Life cycle analysis of ethanol: issues, results, and case simulations Jeongwoo Han Systems Assessment Group Center for Transportation Research Argonne National Laboratory Annual ACE Conference Omaha, August 21, 2015 The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory ( Argonne ). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Ethanol and renewable fuel standard (RFS) Ethanol in 2014 (EIA) Production: 14.3 billion gallons Consumption: 13.5 billion gallons (c.f. gasoline: 136.8 billion gallons) Net export: 0.77 billion gallons Renewable fuel standard (RFS) Ethanol Category (D code) RINs generated in 2014 (gallons) RFS Mandate (gallons) Cellulosic ethanol Cellulosic biofuel (D3) 728,509 17,000,000 Sugarcane ethanol Advanced biofuel (D5) 90,298,203 2,200,000,000 Corn ethanol Renewable fuel (D6) 14,016,510,139 15,210,000,000 Renewable fuel, advanced biofuel and cellulosic biofuel should meet the 20%, 50% and 60% life-cycle GHG emissions reduction threshold relative to gasoline, respectively 2
Life cycle analysis of transportation fuels Life cycle analysis (LCA): Systematic accounting of the energy use and emissions at every stage of the production, use, disposal and recycle of a product Well-To-Wheel (WTW) analysis: Specific to transportation fuels WTW analysis takes into account the direct fuel use and its upstream energy use and associated emissions 3
GREET overview Several DOE programs have supported GREET development since 1995 A publicly available LCA tool for consistently examining life-cycle energy and emissions of vehicle/fuel systems Available for free download at greet.es.anl.gov Fuel types include petroleum fuels, NG-based fuels, hydrogen, electricity, and many biofuel types End use transportation applications Over 85 on-road vehicle/fuel systems (conventional tech., hybrids, plug-in hybrids, battery electric vehicles, fuel cell vehicles) Marine transportation, air transportation, and rail transportation GREET produces results for Greenhouse gas emissions (CO 2 e of CO 2, CH 4, N 2 O, black carbon) Criteria pollutant emissions (VOC, CO, NO x, SO x, PM 2.5, and PM 10 ); separated into total and urban emissions Energy use by total energy, fossil energy, petroleum energy Biofuels have been an important fuels group in GREET development and applications 4
Corn ethanol life cycle 5
Key Issues in corn ethanol LCA Agriculture and conversion technology advancements Agriculture technology advancements Advanced ethanol plant: process fuel and co-products Land-use change Co-product allocation methodology 6
Key Issues in corn ethanol LCA Agriculture and conversion technology advancements Agriculture technology advancements Advanced ethanol plant: process fuel and co-products Land-use change Co-product allocation methodology 7
Fertilizer use in U.S. corn farming has declined significantly in the past 40 years 8
Intensity of fertilizer use in U.S. corn farming and energy use and GHG emissions of fertilizer production and use Nitrogen Phosphate Potash Lime Fertilizer Use Intensity: lb of nutrient per bushel of corn 0.96 0.34 0.40 2.44 Energy Use for Fertilizer Production: Btu/lb of nutrient 20,741 5,939 3,719 3,398 GHG Emissions of Fertilizer Production: g CO 2e /lb of nutrient 1,359 460 302 274 GHG Emissions from Fertilizer in Field: g CO 2e /lb of nutrient 2,965 a 0 0 200 b Total GHG Emissions: g CO2e/lb of fertilizer nutrient 4,324 460 302 474 Total GHG Emissions: g CO2e/bushel of corn 4,151 156 121 1,157 a This is CO 2e emissions of N 2 O from nitrification and denitrification of nitrogen fertilizer in cornfields. b This is CO 2 emissions of converting calcium carbonate (limestone) to calcium oxide (burnt lime) in cornfields. 9
Trend of 35 studies in the past 35 years: Energy use in U.S. corn ethanol plants has decreased significantly Historical Ethanol Plant Energy Use: Btu/Gallon 140,000 Dry Mill Wet Mill Average 120,000 100,000 80,000 60,000 40,000 20,000 0 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 In Wang et al. (2011), Biomass and Bioenergy Journal 10
Selection of corn ethanol plant type affects LCA results Dry mill (nearly 90% of fleet) Wet mill Process fuel Natural gas Coal Biomass Corn oil extraction Integrated production of corn and stover ethanol 11
Comparison among pathways to ethanol 12
System boundary for ethanol production from an integrated corn and corn stover biorefinery process 13
The share of CHP energy for each ethanol production process is a key parameter Fulfill Corn Stover Demand Ethanol Production Allocation (73/27) Fulfill Corn Grain Demand 14
Key Issues in corn ethanol LCA Agriculture and conversion technology advancements Agriculture technology advancements Advanced ethanol plant: process fuel and co-products Land-use change Co-product allocation methodology 15
Land use change overview Biofuel production increases Computational General Equilibrium (CGE) Model: GTAP Lands transition to feedstock production Grasslands Forests Croplands Change in carbon stocks in lands Aboveground carbon Belowground carbon, including soil organic carbon Carbon Stock Model: Century Winrock Woods Hole Carbon Calculator for Land Use Change from Biofuels (CCLUB) 16
Estimates of LUC GHG emissions for the corn ethanol pathway have declined from early estimates Effects of several critical factors in CGE models: Biomass yield Available land types Price elasticities Animal feed modeling Baseline food demand and supply 17
Soil carbon change upon land transitions depends on many factors Land use history Yield Climate Soil depth Management practices 18
Key Issues in corn ethanol LCA Agriculture and conversion technology advancements Agriculture technology advancements Advanced ethanol plant: process fuel and co-products Land-use change Co-product allocation methodology 19
Coproduct handling methods for corn ethanol Displacement method Fuel Energy & Emission Burden 100% 0% Main Product Co-product Production of displaced product Displacing conv. product Fuel (Credit) Conventional product Allocate by Energy Market value Allocation method Fuel Energy & Emission Burden 80% 20% Co-product 20% Main Product 80% 20
Displacement ratios between DGS and conventional animal feeds 1 Livestock 2009 DGS Market Share Beef Cattle 41% Dairy Cattle 41% Swine 13% Poultry 5% 2 Displacement Ratio Between DGS and Conventional Feed (kg/kg of DGS) [Dry Matter Basis] Dry DGS Wet DGS Livestock Corn Soybean Meal Urea Corn Soybean Meal Urea Beef Cattle 1.203 0.000 0.068 1.276 0.000 0.037 Dairy Cattle 0.445 0.545 0.000 0.445 0.545 0.000 Swine 0.577 0.419 0.000 Poultry 0.552 0.483 0.000 Average 0.751 0.320 0.024 Dry and Wet DGS Combined 0.788 0.304 0.022 2 1. Renewable Fuels Association 2011 2. In Arora et al. 2010 21
C-E1 C-E2 C-E3 C-E4 C-E5 G-E1 G-E2 G-E3 S-BD1 S-BD2 S-BD3 S-BD4 S-RD1 S-RD2 S-RD3 S-RD4 S-RD5 GHG Emissions (g/mmbtu). Choice of co-product methods can have significant LCA effects for biofuels 80,000 D M E $ P D E $ D M E $ $ D M E H 40,000 0 Gasoline Diesel -40,000-80,000-120,000 PTW WTP WTW Corn Ethanol D: Displacement M: Mass based E: Energy based Switchgrass to Ethanol Biodiesel $: Market value P: Process purpose H: Hybrid allocation Renewable Diesel. Gasoline. Diesel. Corn-EtOH. Switchgrass - EtOH. Biodiesel. Renewable Diesel. In Wang et al. (Energy Policy J., 2011) 22
Conclusions LCA could systematically account for the energy use and emissions at every stage of a product Key issues in ethanol LCA Agriculture and conversion technology advancements Land-use change Co-product allocation methodology ANL continues monitoring the technology advancement in biofuel industry and implement them to estimate the environmental impacts of biofuels more accurately 23
GREET model and supporting materials are available: https://greet.es.anl.gov/main 24