Municipal solid waste landfills are the third largest source of methane emissions in the United States. The three engineered controls that have been found to be most effective in mitigating landfill methane emissions are gas collection and recovery systems, physical barriers of engineered cover materials, and microbially mediated methane oxidation. Biochar has shown promise at enhancing the microbial methane oxidation potential of landfill cover soils. A study in the Journal of Hazardous, Toxic, and Radioactive Waste, “Biogeochemical versus Conventional Landfill Soil Covers: Analysis of Gas Flow Profiles, Microbial Communities, and Mineralogy” focuses on evaluating the performance of nonactivated biochar-amended soil as a component of biogeochemical cover systems.
Researchers Jyoti K. Chetri, Krishna R. Reddy, Dennis G. Grubb, and Stefan J. Green used column incubation experiments to compare a biogeochemical landfill cover system to conventional soil cover. Their study compared gas removal efficiency and microbial activity, evaluated the system performance, and investigated the effect of environmental factors, such as rainfall, on the performance of simulated cover systems. Learn more about their research to mitigate methane, carbon dioxide, and hydrogen sulfide in landfills at https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000708. The abstract is below.
In this study, a novel biogeochemical cover system comprising biochar-amended soil and basic oxygen furnace (BOF) steel slag was explored as a sustainable alternative cover system to mitigate methane (CH4), carbon dioxide (CO2), and hydrogen sulfide (H2S) simultaneously from landfill gas (LFG). Long-term column studies of a simulated biogeochemical cover (BGCC) profile investigated CH4, CO2, and H2S removal potential. The performance of the BGCC system was compared with a conventional soil cover (SC) profile. The CH4 oxidation rates of biochar-amended soil were significantly higher, ranging from 185 to 407 µg CH4/g-day in comparison with the barrier soil in the SC system (6–7.5 µg CH4/g-day), based on the batch incubation of column-exhumed samples. In addition, the biochar-amended soil showed higher relative abundance of methanotrophic bacterial communities (20%–51%) in comparison with soil cover (10%–27%). In both columns, complete attenuation of H2S occurred near the inlet (75 cm bgs) and sulfur oxidizing bacteria (e.g., Thiobacillus) and methanotrophs were both detected. The sulfur content was elevated (0.68%) at the base of both columns and H2S may have imparted an inhibitory effect on CH4 oxidation rate in the SC system. The BOF slag showed a CO2 removal potential of 67 g CO2/kg BOF slag. Overall, the BGCC system outperformed the SC system, effectively mitigating CH4, CO2, and H2S simultaneously.
Read the paper in full in the ASCE Library: https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000708