How much biogas is produced by one cubic meter. Biogas Plant: Recycling Organic Waste for Benefits

A prudent owner dreams of cheap energy resources, efficient waste disposal and obtaining fertilizers. A do-it-yourself home biogas plant is an inexpensive way to make dreams come true.

Self-assembly of such equipment will cost reasonable money, and the gas produced will be a good help in the household: it can be used for cooking, heating the house and other needs.

Let's try to understand the specifics of this equipment, its advantages and disadvantages. And also whether it is possible to independently build a biogas plant and whether it will be effective.

Biogas is formed as a result of the fermentation of a biological substrate. It is decomposed by hydrolytic, acid- and methane-forming bacteria. The mixture of gases produced by bacteria turns out to be combustible, because. contains a large percentage of methane.

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

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

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

They are placed in a bioreactor where processing takes place:

• for some time, the biomass is exposed to bacteria. The fermentation period depends on the volume of raw materials;
• as a result of the activity of anaerobic bacteria, a combustible mixture of gases is released, which includes methane (60%), carbon dioxide (35%) and some other gases (5%). Also, during fermentation, potentially dangerous hydrogen sulfide is released in small quantities. It is poisonous, so it is highly undesirable for people to be exposed to it;
• the mixture of gases from the bioreactor is cleaned and enters the gas tank, where it is stored until it is used for its intended purpose;
• gas from a gas tank can be used in the same way as natural gas. It goes to household appliances - gas stoves, heating boilers, etc.;
• decomposed biomass must be regularly removed from the fermenter. This is an additional effort, but the effort pays off. After fermentation, the raw material turns into high-quality fertilizer, which is used in fields and gardens.

A biogas plant is beneficial for the owner of a private house only if he has constant access to waste from livestock farms. On average, out of 1 cubic meter. substrate can be obtained 70-80 cubic meters. biogas, but gas production is uneven and depends on many factors, incl. biomass temperature. This complicates the calculations.

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 production. 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.

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

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

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

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

The chemical composition of the gas is highly dependent on what processes take place in the reactor. Most often, the process of methane fermentation takes place there, as a result of which a gas with a high percentage of methane is formed. But instead of methane fermentation, a process with the formation of hydrogen may well occur. But in my opinion, hydrogen is not needed for an ordinary consumer, and maybe even dangerous. Remember at least the death of the airship Hindenburg. Now let's figure out what biogas can be obtained from.

Where can you get biogas from?

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

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

Block diagram of a biogas plant.

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

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

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

Biogas for a private house.

Many owners of small farms are thinking about using biogas for domestic needs. But having found out in more detail about how it all works, the majority leaves this idea. This is due to the fact that equipment for processing manure or silage costs a lot of money, and the gas yield (depending on the raw material) can turn out to be small. This, in turn, makes the installation of equipment unprofitable. Usually, for private houses of farmers, primitive installations are installed that work on manure. They, most often, are able to provide gas only to the kitchen and a low-power wall-mounted gas boiler. At the same time, a lot of energy will have to be spent on the technological process itself - for heating, pumping, and compressor operation. Expensive filters also cannot be excluded from view.

In general, the moral here is this - the larger the installation itself, the more profitable its work. And for home conditions, this is almost always impossible. But this does not mean that no one does home installations. I suggest you watch the following video to see how it looks from improvised materials:

Summary.

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

Since technologies are now rapidly stepping forward, a wide variety of organic wastes can become raw materials for biogas production. The indicators of biogas yield from various types of organic raw materials are given below.

Table 1. Biogas output from organic raw materials

Cattle manure

All over the world, among the most popular are those that involve the use of cow dung as the base raw material. Keeping one head of cattle makes it possible to provide 6.6–35 tons of liquid manure per year. This volume of raw materials can be processed into 257–1785 m 3 of biogas. According to the calorific value parameter, these indicators correspond to: 193–1339 cubic meters of natural gas, 157–1089 kg of gasoline, 185–1285 kg of fuel oil, 380–2642 kg of firewood.

One of the key benefits of using cow manure for biogas production is the presence of colonies of methane-producing bacteria in the gastrointestinal tract of cattle. This means that there is no need for additional introduction of microorganisms into the substrate, and therefore no need for additional investments. At the same time, the homogeneous structure of manure makes it possible to use this type of raw material in continuous cycle devices. Biogas production will be even more efficient if cattle urine is added to the fermentable biomass.

