A decision support tool for modifications in crop cultivation method based on life cycle assessment: a case study on greenhouse gas emission reduction in Taiwanese sugarcane cultivation
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Background, aim, and scope
Nowadays, various crops are cultivated to supply emerging needs in sustainable fuels and materials. In addition to the development of crop processing technologies, cultivation processes in a cropping system could be modified to meet the emerging needs, along with the conventional needs in food supply. This study provides a decision tool for modifications in cultivation of crops based on life cycle assessment. Sugarcane cultivation in Taiwan is chosen as a case study to present such a decision tool, because it is an important potential indigenous resource for energy (for example, bio-ethanol) and materials (for example, bio-plastics). First, this study presents the amount of greenhouse gas (GHG) emissions associated with the production of 1 ton of sugarcane in Taiwan, which makes it possible to understand how it is consistent to develop this bio-resource in terms of both objectives: i.e., resource security and reduction of global warming impact. Next, sensitivity of the parameters in cropping systems, such as amount of irrigation, fertilization and tillage are assessed from a viewpoint of GHG emissions, using the LCI model constructed in the first step. Finally, equivalent impact level (EIL) lines are presented for some important parameters in the cropping system to support considerations in modification of agricultural methods. Because the objective is to discuss parameters in cultivation processes, the scope of study is limited to cradle-to-gate of raw sugarcane transported to the cane processing plant.
Materials and methods
In addition to GHG emissions from cultivation processes, such as soil preparation, growing, harvesting and transportation, auxiliary processes such as agrochemicals production, power generation and fossil diesel fuel refining was accounted for. To quantify the nitrous oxide emission from the soil ecosystem, a denitrification-decomposition (DNDC) model was used with the localized data obtained in this study. EIL lines were developed aiming at supporting decisions about modifying agricultural methods that should be made considering consequential changes in environmental impacts. For example, if the envisioned improvement in yield as a result of modification of parameters such as irrigation, tillage and fertilization is likely to achieve a value above the EIL line, GHG emission per ton of sugarcane would be decreased. An iterative procedure is applied to draw nonlinear EIL lines using Intergovernmental Panel on Climate Change (IPCC) Tier 3 method for nitrous oxide emission from soil.
A 3 year crop cycle was assumed, and the net GHG emissions associated with the sugarcane produced was -280 kg-CO2-equiv. per ton of raw sugarcane. The emission of nitrous oxide from soil during cultivation accounted for 50.4% of the total emissions. One-at-a-time sensitivity analysis indicates that this result is most sensitive to yield and amount of nitrogen fertilizer applied, which are correlated to each other. The EIL lines were drawn for yield over five parameters in cultivation including amount of nitrogen fertilizer applied with respect to GHG emission. For example, if an additional 5% of nitrogen fertilizer application realizes enhancement of yield by 5 tons per hectare, such modification simultaneously reduces total GHGs associated with sugarcane production.
The EIL lines drawn with respect to various environmental impacts aims to provide a simple-to-use guidance in reconsideration of agricultural options. The cradle-to-gate LCA of sugarcane provides information useful in development of bioethanol and bioplastics derived from sucrose in the cane juice. In doing so, it must be noted, if extension of farm area is among the options to be assessed, that release of the carbon stock from the original state of use should be accounted for in addition to the result presented in this study. Absorbed CO2 should be quantified separately based on the content of the sugarcane, which could be varied for different cultivars.
This study presents a decision tool to allow introduction of an environmental life cycle perspective in modification of cultivation methods, which has already been undergoing as driven by economic reasons. The data and inventory method presented in this study can be applied for varied end products derived from sugarcane. The algorithm to develop an EIL line for correlated parameters in the inventory model was presented.
Recommendations and perspectives
Results from this study require appropriate modification if they are to be used for studies for other regions. Such modifications would be straightforward, because all inventory data and assumptions are presented in this paper. Essentially, the functional unit used in this study is unit amount (by weight) of sugarcane. If some specific content (for example, sucrose or cellulose) is important in a study which attempts to use results from this study, variations in the content over cultivation methods and cultivar of sugarcane must be investigated further.
