title: Uncertainty in the Life Cycle Greenhouse Gas Emissions from U.S. Production of Three Biobased Polymer Families.
abstract: Interest in biobased products has been motivated, in part, by the claim that these products have lower life cycle greenhouse gas (GHG) emissions than their fossil counterparts. This study investigates GHG emissions from U.S. production of three important biobased polymer families: polylactic acid (PLA), polyhydroxybutyrate (PHB) and bioethylene-based plastics. The model incorporates uncertainty into the life cycle emission estimates using Monte Carlo simulation. Results present a range of scenarios for feedstock choice (corn or switchgrass), treatment of coproducts, data sources, end of life assumptions, and displaced fossil polymer. Switchgrass pathways generally have lower emissions than corn pathways, and can even generate negative cradle-to-gate emissions if unfermented residues are used to coproduce energy. PHB (from either feedstock) is unlikely to have lower emissions than fossil polymers once end of life emissions are included. PLA generally has the lowest emissions when compared to high emission fossil polymers, such as polystyrene (mean GHG savings up to 1.4 kg CO2e/kg corn PLA and 2.9 kg CO2e/kg switchgrass PLA). In contrast, bioethylene is likely to achieve the greater emission reduction for ethylene intensive polymers, like polyethylene (mean GHG savings up to 0.60 kg CO2e/kg corn polyethylene and 3.4 kg CO2e/kg switchgrass polyethylene).
authors.affiliation: Department of Engineering & Public Policy and ‡Department of Civil & Environmental Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: I Daniel
authors.initials: ID
authors.lastname: Posen
authors.affiliation: Department of Engineering & Public Policy and ‡Department of Civil & Environmental Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Paulina
authors.initials: P
authors.lastname: Jaramillo
authors.affiliation: Department of Engineering & Public Policy and ‡Department of Civil & Environmental Engineering, Carnegie Mellon University , 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213, United States.
authors.forename: W Michael
authors.initials: WM
authors.lastname: Griffin
mesh_terms: D000393:Air Pollutants; D056804:Biofuels / Q000032:analysis*; D017752:Greenhouse Effect; D008962:Models, Theoretical; D009010:Monte Carlo Method; D008897:Panicum; D011108:Polymers / Q000737:chemistry* / Q000145:classification; D035501:Uncertainty; D014481:United States; D003313:Zea mays
chemical_list: D000393:Air Pollutants; D056804:Biofuels; D011108:Polymers