Landfills are significant sources of methane, a potent greenhouse gas. This study uses metagenomic approaches to characterize microbial methane cycling in a landfill over 39 years. Newer waste supported more diverse communities with similar compositions compared to older waste, which had lower diversity and more varied communities. Older waste contained primarily autotrophic organisms with versatile redox metabolisms, while newer waste was dominated by anaerobic fermenters. Methane-producing microbes were more abundant, diverse, and metabolically versatile in new waste. The findings suggest that predictive models for methane emission overlook methane oxidation in the absence of oxygen and certain microbial lineages contributing to methane sinks.

Daniel S. Grégoire, Nikhil A. George, Laura A. Hug