home Heating radiators Bioreactor at home. Biogas plant for a private home: we extract energy resources with our own hands

Bioreactor at home. Biogas plant for a private home: we extract energy resources with our own hands

Biogas is produced in special, corrosion-resistant cylindrical sealed tanks, also called fermenters. The fermentation process takes place in such containers. But before entering the fermenter, the raw materials are loaded into a receiver container. Here it is mixed with water until smooth, using a special pump. Next, the prepared raw material is introduced into the fermenters from the receiver tank. It should be noted that the mixing process does not stop and continues until there is nothing left in the receiver container. After it is empty, the pump stops automatically. After the fermentation process begins, biogas begins to be released, which flows through special pipes into a gas holder located nearby.

Figure 5. Generalized diagram of a biogas plant

Figure 6 shows a diagram of the installation for producing biogas. Organic waste, usually liquid manure, enters receiver-heat exchanger 1, where it is heated by heated sludge supplied through a heat exchanger pipe by pump 9 from digester 3, and diluted with hot water.

Figure 6. Installation diagram for biogas production

Additional dilution of wastewater with hot water and heating to the required temperature is carried out in apparatus 2. Field waste is also supplied here to create the required C/N ratio. The biogas generated in the digester 3 is partially burned in the water heater 4, and the combustion products are discharged through the pipe 5. The rest of the biogas passes through the cleaning device 6, is compressed by the compressor 7 and enters the gas tank 8. The sludge from the apparatus 1 enters the heat exchanger 10, where additionally cooling, it heats up cold water. Sludge is a disinfected, highly effective natural fertilizer that can replace 3-4 tons of mineral fertilizer such as nitrophoska.

2.2 Biogas storage systems

Typically, biogas comes out of the reactors unevenly and with low pressure (no more than 5 kPa). This pressure, taking into account the hydraulic losses of the gas transmission network, is not enough for the normal operation of gas-using equipment. In addition, the peaks of biogas production and consumption do not coincide in time. The simplest solution for eliminating excess biogas is to burn it in a flare, but this results in irreversible loss of energy. A more expensive, but ultimately economically justified way to level out the unevenness of gas production and consumption is the use of gas holders of various types. Conventionally, all gas tanks can be divided into “direct” and “indirect”. “Direct” gas tanks constantly contain a certain volume of gas, injected during periods of decline in consumption and withdrawn at peak load. “Indirect” gas tanks provide for the accumulation not of the gas itself, but of the energy of an intermediate coolant (water or air), heated by the combustion products of the burned gas, i.e. thermal energy is accumulated in the form of a heated coolant.

Biogas, depending on its quantity and the direction of subsequent use, can be stored under different pressures; accordingly, gas storage facilities are called gas holders of low (not higher than 5 kPa), medium (from 5 kPa to 0.3 MPa) and high (from 0.3 to 1. 8 MPa) pressure. Low-pressure gas tanks are designed to store gas at a slightly fluctuating gas pressure and a significantly varying volume, therefore they are sometimes called gas storage facilities of constant pressure and variable volume (provided by the mobility of the structures). Gas tanks of medium and high pressure, on the contrary, are arranged according to the principle of constant volume, but changing pressure. In the practice of using biogas plants, low-pressure gas tanks are most often used.

The capacity of high-pressure gas tanks can vary from several liters (cylinders) to tens of thousands of cubic meters (stationary gas storage facilities). Storage of biogas in cylinders is used, as a rule, in the case of using gas as fuel for vehicles. The main advantages of high and medium pressure gas holders are their small dimensions with significant volumes of stored gas and the absence of moving parts, but the disadvantage is the need for additional equipment: a compressor unit to create medium or high pressure and a pressure regulator to reduce the gas pressure in front of the burner devices of gas-using units.

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 supplied to 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.

One of the problems that has to be solved in agriculture is the disposal of manure and plant waste. And this is a rather serious problem that requires constant attention. Recycling takes not only time and effort, but also considerable amounts. Today there is at least one way to turn this headache into an income source: processing manure into biogas. The technology is based on the natural process of decomposition of manure and plant residues due to the bacteria they contain. The whole task is to create special conditions for the most complete decomposition. These conditions are the absence of oxygen access and optimal temperature (40-50 o C).

Everyone knows how manure is most often disposed of: they put it in heaps, then, after fermentation, they take it out to the fields. In this case, the resulting gas is released into the atmosphere, and 40% of the nitrogen contained in the initial substance and most of the phosphorus also escape there. The resulting fertilizer is far from ideal.

To obtain biogas, it is necessary that the process of decomposition of manure takes place without access to oxygen, in a closed volume. In this case, both nitrogen and phosphorus remain in the residual product, and the gas accumulates in the upper part of the container, from where it can be easily pumped out. There are two sources of profit: gas directly and effective fertilizer. Moreover, the fertilizer is of the highest quality and 99% safe: most of the pathogenic microorganisms and helminth eggs die, and the weed seeds contained in the manure lose their viability. There are even lines for packaging this residue.

The second prerequisite for the process of processing manure into biogas is maintaining an optimal temperature. The bacteria contained in the biomass are inactive at low temperatures. They begin to act at an ambient temperature of +30 o C. Moreover, manure contains two types of bacteria:

Thermophilic plants with temperatures from +43 o C to +52 o C are the most effective: in them, manure is processed for 3 days, and the output from 1 liter of useful bioreactor area is up to 4.5 liters of biogas (this is the maximum output). But maintaining a temperature of +50 o C requires significant energy expenditure, which is not profitable in every climate. Therefore, biogas plants often operate at mesophilic temperatures. In this case, the processing time can be 12-30 days, the yield is approximately 2 liters of biogas per 1 liter of bioreactor volume.

