How to extract gas from manure. Biogas from manure - production methods, technology advantages

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

Everyone knows how manure is most often disposed of: piled up, then, after fermentation, taken out to the fields. In this case, the resulting gas is released into the atmosphere, and 40% of the nitrogen contained in the original substance and most of the phosphorus also fly there. The resulting fertilizer is far from perfect.

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

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

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

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

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

It turns out that having at least some more or less decent amount of livestock and poultry, you can fully meet the needs of your household in heat, gas and electricity. And if you install gas installations on cars, then fuel for the fleet. Given that the share of energy in the cost of production is 70-80%, you can only save on a bioreactor, and then earn a lot of money. Below is a screenshot of the economic calculation of the profitability of a biogas plant for a small farm (as of September 2014). You can’t call the economy small, but it’s definitely not large either. We apologize for the terminology - this is the author's style.

This is an approximate breakdown of the required costs and possible income. Schemes of self-made biogas plants

Schemes of self-made biogas plants

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

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

The container is not completely filled with the substrate: 10-15% of the volume must remain free to collect gas. A gas pipe is built into the tank lid. Since the resulting gas contains a rather large amount of water vapor, it will not burn in this form. Therefore, it is necessary to pass it through a water seal for drainage. In this simple device, most of the water vapor will condense, and the gas will already burn well. Then it is desirable to purify the gas from non-combustible hydrogen sulfide, and only then it can be fed into the gas holder - a container for collecting gas. And from there it is already possible to breed to consumers: feed it to a boiler or a gas stove. How to make filters for a biogas plant with your own hands, see the video.

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

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

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

There is another way of mixing the layers, but non-mechanical - barbitation: the gas produced under pressure is fed into the lower part of the manure tank. Rising up, gas bubbles will break the crust. Since the same biogas is supplied, there will be no changes in processing conditions. Also, this gas cannot be considered an expense - it will again fall into the gas tank.

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

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

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

The situation is slightly better with trench biogas manure processing plants. They have beveled edges, which makes it easier to load fresh manure. If you make the bottom sloped, then the fermented mass will move by gravity in one direction and it will be easier to select it. In such installations, it is necessary to provide thermal insulation not only for walls, but also for covers. Such a biogas plant with your own hands is easy to implement. But full processing and the maximum amount of gas in it cannot be achieved. Even when heated.

The basic technical issues have been dealt with and you now know several ways to build a manure biogas plant. Remained technological nuances.

What can be recycled and how to achieve good results

In the manure of any animal there are organisms necessary for its processing. More than a thousand different microorganisms have been found to be involved in the digestion process and gas generation. The most important role is played by methane-formers. It is also believed that all these microorganisms are found in optimal proportions in cattle manure. In any case, when processing this type of waste in combination with plant mass, the largest amount of biogas is released. The table shows averaged data for the most common types of agricultural waste. Please note that this amount of gas output can be obtained under ideal conditions.

For good productivity, it is necessary to maintain a certain humidity of the substrate: 85-90%. But water must be used that does not contain foreign chemicals. Solvents, antibiotics, detergents, etc. negatively affect the processes. Also, for the normal course of the process, the slurry should not contain large fragments. The maximum size of the fragments: 1 * 2 cm, smaller ones are better. Therefore, if you plan to add herbal ingredients, then you need to grind them.

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

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

Calculation of the volume of the bunker for processing

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

Home-made installations for the processing of manure into biogas are not the pinnacle of perfection, but they are quite effective

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

Legal registration

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

Technological scheme of the installation.
Layout plan for equipment and components with reference to the installation itself, the installation site of the thermal unit, the location of pipelines and power lines, and the connection of the pump. Lightning rod and access roads should be marked on the diagram.
If the unit is to be located indoors, a ventilation plan will also be required, which will ensure at least eight exchanges of the total air in the room.

As you can see, bureaucracy is indispensable here.

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

Results

By investing some money in the construction of a biogas plant (do it yourself or on a turnkey basis), you will not only provide for your own needs and needs for heat and gas, but also be able to sell gas, as well as high-quality fertilizers resulting from processing.

Consumption ecology. Farmstead: Is it profitable to produce biofuel at home in small quantities in a personal subsidiary plot? If you have a few metal barrels and other iron junk, as well as an abyss of free time and you do not know how to dispose of it - yes.

