With the unprecedented rise of greenhouse gas (GHG) levels in the atmosphere accelerating climate change, its devasting effects can be felt worldwide; the last few years have seen the highest increase in average global temperatures. Of all the GHGs, methane alone contributes to 30-50% of the current rise in temperatures. Being a short-lived GHG, curbing its emissions is the immediate action plan to deter the adverse effects of climate change. Methane emissions from landfills and dumpsites, which are major sources of anthropogenic methane, need immediate intervention to achieve the Paris Agreement's targets (UNEP 2021).
In this study, the efficacy of methanotrophs (a natural sink for methane) in a bio-augmented cover to address the methane emissions from dumpsites was investigated. A prospective methanotrophic bacteria belonging to Methylosarcina sp. (LC4) was isolated from dumpsite leachate. The isolate was thoroughly characterized concerning the biochemical parameters and stoichiometry of methane oxidized. The isolate displayed the high specific methane oxidation rates for pMMO producing methanotrophs of 11.13 μmol⋅mg biomass−1⋅h−1, displayed high carbon conversion efficiency, produced 0.26 equivalent of carbon dioxide per methane consumed, and required lower oxygen per methane oxidized compared to other known methanotrophs and methanotrophic consortia. The efficacy of this isolate was established based on the carbon capture efficiency. Also, the role of micronutrients (unique to methanotrophs) on the methane oxidation rate and biomass production was studied. The effect of immobilization on several matrices on the growth and methane oxidation by the bacteria was evaluated in an indigenously designed low-cost setup to identify a suitable matrix for a bio-augmented cover system. Further, biodiesel as a possible byproduct from the bio-augmented cover system to valorize the methane emissions was explored.