LCA of Bioethanol: Feedstock Options and Processing Pathways

In this article, Life Cycle Assessment (LCA) was applied to investigate the potential environmental impacts of bioethanol production pathways from six biomass feedstock options. The LCA cradle-to-gate modelling case studies involve (i) corn stover, (ii) wheat straw, (iii) rice straw, (iv) sugarcane bagasse, (v) woody biomass, and (vi) microalgae for the final production of 1 kg bioethanol as functional unit. Environmental impact results of GWP (Global Warming Potential), AP (Acidification Potential), and EP (Eutrophication Potential) were evaluated utilizing CML2001, a Life Cycle Impact Assessment (LCIA) methodology featuring midpoint evaluation and baseline environmental categories. Water Footprint (WF) indicators were also measured. Among the six feedstocks, the GWP results indicated the most favourable option to decarbonize bioethanol production is to utilize corn stover feedstock, enabling total-1.04 kg CO2-eq/kg ethanol. Wood waste also displays favourable GWP impacts of −0.9 kg CO2-eq/kg ethanol, along with negligible WF results. Both rice straw and microalgae exhibited the most unfavourable feedstock options, both resulting in GWP impacts of 12.71 kg CO2-eq/kg ethanol and 11.32 kg CO2-eq/kg ethanol respectively. Additionally, rice straw and microalgae require high volumes of WF during cultivation stages. Overall, the set of environmental impact results, based mostly on data derived from lab-scale or pilot scale reports, demonstrated substantial requirements for environmental reduction and management of some specific feedstocks to proceed for large scale set ups.