Let's assume that natural gas has not been and will not be in your village. And even if there is, it costs money. Although much cheaper than ruinous heating with electricity and liquid fuels. The nearest workshop for the production of pellets is a couple of hundred kilometers away, it is expensive to carry. It is getting more and more difficult to buy firewood every year, and it is troublesome to heat it. Against this background, it looks very tempting to get free biogas in your own backyard from weeds, chicken manure, manure from your favorite pig or the contents of the master's toilet. It is enough to make a bioreactor! On TV they tell how thrifty German farmers warm themselves with "dung" resources and now they don't need any "Gazprom". This is where the saying “will remove 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 little is known about the practical application of the technology: everyone and everyone is talking about the production of biogas at home, but few people have seen specific examples in the village, just like the legendary Yo-Mobile on the road. Let's try to figure out why this is so and what are the prospects for progressive bioenergy technologies in the countryside.

What is biogas + a bit of history

Biogas is formed as a result of sequential three-stage decomposition (hydrolysis, acid and methane formation) of biomass by various types of 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, combustible gases are formed during the decomposition of any animal and vegetable residues.

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

People have been trying to use this type of natural fuel for a long time, in medieval chronicles there are references to the fact that the inhabitants of the lowlands of present-day Germany a millennium ago received biogas from rotting vegetation, immersing leather furs in marsh 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 fun fair performances. Industrial biogas plants began to be built with varying degrees of success from 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 plants is in the 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 home and small farming.

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, cooking. However, not everything is as simple as it is shown in the videos scattered on YouTube. Biogas must burn stably in heat generating plants. To do this, its parameters of the gaseous medium must be brought to fairly stringent standards. The content of methane should not be lower than 65% (optimum 90-95%), there should be no hydrogen, water vapor is removed, carbon dioxide is removed, the remaining components are inert to high temperatures.

It is impossible to use biogas of “dung-animal” origin, which is not freed from malodorous impurities, in residential buildings.

The normalized pressure is 12.5 bar, at a value of less than 8-10 bar, 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 jump beyond the norm, 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 burner of the heating boiler may fail. The worst option is that the gas will go out, but its flow will not stop. And this is 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 to produce biogas

Plant 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 are suitable, algae, hay (100 m3 per ton) are good, but it makes sense to use valuable feed for fuel only if there is a clear excess of it. The output of methane from the pulp, which is formed in the manufacture of juices, oils and biodiesel, is low, but the material is free. The lack of vegetable raw materials is a long production cycle, 1.5-2 months. Biogas can also be obtained from cellulose and other slowly decomposing plant waste, but the efficiency is extremely low, little methane is produced, and the production cycle is very long. In conclusion, we say that vegetable raw materials must be finely ground.
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 output of high-quality biogas with a methane concentration of up to 87% reaches 1500 m3 per ton. However, animal raw materials are in short supply and, as a rule, they find other uses for it.

Combustible gas from excrement

Manure is cheap and available in abundance on many farms, but the yield and quality of biogas is much lower than from other types. Cow patties and horse apples can be used in their pure form, fermentation starts immediately, 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 manure are toxic - so that beneficial bacteria can develop, it is mixed with plant waste, silage. Detergent compositions, surfactants, which are used in the cleaning of livestock buildings, present a big problem. Together with antibiotics, which are in large quantities in 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 find a compromise between hygiene and animal disease control on the one hand and maintaining the productivity of bioreactors on the other.
Human excrement, completely free, is also suitable. But it is unprofitable to use ordinary sewage, the concentration of feces is too low and disinfectants and surfactants are high. Technologists say that they could only be used if “products” only come into the sewer from the toilet, provided that the bowl is flushed with only one liter of water (standard 4/8 l). And no detergents, of course.

Additional requirements for raw materials

A serious problem faced by farms that have installed modern equipment for biogas production is that raw materials should not contain solid inclusions; a stone, nut, piece of wire or board that accidentally gets into 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 the feedstock 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 makeshift installation, assembled according to the recommendations of articles on “obtaining biogas with your own hands”, you can barely reach 20% of the maximum level, high-tech installations can achieve values of 60-95%.

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

Biogas plant device

Is biogas production profitable?

