Biogas and biogas plants

Biogas has come to light as a viable alternative in the search for environmentally friendly and sustainable energy sources. The breakdown of organic materials such as food scraps, animal dung, and agricultural residue can produce biogas, which is a renewable substitute for conventional fossil fuels. Its use helps with waste management and environmental conservation in addition to meeting energy needs.

The biogas plant, a specialized facility built to maximize the potential of organic materials, is the hub of biogas production. In order to produce biogas, these plants use anaerobic digestion, a natural process in which microorganisms break down biodegradable matter in the absence of oxygen. Biogas plants are flexible and adaptable to different scales, from small-scale residential units to large industrial installations, due to the process’s efficiency and simplicity.

Biogas has many benefits, one of which is its flexibility in terms of feedstock sources. Biogas can be generated from a variety of organic materials, in contrast to other renewable energy sources that depend on particular inputs like sunlight or wind. Because of its adaptability, biogas production can be adapted to local resources, making it a feasible option in a variety of agricultural settings and geographic locations.

Furthermore, by addressing the issues of waste management and energy, biogas production provides a double benefit. Biogas plants reduce environmental pollution by using organic waste streams that would otherwise break down and release methane, a strong greenhouse gas, into the atmosphere. They also produce a valuable energy source. In addition to lowering greenhouse gas emissions, this mutually beneficial strategy aids in the accomplishment of circular economy goals.

Biogas Production	Using organic waste to produce biogas for heating
Biogas Plants	Facilities that process organic materials into biogas

What factors determine the yield of biogas with higher methane content?

First of all, on temperature. The activity of bacteria fermenting organics is higher the higher the temperature of their environment, at minus temperatures fermentation slows down or stops completely. For this reason, biogas production is most common in subtropical and tropical countries in Africa and Asia. In the Russian climate, obtaining biogas and a complete transition to it as an alternative fuel will require thermal insulation of the bioreactor and the introduction of warm water into the mass of organic matter when the temperature of the external atmosphere drops below freezing.Organic material put into the bioreactor should be biodegradable, it is required to introduce a significant amount of water – up to 90% of the mass of organic material. An important point will be the neutrality of the organic medium, the absence in its composition of components that prevent the development of bacteria, such as cleaning and cleaning agents, any antibiotics. Biogas can be produced from practically any waste of economic and vegetable origin, sewage, manure, etc.д.

The ideal pH range for the anaerobic fermentation of organic materials is between 6.8 and 8.0; higher acidity will impede the production of biogas because the bacteria in this pH range will be occupied with consuming acids and generating carbon dioxide to balance the acidity.

The bioreactor’s nitrogen to carbon ratio should be determined as 1 to 30. This will ensure that the bacteria get the necessary amount of carbon dioxide and that the biogas has the highest methane content.

The ideal temperature range for the fermented organics to produce biogas with a high enough methane content is between 32 and 35 °C; at lower or higher temperatures, the biogas’s quality declines as its carbon dioxide content rises. Three types of bacteria are known to produce methane: mesophilic bacteria operate in the temperature range of +30 to +42 °C; psychrophilic bacteria operate in the range of +5 to +20 °C; and thermophilic bacteria operate in the range of +54 to +56 °C. For the biogas consumer, mesophilic and thermophilic bacteria that ferment organic materials with higher gas yields are most interesting.

Mesophilic fermentation uses less energy to heat the organic material in the bioreactor and is less sensitive to temperature variations of a few degrees from the ideal range. Its drawbacks over thermophilic fermentation include a lower gas yield, a longer processing time of the organic substrate (approximately 25 days), and the possibility of hazardous flora in the decomposed organic material, which makes it suitable for use as a bioreactor for the fermentation of organic matter. The bioreactor’s low temperature does not guarantee perfect sterility.

The maximum biogas yield can be achieved by raising and maintaining the intrareactor temperature at a level that is suitable for thermophilic bacteria; this will result in the complete fermentation of organic matter in 12 days, and the breakdown products of the organic substrate are entirely sterile. Cons: The gas yield will be reduced if the temperature regime is changed by two degrees beyond what thermophilic bacteria can tolerate; high heating requirements translate into high energy costs.

