Drainage

How to install a biogas plant with your own hands. Methods for self-production of biogas Obtaining gas at home

The modern world is built on ever-increasing consumption, so mineral and raw material resources are being depleted especially quickly. At the same time, millions of tons of foul-smelling manure accumulate annually on numerous livestock farms, and considerable resources are spent on its disposal. Humans are also keeping up with the production of biological waste. Fortunately, a technology has been developed that allows us to simultaneously solve these problems: using biowaste (primarily manure) as a raw material, producing 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 gaseous substance that is colorless and completely odorless. It consists of 50-70 percent methane, up to 30 percent of it is carbon dioxide CO2 and another 1-2 percent are gaseous substances - impurities (when purified from them, the purest biomethane is obtained).

The qualitative physical and chemical characteristics of this substance are close to those of ordinary high-quality natural gas. According to research by scientists, biogas has very high calorific properties: for example, the heat released when burning 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 higher temperatures - up to +50 degrees.

Under the influence 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, manure from poultry and pig farms cannot be used in its pure form, because it has a high level of toxicity. To obtain biogas from them, it is necessary to add diluents to such waste: silage mass, green grass mass, as well as cow manure. The last component is the most suitable raw material for producing environmentally friendly fuel, since cows eat only plant foods. However, it must also be monitored for the content of heavy metal impurities, chemical components, and surfactants, which in principle should not be present in the raw material. A very important point is control over antibiotics and disinfectants. Their presence in manure can prevent the process of decomposition of the raw material mass and the formation of volatile gas.

Additional Information. It is impossible to do without disinfectants completely, because otherwise mold begins to form on the biomass under the influence of high temperatures. You should also monitor and promptly clean the manure from mechanical impurities (nails, bolts, stones, etc.), which can quickly damage biogas equipment. The humidity of the raw materials used to produce biogas must be at least 80-90%.

Mechanism of gas formation

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

The full cycle of converting manure into environmental fuel ranges from 12 days to a month, it depends on the composition of the raw materials. From one liter of useful reactor volume, about two liters of biogas are produced. If you use more advanced modernized installations, 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 producing biofuel 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 environmental situation in those areas where it is widely used, since along with reducing the use of polluting fuel, there is a very effective destruction of biowaste and disinfection of wastewater, i.e. biogas equipment acts as a cleaning station;
the raw materials for the production of this organic fuel are renewable and practically free - as long as animals on farms receive food, they will produce biomass, and, therefore, fuel for biogas plants;
the acquisition and use of equipment is economically profitable - once purchased, a biogas production plant will no longer require any investments, and it is simply and cheaply maintained; Thus, a biogas plant for use on a farm begins to pay for itself within three years after launch; there is no need to build utilities and energy transmission lines, the costs of launching a biological station are reduced by 20 percent;
there is no need to install utilities such as power lines and gas pipelines;
biogas production at the station using local organic raw materials is a waste-free enterprise, as opposed to enterprises using traditional energy sources (gas pipelines, boiler houses, etc.), waste does not pollute the environment and does not require storage space;
when using biogas, a certain amount of carbon dioxide and sulfur are released into the atmosphere, however, these amounts are minimal compared to the same natural gas and are absorbed by green spaces during respiration, therefore the contribution of bioethanol to the greenhouse effect is minimal;
Compared to other alternative energy sources, biogas production is always stable; a person can control the activity and productivity of installations for its production (unlike, for example, solar panels), collecting several installations 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, you can also use some types of plants to obtain biomass for fuel, for example, sorghum will help improve soil condition;
When bioethanol is added to gasoline, its octane number increases, and the fuel itself becomes more detonation-resistant, and its auto-ignition temperature decreases significantly.

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

the speed of processing organic raw materials in equipment for the production of biogas is a weak point in the technology compared to traditional sources of energy;
Bioethanol has a lower calorific value than petroleum fuel - it releases 30 percent less energy;
the process is quite unstable; to maintain it, a large amount of enzymes of a certain quality is required (for example, a change in the diet of cows greatly affects the quality of manure);
unscrupulous producers of biomass for processing stations can significantly deplete the soil with increased seeding, this disrupts the ecological balance of the territory;
pipes and containers with biogas may become depressurized, 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 launch a closed production cycle: its use in gas turbines is especially effective. With proper adjustment and complete combination of such a turbine with a biofuel production plant, its cost competes with the cheapest nuclear energy.