Manure of pigs and sheep

Unlike cattle, animals of these groups are kept in rooms without concrete floors, so the processes of biogas production here are somewhat complicated. The use of pig and sheep manure in continuous cycle devices is not possible; only dosed loading is allowed. Together with the raw mass of this type, plant waste often enters the bioreactors, which can significantly increase the period of its processing.

bird droppings

In order to effectively use bird droppings for biogas production, it is recommended to equip bird cages with perches, as this will allow the collection of droppings in large volumes. To obtain significant volumes of biogas, bird droppings should be mixed with cow slurry, which will eliminate excessive release of ammonia from the substrate. A feature of the use of bird droppings in the production of biogas is the need to introduce a 2-stage technology using a hydrolysis reactor. This is required in order to control the level of acidity, otherwise the bacteria in the substrate may die.

Feces

For efficient processing of faeces, it is required to minimize the volume of water per one sanitary appliance: it cannot exceed 1 liter at a time.

With the help of scientific research in recent years, it has been possible to establish that biogas, if feces are used for its production, along with key elements (in particular, methane), many hazardous compounds that contribute to environmental pollution pass into biogas. For example, during methane fermentation of such raw materials at high temperature conditions at wastewater biological treatment plants, almost all samples of the gas phase found about 90 µg/m 3 arsenic, 80 µg/m 3 antimony, 10 µg/m 3 mercury, 500 µg/m 3 tellurium, 900 µg/m 3 tin, 700 µg/m 3 lead. The mentioned elements are represented by tetra- and dimethylated compounds characteristic of autolysis processes. The identified indicators seriously exceed the MPC of these elements, which indicates the need for a more thorough approach to the problem of processing feces into biogas.

Energy crops

The vast majority of green plants provide an exceptionally high yield of biogas. Many European biogas plants operate on corn silage. This is quite justified, since corn silage obtained from 1 hectare allows producing 7800–9100 m 3 of biogas, which corresponds to: 5850–6825 m3 of natural gas, 4758–5551 kg of gasoline, 5616–6552 kg of fuel oil, 11544–13468 kg of firewood.

About 290–490 m 3 of biogas is produced by a ton of various herbs, while clover has a particularly high yield: 430–490 m 3 . A ton of high-quality raw material of potato tops is also capable of providing up to 490 m 3, a ton of beet tops - from 75 to 200 m 3, a ton of waste obtained during the harvesting of rye - 165 m 3, a ton of flax and hemp - 360 m 3, a ton of oat straw - 310 m 3.

It should be noted that in the case of targeted cultivation of energy crops for biogas production, there is a need to invest money in their sowing and harvesting. In this, such cultures differ significantly from other sources of raw materials for bioreactors. There is no need to fertilize such crops. As for the waste of vegetable growing and the production of grain crops, their processing into biogas has an exceptionally high economic efficiency.

"landfill gas"

From a ton of dry MSW, up to 200 m 3 of biogas can be obtained, over 50% of which is methane. In terms of methane emission activity, "landfills" are far superior to any other sources. The use of MSW in the production of biogas will not only provide a significant economic effect, but also reduce the flow of polluting compounds into the atmosphere.

Qualitative characteristics of raw materials for biogas production

Indicators characterizing the yield of biogas and the concentration of methane in it depend, among other things, on the moisture content of the base feedstock. It is recommended to keep it at 91% in summer and 86% in winter.

It is possible to obtain maximum volumes of biogas from fermented masses by ensuring a sufficiently high activity of microorganisms. This task can be realized only with the necessary viscosity of the substrate. The processes of methane fermentation slow down if dry, large and solid elements are present in the raw material. In addition, in the presence of such elements, the formation of a crust is observed, leading to stratification of the substrate and the cessation of biogas output. To exclude such phenomena, before loading the raw mass into bioreactors, it is crushed and gently mixed.

The optimal pH values ​​of the raw materials are parameters in the range of 6.6–8.5. The practical implementation of increasing the pH to the required level is provided by dosed introduction of a composition made from crushed marble into the substrate.