We have already mentioned that in developed countries they build large industrial installations, while in developing countries they build 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 biofuel at home in small quantities on a personal subsidiary plot? If you have a few metal barrels and other iron junk, as well as an abyss 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, from 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, the raw material is loaded daily, that is, its 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 managed to fill, in frosty weather for a heating boiler with a power of 15 kW (a residential building of 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, with technical questions, contact specialists with experience in such work. The practical information obtained in those farms where bioenergy technologies have already been used for some time will be very valuable. published

Typical design

In recent years, it has become fashionable to use various biogas plants for their own needs, which allow you to get energy from waste. As a rule, such a design is a sealed container, where, at a given temperature, fermentation of the organic components of wastewater, various wastes, etc. takes place. Do-it-yourself biogas plant is difficult, but real. The main thing is to know the varieties of these devices and the principle of their operation, as well as deal with the drawings.

The principle of operation of the installation

The process of obtaining biogas from manure or other raw materials is called fermentation, and fermentation is carried out due to the vital activity of special bacteria. At the same time, a crust forms on the surface of the raw material, which must be constantly destroyed. This must be done by thoroughly mixing the contents manually or using special devices inside the reactor. As a result of such manipulations, biogas is released.

The resulting biogas after purification is collected in a special container - a gas holder, from which it is carried through gas pipes to the place of use. Recycled raw materials are converted into biofertilizer. It is discharged through a special opening, and then can be applied to the soil or used as a feed additive for animals, depending on the feedstock.

To get biogas with your own hands, in addition to observing the absence of oxygen, several conditions must also be met:

Availability of nutrients for bacteria.
Compliance with the temperature regime.
Choosing the right time for fermentation.
Compliance with acid and alkaline balance.
Compliance with the proportions of solid particles in raw materials and timely mixing.

Varieties of biogas plants

Note! Today, there are a large number of designs of biogas plants to make biogas production not only convenient, but also efficient.

They are distinguished by their appearance, as well as by the constituent elements of the structure and the materials used in the creation.

By download type

According to the type of loading of raw materials, there are two types of installation - continuous loading and batch.

They differ from each other in the time of fermentation of raw materials and the regularity of loading. The most efficient from the point of view of biogas production is the installation of continuous loading.

By appearance

The appearance of the device depends on the method of accumulation and storage of biogas. It can be collected in a special gas tank, in the upper part of the reactor, or under a flexible dome, floating or standing separately from the reactor.

Creating a do-it-yourself installation

Building a biogas structure with your own hands is a rather complicated and time-consuming process. Such an installation makes biogas production an alternative option that saves money on the purchase of fuel and electricity.

What do you need to know?

Generalized scheme

You can make a design from those means that are available on the farm, but are not used. For example, it is easy to build a reactor of such an installation from old pots, boiling water, basins, but it is better to use cylindrical objects.

Here are some important requirements that the reactor must meet:

Good thermal insulation.
Air and water permeability. After all, when biogas and oxygen are mixed, a reaction occurs, and its destructive force can not only break the reactor, but also blow it up.
Reliability and strength, since a huge amount of energy is released during the reaction.

In order to build a high-quality and efficient bio-installation, it is necessary to adhere to the following sequence:

Choose a place for mounting the future reactor. And be sure to calculate the amount of waste needed for 1 day. This is necessary to determine the dimensions of the structure.
Prepare the basin, then install the discharge and loading pipe.
Install and secure the loading hopper and flue pipe as firmly as possible.
For use, as well as subsequent maintenance and repair of the biogas plant, the manhole cover must be mounted.
Carefully check the reactor for thermal insulation and tightness.

The walls of the future installation should ideally be made of concrete, since the strength of the structure is the key to your safety. In addition, it is very important that the distance from the reactor to the nearest building is at least 500 meters. Indeed, during fermentation, a poisonous gas is released, which has a detrimental effect on a person and can kill him in a matter of minutes.

To get biogas you will need:

The principle of home heating

Mix 2 tons of cow manure and about 4.5 tons of humus from rotted waste, tops and leaves.
Add water to the mixture so that the humidity in the reactor is 70%.
Unload the resulting mass into a pit and heat it up to +40 degrees using a heating installation. After the mixture begins to ferment, its temperature will reach +70 degrees.
Attach a counterweight to the dome, which should be 2 times heavier than the mixture, so that the dome does not fly off the pit due to the released gas.

It should be remembered that the mass loaded into the reactor should not contain antibiotics, solvents and other synthetic substances. They will not only interfere with the reaction, but will completely stop it, and will also cause the destruction of the walls of the reactor.