KeywordsCarbon dioxide Denitrification-decomposition model (DNDC model) Equivalent impact level line (EIL line) Fertilization Greenhouse gases Intergovernmental Panel on Climate Change (IPCC) Irrigation Nitrous oxide Sensitivity analysis Sugarcane Tier 3 method
equivalent impact level
alternative fuel for gasoline fuelled car, 97% gasoline, 3% anhydrous ethanol, by volume
alternative fuel for gasoline fuelled car, 90% gasoline, 10% anhydrous ethanol, by volume
global warming potential
intergovernmental panel on climate change
life cycle assessment
life cycle inventory
atmospheric CO2 absorbed by sugarcane, kg
carbon content in the stem of sugarcane, kg
direct emissions of CO2, CH4 and N2O from soil in the cropping cycles, kg
direct emissions of CO2, CH4 and N2O from fossil fuel combustion, kg
emission from soil under the fallow land conditions, kg
emission from soil under the sugarcane farm conditions, kg
GHG emissions in cradle-to-gate life cycle of chemicals and fossil diesel, kg-CO2-equiv.
GHG emissions derived directly from power generation, kg-CO2-equiv.
- EFfossil diesel
emission factor of fossil diesel, kg/TJ
GHG emission factor of electricity in Taiwan, kg-CO2-equiv./kWh
GHG emission inventory of chemicals and fossil diesel, kg-CO2-equiv./kg or kL
- Qfossil diesel
the quantity of fossil diesel consumed, TJ
the quantity of chemicals and fossil diesel used, kWh
the quantity of electricity generated, kWh
The study was supported in part by a Grant-in-Aid for Young Investigators (C034) from National Cheng Kung University. Preliminary results were presented at the 3rd annual meeting of the Institute of Life Cycle Assessment, Japan, in March 2008. Useful comments from participants in the conference, Mr. Satoshi Ohara of Asahi Breweries and the farmers of Shanhua work place of Taiwan Sugar Corporation are deeply appreciated.
- Agriculture and Food Agency, Council of Agriculture, Executive Yuan, Taiwan, 2006. Available from: <http://www.afa.gov.tw/index.asp, in Chinese, accessed on April 17, 2009>.
- Bureau of Energy, Ministry of Economic Affairs, Taiwan (2005) Conclusion of national energy conference (Quan-guo neng-yuan hui-yi). Available from: <http://www.moeaboe.gov.tw, in Chinese, accessed on April 17, 2009>.
- Bureau of Energy, Ministry of Economic Affairs, Taiwan (2006) Available from: <http://www.moeaboe.gov.tw/, in Chinese, accessed on April 17, 2009>.
- Bureau of Energy, Ministry of Economic Affairs, Taiwan (2007) Available from: <http://www.moeaboe.gov.tw, in Chinese, accessed on April 17, 2009>.
- Central Weather Bureau (2005–2007) Weather statistics. Central Weather Bureau, Ministry of Transportation and Communications, Executive Yuan, TaiwanGoogle Scholar
- Chinese Fertilizer Association (2005) Crop fertilization handbook (Tzuo-wu shih-fei shou-ce). Agriculture and Food Agency, Council of Agriculture, Executive Yuan, Taiwan, pp 36–39 in ChineseGoogle Scholar
- Chung Chuan Machinery Co., Ltd. Available from: <http://www.cnc-pump.com.tw/index.htm, in Chinese, accessed on April 17, 2009>.
- Canadian Industry Program for Energy Conservation (CIPEC) (2003) 2001/2002 Annual Report. Sector Reports on Fertilizer. Available from: <http://oee.nrcan.gc.ca/publications/infosource/pub/cipec/AnnualReport01_02/CIPEC_e_01-02AnnualReport.cfm?attr=24#fertilizer, accessed on April 17, 2009>.
- Common Wealth Magazine (2007) Lay, J.G.’s simulation by geographic information system (GIS). Common Wealth Magazine 369, p. 100 <in Chinese>.Google Scholar
- Department of Soil and Environmental Sciences (1969) Soils of Tainan. National Chung Hsing University, Taiwan in ChineseGoogle Scholar
- Eggelston S, Buendia L, Miwa K, Ngara T, Tanabe K (2006) 2006 IPCC guidelines for national greenhouse gas inventories. Institute for Global Environmental Strategies (IGES) for the Intergovernmental Panel on Climate Change (IPCC). Available from: <http://www.ipcc-nggip.iges.or.jp/public/2006gl/index.htm, accessed on April 17, 2009>.
