Biogas plant for a private house: recommendations for arranging homemade

A smart owner dreams of cheap energy, efficient waste management and fertilizer. Do-it-yourself home biogas plant is an inexpensive way to make your dreams come true.

Self-assembly of such equipment will cost a reasonable price, 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 independently build a biogas plant and whether it will be effective.

The specifics of biogas production

Biogas is formed as a result of fermentation of a biological substrate. It is decomposed by hydrolysis, acid and methane-forming bacteria. A mixture of gases produced by bacteria is combustible, because contains a large percentage of methane.

In its properties, it practically does not differ from natural gas, which is used for industrial and domestic needs.

If desired, each home owner can purchase a biogas plant for industrial production, but it is expensive, and the investment pays off within 7-10 years. Therefore, it makes sense to make efforts and make a bioreactor with your own hands

Biogas is an environmentally friendly fuel, and the technology for its production does not have a special impact on the environment. Moreover, waste materials that need to be disposed of are used as raw materials for biogas.

They are placed in a bioreactor, where processing takes place:

• biomass has been exposed to bacteria for some time. Fermentation time depends on the volume of raw materials;
• as a result of the activity of anaerobic bacteria, a combustible mixture of gases is released, which includes methane (60%), carbon dioxide (35%) and some other gases (5%). Also, during fermentation in small quantities, potentially hazardous hydrogen sulfide is released.It is poisonous, so it is highly undesirable for people to be exposed to it;
• the mixture of gases from the bioreactor is cleaned and enters the gas tank, where it is stored until intended use;
• gas from a gas tank can be used in the same way as natural gas. He goes to household appliances - gas stoves, heating boilers, etc .;
• decayed biomass must be regularly removed from the fermenter. This is an additional work, but the effort pays off. After fermentation, the raw materials turn into high-quality fertilizer, which is used in fields and 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. substrate can be obtained 70-80 cubic meters. biogas, but gas production is uneven and depends on many factors, including biomass temperature. This complicates the calculations.

Biogas plants are ideal for farmers. Animal waste can provide enough gas for proper heating of residential premises and farm buildings

In order for the gas production process to be stable and continuous, it is best to build several biogas plants, and lay the substrate in the fermenters with a time difference. Such plants operate in parallel, and the raw materials are loaded in them sequentially.

This ensures a constant gas production, so that it can be continuously supplied to household appliances.

Ideally, the bioreactor should be heated. Every 10 degrees of heat doubles the gas production. Although the arrangement of heating requires investment, it pays off with greater efficiency of the design

Homemade biogas equipment, assembled from improvised materials, is much cheaper than industrial production plants. Its effectiveness is lower, but it is consistent with the invested funds. If you have access to manure and a desire to make your own efforts for the assembly and maintenance of the structure, this is very beneficial.

Advantages and disadvantages of the system

Biogas plants have many advantages, but there are enough shortcomings, so before starting the design and construction, everything should be weighed:

• Recycling. Thanks to the biogas plant, you can get the maximum benefit from the garbage, which would still have to be disposed of. This disposal is less hazardous to the environment than landfill.
• Renewability of raw materials. Biomass is neither coal nor natural gas, the extraction of which depletes reserves of resources. When farming, raw materials appear constantly.
• Relatively small amount of CO2. When receiving gas, the environment is not polluted, but when it is used, a small amount of carbon dioxide is released into the atmosphere. It is not dangerous and is not able to critically change the environment, because plants absorb it during growth.
• Moderate sulfur release. When biogas is burned, a small amount of sulfur enters the atmosphere. This is a negative phenomenon, but its scale is known by comparison: when burning natural gas, environmental pollution with sulfur oxides is much greater.
• Stable work. Biogas production is more stable than work solar panels or windmills. If the energy of the sun and wind cannot be controlled, then biogas plants depend on human activity.
• You can use several settings. Gas is always a risk. To reduce potential damage in the event of an accident, several biogas plants can be dispersed throughout the site. If you correctly design and assemble a system of several fermenters, it will work more stable than one large bioreactor.
• Benefits for agriculture. To obtain biomass, certain types of plants are planted. You can choose those that improve the condition of the soil.For example, sorghum reduces soil erosion, improves its quality.

Biogas has its drawbacks. Although it is a relatively clean fuel, it still pollutes the atmosphere. There may also be problems with the supply of plant biomass.

Irresponsible plant owners often procure it in such a way that they drain the land and upset the ecological balance.

Calculation of the profitability of the installation

Cow dung is usually used as raw material for biogas production. One adult cow can give him enough to provide 1.5 cubic meters. fuel; pig - 0.2 cubic meters; chicken or crawl (depending on body weight) - 0.01-0.02 cbm. To understand whether it is a lot or a little, one can compare it with more familiar types of resources.

1 cbm biogas provides the same amount of thermal energy as:

• firewood - 3.5 kg;
• coal - 1-2 kg;
• electricity - 9-10 kW / h.

If you know the approximate weight of agricultural waste that will be available in the coming years, and the amount of energy needed, you can calculate the profitability of a biogas plant.

One of the main disadvantages of biogas production is the smell. The possibility of using small compost heaps is a big plus, but you will have to endure the inconvenience and carefully control the process so as not to provoke the spread of pathogens

For laying in the bioreactor, a substrate is prepared, which includes several components in the following proportions:

• manure (best cow or pork) - 1.5 t;
• organic waste (it can be decayed leaves or other components of plant origin) - 3.5 t;
• heated to 35 degrees water (the amount of warm water is calculated so that its mass is 65-75% of the total amount of organic matter).