The efficiency of biogas use 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.

Having determined the household's electricity needs, it is possible to determine what type of biogas plant to use. With a small number of cows, it is best to produce biogas at home using a simple low-power biogas plant.

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

Note! When designing and setting up, you will need the help of qualified specialists.

Biogas plant design

Any biological installation consists of the following main parts:

a bioreactor where the biodecomposition of the manure mixture occurs;
organic fuel supply system;
unit for stirring biological masses;
devices for creating and maintaining the required temperature level;
tanks for placing the resulting biogas in them (gas holders);

containers for placing the resulting solid fractions there.

This is a complete list of elements for industrial automated installations, while a biogas installation for a private home is much more simply designed.

The bioreactor must be completely sealed, i.e. access of oxygen is unacceptable. This 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-made dismountable bioreactors are quickly installed/dismantled and easily moved to a new location.

If a small biogas station is planned, 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. You can place such a bioenergy reactor indoors, but it is necessary to ensure constant air ventilation.

Bunkers for the preparation of biological raw materials are a necessary element of the system, because before entering 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 supply system and a pump for supplying the prepared mass to the reactor.

If the bioreactor is made underground, the container for raw materials is placed on the surface so that the prepared substrate flows into the reactor independently under the influence of gravity. It is also possible to place the raw material receiver at the top of the bunker, in which case it is necessary to use a pump.

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

The resulting biogas is stored in gas holders, which are usually placed on top of the reactor and have a cone or dome shape. Gas tanks are made of iron and painted with oil paint in several layers (this helps to avoid corrosive destruction). In large industrial bioinstallations, biogas containers are made in the form of separate tanks connected to the reactor.

To give the resulting gas flammable properties, it is necessary to rid it of water vapor. The biofuel is piped through a water tank (hydraulic seal), after which it can be supplied through plastic pipes directly for consumption.

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

For effective biofermentation processes to occur, constant stirring 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 are mounted on the side of the reactor in the form of a mixer for mechanical mixing of the mass. For small stations they are manual, for industrial ones they are automatically controlled.

The temperature necessary for the vital activity of anaerobic bacteria is maintained using automated heating systems (for stationary reactors); they begin heating when the heat drops below normal and automatically turn off when normal temperature is reached. You can also use boiler systems, 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 loss from the bioreactor; to do this, it is wrapped in a layer of glass wool or other thermal insulation is provided, for example, from polystyrene foam.

Do-it-yourself biogas

For private homes, the use of biogas is now very important - from practically free manure you can get gas for domestic needs and heating your home and farm. Your own biogas installation is a guarantee against power outages and rising gas prices, as well as an excellent way to recycle 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 will last longer. In the future, the installation can be supplemented with more complex parts. For a house with an area of 50 square meters, a sufficient amount of gas is obtained with a fermentation tank volume of 5 cubic meters. To ensure the constant temperature required 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 strengthened and sealed with plastic, concrete mixture or polymer rings (preferably they have a solid bottom - they will have to be replaced periodically as they are used).

The second stage consists of installing 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 stage is isolation. After this, you can fill the reactor with the prepared substrate, after which it is wrapped in film to increase the pressure.

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

A hatch is placed in the upper part of the gas holder, which closes hermetically; a gas pipe with a valve for equalizing pressure is removed from 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 using steam; this will prevent overheating of raw materials above normal.

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 appropriate documents, you must have a technological diagram and equipment installation map, you must obtain approval from the Sanitary and Epidemiological Station, fire and gas services.

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

Video

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 extraction of which does not require geological exploration, well drilling, or expensive pumping equipment.