Equipment Options

A home-made installation today is a rare type of alternative energy source on farms. But, given the efficiency and payback of such a design, many farmers began to think about building a biogas plant on their own in order to provide themselves with electricity and heat in this way.

Today, there are many variants of this type of equipment for biogas production. Taking into account the climatic conditions of Russia, it is recommended to create the following types of installations.

Reactor with manual loading without agitation

This is the simplest installation for a home, the volume of which can be from 1 to 10 cubic meters. It is able to process up to 200 kg of manure per day.

Manual loading option

It consists of the minimum number of parts:

Bunker for fresh raw materials.
Reactor.
Biogas sampling device.
Capacity for unloading fermented raw materials.

Such an installation can be used for the southern regions, since it works without mixing and heating, and is also designed to function in a psychophilic mode. The used raw material is removed from the reactor through the discharge pipe during the loading of the next portion of manure. This is due to the biogas pressure in the reactor.

When making such a design with your own hands, it is recommended to follow the following sequence:

After calculating the daily volume of manure and choosing the reactor of the required size, it is necessary to determine the location of the future structure, as well as prepare materials for installation.
Then you need to build a loading and unloading pipe, as well as make a pit for installation.
After installing the reactor in the pit, it is necessary to install a loading hopper and a gas outlet, as well as a manhole cover.
Check the structure for leaks, paint it and insulate it.
Launch into operation.

Manual loading, heating and stirring design

A biogas plant can be built with manual loading of raw materials and its periodic mixing. However, it does not require large financial investments from the owner. The design is suitable for a small farm, as its capacity is the processing of up to 200 kg of manure per day. The drawings of such an installation are similar to the drawings of the previous version, and they can be made by contacting a specialist.

This unit can operate in mesophilic and thermophilic modes.

For a stable and most intensive fermentation process, a special reactor heating system is installed. The biogas plant can operate in two modes. The reactor is heated by a hot water boiler that runs on the resulting biogas. The rest of the biogas can be used for household appliances.

Processed raw materials are stored in a special container until they are applied to the soil or used as a nutrient medium for Californian worms.

Installation with a gas tank, pneumatic loading, heating and mixing of raw materials

Such an installation is designed for small and medium-sized farms with processing up to 1.5 tons of manure per day into biogas. Raw materials are heated by a heat exchanger with a water-heating boiler that runs on the resulting gas. The mass unloading pipeline is equipped with a special branch for collecting biofertilizer in storage and for loading into vehicles with subsequent removal to the fields.

The design of such a home-made installation involves pneumatic loading of manure into the reactor, as well as mixing with biogas, the selection of which is carried out automatically. Biogas is stored in a special compartment - a gas holder.

Conclusion

Biogas is a relatively new energy source. Using it, you can forever forget about electricity tariffs and even solve such an issue as the production of methane. Properly designed drawings and the efforts made in the manufacture of the installation will significantly save the money of more than one farmer, which is especially important today.

What is biogas

Biogas is a volatile, colorless, odorless, gaseous substance. It consists of 50-70 percent of methane, up to 30 percent of it is carbon dioxide CO2 and another 1-2 percent - gaseous substances - impurities (when cleaned from them, the purest biomethane is obtained).

Qualitative physico-chemical indicators of this substance are approaching the usual high-quality natural gas. According to scientists, biogas has very high calorific properties: for example, the heat released during the combustion of one cubic meter of this natural fuel is equivalent to the heat from one and a half kilograms of coal.

The release of biogas occurs due to the vital activity of a special type of bacteria - anaerobic, while mesophilic bacteria are activated when the environment is heated to 30-40 degrees Celsius, and thermophilic bacteria multiply at a higher temperature - up to +50 degrees.

Under the action of their enzymes, organic raw materials decompose with the release of biological gas.

Raw materials for biogas

Not all organic waste is suitable for processing into biogas. For example, litter from poultry farms and pig farms in its pure form cannot be used categorically, because they have a high level of toxicity. To obtain biogas from them, it is necessary to add diluting substances to such waste: silage mass, green grass mass, as well as cow manure. The last component is the most suitable raw material for obtaining environmentally friendly fuel, since cows eat only plant foods. However, it must also be controlled for the content of heavy metal impurities, chemical components, surfactants, which in principle should not be in the raw material. A very important point is the control of antibiotics and disinfectants. Their presence in manure can prevent the process of decomposition of the raw mass and the formation of volatile gas.

