K.F. Reardon, P. Atanassov, C. Bailey, W. Black, D. Bartholet, J. Chan, S. Decker, S. De Long, P. Ghadermazi, P.C. Gilcrease, M. Hickey, J. Kim, S. Lambrecht, H. Li, E. Lucero, S. Pittman, J.C. Quinn, J. Rico, V. Subramanian, D. Svedruzic, C. Urban
Colorado State University,
United States
Keywords: food waste, manure, synthetic biology, electrochemistry, anaerobic digestion
Summary:
Wet organic waste presents problems in disposal cost and environmental impact and represents lost opportunities as inexpensive feedstocks to displace fossil-based products. Traditional anaerobic digestion (AD), composting, and incineration strategies are limited by their CO2 production (wasted C) and low value/uncaptured methane production. Renewable electricity could provide inexpensive electrons to enhance wet waste processing and generate drop-in liquid transportation fuels. The goal of this project is to address the current limitations of wet waste conversion by integrating chemical and electrochemical approaches to block methanogenesis and increase production of volatile fatty acids (VFAs), producing additional VFAs via electrosynthesis from CO2, and elongating VFA chains to produce higher-value medium chain fatty acids. In addition, a bioconversion strain of E. coli has been developed to convert short and medium chain fatty acids to the corresponding alcohols. The new technology is being developed at the bench scale and demonstrated in the GasCube, a 2,000-L, 2-stage anaerobic digester. The project is on track to demonstrate more than 25% improvement in both the levelized cost of energy production and the net levelized cost of disposal. Our concept combines established technologies, emerging concepts, and new ideas into a novel integrated waste conversion process to produce high-value biofuels and bioproducts. Technical accomplishments to date include identification of conditions yielding high VFA levels, including high levels of C4 and higher acids; conversion of acids to alcohols using synthetic biology; development of software that relates microbiome composition to VFA production; demonstration of scale-up from 2-L to 600-L bioreactors; and technoeconomic and life-cycle analyses based on a comprehensive process model.