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

Biogas heating - history

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

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

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

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

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

Biogas - what is it

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

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

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

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

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

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

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

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

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

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

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

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

Biogas plants

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

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

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

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

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

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

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

DIY biogas plant

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

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

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It is not easy for farms to dispose of manure. It is produced in excess, and a lot of money has to be spent on removal and disposal. In small private farms, manure is actively used as a free and effective fertilizer. It turns out that there is another way to usefully use this raw material, which makes it possible to obtain natural gas.

Many farms are already producing biogas from manure, using environmentally friendly technology that allows them to obtain a valuable product. Biomethane from manure is of high quality, which is why it is used in many countries.

What is biogas

Biogas from manure is an environmentally friendly fuel. According to its characteristics, it is close to natural gas, which is extracted from the bowels of the earth industrially.

Biogas can be an alternative to conventional fuel, because it is made from the waste of animals and birds, which can be found in abundance in any agriculture. With proper processing of raw materials, you can obtain colorless biogas without a characteristic odor, which contains at least 70% methane.

Biogas has good characteristics. One cubic meter of such fuel from manure produces the same amount of heat as one and a half kg of coal.

Process Benefits

Manure was processed to produce biogas back in Soviet times. Today, many countries are engaged in this type of industry, as it is profitable, easy and does not pose a threat to the environment.

Such alternative biogas does not require labor-intensive extraction of raw materials for production, the process of its creation is relatively cheap, and no toxic substances are released into the environment.

Of course, manure can be used simply as fertilizer if there are only a few cows on the farm. It is much more difficult for large farmers with hundreds of heads of livestock, because every year they have to get rid of several tons of manure.

In order for manure to become a high-quality fertilizer, it must be stored at a controlled temperature. But this requires extra expenses, so most farmers simply collect it in a certain place and then transport it to arable land.

If stored improperly, manure loses almost half of the nitrogen compounds in it and most of the phosphorus, so its performance becomes much worse. Methane gas is continuously released into the atmosphere from manure, which worsens the environmental situation.

The latest technologies for producing biomethane make it possible to process raw materials in such a way that the resulting biogas does not have a toxic effect on the environment. Biogas releases an incredible amount of energy when burned, and heated manure, after its use, becomes a very valuable anaerobic fertilizer.

Biogas technology

Biogas can be produced using bacteria, which do not require oxygen to function. Therefore, to produce biogas, it is necessary to build sealed containers in which the fermentation of raw materials will occur. The exhaust pipes are designed in containers in such a way that air from the external environment is not able to leak inside.

First, the reservoir is filled with liquid raw materials and the temperature is raised to the required level so that the world organisms begin to work. Methane rises up from liquid manure and accumulates in special tanks in which it undergoes a filtration stage. Then it is collected in gas cylinders. Used masses of manure accumulate at the bottom of containers, from where they are periodically removed and stored in other places. After pumping out the waste liquid, new manure is supplied to the tank.

Temperature regime of bacteria functioning

Methane can be released from manure only when a suitable temperature regime is created for it. Manure contains different bacteria that are activated and release biogas at different temperatures and at different speeds:

Mesophilic bacteria. They start working if the ambient temperature rises above 30 degrees. Biogas is produced very slowly - the products can be collected after half a month.
Thermophilic bacteria. To activate them, a temperature of 50-65 degrees is required. Biogas can be collected in just three days. Of particular value is sludge - manure waste after strong heating. This is a useful fertilizer and, most importantly, harmless - any helminths, weed seeds, pathogenic microorganisms are destroyed when heated.
There is also another type of thermophilic bacteria that survive when heated to a temperature of 90 degrees. They are additionally included in manure so that fermentation occurs faster.

As temperatures drop, all types of bacteria become less active. In a small farm, mesophylls are usually used, because in this case additional heating is not required. Further, primary biogas can be used to artificially heat manure and activate thermophilic bacteria.

The disadvantage of storing raw materials is that they should not be subject to temperature fluctuations. Therefore, in winter, it is necessary to take care of a warm room for storing manure.

Preparation of raw materials for pouring into the reactor

As a rule, there is no need to further enrich manure with microorganisms, since they are already contained in it. All that needs to be done is to properly prepare the manure solution, monitor the temperature and change the raw materials in the bioreactor on time.

