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Biogas - what is it? General concept and applicability. Production and calculation of biogas Chemical reactions in the production of biogas

Introduction

Production of biogas from digesters and agricultural biogas plants

Biogas storage systems

Biogas composition

Preparation of biogas for use

Main directions and world leaders in the use of biogas

Conclusion

List of used literature

Introduction

In the global 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 recent years has not only not waned, but continues to increase. Biogases mean methane-containing gases that are formed during the anaerobic decomposition of organic biomass. Depending on the source of production, biogases are divided into three main types:

Digester gas produced at municipal sewage treatment plants (BG STP);

Biogas produced in biogas plants (BGU) during the fermentation of agricultural waste (BG Agricultural Production);

Landfill gas produced at landfills containing organic components (BG MSW).

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


Production of biogas from digesters and agricultural biogas plants

According to technical design, biogas plants are divided into three systems: accumulative, periodic, continuous.

Accumulative systems provide for fermentation in reactors, which also serve as a storage place for fermented manure (substrate) until it is unloaded. The initial substrate is continuously fed into the tank until it is filled. The fermented substrate is unloaded once or twice a year during the period of applying fertilizers to the soil. In this case, part of the fermented sludge is specially left in the reactor and serves as seed material for the subsequent fermentation cycle. The storage volume 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 used very rarely.

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

With a continuous scheme, the initial substrate is continuously or at certain 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 added to the bioreactor, increasing not only the reaction rate, but also the yield and quality of gas. Modern biogas plants are usually designed for a continuous process and are made of steel, concrete, plastics, and brick. For thermal insulation, fiberglass, glass wool, and cellular plastic are used.

Based on 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.

Digester and agricultural biogas plants have no fundamental differences, with the exception of the substrate used. The technological diagram of a biogas agricultural installation is shown in Fig. 1.

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

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

The bioreactor has thermal insulation, which should stably maintain the fermentation temperature and be quickly replaced if it fails. The bioreactor is heated by placing heat exchangers around 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 a low temperature of the coolant is adopted to avoid the death of methane-producing microorganisms and the sticking of substrate particles on the heat exchange surface, which can lead to deterioration of heat transfer. The bioreactor also has devices for constant mixing of manure. The flow of manure into the digester is regulated so that the fermentation process proceeds evenly.

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

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

Table 1

Methane fermentation inhibitors

Biogas produced at solid waste landfills

The process of uncontrolled gas formation at landfills of household and other waste containing a large proportion of organic components can be considered as a process of producing methane-containing gas in an accumulative system; the duration of the process until the complete decomposition of the organic part is much longer than in metatanks.

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

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


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

Gas collectors are pipelines laid in the thickness of the 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 (reservoirs, gravel or crushed stone chambers, etc.).

Prefabricated gas pipelines mean gas pipelines that are under vacuum and lead to part of the prefabricated collectors. To compensate for drawdowns, they have a flexible connection to the gas manifold; instrumentation (for measuring pressure) and fittings for gas sampling are located in the connection unit.

Collecting gas pipelines are combined at a gas collection point. The gas collection point can be made in the form of a pipe, tank, etc. and is located at the lowest point in order to ensure the collection and removal of falling condensate. Instrumentation and automation devices are located at the gas collection point.

A condensate removal system is a device on a gas pipeline for collecting and discharging condensate at the lowest point of the pipeline system. In the vacuum zone, condensate is discharged through siphons, in the area of ​​excess pressure - through adjustable condensate drains. Condensate can also be removed both in the underpressure zone 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.

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

The compressor unit serves to increase the excess gas pressure.

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

The release of flammable gases from decaying waste and biomass was noticed as early as the 17th century.

In 1776, scientist Allesandro Volta concluded that there was a mutual relationship between the mass of decomposing matter and the volume of gas released, and it was later discovered that the main combustible component of the resulting biogas was methane.

Since methane is the main component of natural gas extracted from the subsoil, in the process of studying biogas, installations for its industrial production began to appear as an alternative to fossil fuels.

The first documented biogas plant was built in 1859 in India, and for the first time in Europe, in the UK, biogas began to be used in street lighting in 1895.


Drawing showing a cross section of the first biogas plant

Biochemical processes of biogas formation

The first experimental installations for producing biogas were developed by trial and error, without a true understanding of the processes taking place. With the development of microbiology, it was revealed that gas evolution occurs due to hydrogen and methane biomass fermentation. Since these types of fermentation occur without access to oxygen, the methane-emitting process of biomass decomposition is also called anaerobic.


Anaerobic digestion occurs naturally when swamp gas is formed.

In another way, biogas synthesis is called biodestruction (biological destruction) of organic substances with the release of free gas methane (CH4). Below is a simplified formula demonstrating the release of chemicals from organic compounds during the life of methanogen bacteria, which release methane by-product gas during metabolism:

In other words, microscopic bacteria, consuming organic substances contained in biomass and biological waste, release flammable gas. But even under the most favorable conditions, the release of flammable gas does not occur immediately; first, a fermentation process of biomass is required, the decomposition of which occurs in several stages over certain periods of time.

