Farms need fuel for heating systems, generating electricity and other daily needs. Since energy prices are steadily rising year after year, every home or small business owner has at least once thought about how to produce biogas at home.
Biogas plants are increasingly being used on farms, allowing them to save money on heatingA biogas plant for a private home allows you to organize the production of biogas right in your yard, which solves the fuel problem. Since a significant percentage of village residents have skills in working with welding and plumbing tools, the question of making a gas production unit on their own seems logical. This way you can save not only on work, but also on materials if you use improvised means.
What is biogas and how is it formed: obtaining and production
Biogas is a substance formed during the fermentation of organic waste, which contains methane in sufficient quantities to be used as fuel. When burned, biogas releases heat, which is enough to heat a house or refuel a car. The source of energy is manure, which is easily accessible and cheap or even free if we are talking about a livestock enterprise or a large private farm.
Biogas is an environmentally friendly biofuel that you can produce with your own hands; biological gas is related to natural gas. The gas is produced by processing waste by anaerobic bacteria. Fermentation takes place in an airless container called a bioreactor. The rate of biogas production depends on the amount of waste loaded into the biogenerator. Under the influence of bacteria, a mixture of methane and carbon dioxide with some admixtures of other gaseous substances is released from the raw material. The resulting gas is removed from the bioreactor, purified and used for its own needs. The processed raw materials upon completion of the process become fertilizer, which is used to improve soil fertility. Producing biogas is beneficial for livestock enterprises that have access to free manure and other organic waste.
Benefits of burning fuel from manure (farm fertilizer) for heating: electricity from methane
The advantages of biogas as a fuel include:
- Efficient and environmentally friendly waste recycling
- Availability of raw materials for gas production in rural areas
- The ability to organize a closed cycle of waste-free production of gas and fertilizers from manure
- Non-exhaustible, self-replenishing source of raw materials
How to build a bioreactor (installation) with your own hands
Biogas plants that produce gas from manure can be easily assembled with your own hands on your own site. Before assembling a bioreactor for processing manure, it is worth drawing drawings and carefully studying all the nuances, because a container containing a large amount of explosive gas can be a source of great danger if it is used incorrectly or if there are errors in the design of the installation.
Biogas production schemeThe capacity of the bioreactor is calculated based on the amount of raw material that is used to produce methane. In order for operating conditions to be optimal, the reactor capacity is filled with waste to at least two-thirds. For these purposes, a deep pit is used. To ensure high tightness, the walls of the pit are reinforced with concrete or reinforced with plastic, and sometimes concrete rings are installed in the pit. The surface of the walls is treated with moisture-proofing solutions. Tightness is a necessary condition for efficient operation of the installation. The better the container is insulated, the higher the quality and quantity. In addition, waste breakdown products are poisonous and, if leaked, can be harmful to health.
A stirrer is installed in the waste container. It is responsible for mixing waste during fermentation, preventing uneven distribution of raw materials and the formation of a crust. Following the mixer, a drainage structure is installed in the manure, which facilitates the removal of gas into the storage tank and prevents leakage. It is necessary to remove the gas for safety reasons, as well as to improve the quality of the fertilizers remaining in the reactor after processing. A hole is made in the bottom of the reactor for. The hole is equipped with a tight lid so that the equipment remains sealed.
How to ensure active fermentation of biomass at home using a generator and other equipment: waste processing, composition and extraction
In order for the processing process in a bioreactor to proceed faster, heating is necessary. The ambient temperature is sufficient for manure processing to occur without outside help. But under unfavorable weather conditions, in the winter, a mini-biogas plant needs an additional heat source, otherwise gas production becomes impossible. For bacteria to convert waste into gas, the temperature in the reactor must be above 38 degrees Celsius. It is not difficult to obtain biogas with your own hands; the main thing is to know certain manufacturing rules.
The container is heated using a coil, which is located under the reactor, or by installing electric heaters to directly heat the reservoir. , which process waste into gas, are already in the raw material. To activate microorganisms and start the process of biogas production, the temperature in the container must be sufficient for fermentation. To make it easier to control compliance with temperature conditions, automatic heating is connected to the reactor. It heats the container when fuel is loaded into it to the desired temperature and turns off the heating when the desired mark on the thermometer is reached. A temperature control device for, which is easy to find in a gas equipment store, can handle the role of an automatic heater.