The moisture content of the raw materials should be at least 90% (the consistency of liquid sour cream). Therefore, before use, dry droppings (goats, sheep, horses, rabbits) are mixed with water. There is no need to dilute pig manure due to its high urine content.

It is also important that the manure is homogeneous and free of solid particles. The amount of biogas produced at the outlet depends on the fineness of the fractions. For this reason, a constantly running mixer is installed inside the equipment, destroying the hard crust on the surface of the raw material and preventing the release of methane.

Highly acidic waste (pig and cow manure) is best suited for the process. When the acidity level decreases, the bacteria slow down their work, so it is important to find out for the first time how long it takes to completely process one portion of the manure solution, and only then refill it.

The resulting product contains about seventy percent methane, one percent impurities (hydrogen sulfide and some volatile elements) and just under thirty percent carbon dioxide.

It can be used as fuel only after purification from impurities. Hydrogen sulfide compounds are removed using special filters. This must be done for the reason that such a substance, forming an acid with water, accelerates the corrosion processes of metals, pipes, tanks and the entire biogas plant, if it is metal.

Carbon dioxide also needs to be removed from the fuel, but this takes a lot of time:

First of all, biogas is compressed under high pressure.
Water is sent into the container, in which the impurity will dissolve.

If biogas is produced on a large scale, then purification is carried out with lime, activated carbon and special filters.

Reducing moisture content

At this stage, the purification of raw materials is carried out in different ways.

The first method is similar to the operation of a moonshine still. Biogas is directed upward through cold tubes. The water turns into condensate and flows down the tube, while the methane is sent to a reservoir for further storage.

Another way is to use a water seal. The resulting biogas is mixed with water, where all impurities remain. This method requires less time for cleaning, since water gets rid of both excess liquid and unnecessary elements.

For the manufacture of an installation near farms, a design that can subsequently be easily disassembled and moved to another area is best suited. The main equipment of the entire installation is a bioreactor - a container for pouring manure and fermenting it. Large enterprises use tanks of 50 cubic meters.

Small private farms use an underground reservoir instead of tanks. It is laid out with bricks in a dug hole. For tightness and strength, everything is fixed with cement mass. The volume depends on the amount of manure produced daily.

For above-ground installation, tanks made of plastic, metal or polyvinyl chloride can be used.

Installations can be either automated (in which the entire process occurs without human intervention) or mechanical (you must pump out, add raw materials, take in biogas, monitor pressure and temperature yourself).

On a small farm, it is advisable to use electric pumps, mixers, and grinders, which will prevent the appearance of crusts on the surface of manure and clean the structure of waste.

The most important rule is the absence of oxygen in the reactor. If present, an explosion may occur.

To prevent the reactor lid from being blown off by high pressure, counterweights and protective gaskets between the tanks and lids are needed.

The reservoir should never be completely full. It is advisable to leave a fifth of its volume unfilled.

At the site before installation, the equipment must:

choose the right location (preferably as far as possible from a residential building)
calculate the daily volumes of manure produced
select a location for pipes (shipping, loading, condensing)
find a place for manure waste
dig a pit
purchase a container for the tank and secure it to the bottom of the pit
seal all joints
construct a hatch for inspecting the reactor (be sure to place a gasket between the hatch and the reactor)

If the installation takes place in a cold climate, then you should definitely consider ways to heat it.

The final stage of construction is checking the equipment for leaks.

Gas quantity calculation

On average, a ton of manure will provide the owner with hundreds of cubic meters of biogas. In order to calculate the amount of biogas produced, it is necessary to multiply the daily mass of manure from each livestock by the number of animals.

Naturally, different animals and birds produce different amounts of manure:

poultry (primarily chickens) – 150-170 g per day
cow - 34-36 kg
goat – 900 – 1100 g
horse – 14-16 kg
sheep – 900 – 1100 g
pig – 4-6 kg

Pig and cow manure provides more fuel. The amount of biogas released can be increased by adding millet, beet tops, marsh plants, algae or corn to the mixture (the presence of chlorophyll in biomass improves methane release).

