LCA of a biorefinery concept producing bioethanol, bioenergy, and chemicals from switchgrass
- 2.7k Downloads
Background, aim, and scope
The availability of fossil resources is predicted to decrease in the near future: they are a non-renewable source, they cause environmental concerns, and they are subjected to price instability. Utilization of biomass as raw material in a biorefinery is a promising alternative to fossil resources for production of energy carriers and chemicals, as well as for mitigating climate change and enhancing energy security. This paper focuses on a biorefinery concept which produces bioethanol, bioenergy, and biochemicals from switchgrass, a lignocellulosic crop. Results are compared with a fossil reference system producing the same products/services from fossil sources.
Materials and methods
The biorefinery system is investigated using a Life Cycle Assessment approach, which takes into account all the input and output flows occurring along the production chain. This paper elaborates on methodological key issues like land use change effects and soil N2O emissions, whose influence on final outcomes is weighted in a sensitivity analysis. Since climate change mitigation and energy security are the two most important driving forces for biorefinery development, the assessment has a focus on greenhouse gas (GHG) emissions and cumulative primary energy demand (distinguished into fossil and renewable), but other environmental impact categories (e.g., abiotic depletion, eutrophication, etc.) are assessed as well.
The use of switchgrass in a biorefinery offsets GHG emissions and reduces fossil energy demand: GHG emissions are decreased by 79% and about 80% of non-renewable energy is saved. Soil C sequestration is responsible for a large GHG benefit (65 kt CO2-eq/a, for the first 20 years), while switchgrass production is the most important contributor to total GHG emissions of the system. If compared with the fossil reference system, the biorefinery system releases more N2O emissions, while both CO2 and CH4 emissions are reduced. The investigation of the other impact categories revealed that the biorefinery has higher impacts in two categories: acidification and eutrophication.
Results are mainly affected by raw material (i.e., switchgrass) production and land use change effects. Steps which mainly influence the production of switchgrass are soil N2O emissions, manufacture of fertilizers (especially those nitrogen-based), processing (i.e., pelletizing and drying), and transport. Even if the biorefinery chain has higher primary energy demand than the fossil reference system, it is mainly based on renewable energy (i.e., the energy content of the feedstock): the provision of biomass with sustainable practices is then a crucial point to ensure a renewable energy supply to biorefineries.
This biorefinery system is an effective option for mitigating climate change, reducing dependence on imported fossil fuels, and enhancing cleaner production chains based on local and renewable resources. However, this assessment evidences that determination of the real GHG and energy balance (and all other environmental impacts in general) is complex, and a certain degree of uncertainty is always present in final results. Ranges in final results can be even more widened by applying different combinations of biomass feedstocks, conversion routes, fuels, end-use applications, and methodological assumptions.
Recommendations and perspectives
This study demonstrated that the perennial grass switchgrass enhances carbon sequestration in soils if established on set-aside land, thus, considerably increasing the GHG savings of the system for the first 20 years after crop establishment. Given constraints in land resources and competition with food, feed, and fiber production, high biomass yields are extremely important in achieving high GHG emission savings, although use of chemical fertilizers to enhance plant growth can reduce the savings. Some strategies, aiming at simultaneously maintaining crop yield and reduce N fertilization application through alternative management, can be adopted. However, even if a reduction in GHG emissions is achieved, it should not be disregarded that additional environmental impacts (like acidification and eutrophication) may be caused. This aspect cannot be ignored by policy makers, even if they have climate change mitigation objectives as main goal.
KeywordsBiorefinery Bioenergy Biochemicals Switchgrass
- Bullard M, Metcalfe P (2001) Estimating the energy requirements and CO2 emissions from production of the perennial grasses miscanthus, switchgrass and reed canary grass. ETSU Report Number B/U1/00645/REP. DTI/Pub URN 01/797, Contractor ADAS Consulting LtdGoogle Scholar
- CAST—Council for Agricultural Science and Technology (2004) Climate change and greenhouse gas mitigation: challenges and opportunities for agriculture. CAST, Ames, IA, p 120Google Scholar
- Cherubini F, Ulgiati S (2009) Crop residues as raw materials for biorefinery systems - A LCA case study. Appl Energy 53(8):434–447Google Scholar
- Cherubini F, Jungmeier G, Mandl M, Philips C, Wellisch M, Jørgensen H, Skiadas I, Boniface L, Dohy M, Pouet JC, Willke T, Walsh P, van Ree R, de Jong E (2009b) IEA Bioenergy Task 42: Report on Participating Countries. Document of IEA Bioenergy Task 42 ‘Biorefineries’, www.biorefinery.nl/ieabioenergy-task42/
- Cherubini F, Jungmeier G, Wellisch M, Willke T, Skiadas I, van Ree R, de Jong E (2009c) Towards a classification approach for biorefinery systems. Biofuels, Bioproducts and Biorefining 3(5):534–546Google Scholar
