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Development of Methodological Framework and its Application for Life Cycle Assessment of Renewable Fuels for Transportation
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- Author / Creator
- Mahbub, Nafisa
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There is scientific consensus on climate change and the adverse impacts of anthropogenic greenhouse gas (GHG) emissions. In order to reduce GHG emissions, all-encompassing transitions in energy, transportation, buildings, industrial systems, and land are required. The extraction, production, and combustion of fossil fuels used in transportation are responsible for GHG emissions. Blending liquid biofuels such as biodiesel with fossil fuels has the potential to reduce life cycle GHG emissions. There has been an increase in the production and use of renewable fuels, including new biofuel technologies such as oxymethylene ether (OME). However, a thorough quantitative assessment of the environmental, economic, and social implications of emerging biofuel technologies is crucial to understand both the short- and long-term consequences of their wide deployment. This can be achieved through life cycle assessment (LCA).
In this research, an environmental LCA model was developed to assess the environmental characteristics of OME production and combustion in vehicles as a diesel additive from two different types of woody biomass, such as whole tree and forest residue. The forest residue pathway was found to produce a lower environmental burden than the whole tree. The upstream GHG emissions from the forest residue pathway (18g CO2eq/MJ) were significantly lower than those of the whole tree pathway (27 g CO2eq/MJ) because the forest residue pathway did not consider emission-intensive road construction operation. The environmental LCA was broadened from its solely environmental scope to include the economic and social components by developing a life cycle sustainability assessment (LCSA) framework combining the three sustainability dimensions namely environmental, social, and economic aspects. A multicriteria decision model was integrated into the LCSA framework to compare and identify the most sustainable pathway. The forest residue pathway outranked the whole tree pathway based on eight different sustainability indicators, namely GHG emissions, soot emissions, water depletion, capital cost, operating cost, overall cost, employment potential, and employee wage and benefits. For OME-diesel blend scenarios, higher OME ratios were found less preferred than lower ones considering all three sustainability dimensions.
In this thesis, we proposed a framework to determine the coproduct credits and the net environmental impacts from using coproducts; this framework can be used for any biofuel coproduct. This thesis discussed the environmental significance of applying credits to bio-ethanol and biodiesel coproducts based on their potential applications as energy substitutes, animal feed, and fertilizer. The largest coproduct credits were found from using DDGs pellets for heating (as an alternative to coal firing) in the bioethanol pathway. The coproduct credits ranged from 13.43-67.14g CO2eq/MJ of ethanol based on the percentage of use. In the canola to biodiesel pathway, the highest coproduct credit was earned when the crude glycerine obtained from the biodiesel processing replaced synthetic glycerine. The coproduct credits ranged from 17.13-3.95 g CO2eq/MJ when crude glycerine was processed into synthetic glycerine depending on its percentage use.
Earlier proposed LCA methodologies and frameworks looked at the environmental, economic, and social consequences of emerging and existing biofuel developments from a short-term perspective; this approach fails to reflect the long-term sustainability impacts of an energy system. To assess credibility, market competitiveness, and financial and technological feasibility and to gain public and investor trust, a thorough quantitative environmental assessment of biomass energy technology is needed. This can be done through a consequential life cycle assessment (C-LCA). In this thesis, a thorough literature review of the C-LCA approach has been conducted, focusing on both the methodological aspects and the application areas for biofuels, along with their strengths and limitations. Key research gaps were identified and recommendations for further investigation were made. The thesis provides scientific contributions to decision makers and researchers working on biofuel technologies.
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- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.