Temperature control module. It can be purchased at any hardware storeCorrect gas removal from the bioreactor: drawings, use of technology
To easily remove the formed gas from the tank, biogas plants are equipped with a number of devices:
- Vertically arranged plastic pipes with a large number of holes to facilitate the separation of gas from the raw material. The top of the pipe should protrude above the waste mass, allowing gas to escape freely.
- A film laid over the container and creating a kind of greenhouse effect. It maintains the desired temperature inside the container and also prevents gas from mixing with air.
Sometimes the container is covered with a dome made of concrete or other material. To prevent such a dome from flying away under the pressure of the resulting gas, it is carefully attached to the structure and tied with cables.
- A gas exhaust pipe is placed at the top of the reactor. The pipe is equipped with a tight locking mechanism so as not to violate the tightness of the structure. The newly released biogas, entering the outlet pipe, is saturated with water vapor and contains many impurities. occurs by condensation: when cooled to ambient temperature, water settles in the form of condensation on the walls of the pipe. To avoid corrosion, the discharge pipe is installed in such a way as to facilitate the removal of condensate through the separator.
- To remove hydrogen sulfide impurities from biogas, a filter made of specially treated activated carbon is installed on its way to the storage facility, in which the mixture is oxidized into sulfur and deposited in the sorbent.
WATCH THE VIDEO
A self-assembled biogas plant, processing manure into biogas at home, significantly reduces heating and electricity costs. Such an installation will reduce the cost of providing a private home with heat, reduce the cost of farm products, thereby increasing the profitability of the farm. – the ability to turn waste into a source of energy and an alternative to natural gas. Biogas is environmentally friendly and modern.
The theoretical basis for the production of methane gas from biomass by anaerobic digestion was presented.
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. This article will present practical implementations of biogas plants, with a description of some home-made designs.
Since energy prices are rising, and many owners of livestock farms and small farms have problems with waste disposal, industrial complexes for the production of biogas and small biogas plants for private homes have become available for sale. Using search engines, an Internet user can easily find an affordable ready-made solution so that the biogas plant and its price meet the needs, get in touch with equipment suppliers and agree on the construction of a biogas generator at home or on the farm.
Industrial complex for biogas production
Bioreactor - the basis of a biogas plant
The container in which anaerobic decomposition of biomass occurs is called bioreactor, fermenter, or methane tank. Bioreactors can be completely sealed, with a fixed or floating dome, and have a diving bell design. Bell psychrophilic (not requiring heating) bioreactors have the form of an open reservoir with liquid biomass, into which a container in the form of a cylinder or bell is immersed, where biogas is collected.
The collected biogas puts pressure on the cylinder, causing it to rise above the tank. Thus, the bell also serves as a gas holder - a temporary storage facility for the generated gas.
Floating dome bioreactor The disadvantage of the bell design of the biogas reactor is the impossibility of mixing the substrate and heating it during cold periods of the year. Also a negative factor is a strong odor, 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 hot climates.
Another example of a floating dome bioreactor To prevent environmental pollution and eliminate unpleasant odors, reactors in biogas plants for homes and large industries are designed with a fixed dome. The shape of the structure in the process of gas formation is not of great importance, 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 pipes for adding new portions of biomass and selecting spent substrate.
A type of fixed dome bioreactor Main types of biogas plants
Since the most acceptable design is a fixed dome, most ready-made bioreactor solutions are of this type. Depending on the loading method, bioreactors have different designs and are divided into:
- Portion-based, with a one-time loading of all biomass, and subsequent complete unloading after processing of the raw materials. The main disadvantage of this type of bioreactor is the uneven release of gas during substrate processing;
- continuous loading and unloading of raw materials, thereby achieving uniform release of biogas. Thanks to the design of the bioreactor, during loading and unloading, the production of biogas does not stop and no leaks occur, since the pipes through which biomass is added and removed are made in the form of a water seal that prevents gas leakage.
Example of a batch bioreactor Batch biogas reactors can have any design that prevents gas leakage. For example, at one time in Australia, channel methane tanks with an elastic inflatable roof were popular, where a slight excess pressure inside the bioreactor inflated a bubble made of durable polypropylene. When a certain pressure level inside the bioreactor was reached, a compressor was turned on, pumping out the produced biogas.
