Comparative life cycle assessment of fossil and bio-based polyethylene terephthalate (PET) bottles

Both biofuels and bioplastics are often regarded as sustainable solutions to current environmental problems such as climate change, fossil depletion and acidification. However, both have been criticized for being economically costly, competing with other societally beneficial goods such as food, and offering limited environmental benefits compared to their fossil counterparts. This study provides a comparative environmental Life Cycle Analysis (LCA) for 100% bio-based polyethylene terephthalate (PET) bottles, versus fully fossil-based and partially bio-based PET bottles. An attributional life cycle assessment (aLCA) and sensitivity analysis of key assumptions is carried out to compare cradle-to-factory-gate impacts (i.e. feedstock extraction, component production and product manufacturing) of twelve PET bottle production scenarios. Results indicate that woody-biomass based PET bottles have 21% less global warming potential and require 22% less fossil fuel than their fossil based counterparts, but perform worse in other categories such as ecotoxicity and ozone depletion impacts. Results are sensitive to impact allocation assumptions as well as parameter input assumptions related to isobutanol production. In most categories, with avoided impact credits considered, forest residue feedstocks result in overall better environmental performance than corn stover feedstocks for bio-PET bottle production. The variability in avoided burdens could alter the relative environmental rankings for fossil and bio-PET bottles. Depending on the biomass feedstock, extraction and pre-processing are likely more emission-intensive than the corresponding fossil refinery processes due to the significant upstream emissions embodied in the application of fertilizers, and the significant chemical and energy inputs required to break recalcitrant lignocellulosic bonds.