The composition of the gas varies depending on the raw materials and processing conditions, but it is approximately as follows: methane - 50-70%, carbon dioxide - 30-50%, and also contains a small amount of hydrogen sulfide (less than 1%) and very small amounts of ammonia, hydrogen and nitrogen compounds. Depending on the design of the plant, biogas may contain a significant amount of water vapor, which will require drying (otherwise it simply will not burn). What an industrial installation looks like is demonstrated in the video.

This can be said to be an entire gas production plant. But for a private farmstead or small farm such volumes are useless. The simplest biogas plant is easy to make with your own hands. But the question is: “Where should the biogas be sent next?” The heat of combustion of the resulting gas is from 5340 kcal/m3 to 6230 kcal/m3 (6.21 - 7.24 kWh/m3). Therefore, it can be supplied to a gas boiler to generate heat (heating and hot water), or to an electricity generation installation, to a gas stove, etc. This is how Vladimir Rashin, a biogas plant designer, uses manure from his quail farm.

It turns out that if you have at least a decent amount of livestock and poultry, you can fully meet your farm’s needs for heat, gas and electricity. And if you install gas installations on cars, then it will also provide fuel for the fleet. Considering that the share of energy resources in the cost of production is 70-80%, you can only save on a bioreactor, and then earn a lot of money. Below is a screenshot of an economic calculation of the profitability of a biogas plant for a small farm (as of September 2014). The farm cannot be called small, but it is definitely not large either. We apologize for the terminology - this is the author's style.

This is an approximate breakdown of the required costs and possible income Schemes for homemade biogas plants

Schemes of homemade biogas plants

The simplest scheme of a biogas plant is a sealed container - a bioreactor, into which the prepared slurry is poured. Accordingly, there is a hatch for loading manure and a hatch for unloading processed raw materials.

The simplest scheme of a biogas plant without any bells and whistles

The container is not completely filled with the substrate: 10-15% of the volume should remain free to collect gas. A gas outlet pipe is built into the tank lid. Since the resulting gas contains a fairly large amount of water vapor, it will not burn in this form. Therefore, it is necessary to pass it through a water seal to dry it. In this simple device, most of the water vapor will condense, and the gas will burn well. Then it is advisable to clean the gas from non-flammable hydrogen sulfide and only then can it be supplied to a gas holder - a container for collecting gas. And from there it can be distributed to consumers: fed to a boiler or gas oven. Watch the video to see how to make filters for a biogas plant with your own hands.

Large industrial installations are placed on the surface. And this, in principle, is understandable - the volume of land work is too large. But on small farms the bunker bowl is buried in the ground. This, firstly, allows you to reduce the cost of maintaining the required temperature, and secondly, in a private backyard there are already enough all kinds of devices.

The container can be taken ready-made, or made from brick, concrete, etc. in a dug pit. But in this case, you will have to take care of the tightness and impermeability of air: the process is anaerobic - without air access, therefore it is necessary to create a layer impenetrable to oxygen. The structure turns out to be multi-layered and the production of such a bunker is a long and expensive process. Therefore, it is cheaper and easier to bury a ready-made container. Previously, these were necessarily metal barrels, often made of stainless steel. Today, with the advent of PVC containers on the market, you can use them. They are chemically neutral, have low thermal conductivity, a long service life, and are several times cheaper than stainless steel.

But the biogas plant described above will have low productivity. To activate the processing process, active mixing of the mass located in the hopper is necessary. Otherwise, a crust forms on the surface or in the thickness of the substrate, which slows down the decomposition process, and less gas is produced at the outlet. Mixing is carried out in any available way. For example, as demonstrated in the video. In this case, any drive can be made.

There is another way to mix the layers, but it is non-mechanical - barbitation: the generated gas is fed under pressure into the lower part of the container with manure. Rising upward, gas bubbles will break the crust. Since the same biogas is supplied, there will be no changes in processing conditions. Also, this gas cannot be considered a consumption - it will again end up in the gas tank.

As mentioned above, good performance requires elevated temperatures. In order not to spend too much money on maintaining this temperature, you need to take care of insulation. What type of heat insulator to choose, of course, is up to you, but today the most optimal one is polystyrene foam. It is not afraid of water, is not affected by fungi and rodents, has a long service life and excellent thermal insulation performance.

The shape of the bioreactor can be different, but the most common is cylindrical. It is not ideal from the point of view of the complexity of mixing the substrate, but it is used more often because people have accumulated a lot of experience in building such containers. And if such a cylinder is divided by a partition, then they can be used as two separate tanks in which the process is shifted in time. In this case, a heating element can be built into the partition, thus solving the problem of maintaining temperature in two chambers at once.

In the simplest version, homemade biogas plants are a rectangular pit, the walls of which are made of concrete, and for tightness they are treated with a layer of fiberglass and polyester resin. This container is equipped with a lid. It is extremely inconvenient to use: heating, mixing and removal of the fermented mass is difficult to implement, and it is impossible to achieve complete processing and high efficiency.