Stages of biogas synthesis

For the reproduction and vital activity of methane-emitting methanogens, a nutrient medium is needed, which is formed in the installation for producing biogas by previous generations of other bacteria. In the first stage, proteins, fats and carbohydrates present in the biomass, under the influence of hydrolytic enzymes, break down into simple organic compounds: amino acids, sugar, fatty acids. This stage occurs under the influence of acetogenic bacteria and is called hydrolysis.


Various bacteria seen under a microscope

In the second stage, under the influence of heteroacetogenic bacteria, hydrolytic oxidation of part of the organic compounds occurs, resulting in carbon dioxide, free hydrogen and acetate.

The non-oxidized part of the simple organic compounds obtained in the first stage, when interacting with the acetate formed in the second stage, forms the simplest organic acids, which are the necessary nutrient medium for bacteria that produce methane in the third stage.


Stages of life activity of microorganisms during the formation of methane

It is at the third stage that biogas is produced, the intensity of which depends on the following main factors:

  • Biomass composition;
  • Temperature of the nutrient medium;
  • Pressure inside the installation;
  • Acid-base balance pH;
  • Ratio of water and loaded biomass;
  • Grinding of raw materials and frequency of substrate mixing;
  • The presence of stimulating and inhibiting components in the environment;
  • Ratios of carbon, phosphorus, nitrogen and other elements.

Schematic representation of the main components of a biogas plant

Optimal composition of raw materials for biogas production

Since proteins, fats and carbohydrates are contained in any biomass of plant or animal origin, as well as in waste and food industry, in addition to scientific laboratories and industrial installations, it is quite possible to obtain biogas at home.

But in a DIY home setup, it will be very difficult to control the parameters described above. The video below shows an example of an industrial biogas plant for a home:


Continuing this topic, the next article will talk in detail about the existing types of biogas generators and homemade biogas plants that craftsmen make with their own hands.

At this stage it is worth recalling that biogas is flammable and explosive, and excessive pressure can rupture the biogas plant with a subsequent gas explosion. Therefore, the primary controlled parameter should be the pressure in the installation and the tightness of the structure.


Examples of raw materials for biogas production

The maximum amount of biogas can be obtained from animal fats - about 1500 m3 from a ton of raw materials with a methane concentration of 87%. Also, a significant yield of biogas is obtained from overcooked vegetable oil - about 1200 m3 with a CH4 concentration of 68%.

Significantly less biogas is obtained from the seeds of various plants from 500 m3 - 54% CH4 (oats) to 644 m3 - 65.7% CH4 (rapeseed). From corn silage, grass and other plants, 450-100 m3 can be obtained with an average methane concentration of 55-50%.


Possible production of biogas from various seeds and root crops

Biogas from animal waste

The gas yield from animal manure is much smaller, since after passing through the food tract the amount of nutrients for methane-forming microorganisms in the waste is small.

Since birds have a digestive system designed to quickly extract the bulk of nutrients from food, with frequent bowel movements to facilitate flight, the biogas output from the droppings will be the largest - about 100 m3 at 65% CH4.


The use of a biogas plant is most beneficial on poultry farms where there is a problem with the disposal of bird droppings

Whereas cattle manure has the lowest biogas yield, averaging 25 m3 at 55% CH4, due to the digestive tract designed to extract maximum nutrients from the feed over a long period of time with repeated mastication of the food.

The yield of biogas from manure increases when it is mixed with bedding and feed residues. The humidity and freshness of the manure also matters - for more detailed data you need to study special tables.


Possible production of biogas from farm animal manure

The fermentation rate and methane concentration in biogas are greatly influenced by the quality of water and the presence of impurities. Highly chlorinated tap water used to dilute manure will inhibit the fermentation process.

If bactericidal substances and chemical detergents are used when cleaning stalls, the reaction rate in the biogas plant will slow down significantly. For the same reason, significant difficulties arise in the gasification of sewage waste from human housing due to low profitability and high concentration of detergents.

Despite the low yield of biogas from the waste of organisms, in home-made biogas plants it is necessary to add manure to other types of raw materials to multiply in the substrate all the required types of bacteria that initially live in the digestive tract


Manure containing bacteria must be added to the substrate to produce biogas.

Composition of the biogas mixture

As mentioned above, at different stages in the biosynthesis process, in addition to methane, carbon dioxide and hydrogen are released. Also, depending on the raw material, ammonia and hydrogen sulfide are released. Although hydrogen is flammable, its volatility does not allow this gas to be used in standard gas installations.

Ammonia and hydrogen sulfide are toxic compounds that harm both the bacteria inside the biogas plant and the environment. Carbon dioxide is a ballast, and its large amount in the mixture significantly reduces the flammability and calorific value of biogas.


Average percentage of impurities in biogas obtained from various raw materials

Obviously, due to the large number of impurities, the use of biogas in conventional boilers and cookers is only possible after careful cleaning synthesized gas mixture. The resulting biogas is purified in several stages, but it is almost impossible to achieve perfectly pure methane, the main thing is that the concentration of impurities does not exceed the established standards.


