Owners of private houses located in regions with limited access to traditional fuels should definitely turn their attention to modern biogas plants. Such units make it possible to obtain biogas from a variety of organic waste and use it for personal needs, including heating residential premises.
Gas can be obtained from almost any biomass - waste from the livestock industry, food production, agriculture, foliage, etc. At the same time, you can build such an installation with your own hands.
Both homogeneous raw materials and mixtures of various biomass are suitable for producing biogas. A biogas plant is a volumetric sealed structure equipped with devices for supplying raw materials, heating biomass, mixing components, discharging the resulting biogas into a gas collector and, of course, protecting the structure.
In the reactor, under the influence of anaerobic bacteria, rapid decomposition of biomass occurs. During the fermentation of organic raw materials, biogas is released. Approximately 70% of the composition of such gas is represented by methane, the remaining part is carbon dioxide.
Biogas is characterized by excellent calorific value; it has no pronounced odor or color. In terms of its properties, biogas is practically in no way inferior to more traditional natural gas.
In developed countries, additional installations are used to purify biogas from carbon dioxide. If you wish, you can buy the same installation and obtain pure biomethane.
Biogas plants on silos. 1 Silo pits. 2 Biomass loading system. 3 Reactor. 4 Post-fermentation reactor. 5 Substrater. 6 Heating system. 7 Power plant. 8 Automation and control system. 9 Gas pipeline system
On average, one cow or other animal weighing half a ton is capable of producing enough manure per day to produce approximately 1.5 m3 of biogas. Daily manure from one average pig can be processed into 0.2 m3 of biogas, and a rabbit or chicken into 0.01-0.02 m3 of fuel.
For comparison: 1 m3 of biogas from manure provides approximately the same amount of thermal energy as 3.5 kg of firewood, 1-2 kg of coal, 9-10 kW/h of electricity.
The simplest recipe for a mixture for producing biogas includes the following components:
This amount of biomass will be enough to produce biogas for six months of operation with moderate consumption. On average, biogas begins to be released within 1.5-2 weeks after the mixture is loaded into the installation.
Gas can be used to heat a home and a variety of commercial and domestic buildings.
The main components of a complete biogas system are:
A household installation will have a somewhat simplified design, however, for a complete understanding, you are invited to read the description of all the listed elements.
This part of the installation is usually assembled from stainless steel or concrete. Externally, the reactor looks like a large sealed container, on top of which is a dome, usually spherical in shape.
Currently, the most popular are reactors with a collapsible design, made using innovative technologies. Such a reactor can be easily assembled with your own hands with minimal time investment. If necessary, it can be easily disassembled and transported to another place.
Steel is convenient because you can easily create holes in it to connect other elements of the system. Concrete is superior to steel in terms of strength and durability.
This part of the installation includes a hopper for receiving waste, a supply pipeline for water supply and a screw pump designed to send humus to the reactor.
A front loader is used to load the dry component into the hopper. At home, this task can be accomplished without a loader, using various available tools, for example, shovels.
In the hopper the mixture is moistened to a semi-liquid state. After reaching the desired level of moisture, the screw transfers the semi-liquid mass to the lower compartment of the reactor.
Fermentation of humus in the reactor should occur evenly. This is one of the most important conditions for ensuring intensive release of biogas from the mixture. It is to achieve the most uniform fermentation process of the mixture that the design of a typical biogas plant includes mixers with electric drives.
There are submersible and inclined type mixers. Submersible mechanisms can be lowered into the biomass to the required depth to ensure intensive and uniform mixing of the substrate. Usually such mixers are placed on a mast.
Installation of inclined mixers is carried out on the side surfaces of the reactor. An electric motor is responsible for rotating the screw in the fermenter.
To successfully produce biogas, the temperature inside the system must be maintained at +35-+40 degrees. For this purpose, automated heating systems are included in the design.
The heat source in this case is a hot water boiler; in some situations, electric heating units are used.
Biogas is collected in this structural element. Most often, the gas holder is placed on the roof of the reactor.
The production of modern gas tanks is usually carried out using polyvinyl chloride, a material that is resistant to sunlight and various adverse natural phenomena.