The situation is a little better with trench biogas manure processing plants. They have beveled edges, making it easier to load fresh manure. If you make the bottom at a slope, then the fermented mass will shift to one side by gravity and it will be easier to select it. In such installations, it is necessary to provide thermal insulation not only for the walls, but also for the lid. It is not difficult to implement such a biogas plant with your own hands. But complete processing and the maximum amount of gas cannot be achieved in it. Even with heating.

The basic technical issues have been dealt with, and you now know several ways to build a plant for producing biogas from manure. There are still technological nuances.

What can be recycled and how to achieve good results

The manure of any animal contains the organisms necessary for its processing. It has been discovered that more than a thousand different microorganisms are involved in the fermentation process and gas production. Methane-forming substances play the most important role. It is also believed that all these microorganisms are found in optimal proportions in cattle manure. In any case, when processing this type of waste in combination with plant matter, the largest amount of biogas is released. The table shows average data for the most common types of agricultural waste. Please note that this amount of gas output can be obtained under ideal conditions.

For good productivity it is necessary to maintain a certain substrate humidity: 85-90%. But water must be used that does not contain foreign chemicals. Solvents, antibiotics, detergents, etc. have a negative effect on processes. Also, for the process to proceed normally, the liquid should not contain large fragments. Maximum fragment sizes: 1*2 cm, smaller ones are better. Therefore, if you plan to add herbal ingredients, you need to grind them.

It is important for normal processing in the substrate to maintain an optimal pH level: within 6.7-7.6. Usually the environment has normal acidity, and only occasionally acid-forming bacteria develop faster than methane-forming bacteria. Then the environment becomes acidic, gas production decreases. To achieve the optimal value, add regular lime or soda to the substrate.

Now a little about the time it takes to process manure. In general, the time depends on the conditions created, but the first gas can begin to flow already on the third day after the start of fermentation. The most active gas formation occurs when manure decomposes by 30-33%. To give you a sense of time, let’s say that after two weeks the substrate decomposes by 20-25%. That is, optimally the processing should last a month. In this case, the fertilizer is of the highest quality.

Calculation of bin volume for processing

For small farms, the optimal installation is a constant one - this is when fresh manure is supplied in small portions daily and removed in the same portions. In order for the process not to be disrupted, the share of the daily load should not exceed 5% of the processed volume.

Homemade installations for processing manure into biogas are not the pinnacle of perfection, but are quite effective

Based on this, you can easily determine the required tank volume for a homemade biogas plant. You need to multiply the daily volume of manure from your farm (already in a diluted state with a humidity of 85-90%) by 20 (this is for mesophilic temperatures, for thermophilic temperatures you will have to multiply by 30). To the resulting figure you need to add another 15-20% - free space for collecting biogas under the dome. You know the main parameter. All further costs and system parameters depend on which biogas plant scheme is chosen for implementation and how you will do everything. It is quite possible to make do with improvised materials, or you can order a turnkey installation. Factory developments will cost from 1.5 million euros, installations from the Kulibins will be cheaper.

Legal registration

The installation will have to be coordinated with the SES, gas inspectorate and firefighters. You will need:

Technological diagram of the installation.
Layout plan for equipment and components with reference to the installation itself, the installation location of the thermal unit, the location of pipelines and energy mains, and pump connections. The diagram should indicate the lightning rod and access roads.
If the installation will be located indoors, then a ventilation plan will also be required, which will provide at least an eightfold exchange of all the air in the room.

As we see, we cannot do without bureaucracy here.

Finally, a little about the performance of the installation. On average, per day a biogas plant produces a volume of gas twice the useful volume of the reservoir. That is, 40 m 3 of slurry will produce 80 m 3 of gas per day. Approximately 30% will be spent on ensuring the process itself (the main expense item is heating). Those. at the output you will receive 56 m 3 of biogas per day. According to statistics, to cover the needs of a family of three and to heat an average-sized house, 10 m 3 is required. In net balance you have 46 m3 per day. And this is with a small installation.

Results

By investing a certain amount of money in setting up a biogas plant (with your own hands or on a turnkey basis), you will not only meet your own needs and needs for heat and gas, but will also be able to sell gas, as well as high-quality fertilizers resulting from processing.

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

Biogas is a gas obtained as a result of fermentation (fermentation) of organic substances (for example: straw; weeds; animal and human feces; garbage; organic waste from domestic and industrial wastewater, etc.) under anaerobic conditions. Biogas production involves different types of microorganisms with a varied number of catabolic functions.

Composition of biogas.

More than half of biogas consists of methane (CH 4). Methane makes up approximately 60% of biogas. In addition, biogas contains carbon dioxide (CO 2) about 35%, as well as other gases such as water vapor, hydrogen sulfide, carbon monoxide, nitrogen and others. Biogas obtained under different conditions varies in its composition. Thus, biogas from human excrement, manure, and slaughter waste contains up to 70% methane, and from plant residues, as a rule, about 55% methane.

Microbiology of biogas.

Biogas fermentation, depending on the microbial species of bacteria involved, can be divided into three stages:

The first is called the beginning of bacterial fermentation. Various organic bacteria, when multiplying, secrete extracellular enzymes, the main role of which is to destroy complex organic compounds with the hydrolytic formation of simple substances. For example, polysaccharides to monosaccharides; protein into peptides or amino acids; fats into glycerol and fatty acids.

The second stage is called hydrogen. Hydrogen is produced as a result of the activity of acetic acid bacteria. Their main role is the bacterial decomposition of acetic acid to produce carbon dioxide and hydrogen.