The flame of burning biogas must be clean, like all biological energy

At the first stage of purification, biogas passes through a water filter, where most of the carbon dioxide, ammonia and various aromatic compounds are dissolved. Water with a high concentration of dissolved carbon dioxide and ammonia can be used to grow algae, which, in turn, will be used to synthesize biogas in a biogas plant.


Biogas purification systems in an industrial biogas plant

After water cleaning, the biogas goes to a hydrogen sulfide removal filter. The simplest is a filter made of metal shavings and sawdust on which sulfur is deposited. Industrial filters use special catalysts and sulfur precipitating solutions. The best quality of biogas is obtained after passing through a membrane filter, where molecules of unwanted impurities are eliminated at the molecular level.


Biogas purification to pure methane using a membrane filter

Description of the influence of some factors on the release of biogas

To determine the rate of fermentation and the intensity of biogas release, one of the decisive factors is the temperature of the mixture. You need a thermometer, or better yet, an electrical sensor to control the temperature.

In industrial biogas plants, the temperature and other parameters are controlled by special controllers. Sometimes the heat of reaction is enough to maintain the optimal temperature, but most often the substrate has to be heated, especially during the cold season.


Computerized biogas plant controller with gas analyzers

Based on temperature conditions, three types of anaerobic fermentation are distinguished:

  • Psychrophilic installations operating without heating, where the temperature is spontaneously maintained at 15-25ºC. Used in countries with warm climates;
  • Mesophilic, require additional minor heating to maintain a temperature of 25-40ºC. They have the richest composition of environmentally friendly fertilizers formed after generation, which is why they are optimally suited for small farms;
  • Thermophilic biogas plants require large amounts of energy to maintain temperatures above 40ºC, maximum 90ºC. At this temperature, pathogenic bacteria in the resulting fertilizers die, and the highest yield of biogas is obtained, which is why it is widely used in the industrial production of biological gas.

Thermal insulation of a thermophilic biogas plant reactor

Along with temperature, the size of solid particles of manure, waste and biomass is of great importance. The smaller the raw material particles, the greater the contact area between bacteria and the nutrient medium. Therefore, the most important thing when preparing raw materials is its grinding.

Contact of bacteria with food is hampered during the biosynthesis process due to the accumulation of waste products of microorganisms. Therefore, timely mixing of the substrate during the fermentation process is also a significant factor for the gasification of biomass. An example of an industrial biogas plant with control of all parameters:

Profitability of biogas production

Germany is a leader in the production of high-quality biogas from cultivated raw materials and waste from livestock farms. The profitability of gas biosynthesis is determined by the high cost of energy resources, on the one hand, and the presence of incentive government programs.

The incentive to implement biogas technologies is both a significant subsidy for the purchase of environmental energy resources from manufacturers and an impressive fine for environmental pollution with unprocessed manure.


Environmentally friendly biogas complex in an economically developed country

In poor villages in India and China, owners of semi-artisanal biogas plants practically do not purify their gas, burning it immediately in a stove or gas burner. In these countries, the production of biological gas from household waste and specially grown plant materials pays off due to the low cost of manual labor of peasants and the low cost of the installations themselves, which lack expensive purification systems and complex automated monitoring and control systems.


An example of semi-artisanal biogas plants in poor villages in Asia

In the press and the Internet you can find many cheerful headlines such as: “Budget savings with a biogas plant”, “Free energy from manure”, “Do-it-yourself biogas”, but in practice, expectations for the payback of expensive equipment and costs are at odds with reality. This is due to the difficulty of controlling all parameters, as well as the need for heating for optimal fermentation speed. An example of an optimistic news story:


The next article will give examples of home-made installations demonstrating gas output in real conditions, and everyone will be able to determine for themselves the profitability of independent biogas production, based on their capabilities and energy tariffs.

A significant advantage of self-production of biogas is the by-product production of high-quality environmentally friendly fertilizer. In the video below, the master explains the theoretical basis of obtaining biogas and obtaining fertilizers.

The issue of methane production is of interest to those owners of private farms who breed poultry or pigs, and also keep cattle. As a rule, such farms produce a significant amount of organic animal waste, which can bring considerable benefits by becoming a source of cheap fuel. The purpose of this material is to tell you how to produce biogas at home using this same waste.

General information about biogas

Home biogas, obtained from various manures and poultry droppings, mostly consists of methane. There it is from 50 to 80%, depending on whose waste was used for production. The same methane that burns in our stoves and boilers, and for which we sometimes pay a lot of money according to the meter readings.

To give an idea of ​​the amount of fuel that can theoretically be produced when keeping animals at home or in the country, we present a table with data on the yield of biogas and the content of pure methane in it:

As you can see from the table, to effectively produce gas from cow dung and silage waste, a fairly large amount of raw material will be needed. It is more profitable to extract fuel from pig manure and turkey droppings.

