Methane removal from air by methanotrophic biofilms in a multi-tray reactor

Abstract

Atmospheric methane (CH₄) concentrations continue to rise rapidly, driven by increased emissions and contributing substantially to global warming. Methanotroph-based CH₄ mitigation offers a promising approach at emission sites, but effective reactor designs supporting both efficient CH₄ removal and biomass harvest remain underdeveloped. Here, we designed, manufactured, and validated a multi-tray reactor that deploys flat “dry” biofilms of Methylotuvimicrobium buryatense 5GB1C for methane removal from air. Results show continuous CH₄ removal from 500 $\mathrm{ppm}$ CH₄ gas flows using M. buryatense 5GB1C and the multi-tray reactor, with either cellulose beads or Whatman papers as the sorbent material for nutrient delivery. Biomass could be harvested without compromising continued CH₄ consumption, and regrowth was observed post-harvest. A mathematical model that describes CH₄ removal performance with good agreement to experimental results was used to analyze the effect of different biotic and abiotic factors to methane removal. Finally, we deployed the reactor at a closed landfill that emits CH₄. This field study demonstrated continuous CH₄ removal from landfill gas for three weeks, with fluctuating inlet CH₄ concentrations (200–4000 $\mathrm{ppm}$) and varying ambient temperatures. The inlet CH₄ concentration strongly correlated with CH₄ removal performance, while temperature showed no significant influence. Together, these results establish the multi-tray reactor encompassing M. buryatense 5GB1C biofilms as a prospective platform for methanotroph-based CH₄ mitigation.