How to get biogas at home. How to get biogas from manure: an overview of the basic principles and design of a production plant All about biogas plants

For owners of large farms, there is an acute issue in the form of manure, poultry droppings, animal remains. To solve the problem, you can use special installations designed for biogas production. They are easy to make at home and operate over a long period with a high yield of a ready-to-use product.

What is biogas?

Biogas is a substance obtained from natural raw materials in the form of biomass (manure, poultry droppings) due to its fermentation. Various bacteria are involved in this process, each of which feeds on the waste products of the previous ones. There are such microorganisms that take an active part in the biogas production process:

• hydrolysis;
• acid-forming;
• methane-forming.

The technology for producing biogas from finished biomass is to stimulate natural processes. Bacteria in the manure should create optimal conditions for rapid multiplication and efficient processing of substances. For this, biological raw materials are placed in a tank closed from oxygen supply.

After that, a group of anaerobic microbes comes into play. They allow you to convert phosphorus, potassium and nitrogen-containing compounds into pure forms. As a result of processing, not only biogas is generated, but also quality approvals. They are ideal for agricultural needs and are more efficient than traditional manure.

The ecological value of biogas production

The efficient processing of biological waste produces a valuable fuel. Establishing this process helps prevent methane emissions into the atmosphere, which have a negative impact on the environment. This compound stimulates the greenhouse effect 21 times more than carbon dioxide. Methane can be stored in the atmosphere for 12 years.

To prevent global warming, which is a global problem, it is necessary to limit the entry and distribution of this substance into the environment. Waste generated from the recycling process is high quality approval. Its use makes it possible to reduce the amount of chemical compounds used. Synthetically made fertilizers pollute groundwater and negatively affect the condition environment.

What affects the productivity of the production process?

With the right organization production process for the production of biogas, from 1 cubic meter m of organic raw materials get about 2-3 cubic meters. m of pure product. Many factors affect its effectiveness:

• ambient temperature;
• the acidity level of organic raw materials;
• humidity of the environment;
• the amount of phosphorus, nitrogen and carbon in the original biological mass;
• particle size of manure or droppings;
• the presence of substances that slow down the processing process;
• the inclusion of stimulating additives in the biomass;
• substrate feed frequency.

List of raw materials used for biogas production

Biogas production is possible not only from manure or poultry manure. For the production of environmentally friendly fuel, you can use other raw materials:

• grain stillage;
• waste from the release of juices;
• beet pulp;
• waste of fish or meat production;
• brewer's grains;
• dairy waste;
• fecal sediment;
• household waste organic origin;
• waste from the production of biodiesel from rapeseed.

Biological gas composition

The composition of biogas after passing all the following:

• 50-87% methane;
• 13-50% carbon dioxide;
• impurities of hydrogen and hydrogen sulfide.

After purification of the product from impurities, biomethane is obtained. It is analogous, but has a different nature of origin. To improve the quality of the fuel, the content of methane in its composition, which is the main source of energy, is normalized.

When calculating the volumes of gases produced, the ambient temperature is taken into account. With its increase, the yield of the product rises and its calorie content decreases. The characteristics of biogas are negatively affected by an increase in air humidity.

Scope of biogas application

Biogas production plays a significant role not only for the preservation of the environment, but also provides the national economy with fuel. It is characterized by a wide range of applications:

• it is used as a raw material for the production of electricity, automobile fuel;
• to meet the energy needs of small or medium-sized enterprises;
• biogas plants play the role of treatment facilities, which makes it possible to solve.

Biogas production technology

For biogas production, actions should be taken to accelerate the natural decomposition of organic matter. Before being placed in a sealed container with a limited supply of oxygen, natural raw materials are thoroughly crushed and mixed with a certain amount of water.

The result is the original substrate. The presence of water in its composition is necessary to prevent the negative impact on bacteria, which can occur when substances from the environment enter. Without a liquid component, the fermentation process slows down significantly and reduces the efficiency of the entire biological plant.

Industrial-type equipment for the processing of organic raw materials is additionally equipped with:

• device for heating the substrate;
• equipment for mixing raw materials;
• devices for controlling the acidity of the environment.

