Abstract
Greenhouse gases influence the global climate by changing the radiative energy balance of the Earth. In anaerobic environments, the final step of organic biodegradation is methanogenesis, which converts compounds such as acetate into methane (CH4) and carbon dioxide (CO2), two major greenhouse gases. On a per molecule basis, CH4 is 25-fold more potent as a greenhouse gas than CO2 over a 100-year horizon, contributing to 20‒30% of the total radiative forcing. Microbial CH4 production is responsible for 56% of organic degradation in anaerobic environments and hence a major source of global CH4. In the presence of an electron acceptor, however, acetate is oxidized to CO2 via microbial respiration, suppressing fermentation and CH4 production. Pyrogenic black carbon, which is produced at the rate of >100 million tons per year through wildfires and deforestation, has been shown to possess a considerable electron storage capacity, a novel property that enables black carbon to serve as an electron acceptor for microbial respiration. This suggests pyrogenic carbon may represent an enormous and previously unrecognized electron reservoir that supports organic oxidation and prevents fermentation, in effect diverting CH4 to CO2 and drastically reducing the climate impact of organic biodegradation. My proposed work aims at revealing and quantifying the climate impact of pyrogenic black carbon through alterations of greenhouse gas emissions from anaerobic environments. The proposed work will be a major step forward toward understanding the climate impacts of electron flow and carbon cycling in anaerobic environments. The proposed work will also help estimate CH4 emissions from post-fire sites and to develop black carbon-based, innovative engineering means to mitigate CH4 emissions from periodically anaerobic ecosystems such as marshes.
Greenhouse gases influence the global climate by changing the radiative energy balance of the Earth. In anaerobic environments, the final step of organic biodegradation is methanogenesis, which converts compounds such as acetate into methane (CH4) and carbon dioxide (CO2), two major greenhouse gases. On a per molecule basis, CH4 is 25-fold more potent as a greenhouse gas than CO2 over a 100-year horizon, contributing to 20‒30% of the total radiative forcing. Microbial CH4 production is responsible for 56% of organic degradation in anaerobic environments and hence a major source of global CH4. In the presence of an electron acceptor, however, acetate is oxidized to CO2 via microbial respiration, suppressing fermentation and CH4 production. Pyrogenic black carbon, which is produced at the rate of >100 million tons per year through wildfires and deforestation, has been shown to possess a considerable electron storage capacity, a novel property that enables black carbon to serve as an electron acceptor for microbial respiration. This suggests pyrogenic carbon may represent an enormous and previously unrecognized electron reservoir that supports organic oxidation and prevents fermentation, in effect diverting CH4 to CO2 and drastically reducing the climate impact of organic biodegradation. My proposed work aims at revealing and quantifying the climate impact of pyrogenic black carbon through alterations of greenhouse gas emissions from anaerobic environments. The proposed work will be a major step forward toward understanding the climate impacts of electron flow and carbon cycling in anaerobic environments. The proposed work will also help estimate CH4 emissions from post-fire sites and to develop black carbon-based, innovative engineering means to mitigate CH4 emissions from periodically anaerobic ecosystems such as marshes.