In some situations, instead of a regular gas tank, special bags are used. Also, these devices allow you to temporarily increase the volume of the produced biogas.
To make a gas holder bag, a special polyvinyl chloride with elastic properties is used, which can inflate as the volume of biogas increases.
This part of the system is responsible for drying waste humus and obtaining, if necessary, high-quality fertilizers.
The simplest separator consists of a screw and a separator chamber. The chamber is made in the form of a sieve. This allows the biomass to be separated into a solid component and a liquid part.
The dried humus is sent to the shipping compartment. The system directs the liquid part back to the receiving chamber. Here the liquid is used to moisten the new feedstock.
A household biogas installation will have a somewhat simplified design, but its manufacture should be approached with maximum responsibility.
First step. Dig a hole. At its core, a biogas plant is a large pit with a special finish. The most important and at the same time difficult part of manufacturing the system in question is the correct preparation of the walls of the bioreactor and its base.
The pit must be sealed. Strengthen the base and walls with plastic or concrete. Instead, you can purchase ready-made polymer rings with a solid bottom. Such devices make it possible to ensure the necessary tightness of the system. The material will retain its original characteristics for many years, and if necessary, you can easily replace the old ring with a new one.
Second step.
Install a gas drainage system. This will save you from the need to purchase and install agitators, due to which the time and money spent on assembling the installation will be significantly reduced.
The simplest version of a gas drainage system is vertically fixed sewer pipes made of polyvinyl chloride with many holes throughout the body.
Select pipes of such length that their upper edges rise slightly above the upper level of the loaded humus.
Third step. Cover the outer layer of the substrate with film insulation. Thanks to the film, conditions will be created for the accumulation of biogas under the dome under conditions of slight excess pressure.
Fourth step.
Gas consumption should be regular. Otherwise, the dome over the biomass container may simply explode. In summer, gas is formed more intensively than in winter. To solve the latter problem, purchase and install suitable heaters.
Procedure and conditions for successful use of a biogas plant
Thus, it is not difficult to assemble a simple biogas plant yourself. However, for its successful operation, you must remember and follow a few simple rules.
Remember: a biogas installation is a potentially explosive unit, so follow all safety regulations relevant for the operation of any gas equipment.
Thus, even manure and, in principle, almost everything that you previously tried your best to get rid of, can be useful on the farm. You just need to properly build a home biogas installation, and very soon your home will be warm. Follow the recommendations received, and you will no longer have to spend enormous sums on heating.
Good luck!
Biogas is a completely new source of energy. Using it, you can simply forget about the hated electricity tariffs.
The simplest example of biogas is the gas that is released when manure or other household waste rots.
The process of creating a biogas plant with your own hands is quite labor-intensive, but possible. This setup will help save your money: now you don't need to buy fuel and electricity, you will produce it yourself.
You can also recreate a future installation using available materials. For example, the reactor of a future installation can be made from old pots, basins, and leftovers. It is best to choose cylindrical objects.
The main requirements that any reactor must meet:
To build a good bio-installation, you need to adhere to the following sequence:
It is best to make the walls of the future installation from concrete, since the strength of your reactor is the key to safety.
It is also important that the distance to the nearest residential building is at least 500 meters. This measure is due to the fact that during the fermentation process poisonous gas is released, which can kill a person in a matter of minutes.
It should be remembered that biogas is an explosive product, and in the event of an explosion it will destroy everything within a radius of 200-300 meters.
To obtain the biogas itself, you need:
5.5-6 tons of mixture will be enough for a biogas plant to operate for six months.
Remember that the mass you load into the reactor should not contain antibiotics, dyes, solvents or other synthetic substances. Otherwise, they will not only interfere with the entire reaction and stop it, but also ruin the walls of your reactor.
As can be noted, the operating principle of a biogas plant is very simple. Simply put, they install in the pit sealed tank where raw materials are stored for processing. Having loaded them, you just have to wait until the microorganisms, they are the ones who ensure the entire process, decompose the mass, and only after that you can collect the finished gas.
Fermented raw materials can also be used. You can easily use it in agriculture as fertilizer.