The remaining share of substances (25-45%) that make up home biogas is carbon dioxide (up to 43%) and hydrogen sulfide (1%). The fuel also contains nitrogen, ammonia and oxygen, but in small quantities. By the way, it is thanks to the release of hydrogen sulfide and ammonia that the manure heap emits such a familiar “pleasant” smell. As for the energy content, 1 m3 of methane can theoretically release up to 25 MJ (6.95 kW) of thermal energy when burned. The specific heat of combustion of biogas depends on the proportion of methane in its composition.

For reference. In practice, it has been verified that heating an insulated house located in the middle zone requires about 45 m3 of biological fuel per 1 m2 of area during the heating season.

Nature arranges it in such a way that biogas from manure is formed spontaneously and regardless of whether we want to receive it or not. A manure heap rots within a year to a year and a half, simply by being in the open air and even at sub-zero temperatures. All this time it releases biogas, but only in small quantities, since the process is extended over time. The cause is hundreds of types of microorganisms found in animal excrement. That is, nothing is needed to start gas evolution; it will happen on its own. But to optimize the process and speed it up, special equipment will be required, which will be discussed further.

Biogas technology

The essence of effective production is to accelerate the natural process of decomposition of organic raw materials. To do this, the bacteria in it need to create the best conditions for reproduction and waste processing. And the first condition is to place the raw material in a closed container - a reactor, otherwise - a biogas generator. The waste is crushed and mixed in a reactor with a calculated amount of clean water until the initial substrate is obtained.

Note. Clean water is necessary to ensure that substances that adversely affect the life of bacteria do not get into the substrate. As a result, the fermentation process can slow down greatly.

An industrial biogas production plant is equipped with substrate heating, means of mixing and control of the acidity of the environment. Stirring is carried out in order to remove the hard crust from the surface, which occurs during fermentation and interferes with the release of biogas. The duration of the technological process is at least 15 days, during which time the degree of decomposition reaches 25%. It is believed that the maximum fuel yield occurs up to 33% of biomass decomposition.

The technology provides for daily renewal of the substrate, which ensures intensive production of gas from manure; in industrial installations it amounts to hundreds of cubic meters per day. Part of the waste mass, amounting to about 5% of the total volume, is removed from the reactor, and the same amount of fresh biological raw materials is loaded in its place. The waste material is used as organic fertilizer for fields.

Biogas plant diagram

When producing biogas at home, it is impossible to create such favorable conditions for microorganisms as in industrial production. And first of all, this statement concerns the organization of generator heating. As is known, this requires energy expenditure, which leads to a significant increase in the cost of fuel. It is quite possible to control compliance with the slightly alkaline environment inherent in the fermentation process. But how can it be corrected in case of deviations? Costs again.

Owners of private farms who want to produce biogas with their own hands are recommended to make a reactor of a simple design from available materials, and then modernize it according to their capabilities. What need to do:

  • hermetically sealed container with a volume of at least 1 m3. Various small tanks and barrels are also suitable, but little fuel will be released from them due to the insufficient amount of raw materials. Such production volumes will not suit you;
  • When organizing biogas production at home, you are unlikely to heat the container, but you definitely need to insulate it. Another option is to bury the reactor in the ground, thermally insulating the upper part;
  • install a manual stirrer of any design in the reactor, extending the handle through the top cover. The handle passage assembly must be sealed;
  • provide pipes for supplying and unloading the substrate, as well as for collecting biogas.

Below is a diagram of a biogas plant located below ground level:

1 – fuel generator (container made of metal, plastic or concrete); 2 — hopper for filling the substrate; 3 – technical hatch; 4 – vessel acting as a water seal; 5 – outlet for unloading waste waste; 6 – biogas sampling pipe.

How to get biogas at home?

The first operation is grinding waste to a fraction whose size is no more than 10 mm. This makes it much easier to prepare the substrate, and it will be easier for bacteria to process the raw materials. The resulting mass is thoroughly mixed with water, its quantity is about 0.7 liters per 1 kg of organic matter. As mentioned above, only clean water should be used. Then a self-made biogas plant is filled with the substrate, after which the reactor is hermetically sealed.

Several times during the day you need to visit the container to mix the contents. On the 5th day, you can check for the presence of gas, and if it appears, periodically pump it out with a compressor into a cylinder. If this is not done in time, the pressure inside the reactor will increase and fermentation will slow down, or even stop altogether. After 15 days, it is necessary to unload part of the substrate and add the same amount of new one. You can find out more by watching the video:

Conclusion

It is likely that the simplest biogas installation will not meet all your needs. But, given the current cost of energy resources, this will already be of considerable help in the household, because you do not have to pay for the raw materials. Over time, being closely involved in production, you will be able to grasp all the features and make the necessary improvements to the installation.

