(23d) Carbon Footprint and Land Use Reductions of Electromicrobial Production Systems Quantified By Process Modelling and Comparative Life Cycle Assessment

The reliance of most industrial bioprocesses on heterotrophic organisms such as Escherichia coli has generated concerns around the environmental impacts of feedstock production, including the impact of land use on ecosystems, increased pollution from fertilizer production and application, and competition with food production. To circumvent these challenges, researchers have proposed various electromicrobial production (EMP) systems, a broad strategy in which electrochemically generated mediator molecules provide energy for microbes to fix carbon dioxide and produce value-added products. Based on previous work in modelling bioreactors for use in EMP systems, we have developed process models and performed cradle-to-gate life cycle impact assessments (LCIA) of three proposed electro-microbial production systems: a Knallgas bacteria-based system, a formatotroph-based system, and an acetogen-based system. The generation of various products, including biomass, industrial enzymes, and lactic acid is studied. The life cycle impact assessment demonstrates that all three systems will have a lower global warming potential than a traditional glucose-fed bioproduction system if the electricity is provided by a renewable source such as solar or wind energy. Additionally, the LCIA shows that the EMP systems have less than 5% of the land occupation footprint compared to the traditional bioproduction system analyzed. When comparing the systems to each other, we found that the hydrogen-fed Knallgas bacteria-based system uses the least amount of energy and has the lowest carbon footprint compared to the other two EMP systems. We also identified the environmental hotspots of each proposed EMP system and discuss strategies to overcome these bottlenecks. This analysis demonstrates the potential of electro-microbial production systems as a sustainable bioproduction strategy and identifies conditions under which they become attractive alternatives.