Additional Information. It is impossible to completely do without disinfectants, because otherwise mold begins to form on the biomass under the influence of high temperatures. It is also necessary to monitor and clean the manure masses in time from mechanical impurities (nails, bolts, stones, etc.), which can quickly damage biogas equipment. Humidity of the raw materials going to obtain biogas should be at least 80-90%.

Mechanism of gas formation

In order for biogas to be released from organic raw materials during airless fermentation (scientifically called anaerobic fermentation), appropriate conditions are necessary: a sealed container and elevated temperature. If done correctly, the gas produced rises to the top where it is selected for use, and what remains is an excellent bio-organic agricultural fertilizer, rich in nitrogen and phosphorus, but free from harmful microorganisms. For the correct and complete flow of processes, the temperature regime is very important.

The full cycle of converting manure into ecological fuel is from 12 days to a month, it depends on the composition of the raw material. About two liters of biogas are obtained from one liter of useful volume of the reactor. If more advanced modernized installations are used, then the biofuel production process is accelerated to 3 days, and biogas production increases to 4.5-5 liters.

People began to study and use the technology of extracting biofuels from organic natural sources since the end of the 18th century, and in the former USSR, the first device for producing biogas was developed back in the 40s of the last century. Nowadays, these technologies are becoming increasingly important and popular.

Advantages and disadvantages of biogas

Biogas as an energy source has undeniable advantages:

it serves to improve the ecological situation in those areas where it is widely used, since, along with a reduction in the use of polluting fuel, there is a very effective destruction of biowaste and disinfection of effluents, i.e. biogas equipment acts as a cleaning station;
the raw materials for the production of this fossil fuel are renewable and practically free - as long as the animals on the farms are fed, they will produce biomass, and, therefore, fuel for biogas plants;
the acquisition and use of equipment is economically beneficial - once purchased, a biogas plant will no longer require any investments, and it is easy and cheap to maintain; for example, a biogas plant for use in a farm begins to pay off already three years after launch; there is no need to build engineering communications and power transmission lines, the cost of launching a biostation is reduced by 20 percent;
there is no need to bring such engineering communications as power lines and gas pipelines;
biogas production at the plant using local organic raw materials is a non-waste enterprise, as opposed to enterprises using traditional energy sources (gas pipelines, boiler houses, etc.), waste does not pollute the environment and does not require a place for its storage;
when using biogas, a certain amount of carbon dioxide, as well as sulfur, is released into the atmosphere, however, these amounts are minimal compared to the same natural gas and are assimilated by green spaces during breathing, so the contribution of bioethanol to the greenhouse effect is minimal;
compared to other alternative energy sources, biogas production is always stable, the activity and productivity of biogas production plants can be controlled by a person (unlike, for example, solar batteries), by assembling several plants into one or, conversely, splitting them into separate sections to reduce risk accidents;
in exhaust gases when using biofuels, the content of carbon monoxide is reduced by 25 percent, and nitrogen oxides - by 15;
in addition to manure, some types of plants can be used to obtain biomass for fuel, for example, sorghum will help improve soil conditions;
When bioethanol is added to gasoline, its octane number increases, and the fuel itself becomes more knock-resistant, its auto-ignition temperature is significantly reduced.

Biogas– not an ideal fuel, it and the technology for its production are also not without drawbacks:

the rate of processing of organic raw materials in biogas production equipment is a weak point in technology compared to traditional energy sources;
bioethanol has a lower calorific value than fuel from oil - 30 percent less energy is released;
the process is rather unstable, it requires a large amount of enzymes of a certain quality to maintain it (for example, a change in the diet of cows greatly affects the quality of manure raw materials);
unscrupulous producers of biomass for processing stations can significantly deplete the soil with increased sowing, this violates the ecological balance of the territory;
pipes and tanks with biogas can be depressurized, which will lead to a sharp decrease in the quality of biofuel.

Where is biogas used?

First of all, this ecological biofuel is used to meet the household needs of the population, as a replacement for natural gas, for heating and cooking. Enterprises can use biogas to start a closed production cycle: its use is especially effective in gas turbines. With proper adjustment and full combination of such a turbine with a biofuel plant, its cost competes with the cheapest nuclear energy.

