Biological Methane Conversion

Abstract

Methanotrophs are microorganisms capable of growing on methane as their sole carbon source. Many scientists from academia and industry have proposed that these microorganisms can upgrade methane into value-added chemicals. Biological processes utilizing these microorganisms may provide a more economical alternative to existing thermo-chemical gas-to-liquid conversion processes, because they are less capitally intensive, do not require extreme operating conditions, and can potentially be deployed at smaller scale to capture gas at remote wells. We evaluate the technical challenges associated with the commercial exploitation of biological methane conversion. To date, only single-cell protein has been produced in an industrial process. Few value-added chemicals are natively produced by methanotrophs, the key ones being polyhydroxyalkanoates and ectoine, although other molecules have been produced at the proof-of-concept stage via genetic modification. A major hurdle to commercial scale-up is the limited solubility of methane and oxygen in fermentation media. Whilst progress has been made on advanced fermentation engineering to enhance gas transfer, this is a field ripe for development. Finally, we note that most studies have relied on pure methane, whereas the suitability of the well-head natural gas for methanotrophs has yet to be properly investigated.