Development of Novel Sustainable Biogeochemical Cover for Mitigating Fugitive Landfill Gas Emissions

Municipal Solid Waste Landfills are the third largest source of anthropogenic methane emissions in the US. Apart from methane, MSW landfills are source of carbon dioxide emissions as well as odor. Methane and carbon dioxide are major greenhouse gases and primary contributor to the global climate change. Moreover, hydrogen sulfide, which is a major odor causing component at the landfills, is a highly toxic gas and can cause adverse health effects at concentrations as low as 2-5 parts per million (ppm) and lethal effects at 1000-2000 ppm. The modern engineered landfills are provided with gas collection systems, however, they are not hundred percent effective in capturing landfill gas due to limited radius of influence of the gas well. Hence, there is a need for development of an alternative landfill cover system which is economically feasible and environmentally sustainable and can capture landfill gases efficiently. Therefore, this research introduces a sustainable biogeochemical cover system which can capture three major components of landfill gas: methane, carbon dioxide and hydrogen sulfide by integrating biochar amended soil and basic oxygen furnace steel slag in the landfill cover system. The potential of the BOF slag to remove carbon dioxide and hydrogen sulfide is tested through a series of laboratory batch and column experiments. Methane removal potential of the biochar amended soil is tested under dynamic landfill gas conditions through large scale column experiments. Moreover, techniques to improve methane oxidation in biochar amended soil is evaluated by activating biochar with methanotrophic bacterial culture consortium. The overall interaction of gas flow, methane oxidation, carbonation and sulfidation reactions, and microbial activity is assessed through a series of large-scale column experiments by simulating various biogeochemical cover profiles exposed to dynamic landfill gas conditions. The activity of methanotrophic bacterial communities in the biogeochemical cover system is investigated through DNA based 16S rRNA gene amplicon sequencing and quantitative polymerase chain reaction (qPCR). Functional performance of biogeochemical cover system is compared with conventional soil cover system by performing infiltration analysis, methane emissions analysis and slope stability analysis. Finally, life cycle impact assessment is performed to assess the overall environmental impacts of the biogeochemical cover and compare with the conventional soil cover system. The proposed biogeochemical cover system shows promise in mitigating all three components of landfill gas (methane, carbon dioxide and hydrogen sulfide). The proposed cover also shows functional equivalency to the conventional soil cover system and provides environmental benefits by reducing greenhouse gas emissions and global warming.