The efficiency of using biogas is very easy to calculate. For example, from one unit of cattle, you can get up to 40 kilograms of manure, from which one and a half cubic meters of biogas is produced, sufficient to generate 3 kilowatts / hours of electricity.

By determining the farm's electricity needs, it is possible to determine which type of biogas plant to use. With a small number of cows, it is best to produce biogas at home using a simple low-capacity biogas plant.

If the farm is very large, and a large amount of biowaste is constantly generated on it, it is advantageous to install an automated industrial-type biogas system.

Note! When designing and commissioning, the help of qualified specialists will be required here.

Construction of a biogas plant

Any bioinstallation consists of the following main parts:

bioreactor, where the biodegradation of the manure mixture takes place;
organic fuel supply system;
unit for mixing biological masses;
devices for creating and maintaining the desired temperature level;
tanks for placing the resulting biogas in them (gas holders);

containers for placing the formed solid fractions there.

This is a complete list of elements for industrial automated plants, while a biogas plant for a private house is much more simply designed.

The bioreactor must be completely sealed, i.e. oxygen access is not allowed. This can be a metal container in the form of a cylinder, installed on the surface of the soil; former fuel tanks with a capacity of 50 cubic meters are well suited for these purposes. Ready collapsible bioreactors are quickly mounted / dismantled and easily moved to a new location.

If a small biogas plant is expected, then it is advisable to place the reactor underground and make it in the form of a brick or concrete tank, as well as metal or PVC barrels. It is possible to place such a bioenergy reactor indoors, however, it is necessary to ensure constant ventilation of the air.

Bunkers for the preparation of biological raw materials are a necessary element of the system, because before getting into the reactor, it must be prepared: crushed into particles up to 0.7 millimeters and soaked in water to bring the moisture content of the raw material to 90 percent.

Raw material supply systems consist of a raw material receiver, a water pipeline and a pump for supplying the prepared mass to the reactor.

If the bioreactor is made underground, the raw material container is placed on the surface so that the prepared substrate flows into the reactor on its own under the action of gravity. It is also possible to place the raw material receiver at the top of the hopper, in which case a pump is required.

The waste outlet is located closer to the bottom, opposite the raw material inlet. The receiver for solid fractions is made in the form of a rectangular box, where the outlet tube leads. When a new portion of the prepared bio-substrate enters the bioreactor, the batch of solid waste of the same volume is fed into the receiver. In the future, they are used on farms as excellent biofertilizers.

The resulting biogas is stored in gas holders, which are placed, as a rule, on top of the reactor and have a conical or domed shape. Gas holders are made of iron and painted over with oil paint in several layers (this helps to avoid corrosive destruction). In large industrial bio-installations, biogas tanks are made in the form of separate tanks connected to the reactor.

To give the resulting gas combustible properties, it is necessary to rid it of water vapor. The biofuel is wired through a pipe through a water tank (hydraulic lock), after which it can be fed through plastic pipes directly for consumption.

Sometimes you can find special bag-shaped PVC gas holders. They are located in close proximity to the installation. As the bags are filled with biogas, they open, their volume increases enough to receive all the produced gas.

For the efficient flow of biofermentation processes, constant mixing of the substrate is necessary. To prevent the formation of a crust on the surface of the biomass and slow down the fermentation processes, it is necessary to constantly actively mix it. To do this, submersible or inclined stirrers in the form of a mixer for mechanical mixing of the mass are mounted on the side of the reactor. For small stations, they are manual, for industrial ones - with automatic control.

The temperature required for the vital activity of anaerobic bacteria is maintained using automated heating systems (for stationary reactors), they start heating when the heat drops below the norm and automatically turn off when the normal temperature is reached. You can also use boiler plants, electric heaters, or install a special heater in the bottom of the container with raw materials. At the same time, it is necessary to reduce heat losses from the bioreactor, for this it is wrapped with a layer of glass wool or other thermal insulation is carried out, for example, from expanded polystyrene.

Biogas do it yourself

For private houses, the use of biogas is now very relevant - from almost free manure, you can get gas for domestic needs and heating houses and farms. Having your own biogas plant is a guarantee against power outages and rising gas prices, as well as a great way to dispose of biowaste, as well as unnecessary paper.

