Advertisement

Reference and functional unit can change bioenergy pathway choices

  • Sonika Choudhary
  • Sai Liang
  • Hua Cai
  • Gregory A. Keoleian
  • Shelie A. Miller
  • Jarod Kelly
  • Ming XuEmail author
LCA FOR AGRICULTURAL PRACTICES AND BIOBASED INDUSTRIAL PRODUCTS

Abstract

Purpose

This study aims to compare the life cycle greenhouse gas (GHG) emissions of two cellulosic bioenergy pathways (i.e., bioethanol and bioelectricity) using different references and functional units. It also aims to address uncertainties associated with a comparative life cycle analysis (LCA) for the two bioenergy pathways.

Methods

We develop a stochastic, comparative life cycle GHG analysis model for a switchgrass-based bioenergy system. Life cycle GHG offsets of the biofuel and bioelectricity pathways for cellulosic bioenergy are compared. The reference system for bioethanol is the equivalent amount of gasoline to provide the same transportation utility (e.g., vehicle driving for certain distance) as bioethanol does. We use multiple reference systems for bioelectricity, including the average US grid, regional grid in the USA according to the North American Electric Reliability Corporation (NERC), and average coal-fired power generation, on the basis of providing the same transportation utility. The functional unit is one unit of energy content (MJ). GHG offsets of bioethanol and bioelectricity relative to reference systems are compared in both grams carbon dioxide equivalents per hectare of land per year (g CO2-eq/ha-yr) and grams carbon dioxide equivalents per vehicle kilometer traveled (g CO2-eq/km). For the latter, we include vehicle cycle to make the comparison meaningful. To address uncertainty and variability, we derive life cycle GHG emissions based on probability distributions of individual parameters representing various unit processes in the life cycle of bioenergy pathways.

Results and discussion

Our results show the choice of reference system and functional unit significantly changes the competition between switchgrass-based bioethanol and bioelectricity. In particular, our results show that the bioethanol pathway produces more life cycle GHG emissions than the bioelectricity pathway on a per unit energy content or a per unit area of crop land basis. However, the bioethanol pathway can offer more GHG offsets than the bioelectricity pathway on a per vehicle kilometer traveled basis when using bioethanol and bioelectricity for vehicle operation. Given the current energy mix of regional grids, bioethanol can potentially offset more GHG emissions than bioelectricity in all grid regions of the USA.

Conclusions

The reference and functional unit can change bioenergy pathway choices. The comparative LCA of bioenergy systems is most useful for decision support only when it is spatially explicit to address regional specifics and differences. The difference of GHG offsets from bioethanol and bioelectricity will change as the grid evolves. When the grids get cleaner over time, the favorability of bioethanol for GHG offsets increases.

Keywords

Bioelectricity Bioethanol Functional unit Life cycle Reference system Switchgrass 

Notes

Acknowledgments

This material is based upon work supported by the National Science Foundation under Grant No. 1132581. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. S.C. also thanks the support provided by the Center for Sustainable Systems at the University of Michigan. S.L. thanks the support from the Dow Sustainability Fellows Program.

Supplementary material

11367_2013_692_MOESM1_ESM.doc (588 kb)
Detailed description of methods, assumptions, and data, and supplementary figures and tables presenting the results of LCA and sensitivity analysis (DOC 588 kb).

