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Parallel production of biodiesel and bioethanol in palm-oil-based biorefineries: life cycle assessment on the energy and greenhouse gases emissions



The main objective of this life cycle assessment (LCA) study is to determine the environmental consequences of the inclusion of second-generation biofuels (bioethanol from palm oil biomass) toward current palm oil biodiesel production through a ‘seed-to-wheel’ LCA analysis. Their energy and greenhouse gas (GHG) emission indicators are evaluated with consequential approach for system delimitation. Although all scenarios provide positive environmental impact, it is found that the inclusion of bioethanol production in the current palm oil processing will decrease the net energy ratio (NER) and net carbon emission ratio (NCER) values by 27.5% and 66.6%, respectively. Moreover, carbon emission savings (CES) value is also found to decrease by a total of 21.9%. This indicates that a higher amount of energy input and GHG emissions is actually required for the bioethanol processing than the amount of energy it will produce and the GHG from fossil fuels it will displace. The sensitivity analysis performed on the yields of bioethanol shows that the minimum conversion threshold should be larger than 60% in order to have a higher energy and GHG emission ratio than current palm oil biodiesel processing. Sensitivity analysis on direct land use change and waste-water treatment is also carried out which discourages the expansion of palm oil plantation to primary forest (including peatland) and emphasizes the need for a biogas harvesting system. Copyright © 2011 Society of Chemical Industry and John Wiley & Sons, Ltd

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