These devices significantly increase the efficiency of bioreactors. Agitation removes a hard crust from the surface of the biomass, which increases the amount of gas emitted. The processing time for organic matter is about 15 days. During this time, it only decomposes by 25%. The maximum amount of natural gas is released when the decomposition rate of the substrate reaches 33%.

Biogas technology involves daily renewal of the substrate. For this, 5% of the mass is removed from the bioreactor, and a new portion of the raw material is placed in its place. The used product is used as an approval.

Biogas production technology at home

The production of biogas at home is carried out according to the following scheme:

1. Shredding of biological mass is carried out. It is necessary to obtain particles, the size of which does not exceed 10 mm.
2. The resulting mass is thoroughly mixed with water. For 1 kg of raw materials, approximately 700 ml of a liquid component is needed. The water used must be potable and free of impurities.
3. The entire reservoir is filled with the resulting substrate, after which it is hermetically closed.
4. It is advisable to thoroughly mix the substrate several times a day, which will increase the efficiency of its processing.
5. On the 5th day of the production process, the presence of biogas is checked and gradually pumped out into prepared cylinders using a compressor. Periodic removal of gaseous products is mandatory. Their accumulation leads to an increase in pressure inside the reservoir, which negatively affects the process of disintegration of biological mass.
6. On the 15th day of production, part of the substrate is removed, and a fresh portion of the biological material is loaded.

To determine the required volume of the reactor for the processing of biomass, it is necessary to calculate the amount of manure produced during the day. The type of raw materials used, the temperature regime that will be maintained in the installation are taken into account without fail. The used tank should be filled to 85-90% of its volume. The remaining 10% is necessary for the accumulation of the obtained biological gas.

The duration of the processing cycle is taken into account without fail. If the temperature is maintained at + 35 ° C, it is 12 days. We must not forget that the raw materials used are diluted with water before being sent to the reactor. Therefore, its quantity is taken into account before calculating the volume of the tank.

Diagram of the simplest biological plant

To produce biogas at home, it is necessary to create optimal conditions for microorganisms that will break down biological mass. First of all, it is advisable to arrange heating of the generator, which will entail additional costs.

• the volume of the waste storage tank must be at least 1 cubic meter. m;
• it is necessary to use a hermetically sealed tank;
• biomass tank insulation is a prerequisite for its efficient operation;
• the reservoir can be deepened into the ground. Thermal insulation is installed only in its upper part;
• a hand mixer is mounted in the container. Its handle is brought out through the sealed assembly;
• nozzles for loading / unloading raw materials, biogas intake are provided.

Underground Reactor Manufacturing Technology

For biogas production, you can install the simplest installation, deepening it into the ground. The manufacturing technology of such a tank is as follows:

1. Dig a pit of the required size. Its walls are poured with expanded clay concrete, which is additionally reinforced.
2. Holes are left from the opposite walls of the hopper. Pipes are installed in them with some slope in order to pump raw materials and extract waste material.
3. The outlet pipe with a diameter of 70 mm is installed practically near the very bottom. Its other end is installed in the tank, into which the waste sludge will be pumped out. It is recommended to make it rectangular.
4. The pipeline for supplying raw materials is placed at a height of 0.5 m relative to the bottom. Its recommended diameter is 30-35 mm. The top of the pipe is brought into a separate tank for receiving prepared raw materials.
5. The top of the bioreactor should be domed or tapered. It can be made from regular roofing iron or other metal sheets. It is allowed to make the lid of the tank using a brick tub. To strengthen its structure, the surface is additionally plastered with the installation of a reinforcing mesh.
6. I make a hatch on top of the tank lid, which should be hermetically closed. A gas outlet pipeline is also taken out through it. Additionally, a pressure relief valve is installed.
7. Several plastic pipes are installed in the tank to mix the substrate. They must be immersed in biomass. Many holes are made in the pipes, which allows the raw materials to be mixed with the help of moving gas bubbles.

Biogas yield calculation

The biogas yield depends on the dry matter content in the feed and its type:

• from 1 ton of manure from large cattle get 50-60 cubic meters. m of a product with a methane content of 60%;
• from 1 ton of plant waste, 200-500 cubic meters are obtained. m of biogas with a methane concentration of 70%;
• from 1 ton of fat, 1300 cubic meters are obtained. m of gas with a methane concentration of 87%.