Biomass waste after gas production

The sludge formed after heating manure is used throughout agriculture in the form of fertilizers.

The carbon dioxide produced is usually purified, but when it is dissolved in water, a useful liquid is obtained.

Full utilization of biogas plant products

With rational use of manure, there may be no waste at all after the formation of biogas. For example, carbon dioxide is used as a fertilizer for vegetable crops.

The sludge is also used for root feeding.

Therefore, if you have a small installation for the production of biogas, it will be useful to install a biogreenhouse, which, due to fertilizers and the resulting energy, can operate all year round.

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

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

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

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

What is biomethane

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

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

Biomethane is used for the following needs:

cooking;

in internal combustion engines of automobiles;

for heating a private house.

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

How is biomethane produced?

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

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

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

Its raw material base includes:

food industry;

livestock farming;

poultry farming;

fisheries and processing plants;

dairies;

production of alcoholic and low-alcohol drinks.

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

Biofuel production technology

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

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

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

Temperature regime of bacteria functioning

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

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

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

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

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

How to prepare raw materials for pouring into the reactor

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

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

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

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

Gas purification technology

When processing manure into biogas, the following is obtained:

70% methane;

30% carbon dioxide;

1% impurities of hydrogen sulfide and other volatile compounds.

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

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

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

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

How to reduce moisture content

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

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

Water seal principle

What installations are used to produce biogas?

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

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

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

By type of control there are:

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

mechanical, where the entire process is controlled manually.

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

Scheme of a homemade installation for producing biogas from manure

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

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

Video: Biogas from bird droppings

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

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

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

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

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

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

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

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

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

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

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

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

Gas quantity calculation

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

chicken – 165 g per day;

cow – 35 kg;

goat – 1 kg;

horse – 15 kg;

sheep – 1 kg;

pig – 5 kg.

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

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

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

Biomass waste after gas production

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

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

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

Full utilization of biogas plant products

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

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

Video: Biogas in 2 days

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

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

Use as fertilizer

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

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

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

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

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

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

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

What nutrients can be obtained after manure processing?

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

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

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

Sludge storage methods

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

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

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

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Every year on our planet energy resources become less and less. It is because of this that we have to constantly look for new, alternative sources of energy. Definitely, after some time our planet will run out of oil and gas deposits, and then the world will have to seriously think about the extraction (collection) and use of biogases as the main source of energy.

What is biogas? Principles of biogas production

As already mentioned, biogas is an alternative source of energy. It is released during the fermentation of various household wastes, as well as waste excreted by animals (manure).

This method has been used since ancient times in China, but later, centuries later, it was unclaimed and as a result was forgotten.

Do-it-yourself biogas production at home

Step 1: Selecting a Barrel

First we need to choose a suitable barrel in which we will store the “energy source”, that is, as you understand, food waste and manure.

Step 2: Making the holes

We make holes at the inlet and outlet of the barrel. It can be done using a drill, but in this case, the hole is made using a heated metal pipe.

Step 3: Installation of pipes

We install pipes at the inlet and outlet into the holes we made earlier. We insert and glue the pipes.

Step 4: Creating and installing a “gas tank” holder

We took a 20-liter paint bucket; this tank will contain the gas we extract. The tank is secured with a valve that plumbers use.

Step 5: Add Cow Manure

Mix cow dung (5 kg per 50 liters) and add water. Place it in the tank.

Step 6: Almost done

You will not receive gas for the first 10-15 days, as this time is necessary for all the necessary processes to go through.

Step 7: Get Rid of Carbon Dioxide

In order for this gas to burn, it is necessary to get rid of carbon dioxide. This can be achieved by using a regular filter, of which there are many in various hardware stores.

Step 8: Done!

You will notice how the “fuel tank” will rise as chemical reactions occur. Then it is necessary to open the valve and obtain biogas.

Biogas can be used for different purposes. It is not recommended to use biogas for cooking, as it can negatively affect the taste (if the flavors are not removed).