References

  1. ANL (2012) The Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation (GREET) Model. Transportation Technology Research and Development Center, Argonne National Laboratory, U.S. Department of Energy. http://greet.es.anl.gov. Accessed August 2012
  2. Bai Y, Luo L, Voet E (2010) Life cycle assessment of switchgrass-derived ethanol as transport fuel. Int J Life Cycle Assess 15(5):468–477. doi: 10.1007/s11367-010-0177-2 Google Scholar
  3. Bessou C, Ferchaud F, Gabrielle B, Mary B (2011) Biofuels, greenhouse gases and climate change. A review. Agron Sustain Dev 31(1):1–79. doi: 10.1051/agro/2009039 CrossRefGoogle Scholar
  4. Brander M, Tipper R, Hutchison C, Davis G (2008) Consequential and Attributional Approaches to LCA: a Guide to Policy Makers with Specific Reference to Greenhouse Gas LCA of Biofuels. ecometrica pressGoogle Scholar
  5. Brinkman N, Wang M, Weber T, Darlington T (2005) Well-to-wheels analysis of advanced fuel/vehicle systems — a north American study of energy use, greenhouse gas emissions, and criteria pollutant emissions. Argonne National Laboratory, ArgonneGoogle Scholar
  6. Brown D, Gassner M, Fuchino T, Marechal F (2009) Thermo-economic analysis for the optimal conceptual design of biomass gasification energy conversion systems. Appl Therm Eng 29(11–12):2137–2152. doi: 10.1016/j.applthermaleng.2007.06.021 CrossRefGoogle Scholar
  7. Campbell JE, Lobell DB, Field CB (2009) Greater transportation energy and GHG offsets from bioelectricity than ethanol. Science 324(5930):1055–1057. doi: 10.1126/science.1168885 CrossRefGoogle Scholar
  8. Carroll A, Somerville C (2009) Cellulosic biofuels. Annu Rev Plant Biol 60:165–182. doi: 10.1146/annurev.arplant.043008.092125 CrossRefGoogle Scholar
  9. Chamberlain JF, Miller SA, Frederick JR (2011) Using DAYCENT to quantify on-farm GHG emissions and N dynamics of land use conversion to N-managed switchgrass in the Southern US. Agric Ecosyst Environ 141(3-4):332–341. doi: 10.1016/j.agee.2011.03.011 CrossRefGoogle Scholar
  10. Cherubini F, Peters GP, Berntsen T, Stromman AH, Hertwich E (2011) CO2 emissions from biomass combustion for bioenergy: atmospheric decay and contribution to global warming. GCB Bioenergy 3(5):413–426. doi: 10.1111/j.1757-1707.2011.01102.x CrossRefGoogle Scholar
  11. Davis EB, Jager HI, West TO, Perlack RD, Brandt CC, Wullschleger SD, Baskaran LM, Wilkerson EG, Downing ME, Gunderson CA (2008) Exploring Potential U.S. Switchgrass Production for Lignocellulosic Ethanol. U.S. Department of Energy Publications. http://digitalcommons.unl.edu/usdoepub/16. Accessed August 2012
  12. DOE (2012) Fuel Economy Guide. U.S. Department of EnergyGoogle Scholar
  13. DSIRE (2012) Renewable Portfolio Standard Policies. Database of State Incentives for Renewables & EfficiencyGoogle Scholar
  14. EIA (2012) Annual Energy Outlook 2012. U.S. Energy Information AdministrationGoogle Scholar
  15. EPA (2012) Emissions & Generation Resource Integrated Database (eGRID). U.S. Environmental Protection Agency, Washington D.C.Google Scholar
  16. Farrell AE, Plevin RJ, Turner BT, Jones AD, O’Hare M, Kammen DM (2006) Ethanol can contribute to energy and environmental goals. Science 311(5760):506–508. doi: 10.1126/science.1121416 CrossRefGoogle Scholar
  17. Fu GZ, Chan AW, Minns DE (2003) Life cycle assessment of bio-ethanol derived from cellulose. Int J Life Cycle Assess 8(3):137–141. doi: 10.1065/lca2003.03.109 Google Scholar
  18. Groode TA (2008) Biomass to ethanol: potential production and environmental impacts. Massachusetts Institute of Technology, CambridgeGoogle Scholar
  19. Hawkins TR, Singh B, Majeau-Bettez G, Strømman AH (2013) Comparative environmental life cycle assessment of conventional and electric vehicles. J Ind Ecol 17(1):53–64. doi: 10.1111/j.1530-9290.2012.00532.x CrossRefGoogle Scholar
  20. Heller MC, Keoleian GA, Volk TA (2003) Life cycle assessment of a willow bioenergy cropping system. Biomass Bioenerg 25(2):147–165. doi: 10.1016/s0961-9534(02)00190-3 CrossRefGoogle Scholar
