About This Project

About 75% of methane emissions are too dilute (<1,000 ppm) to be mitigated by existing technologies. Flow-through bioreactors with methanotrophs are a potential solution, pending major efficiency improvement. We will develop TEA/LCA models integrating biocatalyst and bioreactor parameters to assess cost, environmental impact, and scalability. We will identify key performance targets for biologists and (bio)chemical engineers working with bioreactors for dilute methane removal.

Ask the Scientists

Motivating Factor

CH₄ emissions have contributed ~30% of global warming to date [1]. Technologies for oxidizing atmospheric, area, and point CH₄ sources could substantially mitigate climate change. While CH₄ above ~44,000 ppm can be flared, ~75% of CH₄ pollution is atmospheric (2 ppm) or area emissions below 1,000 ppm that are too dilute to be oxidized at scale using existing technologies [2].

Oxidation of dilute CH₄ at scale may be possible using methanotrophs in flow-through bioreactors at ambient conditions; however, for such reactors to be economical, substantial efficiency improvements over the state-of-the-art are needed [3]. This can only be achieved if all aspects of the system (including biocatalyst efficiency, bioreactor design, air handling, and overall process intensification, etc.) are considered and optimized, which requires system-level techno-economic analysis (TEA) and life-cycle assessment (LCA) for evaluating the feasibility and environmental impact of various technologies.

Specific Bottleneck

CH₄ oxidation efficiency improvements may be achieved by discovering or engineering methanotrophs or MMO variants that operate efficiently at low CH₄ concentrations. However, researchers lack a clear performance target for biological CH₄ oxidation agents, because there is no available analysis describing the relationship between biological oxidation performance and cost across a range of dilute CH₄ concentrations [3]. Further, existing bioreactor systems have generally not been designed to handle CH₄ concentrations below 1,000 ppm [4]. Finally, there is a lack of TEA and LCA models that take both biocatalyst and bioreactor into consideration when extrapolating lab experiments to potential large-scale applications. Development of such system-level models is necessary for illuminating the potential for economic feasibility at scale and for providing biologists and engineers with specific and quantitative technical gaps that need to be bridged in order to achieve scalable targets.

Actionable Goals

TEA and LCA models should consider CH₄ bioreactors that are optimized for low (2-1,000 ppm) CH₄ concentration using methanotrophs, mixed microbial cultures, or cell-free MMO [3]. They should be performed to assess the costs of biological methane oxidation efficiency at scale utilizing recently proposed, specialized bioreactors (e.g., biofilters, attached biofilms, etc.). Rather than treating biocatalyst parameters (e.g., oxidation efficiency) and bioreactor parameters (e.g., mass transfer and energy requirement) as constants, TEA and LCA models should assess the impact of a range of those parameters on cost, to provide targets for biologists and (bio)chemical engineers. The interactions, especially synergism, between biocatalyst and bioreactor should be considered.