Life cycle analysis of corn-stover-derived polymer-grade l-lactic acid and ethyl lactate: greenhouse gas emissions and fossil energy consumption

Co-production of high-value chemicals with biofuels could improve the economic viability of biorefineries while reducing biofuel life-cycle greenhouse gas (GHG) emissions and fossil energy consumption (FEC). Polymer-grade lactic acid (PGLA) is a high-potential bioproduct currently produced from first-generation feedstocks. Opportunity exists to enhance its environmental performance using cellulosic feedstocks. Moreover, ethyl lactate can be used as a functional replacement for high-volume, energy-intensive, and emissions-intensive petroleum-derived chemicals such as N-methyl-2-pyrrolidone and ethyl acetate. Based on material and energy flows from Aspen Plus process models that we incorporated into the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model's bioproducts module, we developed life-cycle GHG emissions and FEC estimates for ethyl lactate and PGLA produced from corn stover. We compared these results to those for fossil-fuel-derived counterparts, identified key LCA drivers, and explored the impact of end-of-life assumptions on LCA results. Irrespective of the end-of-life assumption, all the bioproducts demonstrated lower life-cycle FEC (10-72%) and GHG emissions (23-90%) than fossil-derived compounds for which they could serve as a functional replacement. Additionally, we reviewed the role of LCA in three major bioproduct sustainability certification schemes (the BioPreferred Program, the Roundtable on Sustainable Biomaterials, and International Sustainability and Carbon Certification Plus). None mandate an LCA of the bioproduct to assess whether, across the supply chain, these products offer environmental benefits as compared to conventional chemicals they could displace either directly or functionally. (c) 2016 Society of Chemical Industry and John Wiley & Sons, Ltd