  21. Hertel TW, Golub AA, Jones AD, O’Hare M, Plevin RJ, Kammen DM (2010) Effects of US maize ethanol on global land use and greenhouse gas emissions: estimating market-mediated responses. BioScience 60(3):223–231CrossRefGoogle Scholar
  22. Hill J, Nelson E, Tilman D, Polasky S, Tiffany D (2006) Environmental, economic, and energetic costs and benefits of biodiesel and ethanol biofuels. Proc Natl Acad Sci U S A 103(30):11206–11210. doi: 10.1073/pnas.0604600103 CrossRefGoogle Scholar
  23. Humbird D, Davis R, Tao L, Kinchin C, Hsu D, Aden A, Schoen P, Lukas J, Olthof B, Worley M, Sexton D, Dudgeon D (2011) Process design and economics for biochemical conversion of lignocellulosic biomass to ethanol, vol NREL/TP-5100–47764. National Renewable Energy Laboratory, Golden, ColoradoGoogle Scholar
  24. Hung M-L, H-w M (2009) Quantifying system uncertainty of life cycle assessment based on Monte Carlo simulation. Int J Life Cycle Assess 14(1):19–27. doi: 10.1007/s11367-008-0034-8 Google Scholar
  25. Johnson DR, Willis HH, Curtright AE, Samaras C, Skone T (2011) Incorporating uncertainty analysis into life cycle estimates of greenhouse gas emissions from biomass production. Biomass Bioenerg 35(7):2619–2626. doi: 10.1016/j.biombioe.2011.02.046 CrossRefGoogle Scholar
  26. Kløverpris J, Baltzer K, Nielsen PH (2010) Life cycle inventory modelling of land use induced by crop consumption. Part 2: example of wheat consumption in Brazil, China, Denmark and the USA. Int J Life Cycle Assess 15(1):90–103Google Scholar
  27. Kløverpris J, Wenzel H, Nielsen PH (2008) Life cycle inventory modelling of land use induced by crop consumption. Part 1: conceptual analysis and methodological proposal. Int J Life Cycle Assess 13(1):13–21Google Scholar
  28. Kumar A, Sokhansanj S (2007) Switchgrass (Panicum vigratum, L.) delivery to a biorefinery using integrated biomass supply analysis and logistics (IBSAL) model. Bioresour Technol 98(5):1033–1044. doi: 10.1016/j.biortech.2006.04.027 CrossRefGoogle Scholar
  29. Kumar D, Murthy G (2012) Life cycle assessment of energy and GHG emissions during ethanol production from grass straws using various pretreatment processes. Int J Life Cycle Assess 17(4):388–401. doi: 10.1007/s11367-011-0376-5 Google Scholar
  30. Liang S, Xu M, Zhang T (2012) Unintended consequences of bioethanol feedstock choice in China. Bioresour Technol 125:312–317. doi: 10.1016/j.biortech.2012.08.097 CrossRefGoogle Scholar
  31. Liang S, Xu M, Zhang T (2013) Life cycle assessment of biodiesel production in China. Bioresour Technol 129:72–77. doi: 10.1016/j.biortech.2012.11.037 CrossRefGoogle Scholar
  32. Luk JM, Pourbafrani M, Saville BA, MacLean HL (2013) Ethanol or bioelectricity? Life cycle assessment of lignocellulosic bioenergy use in light-duty vehicles. Environ Sci Technol 47(18):10676–10684. doi: 10.1021/es4006459 Google Scholar
  33. MacLean HL, Spatari S (2009) The contribution of enzymes and process chemicals to the life cycle of ethanol. Environ Res Lett 4(1):014001. doi: 10.1088/1748-9326/4/1/014001 CrossRefGoogle Scholar
  34. Mann MK, Spath PL (1997) Life cycle assessment of a biomass gasification combined-cycle power system. National Renewable Energy Laboratory, Golden, ColoradoGoogle Scholar
  35. Mathews JA, Tan H (2009) Biofuels and indirect land use change effects: the debate continues. Biofuels Bioprod Biorefining 3(3):305–317. doi: 10.1002/bbb.147 CrossRefGoogle Scholar
  36. McKone TE, Nazaroff WW, Berck P, Auffhammer M, Lipman T, Torn MS, Masanet E, Lobscheid A, Santero N, Mishra U, Barrett A, Bomberg M, Fingerman K, Scown C, Strogen B, Horvath A (2011) Grand challenges for life-cycle assessment of biofuels. Environ Sci Technol 45(5):1751–1756. doi: 10.1021/es103579c CrossRefGoogle Scholar
  37. McLaughlin SB, Kszos LA (2005) Development of switchgrass (Panicum virgatum) as a bioenergy feedstock in the United States. Biomass Bioenerg 28(6):515–535. doi: 10.1016/j.biombioe.2004.05.006 CrossRefGoogle Scholar