To determine the efficiency of production, laboratory tests of the raw materials used are carried out. Its composition is calculated, which affects the quality characteristics of biogas.

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

Where does biogas come from and what is it made of?

Biogas is a combustible gas that occurs 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, which is called a reactor, biogas is generated. Inside the reactor will be arranged as follows:

To accelerate 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 consumption for heating. In addition to heating, the fermenting mass must be mixed. Without this, the efficiency of the installation can be significantly reduced. Stirring can be manual or mechanical. It all depends on the budget or the available technical means. The most important thing in a reactor is volume! A small reactor is simply not physically capable of producing a large amount of gas.

The chemical composition of the gas strongly depends on what processes are taking place in the reactor. Most often, the process of methane fermentation takes place there, as a result of which a gas with a high percentage of methane is formed. But instead of methane fermentation, a process with the formation of hydrogen may well occur. But in my opinion, hydrogen is not needed for an ordinary consumer, and maybe even dangerous. Just remember the death of the Hindenburg airship. Now let's figure out what you can get biogas from.

Where can you get biogas?

Gas can be obtained from various types of biomass. Let's list them as a list:

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

Block diagram of a biogas plant.

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

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

• A waste receiver is a kind of container into which raw materials enter 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 the biomass is pumped into 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.
• "Fertilizers" - a container into which fermented sludge falls. It, as is clear from the context, can be used as a fertilizer.
• Filter - a device in which biogas is brought to condition. The filter removes excess gas and moisture impurities.
• Compressor - Compresses the gas.
• Gas storage is a sealed tank in which gas, ready for use, can be stored for as long as desired.

Biogas for a private house.

Many small farm owners are thinking about using biogas for domestic needs. But after finding out in more detail how it all works, most leave this venture. This is due to the fact that equipment for the processing of manure or silage costs a lot of money, and the gas output (depending on the raw material) may turn out to be small. This, in turn, makes the installation of the equipment unprofitable. Usually, for private farmers' houses, primitive installations that run on manure are installed. They, most often, are able to provide gas only to the kitchen and a low-power wall-mounted gas boiler. At the same time, on myself technological process you will have to spend a lot of energy - for heating, pumping, compressor operation. An expensive filter, too, cannot be excluded from the field of view.

In general, the moral here is this - the larger the installation itself, the more profitable its work. And for home conditions, this is almost always impossible. But this does not mean that no one makes home installations. I suggest you watch the following video to see how it looks 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 works the more efficiently, the larger the volume of raw materials is processed. Modern technologies allow you to significantly increase gas production through the use of special catalysts and microorganisms. The main disadvantage of all this is the high price of one cubic meter. For ordinary people, it will often be much cheaper to buy gas in cylinders than to build a waste treatment plant. But, of course, there are exceptions to all the rules, so before deciding to switch to biogas, it is worth calculating the price of a cubic meter and the payback period. That's all for now, write questions in the comments.

Ecology of consumption. The farmstead: Is it profitable to produce biofuels at home in small quantities on a personal subsidiary farm? If you have a few metal drums and other iron junk, as well as a lot of free time and you do not know how to dispose of it - yes.

Suppose there was no natural gas in your village and will not be. And even if there is, it costs money. Although it is an order of magnitude cheaper than ruinous heating with electricity and liquid fuel. The nearest workshop for the production of pellets is a couple of hundred kilometers away, it is expensive to carry. Every year it is more and more difficult to buy firewood, and it is troublesome to heat it. Against this background, the idea of ​​obtaining free biogas from weeds, chicken droppings, manure from a beloved pig or the contents of a master's outhouse looks very tempting. You just need to make a bioreactor! They tell on TV how thrifty German farmers warm themselves with "dung" resources and now they don't need any "Gazprom". This is where the saying "removes the film from feces" is true. The Internet is replete with articles and videos on the topic "biogas from biomass" and "do-it-yourself biogas plant". But we know little about the practical application of the technology: everyone who is not too lazy is talking about the production of biogas at home, but specific examples in the village, just like the legendary Yo-Mobile on the road, few have seen it alive. Let's try to figure out why this is so and what are the prospects for progressive bioenergy technologies in rural areas.

