How is biomethane produced?

Biomethane production

The production of biomethane is a promising process that offers both ecological and economic benefits. Biomethane is produced from biological waste and can be used as a renewable fuel in various applications.

Biomethane is mainly obtained from organic materials such as agricultural waste, food waste, sewage sludge and other biological sources. This waste is treated in an anaerobic digestion plant. This releases the methane gas.

Substrates | Procurement of biomass

The first phase consists of identifying and procuring suitable biomass sources. Various substrates can be used to produce biomethane. Here are some examples:

Organic waste: A common source of biomethane is organic waste such as kitchen waste, garden waste, agricultural waste and food waste. These can be used in so-called fermentation plants or biogas plants to produce biomethane.
Energy cropsCertain plant species that are grown specifically for energy production can serve as a substrate for biomethane production. Examples include corn, grass, alfalfa and beets. These plants are harvested and fermented in biogas plants.
Slurry and manure: Animal excrement such as slurry and manure are also suitable substrates for biomethane production. In combination with other organic materials, they can be used in biogas plants to produce biomethane.
Industrial waste: Some industries produce organic waste that can be used for biomethane production. Examples include food processing waste, waste from the beverage industry and waste from the paper and pulp industry.
Sewage sludge: Sewage sludge, which is a by-product of wastewater treatment, can also be used for biomethane production. By using sewage sludge in biogas plants, not only can biomethane be produced, but the sewage sludge can also be disposed of while capturing the methane gas that would otherwise escape into the atmosphere.

There are other potential substrates for biomethane production and the choice depends on availability, local conditions and technical capacity. It is important to select substrates carefully to ensure efficient and sustainable biomethane production.

Pretreatment of substrates or biomass

The biomass is pre-treated in this phase to prepare it for the fermentation process. This can include shredding, crushing or grinding to increase the surface area and facilitate decomposition.

Anaerobic fermentation

The key to producing biomethane is anaerobic digestion. The natural microorganisms in the waste decompose the organic materials and produce methane gas in the process. The pre-treated biomass is placed in an anaerobic digester, also known as a biogas reactor or bioreactor. The digester is a closed system that prevents oxygen from entering.

The biomass is fermented with the help of anaerobic microorganisms, in particular methane producers. These microorganisms break down the organic compounds in the biomass and produce methane (CH4) as the main component of the biogas.

The fermenter

To create optimal conditions for the microorganisms, the fermenter is kept at a certain temperature (usually between 35°C and 55°C, depending on the microorganisms). In addition, the contents of the fermenter are kept in motion to ensure an even distribution of microorganisms and nutrients. During the fermentation process, the microorganisms decompose the biomass and convert it into biogas.

The biogas consists mainly of methane (50-75%), carbon dioxide (25-50%) and traces of other gases such as nitrogen, hydrogen and hydrogen sulphide. The fermentation process can take several weeks to months, depending on the type of biomass and the conditions in the fermenter.

Preparation and cleaning

After anaerobic fermentation, the gas produced contains methane as well as other impurities such as carbon dioxide, water and sulphur compounds. In order to make the biomethane usable for various applications, it must be purified and freed from these impurities. This process is known as purification and includes steps such as dehumidification and desulphurization.

The carbon dioxide (CO2) is then removed from the biogas to increase the methane content. This can be achieved using various methods such as pressure swing adsorption, water scrubbing or membrane separation.

Feed-in and use

The purified biomethane can be transported in existing natural gas pipelines and used to generate electricity, supply heat or as a fuel. It is a climate-friendly alternative to conventional fossil fuels and significantly reduces CO2 emissions. After processing, the biomethane achieves a purity level of around 97-99% methane and can now be fed into the natural gas grid.

Biomethane for the energy transition

The production of biomethane offers a sustainable solution for generating energy from biological waste. The process of anaerobic digestion and treatment enables the conversion of waste into a renewable gas that can serve various applications. By using biomethane, we can reduce our dependence on fossil fuels and make a positive contribution to reducing greenhouse gas emissions.

These are the basic steps in the production of biomethane. The process may vary depending on the plant configuration and biomass source, but the basic principle of anaerobic digestion remains the same. Biomethane is a renewable energy source as the biomass comes from renewable resources and combustion only releases the carbon dioxide that was absorbed during the growth of the biomass, making the process largely carbon neutral.