Presentation on theme: "Environmental Impacts of Biofuels: Lifecycle greenhouse gas emissions Mississippi State University January 28 2014 Valerie Thomas School of Industrial."— Presentation transcript:
Environmental Impacts of Biofuels: Lifecycle greenhouse gas emissions Mississippi State University January 28 2014 Valerie Thomas School of Industrial and Systems Engineering, and School of Public Policy
Middle East Conflict Six day war - June 5 1967 Arab oil embargo - June 6 Yom Kippur War - 1973 Arab Oil Embargo - 1973 Iranian Revolution - 1979
Crude oil prices since 1861 BP Statistical Review of World Energy 2010
Biofuel motivation 2 Support US farmers Similar motivation for ethanol production from sugar cane in Brazil
Biofuel motivation 3 Reduce greenhouse gas emissions Coal: C 135 H 96 O 9 NS … (or CH for short) Petroleum (octane): C 8 H 18 … Natural Gas (methane): CH 4 1 kg C corresponds to 44/12 kg CO 2 1 kg uncombusted CH 4 corresponds to 25 kg CO 2 e in 100 year time horizon.
Archer, Chp. 4, Greenhouse Gases Water is a Greenhouse Gas Water Excitation Levels
Archer, Chp. 4, Greenhouse Gases CO 2 excitation levels
Effectiveness of Greenhouse Gases Depends on Their Radiative Efficiency and Time Dependent Decay Radiative Efficiency: W/m 2 /kg Time dependent decay: x(t)
Selected Greenhouse Gases IPCC 2007 The CO 2 response function used in this report is based on the revised version of the Bern Carbon cycle model used in Chapter 10 of this report (Bern2.5CC; Joos et al. 2001) using a background CO 2 concentration value of 378 ppm. The decay of a pulse of CO 2 with time t is given by where a 0 = 0.217, a 1 = 0.259, a 2 = 0.338, a 3 = 0.186, τ 1 = 172.9 years, τ 2 = 18.51 years, and τ 3 = 1.186 years.
Global Warming Potential TH is time horizon, a is radiative efficiency of increase of one unit of substance (W/m 2 /kg); x and r are time dependent decay of substance x and reference gas r.
Atmospheric CO 2 for 400,000 years Carbon dioxide concentrations in Antarctica over 400,000 years. “The graph combines ice core data with recent samples of Antarctic air. The 100,000-year ice age cycle is clearly recognizable.” (Data sources: Petit et al. 1999; Keeling and Whorf 2004; GLOBALVIEW-CO2 2007.)
Anthropogenic Carbon Emissions Boden et al. 2011
US Renewable Fuel Stadnard (RFS2) Lifecycle Greenhouse Gas Emissions Requirements Compared to Petroleum Fuels advanced renewable fuels < 50 % cellulosic renewable fuels < 40 % funding for development< 20 %
Lifecycle Energy and GHG Emissions from Ethanol Produced by Algae Ron Chance, Matthew Realff, Valerie Thomas Zushou Hu, Dexin Luo, Dong Gu Choi School of Chemical and Biomolecular Engineering, and School of Industrial and Systems Engineering
LCA Results Depend on Initial Ethanol Concentration
Analysis Framework: Consider Baseline and Two Extensions Baseline Initial Concentration 1 wt% External Energy Supply CHP+ Natural gas Heat Exchange Efficiency 80% Extension 1 Initial Concentration 0.5~5.0 wt% External Energy Supply CHP + Natural gas Grid Electricity+ Natural gas CHP + Solar thermal + Natural gas Heat Exchange Efficiency 80% Initial Concentration 0.5~5.0 wt% External Energy Supply CHP + Natural gas Grid Electricity+ Natural gas CHP + Solar thermal + Natural gas Heat Exchange Efficiency 90% Extension 2
Fertilizer Energy and GHG emissions Production Rate Ethanol: 56,000 l/hectare Waste Biomass: 0.97 ton/ hectare Algae Composition (1) Nitrogen: 8 wt% Phosphorous: 0.3 wt% Fertilizer Parameters (2-3) Nitrogen: 23.7 MJ/kg Nitrogen: 1.675 kg CO 2 e/kg Phosphorous: 5.78 MJ/kg Phosphorous: 0.97 kg CO 2 e/kg Nitrous Dioxide: 0.005 g N 2 O /g N Energy and GHG emissions Nitrogen: 0.0017 MJ/MJ EtOH 0.11 g CO 2 e/MJ EtOH Phosphorous: 0.000017 MJ/ MJ EtOH 0.0026 g CO 2 e/MJ EtOH Nitrous Dioxide: 0.1 g CO 2 e/MJ EtOH 1 (1)ECN, Phyllis: The Composition of Biomass and Waste. 2010. http://www.ecn.nl/phyllis/http://www.ecn.nl/phyllis/ (2)Kongshaug, G., Energy consumption and greenhouse gas emissions in fertilizer production. IFA Technical Conference, Marrakech, Morocco, 1998. (3)US DOE, Agricultural Chemicals: Fertilizers, Energy and Environmental Profile of the U.S. Chemical Industry. Energy and Environmental Profile of the U.S. Chemical Industry, Chapter 5. Technologies, O. o. I. 2000
Bioreactor Production and Disposal Photo-bioreactor systems to be replaced every 5 years; No GHG emissions from drained bioreactors; Assumptions Production of Polyethylene (1) Energy use: 76 MJ/kg GHG emissions: 1.9 kg CO 2 e /kg Dimension of the PBR Length: 50 feet Circumference: 12.6 feet Wall thickness: 5~10 mil Results Energy use: 0.05 MJ/MJ EtOH GHG emissions: 1.3 g CO 2 e/MJ EtOH 2 (1)GREET, ANL 1 2
Ethanol Distribution and Combustion Assumptions from GREET Model 40% barge: 520 miles 0.54 MJ/ton-mile 40% railroad tanks: 800 miles 0.36 MJ/ton-mile 20% trucks: 80 miles 0.9 MJ/ton-mile 0.0031 g CH 4 and 0.0024 g N 2 O per MJ of ethanol combusted Results Distribution: 0.017 MJ/MJ EtOH 1.6 g CO 2 e/MJ EtOH Combustion: 0.84 g CO 2 e/MJ EtOH 3 1 2 3 4
Freight Truck Energy Intensity 1 mile = 1.6 km 1 ton = 0.907 tonnes 1 Btu = 1055 J
CO 2 Delivery and Water Consumption Assumptions Source water pumped from a depth of 100 meters; Water is circulated to the power plant 6 km away; Reverse osmosis seawater desalination; (1) No water loss through evaporation. Results Water pumping: 0.002 kWh/MJ EtOH Carbonation: 0.00090 kWh/MJ EtOH Water consumption 0.926 l/l EtOH Reverse osmosis: 9.5×10 -5 kWh/MJ EtOH 4 (1) National Research Council Review of the Desalination and Water Purification Technology Roadmap; Washington, DC, 2004 1 2 3 4
Ethanol Separation Process Compression Energy Inputs P T 1 HYSYS simulation Efficiencies 0.055 MJ/MJ EtOH 0.051 MJ/MJ EtOH Processes: Vapor Compression Steam Stripping and Distillation 5 2
Ethanol Separation Process Evaporation Energy & Molecular Sieve Inputs wt% T HYSYS simulation Efficiencies heat exchange column eff. 0.16 MJ/MJ EtOH 0.17 MJ/MJ EtOH Evaporation Processes: Vapor Compression Steam Stripping 6 1 2 1 2 7 Final Purification Processes: Molecular Sieve - The total heat requirement : 1 ~ 2 MJ/kg EtOH. (1) - In this study : 1.5 MJ/kg EtOH, or 0.056 MJ/MJ EtOH (1) Cho, J.; Park, J.; Jeon, J.-k., Comparison of three- and two-column configurations in ethanol dehydration using azeotropic distillation. J. Ind. Eng. Chem. (Seoul, Repub. Korea) 2006, 12 (2), 206-215.
Baseline Energy Use per MJ of Ethanol Produced for Process Steps at 1wt% 1 2 3 4 5 6 7
Baseline GHG Emissions for 1wt% at 80% heat exchange efficiency 1 2 3 4 5 6 7
Baseline GHG Emissions for 1wt% at 80% and 90% heat exchange efficiency 1 2 3 4 5 6 7
External Energy Supply Scenarios S1 Electrical energy U.S. grid electricity 700 g CO 2 e/kWhe Process heat Natural gas 50.38 g CO 2 e/MJ EtOH S2 S3 Electrical energy and heat Natural gas fueled CHP 478 g CO 2 e/kWhe Process heat 14 hr Natural gas 50.38 g CO 2 e/MJ EtOH 10 hr Solar thermal 0 g CO 2 e/MJ EtOH Electrical energy and heat Natural gas fueled CHP 478 g CO 2 e/kWhe Extra Process heat Natural gas 50.38 g CO 2 e/MJ EtOH
Lifecycle GHG Emissions for 80% and 90% heat exchange efficiencies 0.5wt%~5wt% DOE target of 40% of the gasoline emission DOE target of 20% of the gasoline emission Ethanol wt % from phtobioreactors g CO 2 e/MJ Ethanol
Life Cycle Inventory Assessment Natural Gas + US Grid Natural Gas CHP Natural Gas CHP + Solar Thermal How does the ethanol concentration and mix of fuels to generate heat and power influence the ability of the system to meet RFS?
Conclusion and Discussion DOE 40% goal (36.5 g CO2e/MJ EtOH ) achievable by all three energy supply scenarios and initial concentration as low as 0.5% DOE 20% goal (18.3 g CO2e/MJ EtOH ) more challenging Advantage 1: the potential to locate production facilities on low-value, arid, non- agricultural land, and the resulting avoidance of competition with agriculture Advantage 2: no-harvest strategy has the potential for more energy efficient separations, lower fertilizer requirements, and lower water usage in comparison to other algae biofuel processes. Technical challenge: the algae- produced ethanol system does not produce extra biomass waste that can be used as energy to power the process
Does making ethanol use more fossil energy and release more greenhouse gases than the gasoline it is designed to replace? Farrell et al. 2006. Ethanol Can Contribute to Energy and Environmental Goals. Science 311:506.
Sources of biomass carbon emissions Production, transport use fossil fuel Soil carbon loss (direct or indirect) Regeneration time
Sample Bioenergy Lifecycle CO 2 e Emissions Thomas and Liu 2013
Assessment of Alternative Fibers Valerie Thomas, Wenman Liu, Norman Marsolan Institute for Paper Science and Technology School of Industrial and Systems Engineering School of Public Policy Georgia Institute of Technology
Arundo donax Perennial Grown for bioenergy High yield Low input Invasiveness
Kenaf Annual Grown for fiber Medium yield Low input
Bamboo Perennial Widely grown in China High yield Low input Invasiveness
Wheat Straw Agricultural residue No additional: - land use - fertilizers - pesticides - irrigation
Northern softwood Biodiversity Carbon storage Low input Bamboo as alternative
Recycled Fiber Moderate - energy use - carbon footprint - environmental impact Kenaf, arundo, wheat straw as alternatives
What drives the results Yield Irrigation Fertilizers Pesticides Agricultural Energy Use Invasiveness Biodiversity Pulping process change
Preliminary Comparison: Nitrogen Fertilizer Eutrophication, energy input, greenhouse gas emissions
Standard Methods Provide Land use Fossil fuel energy use Freshwater use – Irrigation and Processing Greenhouse gases from energy and chemicals Eutrophication Ecotoxicity
Preliminary Results – Illustrative Only Multiple Impact Categories
Net greenhouse gas emissions from each fiber option under a 100-year time horizon
Net greenhouse gas emissions from each fiber option under a 500-year time horizon
Biodiversity Driver for northern forest protection – Effect from reducing northern softwood harvesting – Effect from growing bamboo on southern timberland – Effects of kenaf and arundo Species richness, Ecosystem scarcity, Ecosystem vulnerability
Carbon storage Driver for northern forest protection Effect from reducing northern softwood harvesting Effect from growing bamboo on southern timberland Effects of kenaf and arundo Carbon storage in soils is known to be very highly variable.
Biogenic Global Warming Potentials Data from Guest et al. J. Indust. Ecol. 2012.