What is biogas + a little history

Biogas is formed as a result of sequential three-stage decomposition (hydrolysis, acid and methane formation) of biomass different kinds bacteria. A useful combustible component is methane, hydrogen may also be present.

Bacterial decomposition process that produces combustible methane

To a greater or lesser extent, flammable gases are formed during the decomposition of any residues of animal and plant origin.

The approximate composition of biogas, the specific proportions of the components depend on the raw materials and technology used

People have long been trying to use this type of natural fuel; in medieval chronicles, there are references to the fact that the inhabitants of the low-lying regions of today's Germany, a thousand years ago, received biogas from decaying vegetation, immersing leather skins in a swamp slurry. In the dark Middle Ages and even the enlightened centuries, the most talented meteorists, who, thanks to a specially selected diet, were able to start up and set fire to abundant methane flatus in time, aroused the constant delight of the public at cheerful fair shows. Construction of industrial biogas plants began with varying success in the middle of the 19th century. In the USSR, in the 80s of the last century, a state program for the development of the industry was adopted, but not implemented, although a dozen production facilities were still launched. Abroad, biogas production technology is being improved relatively actively, the total number of operating installations is tens of thousands. In developed countries (EEC, USA, Canada, Australia) these are highly automated large complexes, in developing countries (China, India) - semi-handicraft biogas plants for houses and small peasant farms.

Percentage of the number of biogas plants in the EU countries. It is clearly seen that the technology is actively developing only in Germany, the reason is solid state subsidies and tax incentives.

What is the use of biogas

It is clear that as fuel, since it burns. Heating of industrial and residential buildings, power generation, food preparation. However, not everything is as simple as shown in the videos scattered around youtube. Biogas must burn stably in heat generating plants. To do this, its parameters of the gaseous environment must be brought to fairly stringent standards. The methane content should be at least 65% (optimum 90-95%), hydrogen should be absent, water vapor removed, carbon dioxide removed, the remaining components are inert to high temperatures.

It is impossible to use biogas of "animal manure" origin, which is not free from fetid impurities, in residential buildings.

The rated pressure is 12.5 bar, if the value is less than 8-10 bar, the automation in modern models of heating equipment and kitchen equipment stops the gas supply. It is very important that the characteristics of the gas entering the heat generator are stable. In the event of a pressure surge beyond the normal range, the valve will work, you will have to turn it back on manually. It is bad if outdated gas appliances are used that are not equipped with a gas control system. In the best case, the boiler burner may fail. The worst case scenario is that the gas will go out, but its flow will not stop. And this is already fraught with tragedy. To summarize what has been said: the characteristics of biogas must be brought to the required parameters, and safety precautions must be strictly observed. Simplified process chain for biogas production. An important stage is separation and gas separation

What raw materials are used for biogas production

Vegetable and animal raw materials

• Vegetable raw materials are excellent for biogas production: from fresh grass, you can get the maximum fuel yield - up to 250 m3 per ton of raw materials, methane content up to 70%. Somewhat less, up to 220 m3 can be obtained from corn silage, up to 180 m3 from beet tops. Any green plants, algae, hay are good (100 m3 per ton), but it makes sense to use valuable feed for fuel only when there is an obvious excess. The yield of methane from the pulp, which is formed during the production of juices, oils and biodiesel, is small, but also the material is gratis. Lack of plant materials - long production cycle, 1.5-2 months. It is possible to obtain biogas from cellulose, other slowly decomposing plant waste, but the efficiency is extremely low, little methane is produced, and the production cycle is very long. In conclusion, let us say that plant raw materials must be finely chopped.
• Raw materials of animal origin: traditional horns and hooves, waste from dairies, slaughterhouses and processing plants are also suitable and also in crushed form. The richest "ore" is animal fats, the yield of high-quality biogas with methane concentration up to 87% reaches 1500 m3 per ton. However, animal raw materials are in short supply and, as a rule, find other uses for it.