Channel bioreactors with elastic gas holder The type of fermentation in this biogas plant can be mesophilic (with low 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 that there is no need for an intermediate receiver, but the big disadvantage is the vulnerability of the elastic dome to mechanical damage.
Large channel bioreactor with elastic gas tank Recently, batch bioreactors with dry fermentation of manure without adding water to the substrate have been gaining popularity. Since manure has its own moisture, it will be sufficient for the life of organisms, although the intensity of reactions will decrease.
Dry-type bioreactors look like a sealed garage with tightly closing doors. Biomass is loaded into the reactor using a front-end loader and remains in this state until the full gas formation cycle is completed (about six months), without the need to add a substrate or mix it.
Batch bioreactor with loading through a hermetically sealed door DIY biogas plant
It should be noted that in most bioreactors, as a rule, only the gas formation zone is sealed, and the liquid biomass at the inlet and outlet is under atmospheric pressure. Excessive pressure 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 container.
The red lines in the diagram indicate the difference in levels in the bioreactor and pipes These designs of homemade bioreactors are popular among folk craftsmen who independently make biogas plants with their own hands for the home, allowing for repeated manual loading and unloading of the substrate. When making bioreactors with their own hands, many craftsmen experiment with completely sealed containers, using several rubber tubes from the tires of large vehicles as a gas holder.
Drawing of a gas holder made from tractor inner tubes In the video below, an enthusiast of homemade biogas production, using barrels filled with bird droppings as an example, proves the possibility of actually producing combustible gas at home by processing poultry house waste into useful fertilizer. The only thing that can be added to the design described in this video is that you need to install 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 for owners who have to remove manure every day, this theory is of no use, since thanks to their own practice they know the amount and mass of the future substrate. 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.
Table for obtaining the amount of manure from some animals with an approximate calculation of biogas yield After the calculations have been made and the design of the bioreactor has been approved, its construction can begin. The material can be a reinforced concrete container poured into the ground, or brickwork sealed with a special coating that is used to treat swimming pools.
It is also possible to build the main tank of a home biogas plant from iron coated with anti-corrosion material. Small industrial bioreactors are often made from large-volume, chemical-resistant plastic tanks.
Construction of a bioreactor from brickwork 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 stable and effective strains of methanogen bacteria are created, which can be purchased from companies involved in the production of biogas.
The graph shows that with the use of enzymes, the maximum biogas yield occurs twice as fast The need for pumping out and purifying biogas
Constant gas production 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 instability of the excess pressure in the bioreactor can lead to the disappearance of the flame with subsequent release poisonous gas. The use of such a primitive biogas installation connected to a stove is categorically unacceptable due to the possibility of poisoning by the toxic components of unpurified biogas.
The burner flame when burning biogas must be clean, even and stable. Therefore, almost any biogas installation scheme 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. A container for temporary storage of biogas can be made from inner tubes 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.
In some African countries, inflatable gas holders in the form of a pillow are used for storing and transporting biogas An improved bioreactor with a floating dome can be considered as an alternative to the mandatory use of a gas tank. The improvement consists of adding a concentric partition, which forms a water pocket, acting like a water seal and preventing the biomass from coming into contact with air. The pressure inside the floating dome will depend on its weight. By passing the gas through a cleaning system and a reducer, it can be used in a household stove, periodically venting it from the bioreactor.
Bioreactor with floating dome and water pocket Grinding and mixing the substrate in a bioreactor
Stirring the biomass is an important part of the biogas process, providing bacteria with access to nutrients that may have clumped together at the bottom of the digester. In order for biomass particles to mix better in the bioreactor, they must be crushed mechanically or manually before loading into the methane tank. Currently, in industrial and home-made biogas plants, three methods of mixing the substrate are used:
- mechanical stirrers, driven by an electric motor or manually;
- circulation mixing using a pump or propeller pumping the substrate inside the bioreactor;
- bubbling mixing using purging of liquid biomass with existing biogas. The disadvantage of this method is the formation of foam on the surface of the substrate.
The arrow indicates the mixing circulation screw in a homemade bioreactor Mechanical mixing of the substrate inside the bioreactor can be done 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 is equipped with a mechanical mixing device.
Substrate heating in mesophilic and thermophilic biogas plants
The optimum temperature for gas formation is the substrate temperature within 35-50ºC. To maintain this temperature, various heating systems– water, steam, electric. Temperature control should be carried out using a thermostat or thermocouples connected to an 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 the biomass inside will burn. A burnt substrate will reduce heat transfer and heating quality, 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.
