LIFE-CYCLE ASSESSMENT OF A DISTRIBUTED-SCALE THERMOCHEMICAL BIOENERGY CONVERSION SYSTEM
Keywords:Thermochemical pyrolysis conversion, syngas, biochar, woody biomass, life–cycle inventory (LCI), life-cycle assessment (LCA)
Expanding bioenergy production from woody biomass has the potential to reduce net greenhouse gas (GHG) emissions and improve nation’s energy security. Science-based and internationally accepted life cycle assessment (LCA) is a tool essential for policy makers to decide on expanding renewable energy production from newly developed technologies. A distributed-scale high-temperature thermochemical conversion system, referred to as the Tucker renewable natural gas (RNG) unit was evaluated on producing medium-energy synthesis gas (syngas) and biochar along with its waste from harvested woody biomass. Mass and energy balances, cumulative energy demand (CED), and life cycle inventory (LCI) flows were found based on operational data from a 1-hr continuous run. Emission data summarized from the cradle-to-gate LCI showed biomass and fossil CO2 emissions of 159 g and 534 g, respectively, for each oven-dry kg of wood chips pyrolyzed. LCA, applied in accordance with ISO 14040:2006, was used to determine the potential environmental impacts. Total GHG is 0.595 kg CO2 eq/ OD kg of wood chips processed. Contributions to the total GHG contribution were 20.7% from upstream forest resource extraction and chip processing at sawmill and 77.6% from thermochemical conversion process with propane combustion. The remaining1.62% was from parasitic electricity operating the Tucker RNG unit. Quantifying Global Warming Potential (GWP) showed the carbon benefits (eg low GHG emissions) along with the carbon “hotspots” from burning propane to maintain the endothermic reaction in the Tucker RNG unit. Using low-energy syngas generated from what was originally a waste in the pyrolysis reaction to augment propane combustion would reduce GHG emissions (ie fossil CO2) by about 30.4%.
Bare J (2011) TRACI 2.0: the tool for the reduction and assessment of chemical and other environmental impacts 2.0. Clean Technologies and Environmental Policy, 13(5): 687-696.
Bergman RD, Gu H (2014) Life-cycle inventory analysis of bio-products from a modular advanced biomass pyrolysis system. In: Proceedings, Society of Wood Science and Technology 57th International Convention. June 23-27, 2014. Zvolen, Slovakia: 405–415.
Cherubini F, Stromman AH (2011) Life cycle assessment of bioenergy systems: State of the art and future challenges. Bioresource Technology 102(2):437–451.
CORRIM (2010) Research guidelines for life-cycle inventories. Consortium for Research on Renewable Industrial Materials. University of Washington, Seattle. 40 p.
EISA (2007) Legal Reference—Energy Independence and Security Act of 2007. GPO (Government Printing Office). Gaunt J Lehmann J (2008) Energy balance and emissions associated with biochar sequestration and pyrolysis bioenergy production. College of Agriculture and Life Sciences, Cornell University. Environmental Science & Technology 42: 4152–4158.
Field JL, Keske CMH, Birch GL, Defoort MW, and Cotrufo MF (2013) Distributed biochar and bioenergy coproduction: a regionally specific case study of environmental benefits and economic impacts. Global Change Biology Bioenergy (2013) 5, 177-191. Doi:10.1111/gcbb.12032.
Hertwich EG, Gibon T, Bouman EA, Arvesen A, Suh S, Heath GA, Bergesen JD, Ramirez A, Vega MI, and Shi L (2013) Integraed life-cycle assessment of electricity-supply scenarios confirms global environmental benefit of low-carbon technologies. PNAS special feature. http://www.pnas.org/cgi/doi/10.1073/pnas.1312753111. pp.6. (28 April 2015)
IPCC (2007) The physical scientific basis. Contribution of working group to the fourth assessment report of the intergovernmental panel on climate change, edited by S. Solomon et al, Cambridge Univ. Press, New York.
ISO (2006a) Environmental management—life-cycle assessment—principles and framework. ISO 14040. International Organization for Standardization, Geneva, Switzerland. 20 pp.
ISO (2006b) Environmental management—life-cycle assessment—requirements and guidelines. ISO 14044. International Organization for Standardization, Geneva, Switzerland. 46 pp.
Jungbluth N, Bunsser S, Frischknecht R, Tuchschmid M (2008) Life cycle assessment of biomass-to-liquid fuels, Final report. Berne, Feb.21, 2008.
Pachauri RK, Allen MR, Barros VR, et al (2014) Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). R Pachauri and L Meyer (editors). Geneva, Switzerland. 151 pp ISBN 978-92-9169-143-2.
Perlack PD, Wright LL, Turhollow AF, Graham RL, Stokes RJ, Erbach DC (2005) Biomass as feedstock for a bioenergy and bioproducts industry: The technical feasibility of a billion-ton: Annual supply. April 2005. A joint study sponsored by U.S. Department of Energy and the U.S. Department of Agriculture. http://www1.eere.energy.gov/bioenergy/pdfs/final_billionton_vision_report2.pdf (28 April 2015)
Pierobon F, Ganguly G, Anfodillo T, Eastin IL (2014) Evaluation of environmental impacts of harvest residue-based bioenergy using radiative forcing analysis. The Forestry Chronicle 90(5):577-585.
PRé Consultants (2015) Life-Cycle assessment software package SimaPro 8 Update Instructions. Stationsplein 121, 3818 LE Amersfoort, The Netherlands. http://www.pre-sustainability.com/ (28 April 2015).
Roberts KG, Gloy BA, Joseph S, Scott NR, and Lehmann J. (2010) Life Cycle Assessment of Biochar Systems: Estimating the Energetic, Economic, and Climate Change Potential. Environ. Sci. Technol. 44: 827-833.
Schnepf R, Yacobucci BD (2013) Renewable fuel standard: overview and issues. Congressional Research Service Report for Congress no. 7-5700 https://www.fas.org/sgp/crs/misc/R40155.pdf (28 April 2015).
Sebastian F, Royo J, Gomez M (2011) Co-firing versus biomass-fired power plants: GHG (Greenhouse Gases) emissions savings comparison by means of LCA (Life Cycle Assessment) methodology. Energy 36: 2029-2037.
Sohi SP, Krull E, Lopez-Capel E, Bol R (2010) Chapter 2 – A review of biochar and its use and function in soil. Advances in Agronomy 105:47–82.
Stephenson A, and MacKay DJC (2014) Life cycle impacts of biomass electricity in 2020. ©Crown copyright. Department of Energy & Climate Change, 3 Whitehall Place, London SW1A 2AW. http://www.gov.uk/decc
Steubing B, Zah R, Ludwig C (2011) Life cycle assessment of SNG from wood for heating, electricity, and transportation. Biomass Bioenerg 35(7):2950–2960.
Turconi R, Boldrin A, Astrup T (2013) Life cycle assessment of electricity generation technologies: Overview, comparability and limitations. Renewable and Sustainable Energy Reviews 28: 555–565.
USEIA (2015) Annual Energy Outlook 2015 with projections to 2040: Figure 31. Electricity generation by fuel in the Reference case, 2000-2040 (trillion kilowatthours). United States Energy Information Administration. 154 pp. http://www.eia.gov/forecasts/aeo/pdf/0383(2015).pdf (19 August 2015)
Wang Z, Dunn JB, Han J, Wang MQ (2014) Effects of co-produced biochar on life cycle greenhouse gas emissions of pyrolysis-derived renewable fuels. Biofuels and Bioprod Bioref. 8:189–204.
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.