Combustible excrement gas

• Manure is cheap and in many farms there is plenty, but the yield and quality of biogas is much lower than from other types. Cow cakes and horse apples can be used in pure form, fermentation starts immediately, the biogas yield is 60 m2 per ton of raw materials with a low methane content (up to 60%). The production cycle is short, 10-15 days. Pig manure and chicken droppings are toxic - so that beneficial bacteria can develop, it is mixed with plant waste, silage. Big problem represent detergents, surfactants, which are used when cleaning livestock buildings. Together with antibiotics, which in large quantities enter the manure, they inhibit the bacterial environment and inhibit the formation of methane. It is completely impossible not to use disinfectants, and agricultural enterprises that have invested in the production of gas from manure are forced to seek a compromise between hygiene and control over the morbidity of animals, on the one hand, and maintaining the productivity of bioreactors, on the other.
• Human excrement, completely free, is fine too. But it is unprofitable to use ordinary sewage drains, the concentration of feces and high disinfectants, surfactants are too low. Technologists argue that they could be used only if "products" only from the toilet bowl will enter the sewer system, provided that the bowl is flushed with only one liter of water (standard 4/8 liters). And without detergents, of course.

Additional requirements for raw materials

A serious problem faced by farms that have installed modern equipment for biogas production is that the raw materials should not contain solid inclusions, a stone, nut, piece of wire or a board accidentally caught in the mass will clog the pipeline, disable an expensive fecal pump or mixer. It must be said that the given data on the maximum gas yield from raw materials correspond to ideal laboratory conditions. In order to approach these figures in real production, it is necessary to observe a number of conditions: maintain the required temperature, periodically mix finely ground raw materials, add additives that activate fermentation, etc. On a handicraft installation, assembled according to the recommendations of articles on "getting biogas with your own hands", you can hardly reach 20% of the maximum level, high-tech installations allow you to achieve values ​​of 60-95%.

Sufficiently objective data on the maximum biogas yield for different types raw materials

Biogas plant device

Is it profitable to engage in biogas production?

We have already mentioned that in developed countries they build large industrial installations, and in developing countries mainly small ones, for a small economy. Let's explain why this is so:

Does it make sense to produce biofuels at home?

Is it profitable to produce biofuels at home in small quantities on personal subsidiary plots? If you have a few metal drums and other iron junk, as well as a lot of free time and you do not know how to dispose of it - yes. But the savings, alas, are scanty. And investing in high-tech equipment with small volumes of raw materials and methane production does not make sense in any case.

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Without mixing the raw materials and activating the fermentation process, the methane yield will be no more than 20% of the possible. This means that in the best case, with 100 kg (bunker loading) of selected grass, you can get 5 m3 of gas without taking into account compression. And it will be good if the methane content exceeds 50% and it is not a fact that it will burn in the heat generator. According to the author, raw materials are loaded daily, that is, his production cycle is one day. In fact, the required time is 60 days. The amount of biogas received by the inventor, contained in a 50-liter cylinder, which he was able to fill, in frosty weather for a 15 kW heating boiler (residential building about 150 m2) is enough for 2 minutes.

Those who are interested in the possibility of biogas production are advised to carefully study the problem, especially from a financial point of view, contact specialists with experience in such work with technical questions. Practical information from those farms where bioenergy technologies have been in use for some time will be very valuable. published by

Introduction

Production of biogas from meta tanks and agricultural biogas plants

Biogas storage systems

Biogas composition

Biogas preparation for use

The main directions and world leaders in the use of biogas

Conclusion

List of used literature

Introduction

In the world practice of gas supply, sufficient experience has been accumulated in the use of renewable energy sources, including biomass energy. The most promising gaseous fuel is biogas, the interest in the use of which in last years not only does not decrease, but also continues to increase. Biogas refers to the methane-containing gases that are generated during the anaerobic decomposition of organic biomass. Depending on the source of production, biogas are divided into three main types:

Digester gas obtained at city sewage treatment plants (BG KOS);

Biogas obtained in biogas plants (BGU) during fermentation of agricultural waste (BG SHP);

Landfill gas obtained at landfills containing organic components (MSW).

In my work, I examined the technologies for obtaining these gases, their composition, methods of preparing biogas for use, namely, methods of cleaning from ballast substances. Biogas has a wide range of uses, which I briefly covered in this work.

Production of biogas from meta tanks and agricultural biogas plants

According to their technical design, biogas plants are subdivided into three systems: accumulative, batch, and continuous.