In order to prevent a crust from forming on the bioreactor’s surface and blocking the flow of biogas, the contents must be stirred twice a day. Stirring not only removes it but also allows the organic mass’s temperature and acidity level to be balanced. The maximum biogas yield in continuous cycle bioreactors is achieved by simultaneously loading a volume of fresh organic matter equal to the discharged volume and discharging fermented organic matter. Every 24 hours, organic matter needs to be extracted and added to small volume bioreactors, like the ones found in cottage farms, in an amount that roughly equals 5% of the fermentation chamber’s internal volume.

The kind of organic substrate that is added to the bioreactor directly affects the amount of biogas produced (average data per kg of dry substrate weight are given below):

1. horse manure yields 0.27 m3 of biogas, methane content 57%;
2. Cattle (cattle) manure gives 0.3 m3 of biogas, methane content 65%;
3. fresh cattle manure yields 0.05 m3 of biogas with 68% methane content;
4. chicken droppings – 0.5 m3, methane content will be 60%;
5. pig manure – 0.57 m3, methane content 70%;
6. sheep dung – 0.6 m3 with methane content of 70%;
7. wheat straw – 0.27 m3, with 58% methane content;
8. corn straw – 0,45 m3, with 58% methane content;
9. grass – 0.55 m3, with 70% methane content;
10. tree leaves – 0.27 m3, methane content 58%;
11. fat – 1.3 m3, with 88% methane content.

Who operates the equipment

Modern farms owned by rural residents can benefit from small-scale biogas plants. Serious cattle breeders use larger devices because they cannot function without units that generate the required energy types.

Reactor for biogas

Since all equipment requires power to operate, the accumulation of organic matter in the backyard of a private home or large farm serves as justification for installation.

The world is fighting for environmental ecology, and biogas plants are the best way to do it because they burn alternative fuels instead of clean substances. Because of this, the devices are becoming more and more popular in both domestic and foreign farms.

Home biogas station

The owners of the plant should take the following actions if they want it to generate 0.7–0.9 m3 of biogas per day, which is sufficient to cook food for two people.

1. Load the fermentation chamber with 1 m3 of finely chopped and diluted in water organic waste (remember – fruit and vegetable peelings) in weight ratios of 1 : 10 – 1 : 5.
2. Tightly close it and ensure a constant temperature supply of +25 to +30oC.

A hot water coil that is heated by the same plant’s gas must pass through the chamber in order to keep the temperature there constant. The gas stove and the reactor outlet both need to have taps installed on the gas line.

As an aside, however, our astute rural residents have long considered—and some have even realized—that they could use their own excrement to generate gas for home heating by combining a biogas plant with a septic tank. You can even locate diagrams of it if you search online.

After the fermenter, the gas collector, also known as the gas holder, is the second most crucial component of the biogas plant. It consists of two steel vessels that enter each other without any hindrance, one of which is upside down. To create a hydraulic seal that prevents biogas from entering the cavity of the inverted vessel, water is poured into the outer vessel. There is about a 50 mm annular gap between the vessel walls. A ½ inch tubing connection can be made between the two tanks. Gas from the upside-down vessel is transferred via the same gas pipeline to a traditional gas stove, where methane is burned. It is advised to place an insulated tent over the gasholder’s exterior.

What to do in winter?

This one biogas plant can only operate in the southernmost regions of the nation during the winter. Because heating will need a little bit more gas than it can produce to maintain fermentation in these northern conditions at this time of year.

Diagram showing the flow of a biogas plant using manure as fuel

However, you can take advantage of the winter months by gathering and filling dry biomass chambers. Then, you won’t have to waste time starting the plant when the warm season arrives. Just fill the reactor with water or slurry, and you’ll be producing biogas at home in three or four days. How many birds have we killed with this biogas plant, you ask?

That’s pretty much everything I had to say about producing biogas at home. Keep it a secret from everyone. If not, there won’t be any waste left for you (just kidding). Till the next time, new articles, that is all.

Reactor for a large farm

Easy bioreactor design appropriate for 1-2 animal small farms. Installing an industrial digester that can handle big fuel volumes is the best option if you own a farm. It is recommended that the system be designed and installed by specialized firms.

Bioreactor with membrane

Within industrial complexes are:

• Intermediate storage tanks;
• Mixer installations;
• Bioreactor;
• A small cogeneration plant that provides energy for heating buildings and greenhouses, as well as electricity;
• Tanks for fermented manure used as fertilizer.

The most economical solution is to construct a single complex that serves multiple nearby farms. Energy is generated in proportion to the amount of biomass processed.

The sanitary and epidemiological station, fire inspectorate, and gas inspectorate must approve industrial installations prior to receiving biogas. There are specific guidelines for how each element should be arranged, and they are documented.

Working principle

Fermentation is the process of turning organic feedstock into biogas. The feedstock is placed into a unique container designed to consistently shield the biomass from oxygen exposure. The process known as anaerobic fermentation occurs when oxygen is not present.

Fermentation starts in an anaerobic environment under the influence of specific bacteria. The feedstock forms a crust as fermentation progresses, which needs to be broken down periodically. Thorough mixing is used to carry out the breakdown.

At least twice a day, the contents must be stirred without loosening the process’s integrity. Stirring not only gets rid of the crust but also distributes the temperature and acidity evenly throughout the organic mass. These adjustments result in the production of biogas.

The resultant gas is then piped to the customer after being collected in a gas holder. After the raw materials are processed, biofertilizer is produced that can be applied to the soil or utilized as an animal food additive. Composted humus is the term for this type of fertilizer.

Included in a biogas plant are the following components:

• homogenization tank;
• reactor;
• agitators;
• storage tank (gas-holder);
• heating and water mixing complex;
• gas complex;
• pumping system;
• separator;
• monitoring sensors;
• I&C with visualization;
• safety system;

Figure 2 illustrates an industrial-style biogas plant.

Legal formalization

The installation will require coordination with the gas inspection, firefighters, and the Sanitary and Epidemiological Facility. You’ll require:

• Technological scheme of the installation.
• Layout of the equipment and components with the location of the plant itself, the location of the heating unit, the location of the pipelines and power lines, pump connection. The lightning rod and access roads should be marked on the diagram.
• If the plant will be located indoors, you will also need a ventilation plan, which will provide at least eight times the exchange of all the air in the room.

As we can see, bureaucracy is also necessary in this situation.

It is wrong to squander an energy source if you have one.

And lastly, a brief discussion of the plant’s capacity. A biogas plant generates twice as much gas in a typical day as the tank’s usable capacity. That is, 80 m3 of gas will be produced daily from 40 m3 of slurry. The process itself will cost about thirty percent (heating is a major cost item). Т.е. The outlet will provide you with 56 m3 of biogas per day. Statistically, 10 m3 is needed to heat an average-sized house and meet the needs of a family of three. Every day, your net balance is 46 m3. And that’s only with a modest setup.

Proper venting of the gas

The reactor’s upper cover allows the biogas from the manure to be released. Throughout the fermentation process, it needs to be kept tightly closed. A water shutter is typically employed. It regulates the system’s pressure; if it rises, the lid rises and a release valve is activated. The counterweight in question is a kettlebell. The gas is transported through pipes and purified with water at the outlet. To get rid of the water vapor in the gas so that it burns, water must be purified.

Before biogas can be turned into energy, it needs to be stored. It ought to be kept in a gas holder:

• It is made in the form of a dome and installed at the reactor outlet.
• Most often it is made of iron and covered with several layers of paint to prevent corrosion.
• In industrial complexes, the gas holder is a separate tank.

Alternatively, you could use a PVC bag to create a gas holder. When the bag is filled, the elastic material stretches. If necessary, it can hold a lot of biogas in storage.

Raw materials used

Any animal or plant residue that decomposes releases some amount of combustible gas. Blends with varying compositions work well for raw materials such as grass, straw, manure, and different wastes. The feedstock needs to be diluted with water because the chemical reaction requires a moisture content of 70%.

Chlorine, cleaning products, and washing powders should not be used with organic biomass because they can harm the reactor and impede chemical reactions. Raw materials containing sawdust from coniferous trees (which contains resins), a high percentage of lignin, and a humidity threshold higher than 94% are also unsuitable for the reactor.

Plant-based. Plant feedstock is a great way to produce biogas. Fresh grass provides the highest fuel yield; one ton of raw material produces approximately 250 m3 of gas with a 70% methane fraction. There is a little less corn silage (220 m3). Beet residue: 180 m³.

Biomass can be produced from almost any plant, hay, or algae. The length of the production cycle is the application’s drawback. The production of biogas is a two-month process. The feedstock needs to be chopped finely at all times.

Animated. Biogas plants can use waste from dairy farms, slaughterhouses, processing facilities, etc. Animal fats have a maximum fuel yield of 1500 m3 of biogas (87% methane). The primary drawback is rarity. Ground-up animal feedstocks are also required.

Excreta. The primary benefit of manure is its affordability and accessibility. Cons: Compared to other feedstocks, biogas yields are lower in terms of quantity and quality. Excrement from horses and cows can be processed right away. The production cycle produces 60 m3 with a 60% methane content in about two weeks.

Because they are toxic, pig and chicken manure cannot be used directly. It needs to be combined with silage to initiate the fermentation process. Human-produced materials can also be utilized; however, sewage is not appropriate because it contains very little excrement.

In the quest for sustainable energy solutions, biogas and biogas plants emerge as promising options for heating and powering homes. Biogas, produced through the anaerobic digestion of organic matter like animal waste, food scraps, and crop residues, offers a renewable and environmentally friendly alternative to fossil fuels. Biogas plants are facilities designed to efficiently capture and harness this gas for various applications, including heating systems in homes. By utilizing biogas, households can reduce their reliance on non-renewable energy sources, lower carbon emissions, and contribute to a cleaner, greener future. These plants not only provide a renewable energy source but also offer a means of managing organic waste sustainably. With growing concerns about climate change and the need for sustainable energy solutions, biogas and biogas plants present a practical and eco-friendly option for heating and insulation in homes.

Bioreactor is the basis of a biogas plant

The bioreactor, fermenter, or digester is the tank used for the anaerobic breakdown of biomass. Bioreactors can have a diving bell design, a fixed or floating dome, or be completely sealed. Bell psychrophilic bioreactors, which do not require heating, resemble an open tank filled with liquid biomass that submerges a cylinder or other bell-shaped vessel to collect biogas.

The cylinder rises above the tank as a result of the collected biogas creating pressure inside it. The bell thus doubles as a gas holder, acting as a short-term gas storage space for the produced gas.

Bioreactor with a floating dome

The inability to mix and heat the substrate during the winter months is a drawback of the biogas reactor’s bell-shaped design. Strong smells and unhygienic conditions because of the exposed surface of some of the substrate are other drawbacks.

Furthermore, a portion of the gas generated will leak into the atmosphere, causing environmental pollution. For this reason, artisanal biogas plants in developing nations with hot climates are the only ones using these bioreactors.

One more illustration of a floating dome bioreactor

Large production facilities and residential biogas plants have reactors with fixed dome designs to minimize odors and prevent pollution of the environment. Although the construction’s shape is unimportant in the gas formation process, using a cylinder with a dome-shaped roof results in significant construction material savings. Spigots are used in fixed dome bioreactors to replenish the substrate and remove used biomass.

Numerous fixed dome bioreactor options

Main types of biogas plants

Most pre-made bioreactor solutions are of the fixed dome design since it is the most widely accepted. Bioreactor designs vary depending on the loading technique, and they fall into one of the following categories:

• Batch bioreactors, with a single loading of the entire biomass, followed by a complete discharge after the feedstock has been used up. The main disadvantage of this type of bioreactor is the uneven gas release during the substrate processing;
• continuous feedstock loading and unloading, which results in uniform biogas production. Due to the design of the bioreactor during the loading and unloading of biogas production does not stop and there are no leaks, because the spigots, through which the addition and removal of biomass is carried out, are made in the form of a hydraulic gate, preventing the leakage of the gas.

A batch bioreactor example

Any design that stops gas leaks can be used in batch biogas reactors. For instance, channel digesters with an elastic inflatable vault were once common in Australia, where a tiny amount of internal bioreactor overpressure inflated a robust polypropylene bubble. A compressor is turned on and the biogas is pumped out of the bioreactor once a predetermined pressure is reached inside.

Bioreactors with ducts and elastic gas holding

This biogas plant has the potential to produce mesophilic (slightly heated) fermentation. Channel bioreactors can only be installed in heated rooms or in areas with a hot climate due to the size of the inflating dome. The lack of an intermediate receiver is a benefit of the design, but the elastic dome’s susceptibility to mechanical harm is a significant drawback.

Huge bioreactor channel with flexible gas container

Batch bioreactors that ferment dry manure without adding water to the substrate are becoming more and more common. Even though the intensity of reactions will be lower, the manure’s inherent humidity will be sufficient for the vital activity of organisms.

Dry type bioreactors resemble a sealed garage with doors that close tightly. Without the need for substrate addition or mixing, the biomass is loaded into the reactor using a front-end loader and stays there until the entire gassing cycle is finished, which takes about six months.

Batch bioreactor with a hermetically sealed door for loading

Heating system and thermal insulation

Psychophilic bacteria will multiply in the processed slurry if it is not heated. In this instance, the processing time will be around 30 days, and the yield of gas will be minimal. When mesophilic bacteria start to develop, temperatures as high as 40 degrees Celsius can be reached in the summer if thermal insulation and load preheating are present. However, in the winter, such a plant is essentially unusable because the processes are extremely sluggish. They nearly freeze at temperatures below +5°C.

Temperature-dependent manure processing time into biogas

How to heat and where to place them

The use of heating produces better outcomes. The boiler-based water heating system makes the most sense. The boiler can be powered by electricity, solid or liquid fuel, or even produced biogas. The highest point at which water needs to be heated is +60°C. Reduced heating efficiency can occur from particles sticking to the surface of hotter pipes.

Direct heating, which involves inserting heating elements, is also an option. However, this method has two drawbacks: the substrate will stick to the surface and reduce heat output, and the heating elements will burn out quickly.

Standard heating radiators, which are just pipes twisted into a coil, and welded registers can be used to heat the biogas plant. Polymer pipes, such as polypropylene or metal-plastic, are preferable. While easier to install in cylindrical vertical bioreactors, corrugated stainless steel pipes are also appropriate; however, the corrugated surface encourages sludge buildup, which is detrimental to heat transfer.

The heating elements are situated near the agitator to lessen the chance of particle deposition on them. All that needs to be done is design everything so that the agitator cannot strike the pipes. Although it may seem preferable to put the heaters at the bottom, experience has shown that this is ineffective because of the sediment at the bottom. Therefore, mounting the heaters on the biogas plant’s metatank walls makes more sense.

Methods of water heating

Heating can be internal or external depending on where the pipes are located. Internal arrangements allow for efficient heating, but stopping and pumping out the system is necessary for heater repair and maintenance.

As a result, particular attention is given to the quality of joints and material selection.

Heating shortens the time needed to process raw materials and boosts biogas plant productivity.

Since a lot of heat is lost to heating the walls, more heat is needed (and heating the biogas plant’s contents will cost more) if the heaters are outside. Because the medium is heated from the walls, the system is also more uniformly heated and always available for repair. The fact that the agitators cannot harm the heating system is another benefit of this solution.

What to insulate with

First, a layer of leveling sand is applied to the excavation’s bottom, and then a layer of thermal insulation. It can be slag, expanded clay, or clay combined with straw. You can combine all of these ingredients or pour them in different layers. The container housing the biogas plant is installed and they are leveled to the horizon.

Either contemporary materials or traditional grandfather techniques can be used to insulate the bioreactor’s sides. from the antiquated techniques of using straw and clay. It is put on in multiple layers.

Bioreactors are insulated using contemporary materials.

Mechanism of gas formation from organic raw materials

Biogas is a colorless, odorless, volatile material that has up to 70% methane in it. Its qualitative indicators are comparable to those of natural gas, the conventional fuel. With a good calorific value, one meter-third of biogas releases the same amount of heat as one and a half kilograms of burned coal.

Anaerobic bacteria, which are actively engaged in the breakdown of organic raw materials like farm animal manure, poultry manure, and plant waste, are responsible for the formation of biogas.

For the independent production of biogas, poultry manure and waste materials from both small and large livestock can be utilized. You can use raw materials both pure and in a mixture that includes things like old paper, grass, and leaves (+)

The conditions for bacterial activity must be created in order to initiate the process. They ought to resemble those in which microorganisms grow in the warm, oxygen-starved environment of an animal’s stomach, a natural reservoir.

Actually, these two factors play a major role in the amazing conversion of decomposing manure into valuable fertilizer and eco-friendly fuel.

Biogas can only be produced in a sealed reactor with no air access, where manure fermentation and component breakdown will occur.

• Methane (up to 70%).
• Carbon dioxide (approximately 30%).
• Other gaseous substances (1-2%).

The ensuing gases rise to the top of the tank, where they are pumped out, and down settles the residual product, which is an excellent organic fertilizer that has lost a sizable portion of pathogenic microorganisms and retained all the valuable elements found in the manure, such as nitrogen and phosphorus.

The production of biogas requires a reactor that is entirely oxygen-free and airtight; otherwise, the decomposition of manure will proceed very slowly.

Adherence to the temperature regime is the second crucial requirement for the efficient breakdown of manure and the production of biogas. Temperatures greater than +30 degrees Celsius activate the bacteria that are involved in the process.

Additionally, manure contains two different kinds of bacteria:

• Mesophilic. Their vital activity takes place at a temperature of +30 – +40 degrees;
• Thermophilic. For their reproduction it is necessary to observe a temperature regime of +50 (+60) degrees Celsius.

The first type of plants’ raw material processing time varies from 12 to 30 days, depending on the mixture’s composition. Two liters of biofuel are produced simultaneously from one liter of the reactor’s usable area. The final product can be produced in three days instead of four when the second type of plants are used, and 4.5 liters of biogas are produced.

It is easy to see that thermophilic plants are efficient, but maintaining them is very expensive. For this reason, thorough calculations must be made before selecting a biogas production method (click to enlarge). (+)

Thermophilic plants have a ten-fold increase in efficiency, but they are used far less frequently because it is expensive to maintain high temperatures in the reactor. Because mesophilic type plants require less maintenance and upkeep, most farms use them to produce biogas.

In terms of potential energy content, biogas is marginally less than traditional gas fuel. However, sulfuric acid vapors are present in its composition; this should be considered when selecting the materials for the installation’s construction.

Biogas plant for the home

Industrial-scale biogas plants are already being produced by the industry today. Although the equipment is costly to buy and install, it pays for itself in private homes within 7 to 10 years, assuming that significant amounts of organic materials will be processed. Experience demonstrates that a knowledgeable owner can, with his own hands and the most readily available materials, construct a small biogas plant for a private home if desired.

Preparing the processing hopper

You will need a cylindrical container that is hermetically sealed first. Large pots or boilers can be used, of course, but their small volume will prevent the achievement of sufficient gas production. Thus, the most common plastic barrels used for this purpose range in volume from 1 to 10 m³.

One is something you can make on your own. PVC sheets are easily welded into the desired configuration of a structure because they are readily available and have enough strength and resistance to aggressive media. An adequate-sized metal barrel can also serve as a hopper. It will, however, require anti-corrosion measures, such as painting it both inside and outside with a paint that is moisture-resistant. This is not necessary if the tank is made of stainless steel.

Gas removal system

Because gas accumulates there due to the laws of physics, the gas outlet pipe is installed in the upper portion of the barrel (typically in the lid). The biogas is fed into the odor trap via the connected pipe, after which it is fed into the storage tank (or, if desired, into a cylinder with the aid of a compressor) and finally into the home appliances. Installing a release valve close to the gas outlet is also advised because it will release extra gas if the pressure inside the tank builds up too much.

Feeding and unloading system

The bacteria in the substrate must be continuously (daily) "fed," that is, fresh manure or other organic matter must be added, in order to ensure the continuous production of gas mixture. To free up useful space in the bioreactor, the previously processed raw material from the hopper must be removed.

This is accomplished by drilling two holes in the barrel, one for unloading almost to the bottom and one for loading higher up. They are filled with pipes that are welded (soldered, glued) to a minimum diameter of 300 mm. The funnel-equipped loading pipeline is oriented upwards, and the drain is placed to make it easy to collect the processed slurry—which can be utilized as fertilizer—later on. The joints have a seal.

Heating system

The substrate should be heated and the bioreactor insulated if it is to be placed outside or in an unheated room (which is required for safety reasons). By "wrapping" the barrel in any insulating material or sinking it into the ground, the first requirement is satisfied.

Regarding heating, there are numerous options to take into account. A few artisans insert pipes that run along the barrel’s walls in a coil pattern, circulating water from the heating system. Others position the reactor inside a bigger tank that is heated by electric heaters and contains water. Convenient and far more cost-effective is the first option.

The temperature of the reactor’s contents must be kept at a specific level (not less than 38°C) in order to maximize performance. However, the gas-forming bacteria will simply "cook" and the fermentation process will stop if the temperature rises above 55°C.

Stirring system

Experience has shown that including a manual stirrer in any design greatly boosts the bioreactor’s efficiency. The barrel lid allows the axle—to which the "mixer"’sbladesare welded or screwed—to pass through. After that, a gate handle is attached to it, and the aperture is meticulously closed. Still, home masters don’t always outfit fermenters with these gadgets.

We suggest that you educate yourself on selecting a boiler for a private residence.

Biogas plants

The reactor, organics loading hopper, biogas outlet, and fermented organics unloading hopper are the fundamental components of these devices.

The following categories of biogas plants exist depending on the type of construction:

• without heating and without stirring the fermented organics in the reactor;
• without heating but with stirring of the organic mass;
• with heating and stirring;
• with heating, stirring and devices to monitor and control the fermentation process.

The first type of biogas plant is ideal for small farms and is made for psychrophilic bacteria; it has an internal bioreactor volume of 1–10 m3 and can process 50–200 kg of manure per day. It requires little equipment, and the biogas produced is fed straight into household appliances instead of being stored. This plant is only suitable for use in southern regions; its ideal internal temperature range is 5 to 20 °C.

The decomposed or fermented organic materials are extracted concurrently with the loading of a fresh batch and transported in a container that has a capacity that matches or surpasses the bioreactor’s internal volume. Up until they are injected into the fertilized soil, the contents of the tank are kept inside. With a capacity marginally greater than that of the first type of biogas plants, the second type is also intended for small farms and comes with a stirring device that can be driven by a manual or mechanical means.

In addition to the stirring device, the third type of biogas plant has a forced heating system for the bioreactor and a hot water boiler that runs on alternative fuel that the biogas plant produces. Mesophilic and thermophilic bacteria, depending on the reactor’s temperature and heating intensity, produce methane in these kinds of plants.

The last kind of biogas plants is the most intricate, with multiple biogas consumers in mind. Its design includes a safety valve, water boiler, compressor (which mixes organic materials pneumatically), receiver, gas holder, gas reducer, and an outlet for loading biogas into a vehicle. These plants have automatic biogas extraction, are always running, and can be adjusted to any of the three temperature ranges by means of precisely calibrated heating.

Design of a typical biogas plant

The following are the essential parts of a full biogas system:

• reactor;
• the humus feeding system;
• agitators;
• an automated biomass heating system;
• gas holder;
• separator;
• protective part.

Although the design of the domestic installation will be somewhat simplified, you are still welcome to become familiar with the descriptions of each of the listed elements for the sake of completeness of perception.

Reactor

Typically, concrete or stainless steel are used to assemble this plant component. From the outside, the reactor resembles a sizable, typically spherical, dome-topped, hermetically sealed container.

Reactors built using cutting-edge technologies and featuring a collapsible design are currently the most popular. Such a reactor takes very little time and is simple to assemble with your hands. It can also be disassembled and moved to a different location if needed.

Steel is useful because it can be easily hollowed out to connect other system components without requiring extra work. Contrarily, in terms of strength and longevity, concrete outperforms steel.

Biomass feeding system

This section of the system consists of a screw pump that moves the humus to the reactor, a hopper that collects waste, and a water supply pipe.

The dry component is loaded into the hopper using a front-end loader. Without a forklift, this task can be completed at home with a variety of makeshift tools, like shovels.

The mixture is made semi-liquid in the hopper by adding moisture. The semi-liquid mass is moved to the reactor’s lower compartment by the auger as soon as the required degree of moistening is achieved.

Agitators

The humus in the reactor needs to ferment uniformly. One of the most crucial requirements for guaranteeing the mixture’s intensive production of biogas is this one. In order to achieve the most uniform fermentation of the mixture, electrically driven agitators are typically included in the design of biogas plants.

Agitators that are angled and submersible are available. Submersible mechanisms can be lowered to the necessary depth in the biomass to guarantee thorough and even mixing of the substrate. These agitators are typically mounted on a mast.

Mounted on the reactor’s sides are the inclined agitators. The screw in the fermenter rotates due to the power of an electric motor.

Automated heating system

The system’s internal temperature needs to be kept between +35 and +40 degrees Celsius in order to produce biogas successfully. Automated heating systems are part of the design for this reason.

In this instance, the heat source is a hot water boiler; in other scenarios, electric heating units are employed.

Gasholder

This construction element collects the biogas. The most common location for the gas holder is the reactor’s roof.

Modern gas holders are typically made of polyvinyl chloride, a material that is resistant to sunlight and other adverse natural occurrences.

Special bags are sometimes used in place of standard gas holders. Additionally, the amount of biogas produced can be temporarily increased with the help of these devices.

Gas holder bags are made of a unique kind of polyvinyl chloride that has elastic properties. As the volume of biogas increases, the bags can expand.

Separator

If required, this system component produces high-quality fertilizer and dries the spent humus.

A screw and a separator chamber make up the most basic type of separator. The chamber has a sieve-like shape. This makes it possible to separate the biomass into its liquid and solid components.

The shipping bay receives the dried humus. The system’s liquid component is routed back into the receiving chamber. Here, the new feedstock is moistened with the liquid.

Calculating the profitability of the installation

Typically, feedstock for biogas production is cow dung. A single adult cow can yield 1.5 м.cube of fuel; a pig can yield 0.2 м.cube; and a chicken or rabbit, depending on body weight, can yield 0.01-0.02 м.cube. You can compare it with more well-known types of resources to determine how much it is or is not.

Utility rooms are occasionally used for system installations. While this is safe, it is not convenient for maintenance or inspections. Biomethane has explosive potential.

Consequently, safety concerns should receive extra attention. Feedstock transportation is a different problem that needs to be taken into account when designing a biogas plant. It is preferable to move cargo on the site using trailers or specialized equipment.

Fuel costs should be estimated if long-distance delivery is necessary to see if they will cover the costs. You must consider quality both when purchasing and, more importantly, when creating your own biogas plant containers. Regular maintenance and repairs are also required for the system to function. A farming community may literally find its life saved by a biogas plant. Fuel used to heat and/or light barns is saved. It’s also a fantastic way to get rid of innocuous waste. Nevertheless, it is unlikely that you will be able to rely on a complete output during the initial years.

Building a bioreactor out of an insulated plastic bottle

Easy conveyance of the supporting material

Small-scale industrial facility

A dairy farm’s biogas plant

One cube м. The same quantity of thermal energy is produced by biogas as:

• firewood – 3.5 kg;
• coal – 1-2 kg;
• electricity – 9-10 kWh.

The profitability of a biogas plant can be determined if you know the approximate weight of agricultural waste that will be available over the next few years and the required amount of energy.

Odor is one of the primary drawbacks of producing biogas. The ability to use small compost heaps is a huge plus, but in order to prevent the spread of pathogens, you will need to tolerate inconvenience and closely monitor the process. (+)

A substrate is made with multiple ingredients in the following ratios to be placed in the bioreactor:

• manure (preferably cow or pig manure) – 1.5 т;
• organic waste (it can be decomposed leaves or other components of plant origin) – 3.5 т;
• water heated to 35 degrees Celsius (the amount of warm water is calculated so that its mass is 65-75% of the total amount of organic matter).

Assuming a moderate gas consumption, the substrate is calculated for one tablet over a period of six months. The first signs of the fermentation process will appear after 10 to 15 days when small amounts of gas begin to fill the storage facility. It is possible to anticipate full fuel production in 30 days after 30 days.

In our nation, biogas production equipment is still not very common. This is mostly because people don’t know enough about the benefits and quirks of how biogas systems work. Many small farms in China and India have artisanal plants installed in order to generate extra clean fuel.

The amount of biogas produced by the plant should progressively rise until the substrate has completely decomposed. The rate at which the biomass ferments, which is influenced by the substrate’s temperature and humidity, is directly related to the design’s performance.

A sustainable and environmentally beneficial approach to waste management and energy production is provided by biogas and biogas plants. Utilizing the organic materials’ natural decomposition process, biogas plants produce biogas—a clean energy suitable for cooking, heating, and even power production.

The versatility of biogas is one of its main benefits. It can be made from a variety of organic waste materials, such as food scraps, sewage, and agricultural residues. As a result, biogas plants can be installed in a variety of locations, including urban areas and rural farms, to help meet energy needs while also lowering the environmental effects of organic waste.

Additionally, the production of biogas helps to lower greenhouse gas emissions. Biogas plants aid in the mitigation of climate change by absorbing methane, a powerful greenhouse gas released during the decomposition of organic matter. Furthermore, the digestate, which is rich in nutrients and a byproduct of the biogas production process, can be applied as a fertilizer to enhance soil health and lessen the requirement for artificial fertilizers.

Notwithstanding these advantages, there are obstacles in the way of the broad implementation of biogas technology. The viability of biogas projects varies by region due to differences in regulatory frameworks and the potentially high initial investment costs. Furthermore, careful management of feedstock inputs, temperature control, and maintenance are necessary for biogas plants to operate efficiently, underscoring the significance of appropriate planning and knowledge.

To sum up, biogas and biogas plants offer a viable route to a future in energy that is more resilient and sustainable. Biogas technology uses organic waste streams to generate valuable byproducts and clean energy, which has a positive impact on the environment, society, and economy. But in order to fully utilize biogas, communities, investors, and legislators must work together to overcome obstacles and foster an atmosphere that will support its widespread use.

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