For construction for the first time, it is most logical to use simple schemes, such structures will be more reliable and last longer. In the future, the installation can be supplemented with more complex details. For a house of 50 square meters, a sufficient amount of gas is obtained with a fermentation tank volume of 5 cubic meters. To ensure a constant temperature regime, necessary for proper fermentation, a heating pipe can be used.

At the first stage of construction, they dig a trench for the bioreactor, the walls of which must be reinforced and sealed with plastic, concrete mix or polymer rings (preferably with a blank bottom - they will have to be replaced periodically as they are used).

The second stage consists in the installation of gas drainage in the form of polymer pipes with numerous holes. During installation, it should be taken into account that the tops of the pipes must exceed the planned filling depth of the reactor. The diameter of the outlet pipes should be no more than 7-8 centimeters.

The next step is isolation. After that, it is possible to fill the reactor with the prepared substrate, after which it is wrapped in a film to increase the pressure.

At the fourth stage, the domes and the outlet pipe are mounted, which is placed at the highest point of the dome and connects the reactor to the gas holder. The gas tank can be overlaid with bricks, a stainless steel mesh is mounted on top and covered with plaster.

A hatch is placed in the upper part of the gas tank, which closes hermetically, a gas pipe with a valve for pressure equalization is taken out of it.

Important! The resulting gas must be removed and consumed constantly, since its long-term storage in the free part of the bioreactor can provoke an explosion from high pressure. It is necessary to provide a water seal so that the biogas does not mix with air.

To heat the biomass, you can install a coil coming from the heating system of the house - this is much more economically profitable than using electric heaters. External heating can be provided with the help of steam, this will exclude overheating of raw materials above the norm.

In general, a do-it-yourself biogas plant is not such a complex structure, but when arranging it, you need to pay attention to the smallest details in order to avoid fires and destruction.

Additional Information. The construction of even the simplest bio-installation must be formalized with appropriate documents, it is necessary to have a technological scheme and equipment installation map, and it is necessary to obtain the approval of the Sanitary and Epidemiological Station, fire and gas services.

Nowadays, the use of alternative energy sources is gaining momentum. Among them, a very promising sub-sector of bioenergy is the production of biogas from organic waste such as manure and silage. Biogas production stations (industrial or small home) can solve the problems of waste disposal, obtaining ecological fuel and heat, as well as high-quality agricultural fertilizers.

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How wonderful it would be: I dreamed a little on the toilet, and the kettle was already boiling

What is biogas + a bit of history

Bacterial decomposition process that produces combustible methane

To a greater or lesser extent, combustible gases are formed during the decomposition of any animal and vegetable residues.

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

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

Simplified process chain for biogas production. An important stage is separation and gas separation

What raw materials are used to produce biogas

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 are suitable, algae, hay (100 m3 per ton) are good, but it makes sense to use valuable feed for fuel only if there is a clear excess of it. The output of methane from the pulp, which is formed in the manufacture of juices, oils and biodiesel, is low, but the material is free. The lack of vegetable raw materials is a long production cycle, 1.5-2 months. Biogas can also be obtained from cellulose and other slowly decomposing plant waste, but the efficiency is extremely low, little methane is produced, and the production cycle is very long. In conclusion, we say that vegetable raw materials must be finely ground.
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 output of high-quality biogas with a methane concentration of up to 87% reaches 1500 m3 per ton. However, animal raw materials are in short supply and, as a rule, they find other uses for it.

Combustible gas from excrement

Manure is cheap and available in abundance on many farms, but the yield and quality of biogas is much lower than from other types. Cow patties and horse apples can be used in their pure form, fermentation starts immediately, 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 manure are toxic - so that beneficial bacteria can develop, it is mixed with plant waste, silage. Detergent compositions, surfactants, which are used in the cleaning of livestock buildings, present a big problem. Together with antibiotics, which are in large quantities in 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 find a compromise between hygiene and animal disease control on the one hand and maintaining the productivity of bioreactors on the other.
Human excrement, completely free, is also suitable. But it is unprofitable to use ordinary sewage, the concentration of feces is too low and disinfectants and surfactants are high. Technologists say that they could only be used if “products” only come into the sewer from the toilet, provided that the bowl is flushed with only one liter of water (standard 4/8 l). And no detergents, of course.