Electric and water heating system for the bioreactor Heating the substrate in a bioreactor using heating elements will be beneficial only if alternative electricity is available, obtained from a wind generator or solar panels. In this case, heating elements can be connected directly to a generator or battery, which eliminates expensive voltage converters from the circuit. To reduce heat loss and reduce the cost of heating the substrate in a bioreactor, it is necessary to insulate it as much as possible using various insulation materials.
Insulation of the bioreactor with thermal insulation material Practical experiments inevitable when building biogas plants with your own hands
No matter how much literature a novice enthusiast of self-production of biogas reads, and no matter how many videos he watches, in practice he will have to learn a lot on his own, and the results, as a rule, will be far from the calculated ones.
Therefore, many beginning craftsmen follow the path of independent experiments in producing biogas, starting with small containers, determining how much gas their small experimental biogas plant produces from the available raw materials. Prices for components, methane output and future costs of building a full-fledged working biogas plant will determine its profitability and feasibility.
In the video above, the master demonstrates the capabilities of his biogas installation, measuring how much biogas is produced in one day. In his case, when eight atmospheres are pumped into the compressor receiver, the volume of the resulting gas after recalculation taking into account the volume of the 24 liter container will be about 0.2 m².
This volume of biogas obtained from a two-hundred-liter barrel is not significant, but, as shown in the following video of this master, this amount of gas is enough to burn one stove burner for an hour (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 producing biogas and biologically pure fertilizers by processing organic waste in a biogas plant. It must be borne in mind that the value of environmental fertilizers may exceed the cost of the resulting gas, and then biogas will become a useful by-product of the process of producing 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 growing popularity of alternative methods for producing heat and electricity has led to the desire of many owners of country houses and cottages to gain a certain autonomy from external energy suppliers. Moreover, “purchased” energy shows a constant tendency to increase prices, and the maintenance of a country farm is becoming more and more expensive every day. The biogas plant is an excellent alternative to external energy sources. At a minimum, it can provide the house with flammable gas for the stove, and when the power increases (if there is enough of your own or purchased waste), it can provide both heating and electricity for both the house and the entire household.
Who needs biogas plants
Biogas plants are used to produce combustible gases from biological raw materials. So they are needed wherever flammable gases are required. That is, to obtain thermal and electrical energy.
First of all, biogas plants are necessary for those farms where there is a lot of raw material in the form of biological waste. In this way, it is possible not only to make production waste-free, but also to significantly increase its profitability - due to independent energy production and the absence of costs for the purchase of both thermal and electrical energy.
Vladimir Rashin, a designer of a biogas plant and a farmer from Perm, has proven from his own experience that agricultural production, which independently disposes of waste using an appropriate device, fully meets its needs for thermal and electrical energy, as well as combustible gas. In his quail farm, biogas is used to heat premises (both residential, utility and industrial), to generate electricity, in kitchen stoves, and also to refuel vehicles - all cars on the Rashin farm run on biogas. In this case, the main raw material for the biogas plant is quail droppings. The output, in addition to biogas, also produces organic fertilizer, which also brings additional income to the farm.
Biogas plants like Vladimir Rashin's can significantly increase the profitability of any agricultural production. Not only manure, but also various waste from wood processing industries (bark, sawdust, etc.), and almost any organic substances can be used as a raw material for producing biogas.
In addition, biogas plants can be used in country houses and cottages, even if such farms do not have a farming focus. Household waste from any farm will be enough to provide raw materials for an individual biogas plant, and if the farm is not fully provided with thermal and electrical energy, then at least reduce the cost of purchasing such energy. In addition, in addition to household waste, any country farm also contains waste from the plot (weeds, branch cuttings, and so on). Well, you can even provide a kitchen stove with flammable gas using a mini-biogas installation in a country house.
Principle of biogas production
Biogas is produced by anaerobic (that is, without oxygen) fermentation of biomass, which is provided by special bacteria. Three types of bacteria are involved in the process: hydrolytic, acid-forming and methane-forming.
A biogas plant consists of several parts (containers). First, the raw material enters a preliminary container, where it is thoroughly mixed and crushed (in the case of the solid fraction) to a homogeneous mass. Then the crushed raw material enters the reactor (a container where the biomass is directly fermented).
