TOKYO GAS TOP > Technical development > Low-carbon society > Methane fermentation system

Methane fermentation system

A methane fermentation system is made up of a variety of components, including a pre-treatment system suited to the raw materials being used, a fermentation tank and gas-driven equipment. Biogas containing methane as its primary component, is produced from biomass through a biological decomposition process in methane fermentation tank which is under an anaerobic condition. By using carbon-neutral biogas, a variety of benefits are achieved, among which are a reduction in carbon dioxide emissions and fuel cost and a reduction in biomass volume.



Food factories and sewage treatment plants generate biomass that contains a large amount of water such as food products and sewage sludge. Because such biomass contains organic matter, it can be efficiently used as a resource. By applying methane fermentation technology to biomass, a carbon-neutral energy is produced. The obtained energy can be used at factories, sewage treatment plants and other facilities. With the aim of efficiently producing an even larger amount of energy, we are examining conversion methods tailored to biomass feedstock and approaches to obtain higher efficiency for the system overall.    

Diagram of carbon-neutral process
Diagram of carbon-neutral process


Schematic of methane fermentation process

In the pre-fermentation tank the biomass which serves as the raw materials to be used is broken down by a variety of microorganisms. This chiefly produces organic acids and molecular hydrogen as well as carbon dioxide. These organic acids are then broken down by methane-producing arche in the methane fermentation tank to produce biogas.
Methane fermentation reaction diagram
Methane fermentation reaction diagram
Pre-treatment tank     Methane fermentation tank

Biomass, which is produced from food factories, is firstly diluted to a raw material concentration suitable for methane fermentation. By biological reaction in the methane fermentation tank, the substrate is converted to biogas consisting of approximately 60% CH4 and 40% CO2.
The fermentation cake and dried biomass are applied to combustion treatment because of their low water content. In the following case, biogas from methane fermentation and dried biomass are combusted together at the boiler, achieving a more efficient use of biomass energy.

Example of flow of biomass system (at a food plant)
Example of flow of biomass system (at a food plant)

  • Carbon neutral biomass energy can be obtained.
  • Can be utilized with biomass of differing properties and components.
  • Methane fermentation reaction is operated under less retention time by applying thermopheilic fermentation.
    Required footprint for the fermentation system can be smaller.
  • Generated biogas can be used as fuel for a boiler.


The fermentation conditions and pre-treatment method depend on characteristics of biomass. In addition, converting various biomasses to energy at low cost is required.  Going forward, we will continue to conduct research and development on feasible methods for each biomass.

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