  38. Mullins KA, Griffin WM, Matthews HS (2011) Policy implications of uncertainty in modeled life-cycle greenhouse gas emissions of biofuels. Environ Sci Technol 45(1):132–138. doi: 10.1021/es1024993 CrossRefGoogle Scholar
  39. Peterson D, Haase S (2009) Market assessment of biomass gasification and combustion technology for small- and medium-scale applications. National Renewable Energy Laboratory, Golden, ColoradoCrossRefGoogle Scholar
  40. Pike-Research (2010) Biomass markets and technologies. Pike Research, Boulder, ColoradoGoogle Scholar
  41. Plevin RJ, O’Hare M, Jones AD, Torn MS, Gibbs HK (2010) Greenhouse gas emissions from biofuels’ indirect land use change are uncertain but may be much greater than previously estimated. Environ Sci Technol 44(21):8015–8021. doi: 10.1021/es101946t CrossRefGoogle Scholar
  42. Reinhard J, Zah R (2011) Consequential life cycle assessment of the environmental impacts of an increased rapemethylester (RME) production in Switzerland. Biomass Bioenerg 35(6):2361–2373CrossRefGoogle Scholar
  43. Rowe R, Whitaker J, Freer-Smith PH, Chapman J, Ryder S, Ludley KE, Howard DC, Taylor G (2011) Counting the cost of carbon in bioenergy systems: sources of variation and hidden pitfalls when comparing life cycle assessments. Biofuels 2(6):693–707. doi: 10.4155/bfs.11.131 CrossRefGoogle Scholar
  44. Sanchez ST, Woods J, Akhurst M, Brander M, O’Hare M, Dawson TP, Edwards R, Liska AJ, Malpas R (2012) Accounting for indirect land-use change in the life cycle assessment of biofuel supply chains. J R Soc Interface 9(71):1105–1119. doi: 10.1098/rsif.2011.0769 CrossRefGoogle Scholar
  45. Searchinger T, Heimlich R, Houghton RA, Dong F, Elobeid A, Fabiosa J, Tokgoz S, Hayes D, Yu T-H (2008) Use of US croplands for biofuels increases greenhouse gases through emissions from land-use change. Science 319(5867):1238–1240CrossRefGoogle Scholar
  46. Stratton RW, Wong HM, Hileman JI (2011) Quantifying variability in life cycle greenhouse gas inventories of alternative middle distillate transportation fuels. Environ Sci Technol 45(10):4637–4644. doi: 10.1021/es102597f CrossRefGoogle Scholar
  47. Tonini D, Hamelin L, Wenzel H, Astrup T (2012) Bioenergy production from perennial energy crops: a consequential LCA of 12 bioenergy scenarios including land use changes. Environ Sci Technol 46(24):13521–13530CrossRefGoogle Scholar
  48. Uihlein A, Schebek L (2009) Environmental impacts of a lignocellulose feedstock biorefinery system: an assessment. Biomass Bioenerg 33(5):793–802. doi: 10.1016/j.biombioe.2008.12.001 CrossRefGoogle Scholar
  49. USEPA (2012) Renewable Fuel Standard (RFS). U.S. Environmental Protection Agency, WashingtonGoogle Scholar
  50. Vázquez-Rowe I, Rege S, Marvuglia A, Thénie J, Haurie A, Benetto E (2013) Application of three independent consequential LCA approaches to the agricultural sector in Luxembourg. Int J Life Cycle Assess 18(8):1593–1604Google Scholar
  51. West BH, López AJ, Theiss TJ, Graves RL, Storey JM, Lewis SA (2007) Fuel Economy and Emissions of the Ethanol-Optimized Saab 9–5 Biopower. SAE Technical PaperGoogle Scholar
  52. Whitaker J, Ludley KE, Rowe R, Taylor G, Howard DC (2010) Sources of variability in greenhouse gas and energy balances for biofuel production: a systematic review. GCB Bioenergy 2(3):99–112. doi: 10.1111/j.1757-1707.2010.01047.x Google Scholar
  53. Yang Y, Bae J, Kim J, Suh S (2012) Replacing gasoline with corn ethanol results in significant environmental problem-shifting. Environ Sci Technol 46(7):3671–3678. doi: 10.1021/es203641p CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Sonika Choudhary
    • 1
  • Sai Liang
    • 1
  • Hua Cai
    • 1
    • 2
  • Gregory A. Keoleian
    • 1
    • 2
  • Shelie A. Miller
    • 1
    • 2
  • Jarod Kelly
    • 1
  • Ming Xu
    • 1
    • 2
    Email author
  1. 1.School of Natural Resources and EnvironmentUniversity of MichiganAnn ArborUSA
  2. 2.Department of Civil and Environmental EngineeringUniversity of MichiganAnn ArborUSA

Personalised recommendations