The reactor is usually made of reinforced concrete, which is acid-resistant. This container is completely sealed. In order to speed up the fermentation process, the liquid in the container is heated and stirred. Most often, a cogeneration unit is used to heat the reactor - in such an installation it is necessary to cool the heat and power generator, and the removed heat enters the reactor. Heat can also come from a special hot water boiler.
After the fermentation process is completed, the produced gas from the reactor enters the gas holder, where the pressure is equalized, and then the biogas enters the heat and power generator (gas or diesel-gas), as a result of which thermal or electrical energy is produced.
In addition to biogas, a solid fraction—organic fertilizers—settles in the reactor, which can then be used in the fields. Liquid fertilizers are also obtained from the reactor after gas is released. Both liquid and solid fertilizers are concentrated and are actively used in agriculture.
Industrial biogas plants have automatic control. Automation is responsible for the flow of raw materials into the installation, and for mixing, controls the temperature, the operation of the generator, and so on. Also, such installations are equipped with emergency flare devices - in case the engine stops, then the gas is simply burned. In addition, industrial biogas plants are often equipped with a line for packaging liquid fertilizers; in this case, the fertilizers are bottled in small (up to 1 liter) bottles.
Individual biogas plant
The operating principle of an individual biogas plant is the same as that of an industrial one. True, mini-installations are rarely equipped with automatic devices for mixing the substrate and other automation - due to the significant increase in the cost of a household installation with such equipment. Most often, these installations only have devices for controlling temperature, generator operation, and so on, and all maintenance of the mini-biogas installation is carried out manually.
Household biogas plants are used mainly for the production of combustible gas for kitchen needs, if the farm does not have livestock or crop production. However, there is an increasing tendency to use mini-installations to provide country houses and cottages with a complete energy complex, that is, not only “kitchen” gas, but also thermal and electrical energy. Moreover, this no longer depends on the presence of large or small livestock on the farm; raw materials for home biogas plants are simply purchased from the nearest farm. This can be either manure or waste from wood processing industries.
DIY biogas plant
The construction of biogas plants, even mini ones, for domestic needs, is not cheap. And, although the payback period for such equipment is relatively short (5-7 years), not every owner is ready or has the opportunity to invest the required amount. Yes, the advantages are obvious: after a short time, with the help of a mini-biogas plant, you can gain almost complete autonomy from purchased energy sources, transfer your farm to self-sufficiency, and even have free fertilizers as additional bonuses. However, you need to pay money today, and the benefits will only appear in a few years. Therefore, many owners of country houses and cottages are wondering: how to make a biogas plant yourself?
A mini biogas plant is not that complicated, and its construction is quite manageable. This saves a significant amount. In addition, there are projects for biogas plants that use improvised means and materials (for example, with a bell reactor, and the bell can be made of rubber, and so on). That is, homemade installations for the production of biogas mean acquiring the desired bonuses for minimal money.
When building a biogas plant, it is necessary to make an accurate calculation of what its productivity should be. To do this, you should take into account all the desired consumers of biogas (for example, a cooker, automotive equipment, and so on). If biogas is planned to be used to produce electrical and/or thermal energy, then the calculation must include all energy consumers. Based on the calculation, a biogas plant project is created.
Homemade biogas production plants are widely available on the Internet. You can find sample calculations, a drawing of the device, and a detailed description. A huge selection of devices will allow you to create both a complex installation with several chambers and a simplified version (for example, such a simple device as a cesspool covered with a rubber bell with a device for venting gas). Anyone can choose a home-made installation in accordance with their desires, capabilities and skills. Descriptions accompanied by step-by-step photographs or videos are especially useful in this case.
Making a biogas plant with your own hands allows you to save up to 50% of the cost of the device, which significantly speeds up the payback of the equipment. In addition, making the simplest installation to begin with allows you to assess the need for such equipment in the household, as well as invest money gradually, which for many is much easier than paying the entire required amount at once.
How does a biogas plant work?
A thrifty owner dreams of cheap energy resources, efficient waste disposal and obtaining fertilizers. A DIY home biogas plant is an inexpensive way to make your dream come true.
Self-assembly of such equipment will cost a reasonable amount of money, and the gas produced will be a good help in the household: it can be used for cooking, heating the house and other needs.
Let's try to understand the specifics of this equipment, its advantages and disadvantages. And also whether it is possible to build a biogas plant yourself and whether it will be effective.