After the gas has been produced, it remains in the reactor when the mass is removed from the reactor through the discharge pipe. It is very important that the volume of the temporary storage tank is no less than the reactor.
Biogas is a substance that contains a large amount of methane. It is obtained as a result of the rotting of various organic wastes. Biogas produces large amounts of energy, which makes it possible to use it for heating or fuel vehicles. The use of manure as an alternative source of energy has recently been of great interest to farmers. A do-it-yourself biogas plant will perfectly cope with the task.
When choosing the type of installation for gas release, you need to rely on the weather and climatic conditions of the region. For Russia the following types are offered:
(Mixing and heating of raw materials in the reactor is not carried out)
This version of a do-it-yourself biogas plant is the simplest of all existing ones. The reactor should contain approximately 1 to 10 cubic meters. Such an installation processes quite a lot of raw materials per day - from 50 kg of manure or more. There are no unnecessary parts in the installation: a reactor, a container for raw materials, a device for selecting and using biogas, a device for unloading waste.
Such a device is perfect for use in hot areas, then you don’t have to heat or mix the processed raw materials. It is used in industrial mode when heated within 5-20°C. Conveniently, the resulting biogas is immediately sent for use in household appliances. All processed raw materials exit through a specially made outlet.
Using the drawings, you can create a similar biogas plant with your own hands without significant effort and expense. Even the most inexperienced beginner can do it. There is absolutely nothing complicated here, but there are some nuances that are worth discussing in detail.
First you need to clearly know: how much manure do you have on your farm? That is, how busy your installation will be. The volume of the future reactor will depend on this. Next, we determine: where will the installation be located? You need to choose a place based on the principle: safe and comfortable.
Then you can start looking for parts for a future source of alternative energy. We will install pipes for loading and unloading raw materials. We arrange the reactor of the device into the pit and secure the loading tank and the gas outlet itself well. Let's start with the final part, installing the top part and the cover.
It is imperative that the reactor be sealed so that nothing unnecessary enters it. To do this, it is necessary to carry out a check after its assembly. The installation must be painted and insulated. That's it, you can finally start working. Avoid exposure of the manufactured device to sunlight. The best way to do this is to use a sunshade panel.
This option is also very convenient and does not require significant financial investments. But if we talk about usefulness and operational efficiency, then this model with manual loading and the ability to mix raw materials wins significantly.
A manufactured installation of this type is more suitable for small farms. The recommended reactor volume is in the range of 1-10 cubic meters. m. The device can process from 50 to 200 kg of manure per day.
For greater efficiency and better fermentation of raw materials, it is best to consider a heating system. The device can operate at temperatures up to 35°C in mesophilic mode and up to 55°C in thermophilic mode.
To heat raw materials, it is best to use water-heating boilers, which is also economical, since it runs on produced biofuel. The raw materials that remain after production are excellent as fertilizer. It is stored in a special container. This essential substance is also suitable for breeding worms.
A home installation for producing biogas can be equipped with a gas holder, which is designed to store the produced fuel. A device for automatic gas pumping is also installed. In this case, loading, as in previous types of installations, remains manual.
In the reactor, it is possible to mix the raw materials pneumatically, using the resulting biogas. It can be equipped with anything to make work easier; the process can be fully automated. A special feature of this model is the ability to work at different temperatures for manure fermentation.
This device is perfect for both small and medium-sized production. It will be able to process up to 1.5 tons of manure per day (minimum amount 0.3 tons). The proposed reactor volume is 5-25 cubic meters.
The pneumatic system is used to load and mix raw materials. But the preparation is carried out manually. Heating carried out in the reactor occurs due to heat exchange with a water heating boiler. The latter also runs on the produced biogas. Waste is unloaded in two ways: through one pipeline, raw materials are supplied to the storage facility for collection, and through the second, for loading onto transport and removal directly to the field.
The extracted biogas is automatically selected and a gas tank is provided for storage. The installation has no temperature restrictions.
Mechanical preparation of raw materials (which is a feature of this model) is carried out using a compressor, which supplies the material to the loading hopper from a special container. The reactor is fed using compressed biogas, which is also used for heating. Gas is withdrawn automatically into the gas tank. This do-it-yourself biogas plant can be used in large and medium-sized farms at different fermentation temperature conditions.
