Opportunity and challenge of seaweed bioethanol based on life cycle CO2 assessment

Abstract

Seaweed bioethanol technology is being developed to mitigate climate change and to overcome economic and environmental drawbacks that terrestrial bioethanol has: biomass demand competition for food and energy, and land-use change impacts. To investigate whether seaweed bioethanol is better than terrestrial bioethanol, we compare the global warming potentials (GWPs) of seaweed and terrestrial bioethanols from a life cycle perspective including land-related GWP effects from carbon debt, soil carbon sequestration, and N2O emission. Our results demonstrated that seaweed bioethanol has lower GWP in the long term than terrestrial bioethanols from corn grain, corn stover, and switchgrass, primarily because seaweed cultivation does not consume fertilizers and incur carbon debt and N2O emission. It was noted that future R&D strategy for low-carbon seaweed bioethanol needs to be directed to developing biomaterial-based cultivation equipment and reusing existing equipment, as well as enhancing bioethanol conversion yield and biomass productivity. Due to the vast sea available for seaweed cultivation, seaweed bioethanol could significantly contribute to mitigating climate change. (c) 2016 American Institute of Chemical Engineers Environ Prog, 36: 200-207, 2017