Biogas is formed as a result of fermentation of a biological substrate. It is decomposed by hydrolytic, acid- and methane-forming bacteria. The mixture of gases produced by bacteria is flammable, because contains a large percentage of methane.
Its properties are practically no different from natural gas, which is used for industrial and domestic needs.
If desired, every home owner can purchase an industrial-made biogas plant, but it is expensive, and the investment pays off within 7-10 years. Therefore, it makes sense to make an effort and make a bioreactor with your own hands
Biogas is an environmentally friendly fuel, and the technology for its production does not have much impact on the environment. Moreover, waste products that need to be disposed of are used as raw materials for biogas.
They are placed in a bioreactor, where processing occurs:
- the biomass is exposed to bacteria for some time. The fermentation period depends on the volume of raw materials;
- As a result of the activity of anaerobic bacteria, a flammable mixture of gases is released, which includes methane (60%), carbon dioxide (35%) and some other gases (5%). Fermentation also releases potentially dangerous hydrogen sulfide in small quantities. It is poisonous, so it is highly undesirable for people to be exposed to it;
- the mixture of gases from the bioreactor is purified and enters a gas tank, where it is stored until it is used for its intended purpose;
- gas from a gas tank can be used in the same way as natural gas. It goes to household appliances - gas stoves, heating boilers, etc.;
- Decomposed biomass must be regularly removed from the fermenter. This is additional labor, but the effort pays off. After fermentation, the raw material turns into high-quality fertilizer, which is used in fields and vegetable gardens.
A biogas plant is beneficial for the owner of a private house only if he has constant access to waste from livestock farms. On average, from 1 cubic meter. You can get 70-80 cubic meters of substrate. biogas, but gas production is uneven and depends on many factors, including biomass temperatures. This complicates calculations.
Many household owners are concerned about how to reduce costs for home heating, cooking and electricity supply. Some of them have already built biogas plants with their own hands and have partially or completely isolated themselves from energy suppliers. It turns out that getting almost free fuel in a private household is not very difficult.
What is biogas and how can it be used?
Owners of homestead farms know: by putting any plant material, bird droppings and manure in a heap, over time you can obtain valuable organic fertilizer. But few of them know that biomass does not decompose on its own, but under the influence of various bacteria.
By processing the biological substrate, these tiny microorganisms release waste products, including a gas mixture. Most of it (about 70%) is methane - the same gas that burns in the burners of household stoves and heating boilers.
The idea of using such eco-fuels for various economic needs is not new. Devices for its extraction were used in ancient China. Soviet innovators also explored the possibility of using biogas in the 60s of the last century. But the technology experienced a real revival in the early 2000s. Currently, biogas plants are actively used in Europe and the USA for heating homes and other needs.
How does a biogas plant work?
The operating principle of the biogas production device is quite simple:
- biomass diluted with water is loaded into a sealed container, where it begins to “ferment” and release gases;
- the contents of the tank are regularly updated - the raw materials processed by bacteria are drained and fresh ones are added (on average about 5-10% daily);
- The gas accumulated in the upper part of the tank is supplied through a special tube to the gas collector, and then to household appliances.
Diagram of a biogas plant.
What raw materials are suitable for bioreactor?
Installations for producing biogas are profitable only where there is a daily replenishment of fresh organic matter - manure or droppings of livestock and poultry. You can also mix chopped grass, tops, leaves and household waste (in particular, vegetable peelings) into the bioreactor.
The efficiency of the installation largely depends on the type of raw material being loaded. It has been proven that, with the same mass, the highest biogas yield is obtained from pig manure and turkey droppings. In turn, cow excrement and silage waste produce less gas for the same load.
Use of bio-raw materials for home heating.
What cannot be used in a biogas plant?
There are factors that can significantly reduce the activity of anaerobic bacteria, or even completely stop the process of biogas production. Raw materials containing:
- antibiotics;
- mold;
- synthetic detergents, solvents and other “chemicals”;
- resins (including sawdust from coniferous trees).
It is ineffective to use already rotting manure - only fresh or pre-dried waste can be loaded. Also, the raw materials should not be allowed to become waterlogged - an indicator of 95% is already considered critical. However, a small amount of clean water still needs to be added to the biomass in order to facilitate its loading and speed up the fermentation process. Manure and waste are diluted to the consistency of thin semolina porridge.
