VTT Technical Research Centre of Finland has developed a method for converting even small sources of methane-rich biogas—from farms, landfills and wastewater treatment plants—into raw materials for animal feed or bioplastic.

Methane-rich biogas is generated by the anaerobic digestion of biological material. Until now, the processing of such gas into biomethane has been viable only on large biogas-producing sites; small biogas sources such as farms have remained largely unexploited.

Metanotrophic protein biomass. Image credit: VTTThe method developed by VTT is based on the ability of methanotrophic bacteria to grow in aerobic conditions in gas fermenters, using methane as the source for carbon and energy. The methane gas generated by anaerobic digestion is first fed into a gas fermenter.

A growth medium containing the methanotrophic bacteria is then circulated through the pipes of the gas fermenter, creating a single-cell biomass with a protein content of around 60%. The cell mass is filtered, pasteurized and dried.

The methanotrophic bacteria and cell mass may also contain polyhydroxybutyrate plastic (PHB)—a natural substance in the cells that enables them to store energy. PHB can be used as a raw material for biodegradable packaging material instead of oil-based and non-biodegradable plastics, such as polypropylene.

VTT says it is working to improve the process' production rate, as well as to confirm the suitability of the protein as a feed component.