In accumulative systems, fermentation is provided in reactors, which simultaneously serve as a storage place for fermented manure (substrate) before it is unloaded. The original substrate is continuously fed into the reservoir until it is full. The unloading of the fermented substrate is carried out once or twice a year during the period of fertilizing the soil. In this case, part of the fermented sludge is specially left in the reactor and serves as a seed material for the subsequent fermentation cycle. The volume of the storage combined with the bioreactor is calculated for the total volume of manure removed from the complex during the inter-sowing period. Such systems require large amounts of storage and are rarely used.

A batch system for biogas production involves a one-time loading of the initial substrate into the reactor, feeding there the seed material and unloading the fermented product. Such a system is characterized by a rather large labor intensity, a very uneven gas output and requires at least two reactors, a reservoir for the accumulation of the original manure and storage of the fermented substrate.

With a continuous scheme, the original substrate is continuously or at regular intervals (1-10 times a day) loaded into the fermentation chamber, from where the same amount of fermented sediment is simultaneously removed. To intensify the fermentation process, various additives can be introduced into the bioreactor, increasing not only the reaction rate, but also the yield and quality of the gas. Modern biogas plants are designed, as a rule, for a continuous process and are made of steel, concrete, plastics, bricks. Fiberglass, glass wool, cellular plastic are used for thermal insulation.

In terms of daily productivity, existing biogas systems and installations can be divided into 3 types:

small - up to 50 m 3 / day;

medium - up to 500 m 3 / day;

large - up to 30 thousand m 3 / day.

Meta-tank and agricultural biogas plants do not have any fundamental differences, with the exception of the substrate used. The technological scheme of a biogas agricultural plant is shown in Fig. one.

According to this scheme, manure from the livestock building (1) enters the storage tank (2), then with a fecal pump (3) it is loaded into the digester - a tank for anaerobic digestion (4). Biogas generated in the fermentation process enters the gas tank (5) and then to the consumer. To heat the manure to the fermentation temperature and maintain thermal conditions in the digester, a heat exchanger (6) is used, through which flows hot water heated in a boiler (7) Fermented manure is discharged into a manure storage (8).

Fig. 1. Generalized scheme for biogas production (agricultural biogas

The bioreactor has thermal insulation, which must stably maintain the fermentation temperature and can be quickly replaced in case of failure. The bioreactor is heated by placing heat exchangers along the perimeter of the walls in the form of a spiral of pipes through which hot water circulates with an initial temperature of 60-70 ° C. Such low temperature the coolant is adopted in order to avoid the death of methane-forming microorganisms and the adhesion of substrate particles to the heat-exchange surface, which can lead to a deterioration in heat exchange. The bioreactor also has devices for constant mixing of manure. The supply of manure to the digester is regulated so that the fermentation process proceeds evenly.

During fermentation, microflora develops in the manure, which sequentially destroys organic substances to acids, and the latter, under the action of syntrophic and methane-forming bacteria, turn into gaseous products - methane and carbon dioxide.

The digesters provide all the necessary process parameters - temperature (33-37º С), concentration of organic substances, acidity (6.8-7.4), etc. The growth of cells of methane biocenosis is also determined by the C: N ratio, and its optimal value is 30 :one. Some substances contained in the original substrate can inhibit methane fermentation (Table 1). For example, chicken manure often inhibits methane fermentation with excess NH3.

Table 1

Methane digestion inhibitors

Biogas from solid waste landfills

The process of uncontrolled gas formation at landfills of household and other wastes containing a large proportion of organic components can be considered as a process of obtaining methane-containing gas in an accumulative system, the duration of the process until the complete decomposition of the organic part is much longer here than in meta tanks.

In domestic practice, biogas utilization systems at solid waste landfills have not yet become widespread, therefore, when further considering the design features of biogas collection and transport systems, foreign experience will be taken into account. A schematic diagram of one of these systems at a solid waste landfill is shown in Fig. 2. The system consists of two main parts: a gas collection network under vacuum and a distribution network of biogas consumers under excessive low or (less often) medium pressure.

Rice. 2. Construction of a degassing system for solid waste landfills

Below are the definitions of the most important elements of the gas collection system at the landfill, presented in Fig. 2, and requirements for individual elements of the system.

