POLCAGE 1.0—a possibilistic life-cycle assessment model for evaluating alternative transportation fuels
Introduction
Automotive transport is a major contributor to local and global air pollution as well as fossil fuel resource depletion. In the Philippines, for example, road vehicles accounted for 13% of the country’s primary energy consumption in the late 1990s, as well as a proportionate share of the estimated 63×106 ton per annum national CO2 emission inventory (World Resources Institute, 2000). Urban air pollution has been recently cited as a major obstacle to the Philippines’ development (The World Bank, 1999). A number of measures have been taken by the government, particularly the ratification of the Clean Air Act in the late 1990s. (Philippine Department of Environment and Natural Resources, 2000).
Alternative propulsion systems are considered to be the most promising long-term solution to the environmental impacts resulting from road vehicle use (Poulton, 1994). In the Philippines, there is considerable interest in developing commercial petroleum alternatives such as natural gas or biodiesel (Philippine Department of Energy, 2000). However, efforts have largely been disorganized, in part due to the lack of an effective means of screening alternative technologies. Since the social and economic impacts of a large-scale technological transition in the automotive transport sector are considerable, it is essential that the alternative fuels or vehicle systems selected will deliver the environmental benefits anticipated. A decision support system (DSS) can help make the assessment process more rational, consistent and reliable (Huang et al., 1995). In this study, a software-based DSS using life-cycle modeling concepts was developed to aid in determining the best environmental option (BEO) from a list of alternative technologies.
Section snippets
Life-cycle assessment
Life-cycle assessment (LCA) is a holistic procedure for estimating environmental impacts of a technological system on a cradle-to-grave basis. In the past decade, LCA has become accepted as an effective tool for environmental management, particularly in the context of decision support. International standardization efforts were started by the Society of Environmental Toxicology and Chemistry (SETAC, 1991); more recently, the International Organization for Standardization developed the ISO 14040
Alternative fuel cycles simulated in POLCAGE 1.0
POLCAGE 1.0 focuses on the life cycles of eight alternative fuels and energy carriers:
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Electricity for use in electric vehicles (EVs).
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Liquid (LH2) and gaseous or compressed hydrogen (GH2) produced by water electrolysis, for use in fuel cell vehicles (FCVs).
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Bioethanol (BioEtOH) derived from cellulosic agricultural residue, for use as a neat (pure) fuel in vehicles with spark-ignition (SI) engines.
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Biodiesel (BD) derived from coconut oil, for use in vehicles with compression-ignition (CI) engines.
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The GREET fuel-cycle inventory submodel
The GREET model was developed by the Argonne National Laboratory in the mid-1990s for the United States Department of Energy (Wang, 1996). This public-domain model can be downloaded from the Argonne website (http://www.transportation.anl.gov). GREET version 1.5a (Wang, 1999) was used as the inventory submodel of POLCAGE. It is coded in Microsoft Excel and Visual Basic, and its modular structure allows users to create new fuel pathways or modify existing ones. The most recent version of this
Operational features of POLCAGE 1.0
The POLCAGE 1.0 prototype is coded in Microsoft Excel and Visual Basic. It consists of the GREET 1.5a spreadsheet model with additional sheets and modules, as well as new fuel cycles. Fig. 4 shows the user’s view of the POLCAGE screen. Only eight sheets are immediately visible when the model is opened: the copyright sheet of the original GREET model, the inventory plots sheet containing crisp (non-fuzzy) inventory displays, and six sheets that comprise the new computational and display
Case study: comparison of alternative fuels for Philippine automotive transport
Since the model is intended to provide decision support for policy makers trying to identify clean transportation fuels, the following case study is provided to illustrate how exactly the model assists the human user. Simulation assumptions used are based on the best available Philippine data.
Conclusion
The composite software tool POLCAGE 1.0 was developed to provide users with a decision support model capable ranking alternative motor vehicle fuels using comprehensive LCA. In contrast, the GREET model, which is used as a subcomponent of POLCAGE, by itself is capable only of inventory analysis and calculation of total greenhouse gases. The enhanced model incorporates impact classification and aggregation using the EDIP method. Methodological weaknesses of conventional LCA models were addressed
Acknowledgements
The authors wish to acknowledge the financial support of De La Salle University—Manila, through the Faculty Development Program, and The British Council. We are also grateful to Dr. Stanley Santos for his assistance in miscellaneous aspects of our work.
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