The third stage is called methanogenic. It involves a type of bacteria known as methanogens. Their role is to use acetic acid, hydrogen and carbon dioxide to produce methane.

Classification and characteristics of raw materials for biogas fermentation.

Almost all natural organic materials can be used as feedstock for biogas fermentation. The main raw materials for biogas production are wastewater: sewage; food, pharmaceutical and chemical industries. In rural areas, this is waste generated during harvesting. Due to differences in origin, the formation process, chemical composition and structure of biogas are also different.

Sources of raw materials for biogas depending on origin:

1. Agricultural raw materials.

These raw materials can be divided into raw materials with a high nitrogen content and raw materials with a high carbon content.

Raw materials with high nitrogen content:

human feces, livestock manure, bird droppings. The carbon-nitrogen ratio is 25:1 or less. Such raw food has been completely digested by the gastrointestinal tract of a person or animal. As a rule, it contains a large number of low molecular weight compounds. The water in such raw materials was partially transformed and became part of low molecular weight compounds. This raw material is characterized by easy and rapid anaerobic decomposition into biogas. And also a rich methane output.

Raw materials with high carbon content:

straw and husk. The carbon-nitrogen ratio is 40:1. It has a high content of high-molecular compounds: cellulose, hemicellulose, pectin, lignin, vegetable waxes. Anaerobic decomposition occurs quite slowly. In order to increase the rate of gas production, such materials usually require pre-treatment before fermentation.

2. Urban organic water waste.

Includes human waste, sewage, organic waste, organic industrial wastewater, sludge.

3. Aquatic plants.

Includes water hyacinth, other aquatic plants and algae. The estimated planned capacity utilization of production capacities is characterized by a high dependence on solar energy. They have high profitability. Technological organization requires a more careful approach. Anaerobic decomposition occurs easily. The methane cycle is short. The peculiarity of such raw materials is that without pre-treatment it floats in the reactor. In order to eliminate this, the raw materials must be slightly dried or pre-composted for 2 days.

Sources of raw materials for biogas depending on humidity:

1.Solid raw materials:

straw, organic waste with a relatively high dry matter content. They are processed using the dry fermentation method. Difficulties arise with removing large amounts of solid deposits from the rector. The total amount of raw materials used can be expressed as the sum of the solids content (TS) and volatile substances (VS). Volatiles can be converted to methane. To calculate volatile substances, a sample of raw materials is loaded into a muffle furnace at a temperature of 530-570°C.

2. Liquid raw materials:

fresh feces, manure, droppings. Contains about 20% dry matter. Additionally, they require the addition of water in an amount of 10% for mixing with solid raw materials during dry fermentation.

3. Organic waste of medium humidity:

stillage from alcohol production, wastewater from pulp mills, etc. Such raw materials contain varying amounts of proteins, fats and carbohydrates, and are good raw materials for the production of biogas. For this raw material, devices of the UASB type (Upflow Anaerobic Sludge Blanket - upward anaerobic process) are used.

Table 1. Information on the flow rate (rate of formation) of biogas for the conditions: 1) fermentation temperature 30°C; 2) batch fermentation

Name of fermented waste	Average biogas flow rate during normal gas production (m 3 /m 3 /d)	Biogas output, m 3 /Kg/TS	Biogas production (% of total biogas production)
Name of fermented waste		Biogas output, m 3 /Kg/TS	0-15 d	25-45 d	45-75 d	75-135 d
Dry manure	0,20	0,12	11	33,8	20,9	34,3
Chemical industry water	0,40	0,16	83	17	0	0
Rogulnik (chilim, water chestnut)	0,38	0,20	23	45	32	0
Water salad	0,40	0,20	23	62	15	0
Pig manure	0,30	0,22	20	31,8	26	22,2
Dry grass	0,20	0,21	13	11	43	33
Straw	0,35	0,23	9	50	16	25
Human excrement	0,53	0,31	45	22	27,3	5,7

Calculation of the process of methane fermentation.

The general principles of fermentation engineering calculations are based on increasing the loading of organic raw materials and reducing the duration of the methane cycle.

Calculation of raw materials per cycle.

The loading of raw materials is characterized by: Mass fraction TS (%), mass fraction VS (%), concentration COD (COD - chemical oxygen demand, which means COD - chemical indicator of oxygen) (Kg/m 3). The concentration depends on the type of fermentation devices. For example, modern industrial wastewater reactors are UASB (upstream anaerobic process). For solid raw materials, AF (anaerobic filters) are used - usually the concentration is less than 1%. Industrial waste as a raw material for biogas most often has a high concentration and needs to be diluted.

Download speed calculation.

To determine the daily reactor loading amount: concentration COD (Kg/m 3 ·d), TS (Kg/m 3 ·d), VS (Kg/m 3 ·d). These indicators are important indicators for assessing the efficiency of biogas. It is necessary to strive to limit the load and at the same time have a high level of gas production volume.

Calculation of the ratio of reactor volume to gas output.

This indicator is an important indicator for assessing the efficiency of the reactor. Measured in Kg/m 3 ·d.

Biogas yield per unit mass of fermentation.

This indicator characterizes the current state of biogas production. For example, the volume of the gas collector is 3 m 3. 10 Kg/TS is supplied daily. The biogas yield is 3/10 = 0.3 (m 3 /Kg/TS). Depending on the situation, you can use the theoretical gas output or the actual gas output.

The theoretical yield of biogas is determined by the formulas:

Methane production (E):

E = 0.37A + 0.49B + 1.04C.