In order to maximize the yield of biogas, most of the different types of raw materials can be mixed with other types through cavitation processing of the substrate. At the same time, optimal ratios of carbon dioxide and nitrogen are achieved: in the processed biomass, they should be provided in a ratio of 16 to 10.

Thus, when choosing raw materials for biogas plants it makes sense to pay close attention to its qualitative characteristics.

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

In the food chain, subsequent bacteria feed on the waste products of the previous ones.
The first type is hydrolytic bacteria, the second is acid-forming, the third is methane-forming.
In the production of biogas, not only bacteria of the methanogen class are involved, but all three species. During the fermentation process, biogas is produced from biowaste. This gas can be used like ordinary natural gas - for heating, power generation. It can be compressed, used to refuel a car, accumulated, pumped. In fact, as the owner and full owner, you get your own gas well and income from it. You do not need to register your own installation anywhere yet.

Composition and quality of biogas

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

The volume of gases depends on temperature and pressure. High temperatures lead to expansion of the gas and to a decrease in the calorific value along with the volume, and vice versa. With an increase in humidity, the calorific value of the gas also decreases. In order to be able to compare the gas outputs with each other, it is necessary to correlate them with the normal state (temperature 0 C, atmospheric pressure 1 bar, relative humidity of the gas 0%). In general, gas production data are expressed in liters (l) or cubic meters of methane per kilogram of organic dry matter (oDM); this is much more accurate and more eloquent than the data in cubic meters of biogas in cubic meters of fresh substrate.

Raw materials for biogas production

List of organic wastes suitable for biogas production: manure, bird droppings, grain and molasses post-alcohol stillage, brewer's grains, beet pulp, fecal sludge, waste from fish and slaughter shops (blood, fat, intestines, canyga), grass, household waste, waste dairies - salted and sweet whey, biodiesel production waste - technical glycerin from rapeseed biodiesel production, juice production waste - fruit, berry, vegetable, grape pomace, algae, starch and molasses production waste - pulp and syrup, potato processing waste , chips production - peelings, skins, rotten tubers, coffee pulp.

Calculation of useful biogas in a farm

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

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

In order to calculate the yield of biogas from a particular feedstock, it is necessary to conduct laboratory tests or look at reference data, and then determine the content of fats, proteins and carbohydrates. When determining the latter, it is important to know the percentage of rapidly degradable (fructose, sugar, sucrose, starch) and hardly decomposable substances (cellulose, hemicellulose, lignin).

Having determined the content of substances, you can calculate the gas yield for each substance separately and then add it up. When biogas was associated with manure (in the countryside, this situation still exists today - I asked in the taiga district center, Verkhovazhye, Vologda Oblast), the concept of "animal unit" was used. Today, when they learned how to get biogas from arbitrary organic raw materials, this concept has moved away and has ceased to be used.

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

Landfill gas is one of the varieties of biogas. Obtained in landfills from municipal household waste.

Environmental aspect in the use of biogas

Biogas production helps prevent methane emissions into the atmosphere. Methane contributes 21 times more to the greenhouse effect than a mixture of CO2 and stays in the atmosphere for up to 12 years. Capturing and limiting the spread of methane is the best short-term way to prevent global warming. Here is where, at the junction of research, another, little research so far area of ​​science is revealed.

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

Biogas production

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

A reliable biogas plant must have the necessary parts:

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

Features of biogas plant

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

Beneficial bacteria “live” in the reactor, which feed on waste. Biogas is the product of the vital activity of bacteria. To maintain the life of bacteria, the supply of feed - waste, heating to 35 ° C and periodic mixing is required. The resulting biogas is accumulated in a storage (gas tank), then it passes through a purification system and is supplied to consumers (a boiler or an electric generator). The reactor operates without air access, is practically hermetic and harmless.

For the fermentation of some types of raw materials in their pure form, a special two-stage technology is required.

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

Significant factors influencing the fermentation process:

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

Biogas application

Biogas is used as a fuel for the production of electricity, heat or steam, or as a vehicle fuel. Biogas plants can be used as treatment facilities on farms, poultry farms, distilleries, sugar factories, meat processing plants and, as a special case, they can even replace a veterinary and sanitary plant, where carrion can be disposed of in biogas instead of producing meat and bone meal.