RAISE: CET: Enhancing Microbial CO2 Valorization toward Biofuels by a Dual-Fiber System Powered by Visible Light

Arizona State University, Scottsdale AZ

Investigators

Abstract

This Research Advanced by Interdisciplinary Science and Engineering (RAISE) award is made in response to Dear Colleague Letter 23-109, as part of the NSF-wide Clean Energy Technology initiative. Over-reliance on fossil-derived compounds to generate energy and chemical products has led to substantial emissions of carbon dioxide (CO2) and other greenhouse gases (GHGs). Immediate steps are needed to create a circular carbon economy, where CO2 is effectively reused and valorized into new products. This project advances the science and technology of reusing CO2 captured from air into potentially valuable products, specifically into biofuels. The overarching goal of this project is to achieve full CO2 utilization towards renewable-fuel production via an integrated nanomaterials light-based (photocatalytic) process combined with bioprocesses. The project will develop a core fundamental-level understanding of how nano-scale catalyst structure can controllably result in photocatalytic CO2 reduction to produce the one-carbon compound carbon monoxide (CO), which serves as an intermediate chemical converted to biofuels by bacteria. The project also will help meet the demand for a skilled workforce and accelerate STEM education. The project will train and encourage motivated teachers and students from local high schools and community colleges, particularly those from underserved groups, to participate in the hands-on summer research experience. The experiences will nurture nanotechnology and biotechnology principles in high school science laboratories. The project also will stimulate public interest by disseminating scientific findings through social media supported by the NSF Southwest Sustainability Innovation Engine, Global Center for Water Technology, and the Biodesign Institute at ASU. The research will develop the science and engineering foundations for a new, synergistic system capable of advancing the circular carbon economy. One of the project’s fundamental insights includes advancing reactor design by improving the efficiency of using light energy by employing nanoscale-photocatalysts coated on optical fibers and by understanding how water chemistry affects CO2 reduction. Nanotechnology will be used to optimize the material structures of the catalysts. Novel techniques to apply nanomaterials to optical fibers that side-emit light will eliminate reliance upon slurries of catalysts. The optical fibers also optimize utilization of light supplied into the reactors. To maximize CO2-delivery efficiency, the gas-permeable fibers can prevent bubble formation during gas delivery and achieve 100% transfer efficiency. The combined optical fibers plus gas-permeable fibers in one reactor are a unique technological advance that will be optimized to convert CO2 into CO. Then, the CO will be converted into longer-chain organic compounds via microbial chain elongation using a model bacteria strain. Key to chain elongation will be the ability to manage bacterial biofilms of a synthetic Clostridium coculture through optimized CO delivery and utilization that relies on the control of inter-strain metabolic interactions. The synergistic photocatalytic-bioprocessing platform will achieve efficient CO2 conversion and valorization while promoting environmental and economic sustainability. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.