Additional requirements for raw materials

It must be said that the given data on the maximum gas yield from the feedstock 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 makeshift installation, assembled according to the recommendations of articles on “obtaining biogas with your own hands”, you can barely reach 20% of the maximum level, high-tech installations can achieve values of 60-95%.

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

Biogas plant device

"Home" biogas plant. At a minimum, it is necessary to have two sealed vessels, a bioreactor and an accumulator, into which gas is discharged through a tube. It is desirable to have a third vessel, where biogas will be pumped under pressure, then moisture will partially settle in the second. The design is not much different from the moonshine still. It would be nice to constantly stir the raw materials, for this you need a stirrer and an electric motor or a healthy hardy man. It is not worth counting on high productivity and good quality of biogas.
Industrial plant for the production of biogas. We will not go into details, it is better to give a schematic diagram:

The equipment includes, at a minimum, a reactor and a gas tank, a separator, agitators, pumps, a compressor station, a constant temperature system, safety devices, and controls. To intensify processes, cavitators, devices for analyzing the environment and introducing activators, etc. are also used.

The composition of the resulting biogas must be normalized, after storage it enters the separation and sorption columns, then it is brought to the required pressure in the gas tank and only then it enters the line leading to the heat generators.

Bioenergy production as part of a modern livestock complex. The inclusion of greenhouses and a fertilizer plant in its composition increases profitability.

Is biogas production profitable?

Poor countries. In a makeshift installation, with its monstrous inefficiency, all work can be done manually. For countries where peasants are paid mere pennies for hard work, this is a benefit. Moreover, in warm regions, the crop can be harvested several times a year and cheap plant materials are in abundance. Investments in the simplest system are relatively small, people are ready to put up with the low quality of biogas. It is cheaper for the owner to put a “watcher” to an antediluvian boiler or stove than to purchase equipment for normalizing biogas.

Chinese farmers procure raw materials for biogas production

rich countries. In Germany, the world leader in biogas production, almost half of the poultry and large livestock farms produce their own methane. The processes are automated as much as possible, the quality of biogas is high, and the production capacities are large. Waste raw materials undergo additional processing, mineralization, as a result of which the farms receive a disinfected non-aggressive complex fertilizer. Despite the high rates of methane yield from raw materials, and considerable prices for energy carriers, experts say that biogas energy justifies itself for farmers only because the state subsidizes 50% of the cost of equipment. An additional benefit can be obtained by generating electricity from gas. First, the government buys it at inflated prices; secondly, the consequences of uneven seasonal biogas production can be minimized in this way. The state also pays extra for improving the ecological state of lands as a result of using not aggressive manure, but “soft” fertilizer.

Biogas production in Germany: environmentally friendly, aesthetically pleasing, only possible with financial support from the federal government

Russia. At the very least, biogas energy is also developing in our country. From time to time, the media report on the launch of the next production, in an interview, a joyful scientist, designer or director of the farm reports that the payback period for the installation is one year. But life makes its own adjustments. Over time, it turns out that the operating costs were not taken into account when drawing up the business plan, in practice the gas yield is much lower than planned, and the fermentation time is much longer. Those who have worked for half a year already say the payback period of investments is 5 years. And after this time, people generally try not to give interviews. Unfortunately, we have scattered teams engaged in bioenergy and there are no reliable data on profitability in Russia. In general, it can be assumed that, taking into account lower energy prices than in the West and the availability of local fuels, biogas production in our country is on the verge of profitability, which does not contribute to its development without state support.

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How to extract gas from manure. Biogas from manure - production methods, technology advantages

Schemes of self-made biogas plants

What can be recycled and how to achieve good results

Calculation of the volume of the bunker for processing

Legal registration

Results

The principle of operation of the installation

Varieties of biogas plants

By download type

By appearance

Creating a do-it-yourself installation

What do you need to know?

Equipment Options

Reactor with manual loading without agitation

Manual loading, heating and stirring design

Installation with a gas tank, pneumatic loading, heating and mixing of raw materials

Conclusion

What is biogas

Raw materials for biogas

Mechanism of gas formation

Advantages and disadvantages of biogas

Where is biogas used?

Construction of a biogas plant

Biogas do it yourself

Video

What is biogas + a bit of history

What is the use of biogas

What raw materials are used to produce biogas

Combustible gas from excrement

Additional requirements for raw materials

Biogas plant device

Is biogas production profitable?

Does it make sense to produce biofuels at home?

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