To get a clear idea of the process of obtaining gas from manure and the operation of industrial installations, you can watch the presented video.
Of course, DIY biogas is not for everyone. First, you must be the owner of a private home. A homemade installation has dimensions and installation options for which the apartment conditions are absolutely not suitable. Secondly, at home it is possible only if there is a large amount of organic waste. And thirdly, perhaps most importantly, you need knowledge.
There is no point in inventing an installation - everything has already been invented a long time ago. But in order to implement a ready-made idea using ready-made drawings, this must be understood. A tool, ingenuity, understanding and awareness of the design of the device, and also a desire that will allow you not to deviate from the intended goal - this is all very important.
Let's summarize:
Many European farmers have long switched to this alternative type of fuel. The payback period for a biogenerator is 3-5 years, it all depends on the scale of consumption. For example, Danish owners of mini-farms, with livestock numbers of only 50-100 heads, manage to produce biogas with their own installations, which fully satisfies the needs of both the residential building and the farm itself. Comfort at home and on the farm, thanks to their own biogas, is perceived as something ordinary.
In the entire biological installation, almost every element is important:
The raw materials entering the bioreactor begin to ferment. The gas released is not pure. It contains a proportion of methane (up to 80-90%), carbon dioxide (up to 20-30%), hydrogen (up to 5-10%). Periodic stirring promotes the frequency of gas release. The gas enters the gas tank, then through the filtration system, and then to the consumed unit (boiler, furnace, etc.).
Biogas can be obtained at home in different volumes and different qualities. This is influenced by several factors:
The table shows the volume of gas produced (in m3) from one ton of raw material:
Biogas can be used at home based on its quantity and quality. Usually this is heating of outbuildings or a residential building. With small volumes of gas, it may only be enough to heat water, but in this case, the profitability of the installation needs to be reconsidered.
Some craftsmen have pushed their designs to enormous levels of productivity and completely forgotten about the consumption of government electricity and natural gas.
Humanity has made a giant leap forward, learning to control nature and everyday life. Biogas, as an alternative fuel and form of energy, has now become possible to obtain at home. Of course, the high cost of the equipment is somewhat daunting, but payback calculations show that a bioreactor at home is a profitable and expedient solution.
Rising energy prices make us think about the possibility of providing ourselves with them ourselves. One option is a biogas plant. With its help, biogas is obtained from manure, droppings and plant residues, which, after purification, can be used for gas appliances (stoves, boilers), pumped into cylinders and used as fuel for cars or electric generators. In general, processing manure into biogas can meet all the energy needs of a home or farm.
Construction of a biogas plant is a way to independently provide energy resources
Biogas is a product that is obtained from the decomposition of organic substances. During the process of rotting/fermentation, gases are released, collecting which you can meet the needs of your own household. The equipment in which this process occurs is called a “biogas plant”.
The process of biogas formation occurs due to the vital activity of various kinds of bacteria that are contained in the waste itself. But in order for them to actively “work”, they need to create certain conditions: humidity and temperature. To create them, a biogas plant is being built. This is a complex of devices, the basis of which is a bioreactor, in which waste decomposition occurs, which is accompanied by gas formation.
There are three modes for processing manure into biogas:
The most difficult thing to implement in biogas plants is the thermophilic mode. This requires high-quality thermal insulation of the biogas plant, heating and a temperature control system. But at the output we get the maximum amount of biogas. Another feature of thermophilic processing is the impossibility of additional loading. The remaining two modes - psychophilic and mesophilic - allow you to add a fresh portion of prepared raw materials daily. But, in the thermophilic mode, the short processing time makes it possible to divide the bioreactor into zones in which their share of raw materials will be processed with different loading times.
The basis of a biogas plant is a bioreactor or bunker. The fermentation process occurs in it, and the resulting gas accumulates in it. There is also a loading and unloading hopper; the generated gas is discharged through a pipe inserted into the upper part. Next comes the gas treatment system - cleaning it and increasing the pressure in the gas pipeline to working pressure.
