title: Changing the renewable fuel standard to a renewable material standard: bioethylene case study.
abstract: The narrow scope of the U.S. renewable fuel standard (RFS2) is a missed opportunity to spur a wider range of biomass use. This is especially relevant as RFS2 targets are being missed due to demand-side limitations for ethanol consumption. This paper examines the greenhouse gas (GHG) implications of a more flexible policy based on RFS2, which includes credits for chemical use of bioethanol (to produce bioethylene). A Monte Carlo simulation is employed to estimate the life-cycle GHG emissions of conventional low-density polyethylene (LDPE), made from natural gas derived ethane (mean: 1.8 kg CO2e/kg LDPE). The life-cycle GHG emissions from bioethanol and bio-LDPE are examined for three biomass feedstocks: U.S. corn (mean: 97g CO2e/MJ and 2.6 kg CO2e/kg LDPE), U.S. switchgrass (mean: -18g CO2e/MJ and -2.9 kg CO2e/kg LDPE), and Brazilian sugar cane (mean: 33g CO2e/MJ and -1.3 kg CO2e/kg LDPE); bioproduct and fossil-product emissions are compared. Results suggest that neither corn product (bioethanol or bio-LDPE) can meet regulatory GHG targets, while switchgrass and sugar cane ethanol and bio-LDPE likely do. For U.S. production, bioethanol achieves slightly greater GHG reductions than bio-LDPE. For imported Brazilian products, bio-LDPE achieves greater GHG reductions than bioethanol. An expanded policy that includes bio-LDPE provides added flexibility without compromising GHG targets.
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.forename: W Michael
authors.initials: WM
authors.lastname: Griffin
authors.forename: H Scott
authors.initials: HS
authors.lastname: Matthews
authors.forename: Inês L
authors.initials: IL
authors.lastname: Azevedo
mesh_terms: D000397:Air Pollution / Q000706:statistics & numerical data*; D056804:Biofuels / Q000191:economics / Q000592:standards* / Q000706:statistics & numerical data; D018533:Biomass; D000431:Ethanol; D017752:Greenhouse Effect; D009010:Monte Carlo Method; D059206:Natural Gas; D008897:Panicum; D020959:Polyethylene / Q000138:chemical synthesis* / Q000191:economics; D059205:Renewable Energy / Q000592:standards*; D031786:Saccharum; D014481:United States; D003313:Zea mays
chemical_list: D056804:Biofuels; D059206:Natural Gas; D000431:Ethanol; D020959:Polyethylene