Carbon dioxide production (D):

D = 0.37A + 0.49B + 0.36C. Where A is carbohydrate content per gram of fermentation material, B is protein, C is fat content

Hydraulic volume.

To increase efficiency, it is necessary to reduce the fermentation period. To a certain extent there is a connection with the loss of fermenting microorganisms. Currently, some efficient reactors have fermentation times of 12 days or even less. The hydraulic volume is calculated by calculating the volume of daily feedstock loading from the day the feedstock loading began and depends on the residence time in the reactor. For example, fermentation is planned at 35°C, feed concentration is 8% (total amount of TS), daily feed volume is 50 m 3, fermentation period in the reactor is 20 days. The hydraulic volume will be: 50·20 = 100 m3.

Removal of organic contaminants.

Biogas production, like any biochemical production, has waste. Biochemical production waste can cause environmental damage in cases of uncontrolled waste disposal. For example, falling into the river next door. Modern large biogas plants produce thousands and even tens of thousands of kilograms of waste per day. The qualitative composition and methods of disposal of waste from large biogas plants are controlled by enterprise laboratories and the state environmental service. Small farm biogas plants do not have such controls for two reasons: 1) since there is little waste, there will be little harm to the environment. 2) Carrying out high-quality analysis of waste requires specific laboratory equipment and highly specialized personnel. Small farmers do not have this, and government agencies rightly consider such control to be inappropriate.

An indicator of the level of contamination of biogas reactor waste is COD (chemical indicator of oxygen).

The following mathematical relationship is used: COD of organic loading rate Kg/m 3 ·d= loading concentration of COD (Kg/m 3) / hydraulic shelf life (d).

Gas flow rate in the reactor volume (kg/(m 3 ·d)) = biogas yield (m 3 /kg) / COD of organic loading rate kg/(m 3 ·d).

Advantages of biogas energy plants:

solid and liquid waste have a specific odor that repels flies and rodents;

the ability to produce a useful end product - methane, which is a clean and convenient fuel;

during the fermentation process, weed seeds and some of the pathogens die;

during the fermentation process, nitrogen, phosphorus, potassium and other fertilizer ingredients are almost completely preserved, part of the organic nitrogen is converted into ammonia nitrogen, and this increases its value;

the fermentation residue can be used as animal feed;

biogas fermentation does not require the use of oxygen from the air;

anaerobic sludge can be stored for several months without adding nutrients, and then when virgin feed is added, fermentation can quickly begin again.

Disadvantages of biogas energy plants:

complex device and requires relatively large investments in construction;

requires a high level of construction, management and maintenance;

The initial anaerobic propagation of fermentation occurs slowly.

Features of the methane fermentation process and process control:

1. Temperature of biogas production.

The temperature for biogas production can be in a relatively wide temperature range of 4~65°C. With increasing temperature, the rate of biogas production increases, but not linearly. Temperature 40~55°C is a transition zone for the life activity of various microorganisms: thermophilic and mesophilic bacteria. The highest rate of anaerobic fermentation occurs in a narrow temperature range of 50~55°C. At a fermentation temperature of 10°C, the gas flow rate is 59% in 90 days, but the same flow rate at a fermentation temperature of 30°C occurs in 27 days.

A sudden change in temperature will have a significant impact on biogas production. The design of a biogas plant must necessarily provide for control of such a parameter as temperature. Temperature changes of more than 5°C significantly reduce the productivity of the biogas reactor. For example, if the temperature in a biogas reactor was 35°C for a long time, and then suddenly dropped to 20°C, then the production of the biogas reactor will almost completely stop.

2. Grafting material.

Methane fermentation typically requires a specific number and type of microorganisms to complete. The sediment rich in methane microbes is called inoculum. Biogas fermentation is widespread in nature and places with grafting material are just as widespread. These are: sewer sludge, silt deposits, bottom sediments of manure pits, various sewage sludges, digestive residues, etc. Due to the abundant organic matter and good anaerobic conditions, they develop rich microbial communities.

Inoculum added for the first time to a new biogas reactor can significantly reduce the stagnation period. In the new biogas reactor, it is necessary to manually fertilize with grafting material. When using industrial waste as raw materials, special attention is paid to this.

3. Anaerobic environment.

The anaerobicity of the environment is determined by the degree of anaerobicity. Typically, the redox potential is usually denoted by the value Eh. Under anaerobic conditions, Eh has a negative value. For anaerobic methane bacteria, Eh lies in the range of -300 ~ -350mV. Some bacteria that produce facultative acids are able to live a normal life at Eh -100 ~ + 100 mV.

In order to ensure anaerobic conditions, it is necessary to ensure that biogas reactors are built tightly closed, ensuring that they are watertight and leak-free. For large industrial biogas reactors, the Eh value is always controlled. For small farm biogas reactors, the problem of controlling this value arises due to the need to purchase expensive and complex equipment.

4. Control of the acidity of the medium (pH) in the biogas reactor.

Methanogens require a pH range within a very narrow range. On average pH=7. Fermentation occurs in the pH range from 6.8 to 7.5. pH control is available for small biogas reactors. To do this, many farmers use disposable litmus indicator paper strips. Large plants often use electronic pH monitoring devices. Under normal circumstances, the balance of methane fermentation is a natural process, usually without pH adjustment. Only in isolated cases of mismanagement do massive accumulations of volatile acids and a decrease in pH appear.