Methane “fermentation”, or biomethanogenesis, the process of converting biomass into energy, was discovered by Europeans only in 1776 by Volta, who established the presence of methane in swamp gas. The biogas produced by this process is a mixture of 65% methane, 30% carbon dioxide, 1% hydrogen sulfide and trace amounts of nitrogen, oxygen, hydrogen and carbon monoxide. (A. Sasson)
The first information about the practical use of biogas obtained by Europeans from agricultural waste dates back to 1814, when Davey collected biogas while studying the agrochemical properties of cattle manure. To collect waste, starting in 1881, closed containers began to be used, which, after slight modification, were called “septic tanks”. Back in 1895, street lamps in one of the areas of the city of Exeter (England) were supplied with gas, which was obtained as a result of fermentation of wastewater. Since 1897, water purification in this city was carried out in such containers, from which biogas was collected and used for heating and lighting.
Currently, bioreactors of various designs are known, which provide for the strength of the material from which the installation is created, devices for mass mixing and heat transfer, preparation and heating of the loaded substrate, intake and accumulation of biogas and sediment removal.
Since December 1, 2000, the Karaganda EcoMuseum has been implementing the “BIOGAS” project to introduce biogas technologies in the Karaganda region. This project is the first experience in using biogas technologies in Central Kazakhstan. During the implementation of the project, the Ecological Museum has accumulated quite a lot of experience and information about the construction, startup and operation of biogas plants, and this experience is tied to the local conditions of Central Kazakhstan, where similar technologies have not previously been used.
Employees of the Karaganda Ecological Museum have developed and implemented several technologies for the construction of biogas plants, adapted for peasants and farmers of Kazakhstan.

Why do we need biogas?
Biogas is a metabolic product of methane bacteria, which is formed as a result of the decomposition of organic matter.
Biogas is a high-quality and complete carrier of energy and can be used in many ways as fuel in households and in medium and small businesses for cooking, generating electricity, heating residential and industrial premises, boiling, drying and cooling. The average combustion heat is 6.0 kW/h/cub.m
The extent to which biogas can replace traditional fuel depends on the volume and efficiency of the plant. The Karaganda experience of using BGU shows that an installation with a volume of 8 cubic meters. m. and running on pig manure can completely replace propane gas used for cooking in a family of five. A BGU with a volume of 60 cubic meters can be used to heat residential premises with an area of ​​200 sq.m and an industrial premises with an area of ​​400 sq.m.
When operating a biogas plant, waste raw materials are also a useful product that can improve the economic and environmental conditions of a peasant or farm enterprise. Biosludge is a high-quality fertilizer, raw material for the production of vermicompost, a substrate for growing mushrooms. And with appropriate installation parameters and control over compliance with the temperature regime of operation, the BGU is a feed additive for animals that require animal protein for normal development (pigs, chickens, etc.) and complementary food for fish in fish farms.
To summarize, the use of biogas technologies can bring the following benefits:

Saving time and labor
- Reduces cooking time
- Reduces time spent washing dishes
- Reduces time spent cleaning the kitchen
- Time spent on stove maintenance is freed up (cleaning the stove from ash, removing ash, bringing in fuel, loading the stove, ignition, monitoring the stove and adding fuel)
- Time previously spent on collecting, transporting, drying and storing dung or searching, transporting and reloading coal, and searching, purchasing, cutting, drying and storing firewood is freed up
- The time for weeding is reduced (their seeds die in the storage tank)

Saving money
- Saves money spent on heating oil or electricity
- Extends the life of kitchen utensils
- Save money on the purchase of fertilizers and herbicides

Possibility of receiving additional money
- You can sell excess gas to your neighbors or exchange it for something
- You can sell compost
- When using compost, the productivity of your agricultural crops increases and you can earn more money from their sale.

Environmental benefits
- Reducing emissions of methane (greenhouse gas) into the atmosphere
- Reducing the amount of coal, wood or fuel burned to generate electricity, and as a result, reducing the generated carbon dioxide (greenhouse gas) and harmful combustion products
- Reducing the discharge of polluted water into the environment
- Purification of polluted waters from organic substances and microorganisms
- Preservation of forests from deforestation
- Reduced need for chemical fertilizers
- Cleaning the air in the house and village from coal combustion products
- Reducing air pollution by nitrogen compounds, air deodorization

Space saving
- Frees up space previously occupied by coal or dung

Facilities
- Purifies the air in the house and kitchen
- The volume of unused garbage is reduced (there is less garbage)
- All organic waste is used, including toilet waste
- There are fewer weeds in the garden and field, their seeds die in the storage tank
- The smell from manure in the yard is reduced (the bioaccumulator is anaerobic, that is, it does not have contact with air)
- Reduces the number of flies

Staying healthy
- Reduces the risk of contracting diseases associated with polluted air - respiratory and eye diseases
- The epidemiological situation is improving due to the death of microorganisms in the reservoir and the reduction of insect breeding sites
In order to understand what benefits and profits the operation of a biogas plant can bring in your specific farm or peasant enterprise, you must understand:
1. how much costs will be required for the construction of a biogas plant,
2. how can these costs be reduced?
3. and how long will it take for these costs to pay off.
Answers to the questions posed can be obtained by drawing up a detailed plan for the construction of the installation, its operation and the sale of the resulting products.

