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Background, Aim and Scope:
A well-to-wheel analysis has been conducted for cassava-based ethanol (CE) in Thailand. The aim of the analysis is to assess the potentials of CE in the form of gasohol E10 for promoting energy security and reducing environmental impacts in comparison with conventional gasoline (CG).
Materials and Methods:
In the LCA procedure, three separate but interrelated components: inventory analysis, characterization and interpretation were performed for the complete chain of the fuel life cycle. To compare gasohol E10 and CG, this study addressed their impact potentials per gasoline-equivalent litre, taking into account the performance difference between gasohol and gasoline in an explosion motor.
Results:
The results obtained show that CE in the form of E10, along its whole life cycle, reduces certain environmental loads compared to CG. The percentage reductions relative to CG are 6.1% for fossil energy use, 6.0% for global warming potential, 6.8% for acidification, and 12.2% for nutrient enrichment. Using biomass in place of fossil fuels for process energy in the manufacture of ethanol leads to improved overall life cycle energy and environmental performance of ethanol blends relative to CG.
Discussion:
There are clear advantages of using cassava-based ethanol in the form of either E85 or E10 as a transportation fuel over gasoline in terms of reductions in fossil energy use, petroleum use and global warming potential. The reductions mainly result from the absence of fossil-based liquid fuel and consequently fossil-based CO2 emissions in the combustion of ethanol portion in blends. It is reasonable that the magnitude of the reductions is proportional to the percentage of ethanol mixed with CG. Using E85 is even more advantageous than E10 considering “% change” in total gross energy use and net energy use relative to gasoline.
The life cycle fuel environmental impacts are contributed by upstream (feedstock production, fuel conversion) stages as well as use stage. For low-level ethanol blend (E10), major impacts are governed by end use stage. As ethanol content in blend increases to 85%, the impacts are dominated by the upstream of ethanol fuel life cycle.
Conclusions:
Ethanol fuel used in the form of blends in gasoline can help reduce fossil energy use and GHG emissions. Using E10 substitution for conventional gasoline also results in less acidification and nutrient enrichment. It may, however, lead to increased photochemical smog formation. Substitution of biomass-based for fossil-based energy to generate process steam in ethanol conversion process helps to improve overall ethanol life cycle environmental performance.
Recommendations and
Perspectives:
The LCA brings to light the key areas in the ethanol production cycle that researchers, technicians need to work on to improve ethanol’s performance while minimizing its adverse impacts.
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