For mesophilic and thermophilic modes, a bioreactor heating system is also required to reach the required modes. For this purpose, gas boilers running on produced fuel are usually used. From it, a pipeline system goes to the bioreactor. Usually these are polymer pipes, since they best withstand being in an aggressive environment.
A biogas plant also needs a system for mixing the substance. During fermentation, a hard crust forms at the top, and heavy particles settle down. All this together worsens the process of gas formation. Mixers are needed to maintain a homogeneous state of the processed mass. They can be mechanical or even manual. They can be started by timer or manually. It all depends on how the biogas plant is made. An automated system is more expensive to install, but requires a minimum of attention during operation.
Depending on the type of location, a biogas plant can be:
Recessed ones are more expensive to install - a large amount of excavation work is required. But when used in our conditions, they are better - it is easier to organize insulation, and the heating costs are lower.
A biogas plant is essentially omnivorous - any organic matter can be processed. Any manure, urine, or plant residues are suitable. Detergents, antibiotics, and chemicals negatively affect the process. It is advisable to minimize their intake, as they kill the flora that processes them.
Cattle manure is considered ideal, since it contains large quantities of microorganisms. If there are no cows on the farm, when loading the bioreactor, it is advisable to add some of the manure to populate the substrate with the required microflora. Plant residues are pre-crushed and diluted with water. Plant materials and excrement are mixed in a bioreactor. This “filling” takes longer to process, but at the end of the day, under the correct mode, we have the highest product yield.
To minimize the costs of organizing the process, it makes sense to locate the biogas plant close to the source of waste - near buildings where poultry or animals are kept. It is advisable to develop the design so that loading occurs by gravity. From a barn or pigsty, you can lay a pipeline at a slope through which manure will flow by gravity into the bunker. This greatly simplifies the task of maintaining the reactor, and also removing manure.
It is most advisable to locate the biogas plant so that waste from the farm can flow by gravity
Typically, buildings with animals are located at some distance from a residential building. Therefore, the generated gas will need to be transferred to consumers. But laying one gas pipe is cheaper and easier than organizing a line for transporting and loading manure.
There are quite strict requirements for manure processing tanks:
All these requirements for the construction of a biogas plant must be met, as they ensure safety and create normal conditions for processing manure into biogas.
Resistance to aggressive environments is the main requirement for materials from which containers can be made. The substrate in the bioreactor can be acidic or alkaline. Accordingly, the material from which the container is made must tolerate various environments well.
Not many materials meet these requests. The first thing that comes to mind is metal. It is durable and can be used to make containers of any shape. The good thing is that you can use a ready-made container - some old tank. In this case, the construction of a biogas plant will take very little time. The disadvantage of metal is that it reacts with chemically active substances and begins to collapse. To neutralize this disadvantage, the metal is coated with a protective coating.
An excellent option is a bioreactor container made of polymer. Plastic is chemically neutral, does not rot, does not rust. You just need to choose from materials that can withstand freezing and heating to fairly high temperatures. The reactor walls should be thick, preferably glass fiber reinforced. Such containers are not cheap, but they last a long time.
A cheaper option is a biogas plant with a container made of bricks, concrete blocks, or stone. In order for the masonry to withstand high loads, it is necessary to reinforce the masonry (in every 3-5 rows, depending on the thickness of the wall and the material). After completing the wall construction process, to ensure water and gas impermeability, subsequent multi-layer treatment of the walls is necessary both inside and outside. The walls are plastered with a cement-sand composition with additives (additives) that provide the required properties.
The reactor volume depends on the selected temperature for processing manure into biogas. Most often, mesophilic is chosen - it is easier to maintain and it allows for the possibility of daily reloading of the reactor. Biogas production after reaching normal mode (about 2 days) is stable, without surges or dips (when normal conditions are created). In this case, it makes sense to calculate the volume of the biogas plant depending on the amount of manure generated on the farm per day. Everything is easily calculated based on average statistical data.
The decomposition of manure at mesophilic temperatures takes from 10 to 20 days. Accordingly, the volume is calculated by multiplying by 10 or 20. When calculating, it is necessary to take into account the amount of water that is necessary to bring the substrate to an ideal state - its humidity should be 85-90%. The found volume is increased by 50%, since the maximum load should not exceed 2/3 of the tank volume - gas should accumulate under the ceiling.