WHAT ARE BIOGAS INSTALLATIONS?
For clarity, here are a few definitions of commonly used terms in this chapter:

Bioreactor- a reservoir (vessel, container) in which conditions are created for the life of methane-generating bacteria. As a synonym for the term “reactor”, some literature uses the terms “reactor”, “methane tank”, “methane tank”, “septic tank” - they all have the same meaning

Heating system - a steam (water) heating system that allows you to maintain the operating temperature in the bioreactor, especially in winter.

Mixing device - a device located inside the bioreactor and allowing mixing of the processed mass to speed up complete processing.
Loading and unloading openings are openings in the bioreactor through which raw materials are loaded and processed biomass is unloaded.
All biogas plants are divided into two types according to their operating cycle: continuously operating and periodically operating.
Continuously operating biogas plants are constantly loaded with raw materials, and at the same time processed biomass is shipped. Thus, the operation of the installation is not interrupted.
Biogas plants operating periodically or cyclically are loaded completely to the operating level and hermetically sealed, for a certain period of time the plant actively releases biogas, after complete processing of the biomass the plant is unloaded and the operating cycle is repeated.
The shape of the reactor and the building materials used. During the implementation of the project, biogas plants were developed that could operate in the conditions of Central Kazakhstan.
Cylindrical biogas plants are located horizontally if the plant is of a continuously operating type, and vertically if the plant is cyclically operating.
Ellipsoidal biogas plants have a shape close to egg-shaped. From the point of view of the biomethanogenesis process, this form of bioreactor is the most optimal - natural mixing processes occur in it, as well as sludge removal and sediment runoff. Biogas plants of a similar shape are built from concrete or built from brick.
Equipment used for biogas production. To increase the biogas yield from the installation, additional equipment is used:
1. Sewage pumps are used for pumping out processed biomass and greatly facilitate the maintenance of a biogas plant.
2. Circulation pumps are used in the heating system of the installation and allow maintaining operating temperature with lower energy consumption.
3. Mixing devices are used to mix the processed biomass inside the reactor, which increases the productivity of the installation and reduces the time required for processing biomass.
4. A check valve installed in the gas exhaust system is necessary to prevent air from entering the bioreactor.
5. Gas heating boiler, connected to the heating system of the installations and runs on emitted biogas and consumes up to 5% of the total amount of gas.

BSU productivity
As noted earlier, the products produced by biogas plants are biogas and biosludge.
Biogas productivity - biogas output (m3) per unit of substrate (m3) during the fermentation period.
Biogas productivity depends on the following parameters:
- volume of the reactor of the installation; the larger the installation volume, the greater the gas output
- temperature in the reactor at which fermentation occurs; Methane-forming bacteria in oxygen-free conditions can release gas in the temperature range from 0C to 70C. However, biogas is released most intensively in 2 temperature ranges. It should be noted that different types of methane-generating bacteria “work” at different temperatures. The first interval (mesophilic, because mesophilic bacteria work) from 25C - 38C - the optimal temperature is 37C. The second interval (thermophilic, because thermophilic bacteria work) from 45C - 60C - the optimal temperature is 56C. Each of these intervals has a number of advantages and disadvantages, which can be found in detail below.

MESOPHILIC TYPE OF FERMENTATION

pros
- Gas productivity practically does not decrease when the temperature deviates by 1-2oC from the optimum;
-Less energy costs are required to maintain temperature.

Minuses
- Gas release is less intense;
- It takes more time until the substrate completely decomposes - 25 days;
- Biosludge obtained in this mode is not completely sterile.

THERMOPHILIC TYPE OF FERMENTATION

pros
- Gas release is more intense;
- It takes less time until the substrate completely decomposes - 12 days;
- The biosludge obtained under this mode is completely sterile and therefore can be used as feed additives for animals.

Minuses
- Gas productivity decreases significantly when the temperature deviates by 1-2oC from the optimum;
- More energy is required to maintain temperature.
- from raw materials. The raw materials for BGU can be domestic animal manure, plant matter and other organic residues. Depending on the substrate used, the productivity of biogas varies. Approximate data are shown in table No. 1

Table No. 1. Biogas productivity depending on the raw materials used during the fermentation period (Archea 2000, Germany).

Raw materials (substrate)

Biogas (m3 per m3 substrate)
Chicken droppings 53,71
Horse dung 40,60
Cattle manure 32,40
Cattle manure (fresh) 76,69
Sheep manure 162,00
Pig manure 25,52

Humidity of the loaded substrate; The fermentation process can occur at a humidity of 50% to 95%, but scientists have proven that for livestock waste the process of methane formation occurs optimally at a raw material humidity of 90-95.
- residence time of the substrate in the reactor; The optimal residence time of the substrate in the reactor varies depending on the operating temperature and the type of fermented raw material. With a mesophilic type of fermentation - 25-30 days, with a thermophilic type - 10-15 days.

Operation of biogas plants
1.The installation is started in several stages.
Initially, the installation is loaded with raw materials; a very important aspect of this action is the humidity of the loaded substrate - it should be 85% in winter, and up to 92% in summer. The installation is loaded up to the water seal. To speed up the start of the methanogenesis process, a starter (biosludge or substrate from a working installation) is poured into the loaded substrate. In the absence of a starter, fresh cattle manure is added to the substrate.