Calculation of the substrate is made for one bookmark for six months, based on moderate gas consumption. After about 10-15 days, the fermentation process will give the first results: gas will appear in small quantities and begin to fill the storage. After 30 days, you can expect full fuel production.

Equipment for the production of biogas is not yet particularly common in our country. This is largely due to the poor awareness of people about the benefits and features of biogas systems. In China and India, many small farms are equipped with handicrafts to provide additional clean fuel.

If the installation works correctly, the biogas volume will gradually increase until the substrate decays.The design productivity directly depends on the biomass fermentation rate, which in turn is related to the temperature and humidity of the substrate.

Self-building instruction

If there is no experience in assembling complex systems, it makes sense to select the network or develop the simplest drawing of a biogas plant for a private house.

The simpler the design, the more reliable and durable it is. Later, when there are skills in building and handling the system, it will be possible to remake equipment or mount an additional installation.

In expensive designs of industrial production, biomass mixing systems, automatic heating, gas purification, etc. are provided. Home appliances are not so complicated. It’s better to put together a simple installation, and then add elements that you need

When calculating the volume of the fermenter, it is worth focusing on 5 cubic meters. This installation allows you to get the amount of gas needed to heat a private house with an area of ​​50 square meters, if a gas boiler or stove is used as the heat source.

This is an average indicator, as the calorific value of biogas is usually not higher than 6000 kcal / m3.

In order for the fermentation process to proceed more or less stably, it is necessary to achieve the correct temperature regime. To do this, the bioreactor is installed in an earthen pit or pre-thought out reliable thermal insulation. Constant heating of the substrate can be ensured if a water heating pipe is placed under the base of the fermenter

The construction of a biogas plant can be divided into several stages.

Stage 1 - preparation of the pit for the bioreactor

Almost the entire biogas plant is underground, so much depends on how the pit was dug and finished. There are several options for strengthening the walls and sealing the pit - plastic, concrete, polymer rings.

The best solution is to buy ready-made polymer rings with a blank bottom. They will cost more than improvised materials, but additional sealing will not be required. Polymers are sensitive to mechanical stress, but are not afraid of moisture and chemically aggressive substances. They cannot be repaired, but if necessary they will be easily replaced.

The intensity of substrate fermentation and gas outlet depend on the preparation of the walls and bottom of the bioreactor; therefore, the pit is carefully strengthened, insulated and sealed. This is the most difficult and time-consuming stage of work.

Stage 2 - gas drainage

Buying and installing special mixers for biogas plants is an expensive pleasure. The system can be cheapened by arranging gas drainage. It is a vertically mounted polymer sewer pipesin which many holes have been made.

When calculating the length of the drainage pipes, one should be guided by the planned depth of filling of the bioreactor. The upper parts of the pipes must be above this level.

For gas drainage, you can choose metal or polymer pipes. The former are stronger and the latter more resistant to chemical influences. It is better to give preference to polymers, as metal quickly rusts and rots

You can immediately load the substrate into the finished bioreactor. It is covered with a film so that the gas released during the fermentation process is under slight pressure. When the dome is ready, this will ensure the normal flow of biomethane through the outlet pipe.

Stage 3 - installation of the dome and pipes

The final stage of assembly of the simplest biogas plant is the installation of the domed top. At the highest point of the dome, a gas exhaust pipe is installed and pulled to gas holder, which is indispensable.

The capacity of the bioreactor is closed with a tight lid. To prevent the mixing of biomethane with air, equip a water trap. It also serves to purify gas. It is necessary to provide a release valve that will operate if the pressure in the fermenter is too high.

Read more on how to make biogas from manure. in this material.

The free space of the bioreactor to some extent serves as a gas storage, but this is not enough for the safe operation of the installation. Gas must be consumed constantly, otherwise explosion from excessive pressure under the dome is possible

Methods for heating a bioreactor

Microorganisms processing the substrate are constantly present in biomass, however, for their intensive reproduction, a temperature of 38 degrees and above is needed.

For heating in the cold season, you can use a coil connected to the heating system at home, or electric heaters. The first method is economically more profitable, therefore it is most often used.

It is not necessary to dig a biogas plant into the ground; there are other options for arranging it. An example of a system assembled from barrels is shown in the video below.

The easiest way is to arrange heating from below, laying a pipe from the heating system, but the efficiency of such a heat exchanger is relatively low. It is better to equip external heating, ideally steam, so that the biomass does not overheat

Conclusions and useful video on the topic

Although there is nothing complicated in assembling and equipping biogas equipment, you need to be extremely attentive to details. Errors are not allowed, because may cause explosions and destruction. We offer video instructions that will help you understand the device setup, assemble them correctly and supplement with useful devices for more convenient use of biogas.

The video tells how the standard biogas plant is arranged and works:

An example of a homemade biogas plant. DIY video tutorial on arranging the system:

Video instruction for assembling a biogas plant from a barrel:

Description of the process of manufacturing mixers for the substrate:

A detailed description of the work of a makeshift gas storage:

No matter how simple the biogas plant chosen for a private house is, you should not save on it. If possible, it is better to buy a collapsible bioreactor for industrial production.

If not, make from high-quality and durable materials: polymers, concrete or stainless steel. This will create a truly reliable and safe gas supply system at home.

Have questions about the topic of the article, find any flaws or is there any valuable information that you can share with our readers? Please leave your comments, ask questions, share experiences.