Biogas plant for home
Today, industry is already producing installations for producing biogas on an industrial scale. Their acquisition and installation is expensive; such equipment in private households pays for itself no sooner than in 7-10 years, provided that large volumes of organic matter are used for processing. Experience shows that, if desired, a skilled owner can build a small biogas plant for a private home with his own hands, and from the most affordable materials.
Preparing the processing bunker
First of all, you will need a hermetically sealed cylindrical container. You can, of course, use large pots or boils, but their small volume will not allow achieving sufficient gas production. Therefore, for these purposes, plastic barrels with a volume of 1 m³ to 10 m³ are most often used.
You can make one yourself. PVC sheets are commercially available; with sufficient strength and resistance to aggressive environments, they can be easily welded into the structure of the desired configuration. A metal barrel of sufficient volume can also be used as a bunker. True, you will have to carry out anti-corrosion measures - cover it inside and outside with moisture-resistant paint. If the tank is made of stainless steel, this is not necessary.
Gas exhaust system
The gas outlet pipe is mounted in the upper part of the barrel (usually in the lid) - this is where it accumulates, according to the laws of physics. Through a connected pipe, biogas is supplied to the water seal, then to the storage tank (optionally, using a compressor into a cylinder) and to household appliances. It is also recommended to install a release valve next to the gas outlet - if the pressure inside the tank becomes too high, it will release excess gas.
Raw material supply and unloading system
To ensure continuous production of the gas mixture, the bacteria in the substrate must be constantly (daily) “fed”, that is, fresh manure or other organic matter must be added. In turn, already processed raw materials from the bunker must be removed so that they do not take up useful space in the bioreactor.
To do this, two holes are made in the barrel - one (for unloading) almost near the bottom, the other (for loading) higher. Pipes with a diameter of at least 300 mm are welded (soldered, glued) into them. The loading pipeline is directed upward and equipped with a funnel, and the drain is arranged so that it is convenient to collect the processed slurry (it can later be used as fertilizer). The joints are sealed.
Heating system
Thermal insulation of the bunker.
If the bioreactor is installed outdoors or in an unheated room (which is necessary for safety reasons), then it must be provided with thermal insulation and heating of the substrate. The first condition is achieved by “wrapping” the barrel with any insulating material or by deepening it into the ground.
As for heating, you can consider a variety of options. Some craftsmen install pipes inside through which water from the heating system circulates and install them along the walls of the barrel in the form of a coil. Others place the reactor in a larger tank with water inside, heated by electric heaters. The first option is more convenient and much more economical.
To optimize the operation of the reactor, it is necessary to maintain the temperature of its contents at a certain level (at least 38⁰C). But if it rises above 55⁰C, then the gas-forming bacteria will simply “cook” and the fermentation process will stop.
Mixing system
As practice shows, in designs, a manual stirrer of any configuration significantly increases the efficiency of the bioreactor. The axis to which the “mixer” blades are welded (screwed) is removed through the barrel lid. The gate handle is then placed on it, and the hole is carefully sealed. However, home craftsmen do not always equip fermenters with such devices.
Biogas production
After the installation is ready, biomass diluted with water in a ratio of approximately 2:3 is loaded into it. Large waste must be crushed - the maximum fraction size should not exceed 10 mm. Then the lid is closed - all you have to do is wait for the mixture to begin to “ferment” and release biogas. Under optimal conditions, the first supply of fuel is observed several days after loading.
The fact that the gas has “started” can be judged by the characteristic gurgling sound in the water seal. At the same time, the barrel should be checked for leaks. This is done using a regular soap solution - it is applied to all joints and observed to see if bubbles appear.
The first update of bio-raw materials should be carried out in about two weeks. After the biomass is poured into the funnel, the same volume of waste organic matter will pour out of the outlet pipe. Then this procedure is performed daily or every two days.
How long does the resulting biogas last?
In a small farm, a biogas plant will not be an absolute alternative to natural gas and other available energy sources. For example, using a device with a capacity of 1 m³, you can only get fuel for a couple of hours of cooking for a small family.
But with a 5 m³ bioreactor it is already possible to heat a room with an area of 50 m², but its operation will need to be maintained by daily loading of raw materials weighing at least 300 kg. To do this, you need to have about ten pigs, five cows and a couple of dozen chickens on the farm.
Craftsmen who have managed to independently make working biogas plants share videos with master classes on the Internet:
