How energy is harnessed from biogas?

The process by which biogas is produced, known as anaerobic digestion (AD), also produces a number of gases that can be burned to provide energy. The breakdown of diverse plant and animal materials (sometimes referred to as biomass) by bacteria in an oxygen-free environment is known as anaerobic digestion.  For instance, after adding bacteria to an airtight container containing waste plant material, the bacteria are encouraged to grow and proliferate. As a result, methane and other gases are released as a byproduct of the process.

There are also other by-products created throughout the process that are nutrient-rich and can be used as fertilizer. Any number of biomass products, such as food waste, energy crops, crop residues, slurry, and manure, can be used as inputs in the process. In actuality, the procedure can handle waste from homes, supermarkets, and industry, lowering the amount of waste that ends up in landfills.  Methane (CH4) and carbon dioxide (CO2), which together account for between 60 and 70 percent and 30 to 40 percent, respectively, are the two main gases that make up biogas. Other gases can be detected in very small amounts. Overall, the feedstock or inputs used in the AD process determine how biogas is constructed. In the industrial setting, biogas can be improved to remove all except pure methane and other gases, resulting in biomethane.

Energy from biogas and usage in industry

 
Purely thermal biogas energy

Biogas can simply be burned to generate heat via the combustion process. One cubic meter of biogas burns to produce around 2.0/2.5 kWh of thermal energy.  The digester and the neighboring buildings can be powered by a portion of the heat produced at the facility. Unless it is used to heat and convey hot water through a local pipe network into the dwelling, the leftover heat is released and wasted.

Purely electric biogas energy

The relatively straightforward method of burning biogas can be used to produce electricity, although this requires upgrading the system. Compared to the supply of heat and gas, electricity is simpler to transport and measure, but it must be fed into the grid, which involves complex and potentially expensive infrastructure. By utilizing Feed-in Tariffs (FiTs) or maximizing Renewable Obligation Certificates (ROCs) for industrial scale production, larger players can generate green electricity that will benefit the generators (households and communities).

Biogas energy for combined heat and power (CHP)

Cogeneration, often known as CHP, is a process that generates both usable heat and electricity. Because the various gases must be created using heat, biogas plants are more efficient than other traditional power plants because less energy is wasted throughout the process. The plants also produce electricity, which is delivered and sold like the surplus heat in addition to the heat that is later produced. Generators can effectively utilize the Renewable Heat Incentives (RHI), Feed-in Tariffs (FiTs), and Renewable Obligation Certificates (ROCs) available to them if they can support the cogeneration process.

Biogas energy from liquid biomethane

By removing carbon dioxide and other trace gases from biogas, biomethane can be created, which is a more pure form of methane.

Biomethane energy is used in transportation

Similar to the method used to produce fuel for home heating, biogas energy can be improved to a pure form of biomethane and utilized as a transportation fuel after being further purified from other gases (such as carbon dioxide and trace gases). The Renewable Transport Fuel Obligation allows for funding for biogas.

Advantages of Biogas

• Nutrient-rich byproducts that can be used as fertilizer.
• Plant and animal waste that would otherwise wind up in landfills is used to create biogas.
• Feed In Tariffs and Renewable Obligation Certificates  can be used by biogas power plants to produce electricity, and Renewable Heat Incentives can be used to produce heat.
• CNG or LNG vehicles can run on biomethane (produced from biogas), a fuel that produces fewer greenhouse gases.
• By eliminating CO2 and other trace gases, biogas can be transformed into biomethane, which can be used as a replacement for natural gas for household use.
• Biogas power plants can offer cleaner and more sustainable heating to nearby neighborhoods with the help of a piping infrastructure.
• In comparison to traditional coal, oil, and gas plants, biogas power plants are more effective at utilizing the heat they produce.

 

How electricity is generated from biogas?

Through the use of an internal combustion engine, biogas is transformed into mechanical energy. An electric generator is rotated by mechanical energy, which generates electricity. The biogas is used in a biogas engine to produce mechanical energy. By using the power of the engine pistons going downward and creating a vacuum, biogas is precisely blended with the right amount of air and sucked into the biogas engine. As the piston rises, the mixture of air and biogas is compressed.

Since biogas burns slowly, an engine with a higher compression ratio is necessary for effective combustion. The mixture of compressed air and biogas is ignited by a high-energy spark plug. The quickly heating and expanding mixture of burning biogas and air drives the piston downward, producing torque that rotates the engine.  The spent air and fuel mixture are released into a heat exchanger to recover any remaining combustion energy when the biogas engine exhaust valve opens.

Using the mechanical energy generated by the engine, the generator creates electricity. To generate an electrical current, this mechanical energy turns an iron core encircled in copper wire inside a strong magnet. The biogas is often converted to energy using combustion engines. This has the extra benefit of being a realistic option for regional or even remote use due to the accessibility of new and replacement engines, spare parts, and simple local repairs.