For example, there are 5 cows, 10 pigs and 40 chickens on a farm. The result is 5 * 55 kg + 10 * 4.5 kg + 40 * 0.17 kg = 275 kg + 45 kg + 6.8 kg = 326.8 kg. To bring chicken manure to 85% humidity, you need to add a little more than 5 liters of water (that’s another 5 kg). The total weight is 331.8 kg. For processing in 20 days you need: 331.8 kg * 20 = 6636 kg - about 7 cubic meters only for the substrate. We multiply the found figure by 1.5 (increase by 50%), we get 10.5 cubic meters. This will be the calculated value of the reactor volume of the biogas plant.
Loading and unloading hatches lead directly into the bioreactor tank. In order for the substrate to be evenly distributed over the entire area, they are made at opposite ends of the container.
When installing a biogas plant in-depth, the loading and unloading pipes approach the body at an acute angle. Moreover, the lower end of the pipe should be below the liquid level in the reactor. This prevents air from entering the container. Also, rotary or shut-off valves are installed on the pipes, which are closed in the normal position. They open only during loading or unloading.
Since manure may contain large fragments (litter elements, grass stems, etc.), small diameter pipes will often become clogged. Therefore, for loading and unloading, they must have a diameter of 20-30 cm. They must be installed before the start of work on insulating the biogas plant, but after the container is installed in place.
The most convenient mode of operation of a biogas plant is with regular loading and unloading of the substrate. This operation can be performed once a day or once every two days. Manure and other components are preliminarily collected in a storage tank, where they are brought to the required state - crushed, if necessary, moistened and mixed. For convenience, this container may have a mechanical stirrer. The prepared substrate is poured into the receiving hatch. If you place the receiving container in the sun, the substrate will be preheated, which will reduce the cost of maintaining the required temperature.
It is advisable to calculate the installation depth of the receiving hopper so that waste flows into it by gravity. The same applies to unloading into the bioreactor. The best case is if the prepared substrate moves by gravity. And a shutter will fence it off during preparation.
To ensure the tightness of the biogas plant, the hatches on the receiving hopper and in the unloading area must have a sealing rubber seal. The less air there is in the container, the cleaner the gas will be at the outlet.
Biogas is removed from the reactor through a pipe, one end of which is under the roof, the other is usually lowered into a water seal. This is a container with water into which the resulting biogas is discharged. There is a second pipe in the water seal - it is located above the liquid level. Cleaner biogas comes out into it. A gas shut-off valve is installed at the outlet of their bioreactor. The best option is a ball one.
What materials can be used for the gas transmission system? Galvanized metal pipes and gas pipes made of HDPE or PPR. They must ensure tightness; seams and joints are checked using soap foam. The entire pipeline is assembled from pipes and fittings of the same diameter. No contractions or expansions.
The approximate composition of the resulting biogas is:
In order for biogas to be odorless and burn well, it is necessary to remove carbon dioxide, hydrogen sulfide, and water vapor from it. Carbon dioxide is removed in a water seal if slaked lime is added to the bottom of the installation. Such a bookmark will have to be changed periodically (as soon as the gas starts to burn worse, it’s time to change it).
Gas drying can be done in two ways - by making water seals in the gas pipeline - by inserting curved sections into the pipe under the water seals, in which condensate will accumulate. The disadvantage of this method is the need to regularly empty the water seal - if there is a large amount of collected water, it can block the passage of gas.
The second way is to install a filter with silica gel. The principle is the same as in a water seal - the gas is supplied to the silica gel, and dried out from under the lid. With this method of drying biogas, the silica gel must be dried periodically. To do this, you need to warm it up in the microwave for some time. It heats up and the moisture evaporates. You can fill it up and use it again.
To remove hydrogen sulfide, a filter loaded with metal shavings is used. You can load old metal scourers into the container. Purification occurs in exactly the same way: gas is supplied to the lower part of the container filled with metal. As it passes, it is cleared of hydrogen sulfide, collected in the upper free part of the filter, from where it is discharged through another pipe/hose.
