactor shape is made for each farm individually.

Fabrication theme do-it-yourself biogas plant very extensive. Therefore, I will focus on this in this article. In the next article, we will talk about the choice of other elements of a biogas plant, prices and where it can be purchased.