Measures to mitigate the effects of high acidity pH include:

(1) Partially replace the medium in the biogas reactor, thereby diluting the volatile acid content. This will increase the pH.

(2) Add ash or ammonia to increase pH.

(3) Adjust pH with lime. This measure is especially effective in cases of extremely high acid contents.

5. Mixing the medium in the biogas reactor.

In a typical fermentation tank, the fermentation medium is usually divided into four layers: top crust, supernatant layer, active layer and sediment layer.

Purpose of mixing:

1) relocation of active bacteria to a new portion of primary raw materials, increasing the contact surface of microbes and raw materials to accelerate the rate of biogas production, increasing the efficiency of use of raw materials.

2) avoiding the formation of a thick layer of crust, which creates resistance to the release of biogas. Raw materials such as straw, weeds, leaves, etc. are especially demanding for mixing. In a thick layer of crust, conditions are created for the accumulation of acid, which is unacceptable.

Mixing methods:

1) mechanical mixing with wheels of various types installed inside the working space of the biogas reactor.

2) mixing with biogas taken from the upper part of the bioreactor and supplied to the lower part with excess pressure.

3) mixing with a circulating hydraulic pump.

6. Carbon to nitrogen ratio.

Only an optimal ratio of nutrients contributes to effective fermentation. The main indicator is the carbon to nitrogen ratio (C:N). The optimal ratio is 25:1. Numerous studies have proven that the limits of the optimal ratio are 20-30:1, and biogas production is significantly reduced at a ratio of 35:1. Experimental studies have revealed that biogas fermentation is possible with a carbon to nitrogen ratio of 6:1.

7. Pressure.

Methane bacteria can adapt to high hydrostatic pressures (about 40 meters or more). But they are very sensitive to changes in pressure and because of this there is a need for stable pressure (no sudden changes in pressure). Significant changes in pressure can occur in cases of: a significant increase in biogas consumption, relatively fast and large loading of the bioreactor with primary raw materials, or similar unloading of the reactor from sediments (cleaning).

Ways to stabilize pressure:

2) supply fresh primary raw materials and cleaning simultaneously and at the same discharge rate;

3) installing floating covers on a biogas reactor allows you to maintain a relatively stable pressure.

8. Activators and inhibitors.

Some substances, when added in small quantities, improve the performance of a biogas reactor, such substances are known as activators. While other substances added in small quantities lead to significant inhibition of the processes in the biogas reactor, such substances are called inhibitors.

Many types of activators are known, including some enzymes, inorganic salts, organic and inorganic substances. For example, adding a certain amount of the enzyme cellulase greatly facilitates the production of biogas. The addition of 5 mg/Kg of higher oxides (R 2 O 5) can increase gas production by 17%. The biogas yield for primary raw materials from straw and the like can be significantly increased by adding ammonium bicarbonate (NH 4 HCO 3). Activators are also activated carbon or peat. Feeding a bioreactor with hydrogen can dramatically increase methane production.

Inhibitors mainly refer to some of the compounds of metal ions, salts, fungicides.

Classification of fermentation processes.

Methane fermentation is a strictly anaerobic fermentation. Fermentation processes are divided into the following types:

Classification according to fermentation temperature.

Can be divided into "natural" fermentation temperatures (variable temperature fermentation), in which case the fermentation temperature is about 35°C and the high temperature fermentation process (about 53°C).

Classification by differentialness.

According to the differential nature of fermentation, it can be divided into single-stage fermentation, two-stage fermentation and multi-stage fermentation.

1) Single-stage fermentation.

Refers to the most common type of fermentation. This applies to devices in which acids and methane are simultaneously produced. Single-stage fermentations may be less efficient in terms of BOD (Biological Oxygen Demand) than two- and multi-stage fermentations.

2) Two-stage fermentation.

Based on separate fermentation of acids and methanogenic microorganisms. These two types of microbes have different physiology and nutritional requirements, and there are significant differences in growth, metabolic characteristics and other aspects. Two-stage fermentation can greatly improve the biogas yield and decomposition of volatile fatty acids, shorten the fermentation cycle, bring significant savings in operating costs, and effectively remove organic contaminants from waste.

3) Multi-stage fermentation.

It is used for primary raw materials rich in cellulose in the following sequence:

(1) The cellulose material is hydrolyzed in the presence of acids and alkalis. Glucose is formed.

(2) The grafting material is introduced. This is usually active sludge or wastewater from a biogas reactor.

(3) Create suitable conditions for the production of acidic bacteria (producing volatile acids): pH=5.7 (but not more than 6.0), Eh=-240mV, temperature 22°C. At this stage, the following volatile acids are formed: acetic, propionic, butyric, isobutyric.

(4) Create suitable conditions for the production of methane bacteria: pH=7.4-7.5, Eh=-330mV, temperature 36-37°C

Classification by periodicity.

Fermentation technology is classified into batch fermentation, continuous fermentation, semi-continuous fermentation.

1) Batch fermentation.

Raw materials and grafting material are loaded into the biogas reactor once and subjected to fermentation. This method is used when there are difficulties and inconveniences in loading primary raw materials, as well as unloading waste. For example, not chopped straw or large briquettes of organic waste.

2) Continuous fermentation.

This includes cases when raw materials are routinely loaded into the biorector several times a day and fermentation waste is removed.

3) Semi-continuous fermentation.

