About This Project

Atmospheric methane removal is critical to mitigating climate change. Bio-electrochemical reactors (BERs) can offer a promising strategy to oxidize methane and generate valuable co-products. However, the methane feedstocks tested in existing BERs differ from those needed for scalable greenhouse gas removal. This project aims to bridge that gap by exploring novel extra-cellular electron transfer pathways and BER operation modes that can unlock new biotechnologies for atmospheric methane removal.

Ask the Scientists

Motivating Factor

Methane has led to 30% of global warming, and anthropogenic emissions are increasing [1]. Removing atmospheric methane (2 ppm) is urgent to meet climate goals [2]. However, a technology gap exists as no device can economically oxidize methane at low concentrations (< 1000 ppm) needed for atmospheric methane removal [3]. Therefore, new scalable processes need to be developed. One strategy is methane bioreactors, but they are challenged by slow oxidation rates [3]. Bio-electrochemical reactors (BERs) that employ electrodes to direct microbial metabolisms have been shown to enhance methane oxidation rates and produce value-added products (e.g., electricity, hydrocarbons) [4]. This suggests that BERs could be a cost-effective approach for methane removal. Still, there is a mismatch between the conditions that have been tested at the lab scale and those needed for practical applications. As such, BERs may hold significant untapped potential for methane removal.

Specific Bottleneck

One major bottleneck is that BERs have only been demonstrated under strict anaerobic conditions that are not directly applicable to atmospheric methane removal. This is because conventional extra-cellular electron transfer pathways in BERs require anaerobic environments. This is a problem because separating O2 before operation would likely introduce additional cost constraints. A second bottleneck is that bio-electrochemical methane reactors have almost exclusively been operated at high methane levels (> 1000 ppm) above those needed for atmospheric methane oxidation. Therefore, there is a lack of understanding of bio-electrochemical methane oxidation mechanisms and performance at low methane concentrations below 1000 ppm. A third bottleneck is that high oxidation rates must be achieved for these processes to become scalable. However, few studies have optimized operational parameters (e.g., voltage) for peak methane removal.

Actionable Goals

Designs should be developed for bio-electrochemical reactors that can oxidize methane under aerobic conditions, thereby avoiding the need for O2 scrubbing from the air. This will likely involve developing novel operation modes or reactor configurations. Bio-electrochemical reactors must also be tested with methane levels (near 2 ppm) that match atmospheric concentrations. In all tests, researchers should prioritize understanding the underlying methane oxidation mechanisms and microbial ecology. Researchers must also optimize important operational parameters like voltage to achieve peak methane removal.