- Crutzen PJ, Mosier AR, Smith KA, Winiwarter W (2007) N2O release from agro-biofuel production negates global warming reduction by replacing fossil fuels. Atmos Chem Phys Discuss 7:11191–11205Google Scholar
- De Feber MAPC, Gielen DJ (2000) Biomass for greenhouse gas emission reduction, Task 7: Energy Technology Characterization. ECN-C-99-078Google Scholar
- Delucchi MA, Lipman T (2003) A Lifecycle Emissions Model (LEM): lifecycle emissions from transportation fuels, motor vehicles, transportation modes, electricity use, heating and cooking fuels, and materials. Appendix C: emissions related to cultivation and fertilizer use. Institute of Transportation Studies, University of California, Davis, CA, USAGoogle Scholar
- Downing M, Walsh M, McLaughlin S (1995) Perennial grasses for energy and conservation: evaluating some ecological, agriculture and economic issues. Environmental Enhancement Through Agriculture, Conference Proceedings, Boston MassacusettsGoogle Scholar
- EERE (2009) Biomass Feedstock Composition and Property Database (biomass sample type: Switchgrass Alamo Whole Plant #94). Biomass Program, U.S. Department of Energy, Energy Efficiency and Renewable Energy, http://www1.eere.energy.gov/biomass/feedstock_databases.html (Accessed 07 June 2009)
- Elsayed MA, Matthews R, Mortimer ND (2003) Carbon and energy balances for a range of biofuels options. Sheffield Hallam University/Resources Research Unit, Sheffield UKGoogle Scholar
- EU (2006) Biofuels in the European Union—a vision for 2030 and beyond. Final report of the Biofuels Research Advisory Council, June 2006Google Scholar
- Franck AB, Berdahl JD, Hanson JD, Liebig MA, Johnson HA (2004) Biomass and carbon partitioning in switchgrass. Crop Sci 44:1391–1396Google Scholar
- Gebhart DL, Johnson HB, Mayeux HS, Polley HW (1994) The CRP increases soil organic carbon. J Soil Water Conserv 49:488–492Google Scholar
- Gemis (2009) Global Emission Model for Integrated Systems, Version 4.5. Data set on bioenergy for heat, electricity and transportation biofuel systems, Joanneum Research, Graz, Austria 2008. LCA software tool website: http://www.oeko.de/service/gemis/en/index.htm
- Heijungs R et al (1992) Environmental life cycle assessment of products, Guide. October 1992 CML. Leiden, The Netherlands NOH report 9266Google Scholar
- IEA (2008) IEA (International Energy Agency) Bioenergy Task 42 on Biorefineries. Minutes of the third Task meeting, Copenhagen, Denmark, 25 and 26 March 2008 (www.biorefinery.nl\IEABioenergy-Task42)
- IPCC (2006) Guidelines for national greenhouse gas inventories. Volume 4: Agriculture, forestry and other land useGoogle Scholar
- IPCC (2007) Climate change 2007: the physical science basis. Contribution of working group 1 to the fourth assessment report of the Intergovernmental Panel on Climate Change. In: Solomon S, Qin D, Manning M, Chen Z, Marquis M, Averyt KB, Tignor M, Miller HL (eds), Cambridge: Cambridge University PressGoogle Scholar
- Jungmeier G, Lingitz A, Spitzer J, Hofbauer H and Fürnsinn S (2007) Wood to biofuels: feasibility study for a biofuel plant in the Austrian province of Styria. Proceedings of the 15th European Biomass Conference and Exhibition—From Research to Market Deployment, Berlin, 7–11 May 2007Google Scholar
- Lal R, Kimble LM, Follet RF, Cole CV (1998) The potential of U.S. cropland to sequester carbon and mitigate the greenhouse effect. Ann Arbor Press, Chelsea, MIGoogle Scholar
- Larson E (2005) A review of LCA studies on liquid biofuels for the transport sector. Scientific and Technical Advisory Panel of the Global Environment Facility (STAP) workshop on Liquid Biofuels, 29 August to 1 September 2005. New Delhi, IndiaGoogle Scholar
- Meister JJ (2002) Modification of lignin. J Macromol Sci-Pol R 42(2):235–289Google Scholar
- North Energy (2008) Report to AEA for the RFA review of indirect effects of biofuels. Published on RFA website www.renewablefuelsagency.org, Renewable Fuels Agency
- Paustian K, Antle JM, Sheehan J, Paul EA (2006) Agriculture's role in greenhouse gas mitigation. Pew Center on Global Climate Change, Arlington (VA) Canada, September 2006Google Scholar
- Prather M, Ehhalt D et al (2001) Atmospheric chemistry and greenhouse gases. In: Houghton JT, Ding Y, Griggs DJ et al (eds) Climate change 2001. The Scientific Basis, Cambridge University Press, Cambridge UK, pp 239–287Google Scholar
- Punter G, Rickeard D, Larivé JF, Edwards R, Mortimer N, Horne R, Bauen A, Woods J (2004) Well-to-wheel evaluation for production of ethanol from wheat. A report by the LowCVP fuels working group, WTW sub-group, FWG-P-04-024, October 2004Google Scholar
- RFA—Renewable Fuels Agency (2008) The Gallagher Review of the indirect effects of biofuels production. Published on RFA website (July, 2008): www.dft.gov.uk/rfa/_db/_documents/Report_of_the_Gallagher_review.pdf
- Scholze B (2002) Long-term stability, catalytic upgrading, and application of pyrolysis Ioils—improving the properties of a potential substitute for fossil fuels. Hamburg University, PhD DissertationGoogle Scholar
- Suh YJ, Rousseaux P (2001) Considerations in Life Cycle Inventory analysis of municipal wastewater treatment systems. Oral presentation at COST 624 WG Meeting, Bologna, Italy. http://www.ensic.inpl-nancy.fr/COSTWWTP/
- Zah R, Boni H, Gauch M, Hischier R, Lehmann M, Wager P (2007) Life Cycle Assessment of energy products: Environmental assessment of biofuels. Final Report, EMPA—Technology and society Lab, Auftrag des Bundesamtes für Energie, des Bundesamtes für Umwelt und des Bundesamtes für Landwirtschaft, Bern, 2007Google Scholar