Gas collectors are pipelines laid in the mass of waste, in which a vacuum is created. As a rule, they are performed either vertically in the form of gas wells, or horizontally in the form of perforated pipelines, but in practice other forms are also used (tanks, gravel or crushed stone chambers, etc.).

Prefabricated gas pipelines are understood to be gas pipelines under vacuum and leading to a part of the prefabricated manifolds. To compensate for subsidence, they have a flexible connection to the gas manifold; the connection unit contains instrumentation (for measuring pressure) and fittings for gas sampling.

At the gas collection point, prefabricated gas pipelines are combined. The gas gathering point can be made in the form of a pipe, a reservoir, etc. and is located at the lowest point in order to ensure the collection and removal of the condensate that falls out. The gas collection point houses the instrumentation and automation devices.

A condensate drain is a device on a gas pipeline to collect and drain condensate at the lowest point in the pipeline system. In the vacuum zone, condensate is discharged through siphons, in the overpressure zone - through adjustable steam traps. Condensate can also be removed both in the vacuum and in the overpressure zone using a cooling device.

The suction pipeline is the straight section of the pipeline in front of the injection device; instrumentation and automation devices are also provided here.

Pumping devices (fan, blower, etc.) are used to create a vacuum necessary for transporting gas from a burial body or to create excess pressure when transporting gas to the place of use (to a flare unit, to a utilization system, etc.).

The compressor unit serves to increase the excess gas pressure.

In the engine room there are injection devices. Traditional structures are containers, metal enclosures or small structures (garages, block structures, etc.). In large installations, gas injection devices are located in the machine room, sometimes they can be located in open areas under a canopy.

How to reduce the cost of heating, cooking and electricity is a concern for many household owners. Some of them have already built biogas plants with their own hands and have partially or completely isolated themselves from energy suppliers. It turns out that getting almost free fuel in a private household is not very difficult.

What is biogas and how can it be used?

Household owners know that by piling up any plant materials, poultry droppings and manure, after a while you can get valuable organic fertilizer. But few of them know that biomass does not decompose on its own, but under the influence of various bacteria.

By processing a biological substrate, these tiny microorganisms release waste products, including a gas mixture. Most of it (about 70%) is methane - the same gas that burns in the burners of household stoves and heating boilers.

The idea of ​​using such ecofuel for various economic needs is not new. Devices for its extraction were used in ancient China... The possibility of using biogas was also explored by Soviet innovators in the 60s of the last century. But the technology experienced a real revival in the early 2000s. On the this moment biogas plants are actively used in Europe and the USA for heating houses and other needs.

How does a biogas plant work?

The principle of operation of the device for the production of biogas is quite simple:

• biomass diluted with water is loaded into a sealed container, where it begins to "ferment" and release gases;
• the contents of the tank are regularly updated - the raw materials processed by bacteria are drained and fresh is added (on average, about 5-10% daily);
• the gas accumulated in the upper part of the tank flows through a special tube to the gas collector, and then to household appliances.

Diagram of a biogas plant.

What kind of raw material is suitable for a bioreactor?

Installations for biogas production are profitable only where there is a daily replenishment of fresh organic matter - manure or dung from livestock and poultry. Also, chopped grass, tops, foliage and household waste (in particular, cleaning from vegetables) can be mixed into the bioreactor.

The efficiency of the plant largely depends on the type of feedstock being fed. It has been proven that with the same mass, the largest biogas yield is obtained from pig manure and turkey manure. In turn, cow excrement and silage waste produce less gas for the same load.

Use of bio raw materials for home heating.

What cannot be used in a biogas plant?

There are factors that can significantly reduce the activity of anaerobic bacteria, or even stop the process of biogas production altogether. It should not be allowed that raw materials containing:

• antibiotics;
• mold;
• synthetic detergents, solvents and other "chemicals";
• resins (including sawdust of coniferous trees).

It is ineffective to use already decaying manure - only fresh or previously dried waste can be loaded. Also, overmoistening of raw materials should not be allowed - an indicator of 95% is already considered critical. However, a small amount of pure water should still be added to the biomass in order to facilitate its loading and accelerate the fermentation process. Dilute manure and waste to the consistency of a thin semolina.