The frequency of loading the substrate is determined experimentally for each biogas plant; this parameter depends on many indicators: the temperature of the substrate, the type of animal producing the raw materials, the humidity of the substrate, the volume of the installation, etc. The raw materials are brought to the optimal humidity before loading into the plant. The substrate is diluted with warm water (35-40 degrees), stirred thoroughly, and then poured into the loading hole of the installation. The moisture content of the raw material determines the volume of biogas output, the processing time of the raw material and the degree of its decomposition. In summer, the optimal humidity is 92%; in winter, the optimal humidity is 85%.
3. Maintaining optimal temperature.
In the conditions of Central Kazakhstan, it is necessary to heat up the operating reactor. During construction, tubular heat exchangers are installed inside the reactor, which, depending on the design of the installation, are supplied either to the steam heating of a residential building (small-volume installations) or to an autonomous heating boiler running on biogas. To reduce heat loss, the loaded substrate is diluted with hot (temperature no higher than 60°C) water.
4. Mixing.
Mixing the substrate inside the reactor significantly increases the efficiency of the BGU, as it prevents the formation of sediment and floating crust and ensures the movement of mass in the reactor.
5. Biogas accumulation.
Since biogas is consumed unevenly, and the installation produces it constantly, the question of its accumulation arises. The gas can be collected in rubber bladders used in the wheels of agricultural machines.
6. Use of biogas.
Biogas is used for cooking, heating residential premises, heating industrial premises (greenhouses, poultry houses, etc.).
7. Use of biosludge.
Biosludge is used as fertilizer on farm fields; when the substrate is completely processed in the plant reactor, biosludge can be used as an additive in feed for pigs and poultry. After simple processing (filtration and drying) of biosludge, it can be sold for commercial purposes. Potential buyers of biosludge fertilizer are gardening farms, dacha cooperatives, etc.
8. Safety precautions.
Biogas contains hydrogen sulfide (H2S), carbon dioxide (CO2) and methane. Methane, which is part of biogas, is practically non-toxic. It is lighter than air, flammable and forms an explosive mixture with air (5-15% methane) or oxygen. In the event of a leak, in the presence of ventilation, the gas evaporates without any consequences. Hydrogen sulfide, even if it poses a danger to human health, is found in small quantities and is easily detected by its unpleasant odor. Since hydrogen sulfide is heavier than air, care must be taken to ensure that during leaks this gas cannot accumulate in recesses. At high concentrations, it dulls the perception of odor, which makes it difficult to detect and can lead to fatal poisoning, but once again it can be noted that the proportion of hydrogen sulfide in biogas is very small and amounts to no more than 1%. Carbon dioxide (CO2), which is part of biogas, can also accumulate in deep recesses, since it is heavier than air, causing a suffocation hazard if there are leaks in the installation.

Conclusion
If you were interested in this information in our brochure, and you decided to build a biogas plant on your farm, then I would like to give you some more tips and recommendations.
Tip #1. Before constructing a plant, think carefully about the use of biosludge. The shape of the reactor and temperature conditions depend on this. In the case of using biosludge as fertilizer, the cost of maintenance and construction is reduced. In the case of using biosludge as food additives for livestock and poultry, the cost increases, but the payback time decreases. Livestock and poultry receiving such supplements gain weight faster, mortality decreases, due to which you can make a profit in the home (peasant or farm) economy.
Tip #2. Having decided on the shape and volume of the reactor, you can begin to draw up your construction estimate. Having drawn the line “total”, do not immediately grab your head from the high amounts. Installation costs can be significantly reduced by using, in some cases, waste or “time-tested” building materials.
Tip #3. Having prepared a list of necessary building materials, you may not find something in your city or area. Consult us, we can tell you what building material can be used to replace the one not found.


Every day the amount of electricity consumption is constantly growing. Consumption rates are also increasing, but sooner or later the raw materials for generating electricity will run out. Biogas can be a good alternative to various raw materials for electricity.

What is biogas?

Biogas is an alternative, non-traditional source of energy. This type of energy production was known back in the days of Ancient China, but after many years it was conveniently forgotten. And as they say: “Everything new is well forgotten old.”


Biogas is a product obtained as a result of anaerobic fermentation of organic substances. This entire process occurs without the participation of air.

An example of biogas is the gas that is released when manure or other household waste is fermented. Such gas may well serve as a source of energy in agriculture.

How is biogas produced?

Biogas production is a method of processing various organic and animal wastes to produce biofuels and organic fertilizers. This type of energy production is a solution to many issues: ecology, capital and agrochemistry. The biochemical reaction is based on the processes of rotting manure and litter under anaerobic conditions. This uses a group of anaerobic microbes that help convert phosphorus, potassium and nitrogen into pure forms. Such forms of phosphorus, potassium and nitrogen are much better absorbed by plants and also completely destroy pests. Of course, in order to fertilize the land, it is better to use waste from biogas production. This way you do not use any nitrates or nitrites.