This applies to biogas reactors, for which it is normal to add different primary raw materials from time to time in unequal amounts. This technological scheme is most often used by small farms in China and is associated with the peculiarities of farming. works Biogas reactors with semi-continuous fermentation can have various design differences. These designs are discussed below.

Scheme No. 1. Biogas reactor with fixed lid.

Design features: combining a fermentation chamber and a biogas storage facility in one structure: raw materials ferment in the lower part; biogas is stored in the upper part.

Operating principle:

Biogas comes out of the liquid and is collected under the lid of the biogas reactor in its dome. The biogas pressure is balanced by the weight of the liquid. The higher the gas pressure, the more liquid leaves the fermentation chamber. The lower the gas pressure, the more liquid enters the fermentation chamber. During the operation of a biogas reactor, there is always liquid and gas inside it. But in different proportions.

Scheme No. 2. Biogas reactor with floating cover.

Scheme No. 3. Biogas reactor with fixed lid and external gas holder.

Design features: 1) instead of a floating cover, it has a separately built gas tank; 2) the biogas pressure at the outlet is constant.

Advantages of Scheme No. 3: 1) ideal for the operation of biogas burners that strictly require a certain pressure rating; 2) with low fermentation activity in the biogas reactor, it is possible to provide stable and high pressure of biogas to the consumer.

Guide to building a domestic biogas reactor.

GB/T 4750-2002 Domestic biogas reactors.

GB/T 4751-2002 Quality acceptance of domestic biogas reactors.

GB/T 4752-2002 Rules for the construction of domestic biogas reactors.

GB 175 -1999 Portland cement, ordinary Portland cement.

GB 134-1999 Portland slag cement, tuff cement and fly ash cement.

GB 50203-1998 Masonry construction and acceptance.

JGJ52-1992 Quality Standard for Ordinary Sand Concrete. Test methods.

JGJ53- 1992 Quality standard for ordinary crushed stone or gravel concrete. Test methods.

JGJ81 -1985 Mechanical properties of ordinary concrete. Test method.

JGJ/T 23-1992 Technical specification for testing the compressive strength of concrete by the rebound method.

JGJ70 -90 Mortar. Test method for basic characteristics.

GB 5101-1998 Bricks.

GB 50164-92 Quality control of concrete.

Air tightness.

The design of the biogas reactor provides an internal pressure of 8000 (or 4000 Pa). The leak rate after 24 hours is less than 3%.

Unit of biogas production per reactor volume.

For satisfactory conditions for biogas production, it is considered normal when 0.20-0.40 m 3 of biogas is produced per cubic meter of reactor volume.

The normal volume of gas storage is 50% of the daily biogas production.

Safety factor is not less than K=2.65.

Normal service life is at least 20 years.

Live load 2 kN/m2.

The bearing capacity of the foundation structure is at least 50 kPa.

Gas tanks are designed for a pressure of no more than 8000 Pa, and with a floating lid for a pressure of no more than 4000 Pa.

The maximum pressure limit for the pool is not more than 12000 Pa.

The minimum thickness of the arched vault of the reactor is at least 250 mm.

The maximum reactor load is 90% of its volume.

The design of the reactor provides for the presence of space under the reactor lid for gas flotation, amounting to 50% of the daily biogas production.

The reactor volume is 6 m 3, gas flow rate is 0.20 m 3 /m 3 /d.

It is possible to build reactors with a volume of 4 m3, 8 m3, 10 m3 according to these drawings. To do this, it is necessary to use the correction dimensional values indicated in the table on the drawings.

Preparation for the construction of a biogas reactor.

The choice of biogas reactor type depends on the quantity and characteristics of the fermented raw material. In addition, the choice depends on local hydrogeological and climatic conditions and the level of construction technology.

A household biogas reactor should be located near toilets and premises with livestock at a distance of no more than 25 meters. The location of the biogas reactor should be on the leeward and sunny side on solid ground with a low groundwater level.

To select a biogas reactor design, use the construction material consumption tables below.

Table3. Material Scale for Precast Concrete Panel Biogas Reactor

		Reactor volume, m 3
		4	6	8	10
	Volume, m 3	1,828	2,148	2,508	2,956
	Cement, kg	523	614	717	845
	Sand, m 3	0,725	0,852	0,995	1,172
	Gravel, m 3	1,579	1,856	2,167	2,553
	Volume, m 3	0,393	0,489	0,551	0,658
	Cement, kg	158	197	222	265
	Sand, m 3	0,371	0,461	0,519	0,620
Cement paste	Cement, kg	78	93	103	120
Total amount of material	Cement, kg	759	904	1042	1230
	Sand, m 3	1,096	1,313	1,514	1,792
	Gravel, m 3	1,579	1,856	2,167	2,553

Table4. Material Scale for Precast Concrete Panel Biogas Reactor

		Reactor volume, m 3
		4	6	8	10
	Volume, m 3	1,540	1,840	2,104	2,384
	Cement, kg	471	561	691	789
	Sand, m 3	0,863	0,990	1,120	1,260
	Gravel, m 3	1,413	1,690	1,900	2,170
Plastering the prefabricated building	Volume, m 3	0,393	0,489	0,551	0,658
	Cement, kg	158	197	222	265
	Sand, m 3	0,371	0,461	0,519	0,620
Cement paste	Cement, kg	78	93	103	120
Total amount of material	Cement, kg	707	851	1016	1174
	Sand, m 3	1,234	1,451	1,639	1,880
	Gravel, m 3	1,413	1,690	1,900	2,170
Steel materials	Steel rod diameter 12 mm, kg	14	18,98	20,98	23,00
Steel materials	Steel reinforcement diameter 6.5 mm, kg	10	13,55	14,00	15,00