Biogas plant for home

Today the industry is already producing plants for the production of biogas on an industrial scale. Their purchase and installation is expensive, such equipment pays off in private households not earlier than in 7-10 years, provided that large volumes of organic matter are used for processing. Experience shows that, if desired, a skilled owner can build a small biogas plant for a private house with his own hands, and from the most affordable materials.

Preparing the recycling bunker

First of all, you will need a hermetically sealed cylindrical container. You can, of course, use large pots or boils, but their small volume will not allow you to achieve sufficient gas production. Therefore, for these purposes, most often plastic barrels with a volume of 1 m³ to 10 m³ are used.

You can make this yourself. PVC sheets are commercially available, with sufficient strength and resistance to aggressive environments, they are easily welded in a structure of the desired configuration. A metal barrel of sufficient volume can also be used as a hopper. True, you will have to carry out anti-corrosion measures - cover it inside and out with moisture-resistant paint. If the tank is made of stainless steel, you do not need to do this.

Gas evacuation system

The gas outlet is mounted in the upper part of the barrel (usually in the lid) - it is there that it accumulates, according to the laws of physics. Through the connected pipe, biogas is supplied to the water seal, then to the storage tank (as an option, to the cylinder with the help of a compressor) and to household appliances... It is also recommended to install a drain valve next to the gas outlet - if the pressure inside the tank becomes too high, it will release excess gas.

Raw material feeding and unloading system

To ensure continuous production of the gas mixture, bacteria in the substrate must be constantly (daily) “fed”, that is, fresh manure or other organic matter must be added. In turn, already processed raw materials from the bunker must be removed so that they do not take up a useful place in the bioreactor.

To do this, two holes are made in the barrel - one (for unloading) almost near the bottom, the other (for loading) higher. Pipes with a diameter of at least 300 mm are welded (soldered, glued in) into them. The loading pipeline is directed upward and equipped with a funnel, and the drain is arranged so that it is convenient to collect the processed slurry (it can later be used as fertilizer). The joints are sealed.

Heating system

Bunker thermal insulation.

If the bioreactor is installed outdoors or in an unheated room (which is necessary for safety reasons), then it must be provided with thermal insulation and heating of the substrate. The first condition is achieved by "wrapping" the barrel with any insulating material or deepening into the ground.

As for heating, here you can consider the most different variants... Some craftsmen put pipes inside, through which water from the heating system circulates and mount them along the walls of the barrel in the form of a coil. Others put the reactor in a larger tank of water inside, heated by electric heating. The first option is more convenient and much more economical.

To optimize the operation of the reactor, it is necessary to maintain the temperature of its contents at a certain level (at least 38⁰C). But if it rises above 55⁰C, then the gas-forming bacteria will simply "cook" and the fermentation process will stop.

Stirring system

As practice shows, in designs a hand mixer of any configuration significantly increases the efficiency of the bioreactor. The axis, to which the "mixer" blades are welded (screwed), is removed through the barrel lid. A gate handle is then put on it, the hole is carefully sealed. However, home craftsmen do not always equip fermenters with such devices.

Biogas production

After the installation is ready, it is loaded with biomass diluted with water in a ratio of about 2: 3. In this case, large waste should be crushed - the maximum size of the fraction should not exceed 10 mm. Then the lid closes - it remains to wait for the mixture to "ferment" and release biogas. Under optimal conditions, the first intake of fuel is observed several days after loading.

The fact that the gas "went" can be judged by the characteristic gurgle in the water seal. At the same time, the barrel should be checked for leaks. This is done with the help of a regular soap solution - it is applied to all joints and observe if bubbles have appeared.

The first renewal of bio-raw materials should be carried out in about two weeks. After the biomass is poured into the funnel, the same volume of waste organic matter will pour out of the waste pipe. Further, this procedure is performed daily or every two days.

How long does the produced biogas last?

In a small farm, a biogas plant will not be an absolute alternative natural gas and other available energy sources. For example, using a device with a capacity of 1 m³, you can get fuel only for a couple of hours of cooking for a small family.

But with a bioreactor of 5 m³ it is already possible to heat a room with an area of ​​50 m², but its operation will need to be supported by a daily loading of raw materials weighing at least 300 kg. To do this, you need to have about ten pigs, five cows and a couple of dozen chickens on the farm.

Craftsmen who managed to independently make operating biogas plants share videos with master classes on the Internet: