Production of biogas from organic waste. Biogas plant for a private home: recommendations for arranging a homemade project. Calculation of raw materials per cycle

Good day everyone! This post continues the theme of alternative energy for yours. In it I will tell you about biogas and its use for heating the home and cooking. This topic is most interesting to farmers who have access to a variety of raw materials to obtain this type of fuel. Let's first understand what biogas is and where it comes from.

Where does biogas come from and what does it consist of?

Biogas is a flammable gas that arises as a product of the vital activity of microorganisms in a nutrient medium. This nutrient medium can be manure or silage, which is placed in a special bunker. In this bunker, called a reactor, biogas is formed. The inside of the reactor will be arranged as follows:

To speed up the fermentation process of biomass, it needs to be heated. For this, a heating element or a heat exchanger connected to any heating boiler can be used. We must not forget about good thermal insulation in order to avoid unnecessary energy costs for heating. In addition to heating, the fermenting mass must be stirred. Without this, the efficiency of the installation can be significantly reduced. Mixing can be manual or mechanical. It all depends on the budget or available technical means. The most important thing in a reactor is volume! A small reactor is simply physically unable to produce a large number of gas

The chemical composition of the gas strongly depends on what processes take place in the reactor. Most often, the process of methane fermentation occurs there, which results in the formation of gas with a high percentage of methane. But instead of methane fermentation, a process with the formation of hydrogen may well occur. But in my opinion, hydrogen is not necessary for the average consumer, and may even be dangerous. Just remember the death of the Hindenburg airship. Now let's figure out what biogas can be obtained from.

What can you get biogas from?

Gas can be obtained from various types biomass. Let's list them in list form:

• Waste food production- this could be waste from slaughter or dairy production. Suitable waste from the production of sunflower or cottonseed oil. This is far from full list, but it’s enough to convey the essence. This type raw materials gives the highest methane content in the gas (up to 85%).
• Agricultural crops - in some cases grown to produce gas special types plants. For example, silage corn or seaweed are suitable for this. The percentage of methane content in gas is around 70%.
• Manure is most often used on large livestock farms. The percentage of methane in the gas, when using manure as a raw material, usually does not exceed 60%, and the rest will be carbon dioxide and quite a bit of hydrogen sulfide and ammonia.

Block diagram of a biogas installation.

In order to best understand how a biogas plant works, let's look at the following figure:

The design of the bioreactor was discussed above, so we will not talk about it. Let's look at other components of the installation:

• A waste receiver is a kind of container into which raw materials fall at the first stage. In it, raw materials can be mixed with water and crushed.
• The pump (after the waste receiver) is a fecal pump, with the help of which biomass is pumped inside the reactor.
• Boiler is a heating boiler using any fuel, designed to heat biomass inside the reactor.
• The pump (next to the boiler) is a circulation pump.
• “Fertilizer” is a container into which fermented sludge falls. It, as is clear from the context, can be used as fertilizer.
• A filter is a device in which biogas is brought to condition. The filter removes excess gases and moisture.
• Compressor - compresses the gas.
• Gas storage is a sealed tank in which ready-to-use gas can be stored for as long as desired.

Biogas for a private home.

Many owners of small farms are thinking about using biogas for internal needs. But having found out in more detail about how it all works, most abandon this idea. This is due to the fact that equipment for processing manure or silage costs a lot of money, and the gas output (depending on the raw material) can be small. This in turn makes installation of equipment unprofitable. Typically, farmers install primitive installations that run on manure for private homes. Most often, they are only able to provide gas for the kitchen and a low-power wall-mounted gas boiler. At the same time technological process you will have to spend a lot of energy on heating, pumping, and operating the compressor. Expensive filters also cannot be excluded from view.

In general, the moral here is this: the larger the installation itself, the more profitable its operation. But for home conditions this is almost always impossible. But this does not mean that no one does home installations. I suggest you look next video to see what it looks like from scrap materials:

Summary.

Biogas is a great way useful processing organic waste. The output is fuel and useful fertilizer in the form of fermented sludge. This technology the more efficiently the more raw materials are processed. Modern technologies make it possible to significantly increase gas production using special catalysts and microorganisms. The main disadvantage of all this is the high price of one cubic meter. For ordinary people most often it will be much cheaper to buy gas in cylinders than to build a waste treatment plant. But, of course, there are exceptions to all rules, so before deciding to switch to biogas, it is worth calculating the price per cubic meter and the payback period. That's all for now, write questions in the comments

One of the problems that has to be solved in agriculture— disposal of manure and plant waste. And that's pretty serious problem which 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 natural process 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 phosphorus. 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 itself and effective fertilizer. Moreover, fertilizer 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 optimal temperature. Bacteria contained in biomass, when low temperatures inactive. 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 for an installation for generating electricity, for 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 by any in an accessible 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 great experience construction of similar 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 very simple 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: it is difficult to heat, mix and remove the fermented mass, to achieve complete processing and high efficiency impossible.

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.

With the main technical issues figured it out, 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. The most important role In this case, methane-forming agents play a 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 mass, 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 substances. chemical substances. 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 (either 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.

Producing biogas at home will allow you to save on household gas consumption and obtain fertilizer from weeds. This instructional article shows how an ordinary person can use simple actions make an effective system for extracting biogas from weeds with your own hands.

This simple step by step instructions suggested by Indian Antoni Raj. He experimented for a long time with producing energy from the anaerobic digestion of weeds. And this is what came out of it.

Step 1: Select a container for the biogenerator.

Anaerobic digestion (according to the definition) is a set of processes as a result of which microorganisms, in the absence of oxygen, completely destroy biomaterial, releasing biogas.

First, fill the biogenerator with chopped weeds. At the same time, we will collect information on the amounts of biogas released as a result of fermentation and the amount of energy.
You can read about the biogenerator itself Anthony.

Step 2: Collecting Weeds

The capacity of the fermentation cylinder is 750 l. Let's leave 50 liters in reserve. We dilute 2.5 kg of freshly harvested weeds with enough water to ultimately obtain 20 liters of diluted “biomaterial”. The mixture should ferment for about 35 days. Water after removing solid biomaterial can be used as fertilizer for plants in the garden. From 4 kg of freshly picked weeds, after cutting off the roots and branches, you can get about 2.5 kg of material. Raw material can be stored for up to 3-4 days.

Biogas- gas produced by methane fermentation of biomass. Biomass decomposition occurs under the influence of three types of bacteria.

In the food chain, subsequent bacteria feed on the waste products of the previous ones.
The first type is hydrolytic bacteria, the second is acid-forming, the third is methane-forming.
Not only bacteria of the methanogen class, but all three species are involved in the production of biogas. During the fermentation process, biogas is produced from biowaste. This gas can be used like ordinary natural gas - for heating and generating electricity. It can be compressed, used to refuel a car, accumulated, pumped. Essentially, as the owner and rightful owner, you get your own gas well and income from it. There is no need to register your own installation anywhere yet.

Composition and quality of biogas

50-87% methane, 13-50% CO2, minor impurities of H2 and H2S. After cleaning biogas from CO2, biomethane is obtained; this is a complete analogue natural gas, the only difference is in origin.
Since only methane supplies energy from biogas, it is advisable to describe the quality of gas, gas yield and quantity of gas to refer everything to methane, with its standardized indicators.

The volume of gases depends on temperature and pressure. High temperatures lead to gas stretching and to a calorie level that decreases with volume, and vice versa. As humidity increases, the calorie content of gas also decreases. In order for gas yields to be comparable with each other, it is necessary to correlate them with normal condition(temperature 0 C, Atmosphere pressure 1 bar, relative humidity gas 0%). In general, gas production data is expressed in liters (l) or cubic meters of methane per kilogram of organic dry matter (oDM); this is much more accurate and eloquent than data in cubic meters of biogas in cubic meters of fresh substrate.

Raw materials for biogas production

List of organic waste suitable for biogas production: manure, bird droppings, grain and chalk distillery stillage, spent grains, beet pulp, fecal sludge, waste from fish and slaughter shops (blood, fat, intestines, cane), grass, household waste, dairy waste - salted and sweet whey, biodiesel production waste - technical glycerin from the production of biodiesel from rapeseed, juice production waste - fruit, berry, vegetable pulp, grape pomace, algae, starch and molasses production waste - pulp and syrup, waste potato processing, chip production - peeling, skins, rotten tubers, coffee pulp.

Calculation of useful biogas on a farm

The yield of biogas depends on the dry matter content and the type of raw material used. From a ton of large manure cattle 50-65 m3 of biogas is obtained with a methane content of 60%, 150-500 m3 of biogas from various types of plants with a methane content of up to 70%. The maximum amount of biogas - 1300 m3 with a methane content of up to 87% - can be obtained from fat.
A distinction is made between theoretical (physically possible) and technically feasible gas output. In the 1950-1970s, the technically possible gas yield was only 20-30% of the theoretical one. Today, the use of enzymes, boosters for artificial degradation of raw materials (ultrasonic or liquid cavitators) and other devices makes it possible to increase the biogas yield in a conventional plant from 60% to 95%.

In biogas calculations, the concept of dry matter (DM or English TS) or dry residue (CO) is used. The water contained in biomass itself does not produce gas.
In practice, from 1 kg of dry matter, 300 to 500 liters of biogas are obtained.

To calculate the biogas yield from a specific raw material, it is necessary to conduct laboratory tests or look at reference data, and then determine the content of fats, proteins and carbohydrates. When determining the latter, it is important to find out the percentage of rapidly degradable (fructose, sugar, sucrose, starch) and difficult to decompose substances (cellulose, hemicellulose, lignin).

Having determined the content of substances, you can calculate the gas yield for each substance separately and then add it up. When biogas was associated with manure (in rural areas this situation continues today - I asked in the taiga regional center, Verkhovazhye Vologda region), used the concept of “animal unit”. Today, when they learned to produce biogas from arbitrary organic raw materials, this concept has moved away and ceased to be used.

But, in addition to waste, biogas can be produced from specially grown energy crops, for example from silage corn or silphium, as well as algae. Gas output can reach up to 500 m3 from 1 ton.

Landfill gas is one of the types of biogas. It is obtained in landfills from municipal household waste.

Environmental aspect in the use of biogas

Biogas production helps prevent methane emissions into the atmosphere. Methane affects Greenhouse effect 21 times stronger than the CO2 mixture and remains in the atmosphere for up to 12 years. Capturing and limiting the spread of methane is the best short-term way to prevent global warming. This is where, at the intersection of research, another area of ​​science that has received little research so far is revealed.

Processed manure, stillage and other waste are used as fertilizer in agriculture. This reduces the use of chemical fertilizers and reduces the load on groundwater.

Biogas production

There are industrial and handicraft installations.
Industrial installations differ from artisanal ones in the presence of mechanization, heating systems, homogenization, and automation. The most common industrial method is anaerobic digestion in digesters.

A reliable biogas plant must have the necessary parts:

Homogenization tank;
loader of solid (liquid) raw materials;
the reactor itself;
stirrers;
gas holder;
water and heating mixing system;
gas system;
pumping station;
separator;
control devices;
safety system.

Features of a biogas production plant

In an industrial plant, waste (raw materials) is fed periodically using pumping station or loader into the reactor. The reactor is a heated and insulated reinforced concrete tank equipped with mixers.

They “live” in the reactor beneficial bacteria that feed on waste. The waste product of bacteria is biogas. To maintain the life of bacteria, it is necessary to supply feed - waste, heating to 35 ° C and periodic mixing. The resulting biogas accumulates in a storage facility (gas holder), then passes through a purification system and is supplied to consumers (boiler or electric generator). The reactor operates without air access, is practically sealed and non-hazardous.

To ferment some types of raw materials in their pure form, a special two-stage technology is required.

For example, bird droppings and alcohol stillage are not processed into biogas in a conventional reactor. To process such raw materials, an additional hydrolysis reactor is required. It allows you to control the level of acidity, so bacteria do not die due to an increase in the content of acids or alkalis.

Significant factors influencing the fermentation process:

Temperature;
environmental humidity;
pH level;
ratio C:N:P;
surface area of ​​raw material particles;
substrate supply frequency;
substances that slow down the reaction;
stimulant supplements.

Application of biogas

Biogas is used as a fuel to produce electricity, heat or steam, or as a vehicle fuel. Biogas plants can be used as wastewater treatment plants on farms, poultry farms, distilleries, sugar factories, meat processing plants, etc. special case can even replace a veterinary and sanitary plant, where carrion can be recycled into biogas instead of producing meat and bone meal.

Farmers annually face the problem of manure disposal. The considerable funds required to organize its removal and burial are wasted. But there is a way that allows you not only to save your money, but also to make this natural product serve you for your benefit.

Thrifty owners have long been putting into practice eco-technology that makes it possible to obtain biogas from manure and use the result as fuel.

Therefore, in our material we will talk about the technology for producing biogas, and we will also talk about how to build a bioenergy plant.

Determining the required volume

The volume of the reactor is determined based on the daily amount of manure produced on the farm. It is also necessary to consider the type of raw material, temperature regime and fermentation time. For the installation to fully operate, the container is filled to 85-90% of the volume, at least 10% must remain free for gas to escape.

The process of decomposition of organic matter in a mesophilic installation at average temperature 35 degrees lasts from 12 days, after which the fermented residues are removed and the reactor is filled with a new portion of the substrate. Since waste is diluted with water up to 90% before being sent to the reactor, the amount of liquid must also be taken into account when determining the daily load.

Based on the given indicators, the volume of the reactor will be equal to the daily amount of prepared substrate (manure with water) multiplied by 12 (the time required for biomass decomposition) and increased by 10% (free volume of the container).

Construction of an underground structure

Now let's talk about the simplest installation that allows you to get it at the lowest cost. Consider construction underground system. To make it, you need to dig a hole, its base and walls are filled with reinforced expanded clay concrete.

WITH opposite sides The chambers have inlet and outlet openings, where inclined pipes are mounted for supplying the substrate and pumping out the waste mass.

The outlet pipe with a diameter of approximately 7 cm should be located almost at the very bottom of the bunker, its other end is mounted in a rectangular compensating tank into which waste will be pumped. The pipeline for supplying the substrate is located approximately 50 cm from the bottom and has a diameter of 25-35 cm. Top part pipe enters the compartment for receiving raw materials.

The reactor must be completely sealed. To exclude the possibility of air ingress, the container must be covered with a layer of bitumen waterproofing

The upper part of the bunker is a gas holder, which has a dome or cone shape. It is made of metal sheets or roofing iron. You can also complete the structure with brickwork, which is then covered with steel mesh and plastered. You need to make a sealed hatch on top of the gas tank, remove the gas pipe passing through the water seal and install a valve to relieve gas pressure.

To mix the substrate, you can equip the installation with a drainage system operating on the principle of bubbling. To do this, vertically fix plastic pipes inside the structure so that their upper edge is above the substrate layer. Make lots of holes in them. Gas under pressure will fall down, and rising up, gas bubbles will mix the biomass in the container.

If you do not want to build a concrete bunker, you can buy a ready-made PVC container. To preserve heat, it must be surrounded by a layer of thermal insulation - polystyrene foam. The bottom of the pit is filled with a 10 cm layer of reinforced concrete. Tanks made of polyvinyl chloride can be used if the reactor volume does not exceed 3 m3.

Conclusions and useful video on the topic

You will learn how to make the simplest installation from an ordinary barrel if you watch the video:

The simplest reactor can be made in a few days with your own hands, using available materials. If the farm is large, then it is best to buy a ready-made installation or contact specialists.