This is what the biogas production process looks like

The container in which biogas is produced is called a digester, or reactor.. If you follow the production rules, the biogas yield is about two to three m3 per m3 of organic waste.

Factors that influence the fermentation process:

  • pH level;
  • temperature;
  • ratio of carbon, nitrogen and phosphorus;
  • surface area of ​​raw material particles;
  • environmental humidity;
  • substrate supply frequency;
  • retardants;
  • stimulant supplements.

Biogas characteristics

Biogas is a mixture of carbon dioxide and methane. It is a product of methane fermentation of organic substances of animal and plant origin. Methane fermentation is the result of the natural action of anaerobic bacteria. This process takes place at temperatures from 15 to 60 degrees in three ranges:

  • 15-30 degrees - psychrophilic;
  • 30-45 degrees - mesophilic;
  • 45-60 degrees - thermophilic.

The decomposition of organic matter consists of three stages:

  • dissolution and hydrolysis of organic compounds;
  • acidogenesis;
  • methanogenesis.

Air humidity should be from 10 to 98%, optimal - 91-92%. The methane content in biogas depends on the chemical composition of the raw material and can be 55-90%.

How to clean biogas from impurities?

One-stage biogas purification, or regenerative, involves getting rid of impurities until the biogas acquires the state of biomethane. After such purification, biomethane can easily serve as fuel for a car engine or be used in the gas supply system.

The operating principle of this method is as follows:

  • biogas is compressed to a pressure of 9-11 bar;
  • such gas is supplied to the purification column and purified under cold water pressure;

Thus, carbon dioxide and hydrogen sulfide impurities are removed due to their good solubility in water. The main advantage of such purification is low costs, since the main component of biogas purification is water.


How to reduce the moisture content in biogas?

Reducing the proportion of moisture in biogas can only be done mechanically using specialized equipment. The simplest method for removing moisture is changing the temperature. When exposed to cold temperatures, moisture condenses into steam. After this procedure, the moisture content in the gas will be reduced by 3-5 times. Biogas is passed into an underground pipe, where the water goes down. The temperature then rises, giving the gas the opportunity to rise higher and warm up.

Where is biogas used?

  • As already mentioned, biogas is a raw material for the production of electricity and automobile fuel.
  • In enterprises, the use of biogas will help save a huge amount. And all this because you will not need to build a gas pipeline, electrical lines, or waste containers. This installation will help you save about 30-40% of the cost of the entire biogas system.
  • Biogas plants can be used as wastewater treatment plants. By installing a biogas plant on a farm, factory or industrial complex, you will not only be able to get rid of waste forever, but also receive raw materials for electricity and fuel.

How to install a biogas plant with your own hands?

The process of producing biogas at home is quite labor-intensive. Therefore, think about whether you can cope with this task. This biogas production plant will help you save money on fuel and electricity..

To produce biogas, you need a special installation, which can be made from old and no longer needed things. From old boilings and metal pans you can create a reactor for a future installation. The optimal shape is a cylinder.

The main requirements for the future reactor:

  • water and waterproofness. Mixing air and gas during fermentation is simply dangerous. Your reactor could crack or, in the worst case, explode. Therefore, for greater safety, you need to install a sealed gasket between the lid and the body;
  • sufficient thermal insulation;
  • be reliable. During the reactions that produce biogas, large amounts of gas are released. The pressure can play havoc with your reactor and it may even explode.

To obtain biogas you will need:

  • mix 2 tons of manure and 4 tons of humus;
  • add water to the mixture;
  • Place the mixture in the pit and use heating units to heat it to 45°C. Then the mixture will begin to ferment and without air access it will warm up to 80°C;

To prevent gas pressure from exploding the reactor, it is recommended to attach a counterweight using cables. Six tons of mixture is enough for the installation to operate for six months.

In simple terms, a sealed tank is installed in the pit, which acts as a reactor. Organic waste is stored in it. In such an installation, a gas outlet is mandatory.

Now you just have to wait for the microorganisms to do their job and ferment the mass. After this you will be able to obtain biogas. And waste from biogas production can become an excellent fertilizer.

After the microorganisms have fermented this mass, it needs to be unloaded. This must be done through a special hole. The fermented mass must be temporarily placed in a container, which must be no smaller in volume than the reactor.

To independently produce a biogas plant, it is recommended to adhere to the following sequence:

  • choose a location to install the future reactor, and also calculate the daily amount of waste to determine the volume of the reactor;
  • install the loading and unloading pipes and prepare a pit for the biogas plant;
  • install a loading hopper and a gas outlet pipe;
  • install a hatch cover that will be used for maintenance and repair of the reactor.
  • check the reactor for leaks and thermal insulation.

It is best to make the reactor walls from concrete so that they are more airtight and reliable. The mass that you load into the biogas plant should not contain antibiotics or solvents. They negatively affect the functioning of microorganisms.

When creating such an installation, remember safety precautions. There is no need to place it near your home or business premises.