ReviewA mini review on bioreactor configurations and gas transfer enhancements for biochemical methane conversion

•For natural gas, FCLBs reported the best mass transfer and are most utilized in industry.•For LCME, biotrickle reactor is the most effective in methane removal.•Studies are lacking for gas transfer enhancing agents recycle and effects on cells.•Safety protocols for methane bioconversion are recommended.

Methane is an essential component of the global carbon cycle and one of the most powerful greenhouse gases (GHGs), yet it is also a rich source of carbon and energy. Methanotrophs that use methane as their sole carbon and energy source have drawn renewed interest due to their capability of converting methane under ambient conditions in an environmentally benign fashion. In this work, we provide a mini review on recent progress in process development, particularly on bioreactor design and gas transfer enhancements for biological methane conversion. Bioreactor configurations reported in recent research papers and patents are tabulated, together with their key characteristics, performances, pros and cons. Bioreactor configurations for gas feed with high concentration of methane (e.g., natural gas) and that with low methane concentrations (e.g., anthropogenic emission) are reviewed. For gas transfer promoting agents, recent results on using vectors, polymers, nanoparticles, electrolytes, and non-ionic surfactants to enhance mass transfer of methane are reviewed and summarized with a table. Process safety and future research directions are also briefly discussed.