The purified biogas enters a storage tank - a gas holder. This can be a sealed plastic bag or plastic container. The main condition is gas tightness; shape and material do not matter. The gas holder stores a supply of biogas. From it, with the help of a compressor, gas under a certain pressure (set by the compressor) is supplied to the consumer - to the gas stove or boiler. This gas can also be used to generate electricity using a generator.
To create stable pressure in the system after the compressor, it is advisable to install a receiver - a small device for leveling pressure surges.
In order for the biogas plant to operate normally, it is necessary to regularly mix the liquid in the bioreactor. This simple process solves many problems:
Typically, a small homemade biogas plant has mechanical agitators that are driven by muscle power. In large-volume systems, the agitators can be driven by motors that are activated by a timer.
The second method is to stir the liquid by passing some of the generated gas through it. To do this, after leaving the metatank, a tee is installed and part of the gas flows into the lower part of the reactor, where it exits through a tube with holes. This part of the gas cannot be considered a consumption, since it still enters the system again and, as a result, ends up in the gas tank.
The third method of mixing is to use fecal pumps to pump the substrate from the lower part and pour it at the top. The disadvantage of this method is its dependence on the availability of electricity.
Without heating the processed liquid, psychophilic bacteria will multiply. The processing process in this case will take 30 days, and the gas output will be small. In the summer, if there is thermal insulation and preheating of the load, it is possible to reach temperatures of up to 40 degrees, when the development of mesophilic bacteria begins, but in winter such an installation is practically inoperative - the processes proceed very sluggishly. At temperatures below +5°C they practically freeze.
For best results, use heating. The most rational is water heating from a boiler. The boiler can run on electricity, solid or liquid fuel, and you can also run it on the produced biogas. The maximum temperature to which water needs to be heated is +60°C. Hotter pipes can cause particles to stick to the surface, reducing heating efficiency.
You can also use direct heating - insert heating elements, but firstly, it is difficult to organize mixing, secondly, the substrate will stick to the surface, reducing heat transfer, the heating elements will quickly burn out
A biogas plant can be heated using standard heating radiators, simply pipes twisted into a coil, or welded registers. It is better to use polymer pipes - metal-plastic or polypropylene. Corrugated stainless steel pipes are also suitable; they are easier to install, especially in cylindrical vertical bioreactors, but the corrugated surface provokes sediment sticking, which is not very good for heat transfer.
To reduce the possibility of particles settling on the heating elements, they are located in the stirrer area. Only in this case everything must be designed so that the mixer cannot touch the pipes. It often seems that it is better to place the heaters at the bottom, but practice has shown that due to sediment on the bottom, such heating is ineffective. So it is more rational to place heaters on the walls of the metatank of a biogas plant.
Depending on the method of pipe arrangement, heating can be external or internal. When installed internally, heating is effective, but repair and maintenance of heaters is impossible without stopping and pumping out the system. Therefore, special attention is paid to the selection of materials and the quality of connections.
Heating increases the productivity of the biogas plant and reduces the processing time of raw materials
When the heaters are located externally, more heat is required (the cost of heating the contents of a biogas plant is much higher), since a lot of heat is spent on heating the walls. But the system is always available for repair, and heating is more uniform, since the environment is heated from the walls. Another advantage of this solution is that stirrers cannot damage the heating system.
First, a leveling layer of sand is poured onto the bottom of the pit, then a heat-insulating layer. It can be clay mixed with straw and expanded clay, slag. All these components can be mixed and poured in separate layers. They are leveled to the horizon, and the capacity of the biogas plant is installed.
The sides of the bioreactor can be insulated with modern materials or with classic old-fashioned methods. One of the old-fashioned methods is coating with clay and straw. Apply in several layers.
Modern materials include high-density extruded polystyrene foam, low-density aerated concrete blocks, etc. The most technologically advanced in this case is polyurethane foam (PPU), but the services for its application are not cheap. But the result is seamless thermal insulation, which minimizes heating costs. There is another heat-insulating material - foam glass. It is very expensive in slabs, but its chips or crumbs cost very little, and in terms of characteristics it is almost ideal: it does not absorb moisture, is not afraid of freezing, tolerates static loads well, and has low thermal conductivity.