- Global Emmission Model for Integrated Systems (GEMIS) Version 4.4. Available from: <http://www.oeko.de/service/gemis/, accessed on April 17, 2009>.
- Institute for the Study of Earth (2007) User’s guide for the DNDC model. Institute for the Study of Earth, Ocean and Space, University of New Hampshire. Available from: <http://www.dndc.sr.unh.edu/index.html, accessed on April 17, 2009>.
- Institut für angewandte Ökologie (Öko-Institut (OEKO), Institute for Applied Ecology), scientific partners FhI-UMSICHT, IE Leipzig, IFEU Heidelberg, IZES Saarbrücken and TU München (2004) Material flow analysis of sustainable biomass use for energy. Available from: <http://www.oeko.de/service/bio/, accessed on April 17, 2009>.
- Institut für Energie- und Umweltforschung (2002) (IEFU, Institute for Energy and Environmental Research) eigene berechnungen und abschätzungen, Heidelberg <in German>.Google Scholar
- Interview (2007) Personal communication at Shanhua Works, Taiwan Sugar Corporation.Google Scholar
- Kaltschmitt M, Reinhardt GA (1997) Nachwachsende Energieträger - Grundlagen, Verfahren, Ökologische Bilanzierung. Vieweg, Braunschweig, Wiesbaden <in German>.Google Scholar
- New York Times (2008) A New, Global Oil Quandary: Costly Fuel Means Costly Calories. January 19, 2008Google Scholar
- Patyk A, Reinhardt GA (1997) Düngemittel- Energie- und Stoffstrombilanzen Vieweg, Braunschweig, Wiesbaden. Institut für Energie- und Umweltforschung (IEFU, Institute for Energy and Environmental Research) <in German>Google Scholar
- Searchinger T, Heimlich R, Houghton RA, Dong F, Elobeid A, Fabiosa J, Tokgoz S, Hayes D, Yu TH (2008). Use of U.S. croplands for biofuels increases greenhouse gases through emissions from land-use change. Science 319Google Scholar
- Sheehan J, Camobreco V, Duffield J, Graboski M, Shapouri H (1998). Life cycle inventory of biodiesel and petroleum diesel for use in an urban bus. National Renewable Energy Laboratory (NREL), Colorado State University.Google Scholar
- Taiwan Sugar Corporation (1979) Sugar handbook (Tang-ye shou-ce). Taiwan Sugar Corporation <in Chinese>.Google Scholar
- Taiwan Sugar Research Institute (2009). Summarized history of Taiwanese sugar industry. Taiwan Sugar Corporation. Available from: <http://www.sugarnet.com.tw/, in Chinese, accessed on April 17, 2009>.
- Tokyo Electric Power Company (TEPCO) (2009) Sustainability Report 2008. pp. 38, Available from <http://www.tepco.co.jp/en/challenge/environ/report-e.html, accessed on April 17, 2009>
- United Nations Environment Programme (UNEP) (2007) The fourth global environment outlook: environment for development (GEO-4). Available from: <http://www.unep.org/geo/geo4/media/, accessed on April 17, 2009>.
- Wang GR (2005) Sugarcane, in: Taiwan agriculture encyclopedia- 3 rd edition (Taiwan nong-jia yao-lan- zeng-siou-ding san-ban). Council of Agriculture, Executive Yuan, Taiwan. pp. 171-180 <in Chinese>.Google Scholar
- Water Resources Agency, Ministry of Economic Affairs, Taiwan (2003–2005) Taiwan agricultural water statistics (Taiwan di-qu nong-ye yon-shui ton-ji bao-gao) <in Chinese>.Google Scholar
- Working Group I, IPCC (2007) The physical science basis, IPCC fourth assessment report: climate change 2007. Intergovernmental Panel on Climate Change (IPCC). Available from: <http://www.ipcc.ch/ipccreports/ar4-wg1.htm, accessed on April 17, 2009>.
- Zeng FS, Wu ST (1996). Agronomy (Non-yi). San Min Book Co., Ltd. pp. 635-655 <in Chinese>.Google Scholar