Table5. Material scale for cast-in-place concrete biogas reactor

		Reactor volume, m 3
		4	6	8	10
	Volume, m 3	1,257	1,635	2,017	2,239
	Cement, kg	350	455	561	623
	Sand, m 3	0,622	0,809	0,997	1,107
	Gravel, m 3	0,959	1,250	1,510	1,710
Plastering the prefabricated building	Volume, m 3	0,277	0,347	0,400	0,508
	Cement, kg	113	142	163	208
	Sand, m 3	0,259	0,324	0,374	0,475
Cement paste	Cement, kg	6	7	9	11
Total amount of material	Cement, kg	469	604	733	842
	Sand, m 3	0,881	1,133	1,371	1,582
	Gravel, m 3	0,959	1,250	1,540	1,710

Table6. Symbols in the drawings.

Description	Designation on drawings
Materials:
Pipe (trench in the ground)









Symbols:

Link to detail drawing. The top number indicates the part number. The bottom number indicates the drawing number with a detailed description of the part. If a “-” sign is indicated instead of the lower number, this indicates that a detailed description of the part is presented in this drawing.


Section of the part. Bold lines indicate the plane of the cut and the direction of view, and the numbers indicate the identification number of the cut.
The arrow indicates the radius. The numbers after the letter R indicate the radius value.



Commonly accepted:



Accordingly, the semimajor axis and the short axis of the ellipsoid
Length

Designs of biogas reactors.

Peculiarities:

Type of design feature of the main pool.

The bottom slopes from the inlet port to the outlet port. This ensures the formation of a constant moving flow. Drawings No. 1-9 indicate three types of biogas reactor structures: type A, type B, type C.

Biogas reactor type A: The most simple design. Removal of the liquid substance is provided only through the outlet window by the force of biogas pressure inside the fermentation chamber.

Biogas reactor type B: The main pool is equipped with a vertical pipe in the center, through which during operation it is possible to supply or remove a liquid substance, depending on the need. In addition, to form a flow of substance through a vertical pipe, this type of biogas reactor has a reflective (deflector) partition at the bottom of the main pool.

Biogas reactor type C: It has a similar design to the type B reactor. However, it is equipped with a manual piston pump of a simple design installed in a central vertical pipe, as well as other reflective baffles at the bottom of the main basin. These design features make it possible to effectively control the parameters of the main technological processes in the main pool due to the simplicity of express samples. And also use a biogas reactor as a donor of biogas bacteria. In a reactor of this type, diffusion (mixing) of the substrate occurs more completely, which in turn increases the yield of biogas.

Fermentation characteristics:

The process consists of selecting grafting material; preparation of primary raw materials (finishing density with water, adjusting acidity, adding grafting material); fermentation (control of substrate mixing and temperature).

Human feces, livestock manure, and bird droppings are used as fermentation materials. With a continuous fermentation process, relatively stable conditions for the effective operation of a biogas reactor are created.

Design principles.

Compliance with the “triple” system (biogas, toilet, barn). The biogas reactor is a vertical cylindrical tank. Height of the cylindrical part H=1 m. The upper part of the tank has an arched vault. The ratio of the height of the arch to the diameter of the cylindrical part is f 1 /D=1/5. The bottom slopes from the inlet port to the outlet port. Tilt angle 5 degrees.

The design of the tank ensures satisfactory fermentation conditions. The movement of the substrate occurs by gravity. The system operates when the tank is fully loaded and controls itself based on the residence time of the raw materials by increasing biogas production. Biogas reactors of types B and C have additional devices for processing the substrate.

The tank may not be fully loaded with raw materials. This reduces gas output without sacrificing efficiency.

Low cost, ease of management, widespread popular use.

Description of building materials.

The material of the walls, bottom, and roof of the biogas reactor is concrete.

Square parts such as the loading channel can be made of brick. Concrete structures can be made by pouring a concrete mixture, but can also be made from precast concrete elements (such as: inlet port cover, bacteria tank, center pipe). The bacterial cage is round in cross section and consists of broken eggshells placed in a braid.

Sequence of construction operations.

The formwork pouring method is as follows. The outline of the future biogas reactor is marked on the ground. The soil is removed. First the bottom is filled. Formwork is installed at the bottom to pour concrete in a ring. The walls are poured using formwork and then the arched vault. Steel, wood or brick can be used for formwork. Pouring is done symmetrically and tamping devices are used for strength. Excess flowable concrete is removed with a spatula.

Construction drawings.

Construction is carried out according to drawings No. 1-9.

Drawing 1. Biogas reactor 6 m 3. Type A:

Drawing 2. Biogas reactor 6 m 3. Type A:

The construction of biogas reactors from precast concrete slabs is a more advanced construction technology. This technology is more advanced due to the ease of implementation of maintaining dimensional accuracy, reducing construction time and costs. The main feature of the construction is that the main elements of the reactor (arched vault, walls, channels, covers) are manufactured away from the installation site, then they are transported to the installation site and assembled on site in a large pit. When assembling such a reactor, the main attention is paid to the accuracy of the installation horizontally and vertically, as well as the density of the butt joints.

Drawing 13. Biogas reactor 6 m 3. Details of the biogas reactor made of reinforced concrete slabs: