Life cycle assessment of switchgrass-derived ethanol as transport fuel

Background, aim, and scopeThe increasing gasoline price, the depletion of fossil resources, and the negative environmental consequences of driving with petroleum fuels have driven the development of alternative transport fuels. Bioethanol, which is converted from cellulosic feedstocks, has attracted increasing attention as one such alternative. This study assesses the environmental impact of using ethanol from switchgrass as transport fuel and compares the results with the ones of gasoline to analyze the potential of developing switchgrass ethanol as an environmentally sustainable transport fuel.MethodsThe standard framework of life cycle assessment from International Standards Organization was followed. To compare the environmental impact of driving with E10 and E85 with gasoline, “power to wheels for 1-km driving of a midsize car” was defined as the functional unit. The product system consists of all relevant processes, from agriculture of switchgrass, throughout the production of ethanol, blending ethanol with gasoline to produce E85 and E10, to the final vehicle operations. The transport of all products and chemicals is also included in the system boundaries. An allocation based on energy content was applied as a baseline, and market price-based allocation was applied for a sensitivity analysis.Results and discussionWith regard to global warming potential, driving with switchgrass ethanol fuels leads to less greenhouse gas (GHG) emissions than gasoline: 65% reduction may be achieved in the case of E85. Except for global warming and resource depletion, driving with ethanol fuels from switchgrass does not offer environmental benefits in the other impact categories compared to gasoline. Switchgrass agriculture is the main contributor to eutrophication, acidification, and toxicity. Emissions from bioethanol production cause a greater impact in photochemical smog formation for ethanol-fueled driving.Conclusions and recommendationsSwitchgrass ethanol indeed leads to less GHG emissions than gasoline on a life cycle basis; however, the problem has been shifted to other impacts. Improvement of switchgrass yields and development of ethanol production technologies may be the key to lower environmental impact in the future. For a more comprehensive evaluation of using bioethanol as transport fuel, more impact categories need to be included in the life cycle impact assessment. A comparison with bioethanol from other feedstocks, based on similar methodological choices and background data, would provide more insight in the environmental benefits of switchgrass as a feedstock.

[1]  André Faaij,et al.  Bio-energy in Europe: changing technology choices , 2006 .

[2]  Robert B. Mitchell,et al.  Managing and enhancing switchgrass as a bioenergy feedstock , 2008 .

[3]  Gjalt Huppes,et al.  Life cycle assessment and life cycle costing of bioethanol from sugarcane in Brazil , 2009 .

[4]  S. Polasky,et al.  Land Clearing and the Biofuel Carbon Debt , 2008, Science.

[5]  R. Perrin,et al.  Net energy of cellulosic ethanol from switchgrass , 2008, Proceedings of the National Academy of Sciences.

[6]  Kenneth Kelly,et al.  Federal Test Procedure Emissions Test Results from Ethanol Variable-Fuel Vehicle Chevrolet Luminas , 1996 .

[7]  M. Ruth,et al.  Lignocellulosic Biomass to Ethanol Process Design and Economics Utilizing Co-Current Dilute Acid Prehydrolysis and Enzymatic Hydrolysis Current and Futuristic Scenarios , 1999 .

[8]  T. Nemecek,et al.  Life Cycle Inventories of Agricultural Production Systems , 2007 .

[9]  Shabbir H. Gheewala,et al.  Life cycle assessment of fuel ethanol from cane molasses in Thailand , 2008 .

[10]  Eric Johnson.  Handbook on Life Cycle Assessment Operational Guide to the ISO Standards , 2003 .

[11]  Hans-Jürgen Dr. Klüppel,et al.  The Revision of ISO Standards 14040-3 - ISO 14040: Environmental management – Life cycle assessment – Principles and framework - ISO 14044: Environmental management – Life cycle assessment – Requirements and guidelines , 2005 .

[12]  Albert W. Chan,et al.  Life Cycle assessment of bio-ethanol derived from cellulose , 2003 .

[13]  K. Paustian,et al.  Energy and Environmental Aspects of Using Corn Stover for Fuel Ethanol , 2003 .

[14]  Heather L MacLean,et al.  Life cycle assessment of switchgrass- and corn stover-derived ethanol-fueled automobiles. , 2005, Environmental science & technology.

[15]  H. Hong,et al.  Fuel-cycle assessment of selected bioethanol production. , 2007 .

[16]  Gjalt Huppes,et al.  Allocation issues in LCA methodology: a case study of corn stover-based fuel ethanol , 2009 .

[17]  Jacinto F. Fabiosa,et al.  Use of U.S. Croplands for Biofuels Increases Greenhouse Gases Through Emissions from Land-Use Change , 2008, Science.

[18]  Kiran L. Kadam,et al.  Environmental benefits on a life cycle basis of using bagasse-derived ethanol as a gasoline oxygenate in India. , 2002 .

[19]  D. Johnson,et al.  Strategic Biorefinery Analysis: Analysis of Biorefineries , 2005 .

[20]  Thapat Silalertruksa,et al.  Environmental sustainability assessment of bio-ethanol production in Thailand , 2009 .

[21]  H. Halleux,et al.  Comparative life cycle assessment of two biofuels ethanol from sugar beet and rapeseed methyl ester , 2008 .

[22]  Shahab Sokhansanj,et al.  Large‐scale production, harvest and logistics of switchgrass (Panicum virgatum L.) – current technology and envisioning a mature technology , 2009 .

[23]  Julie Witcover,et al.  2020 GLOBAL FOOD OUTLOOK: TRENDS, ALTERNATIVES, AND CHOICES , 2001 .

[24]  L. Nielsen,et al.  An environmental life cycle assessment comparing Australian sugarcane with US corn and UK sugar beet as producers of sugars for fermentation. , 2008 .