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Proper food waste management has been a growing concern for densely populated urban cities, like Singapore. The current practice of incineration is questionable in terms of environmental and economic sustainability. In order to alleviate the environmental impacts and improve resource recovery, alternative solutions for food waste management i.e. food waste-to-energy biodiesel and anaerobic digestion have been proposed through life cycle assessment. The functional unit of the study was set to be 1 tonne of food waste. The system boundary included the collection, processing, waste conversion and disposal of food waste with three product outputs, electrical energy, hydrochar, and glycerol. Process data were obtained from lab-scale experiments, literature, and SimaPro 7.3 libraries. The impact categories were assessed in terms of acidification potential, eutrophication potential, global warming potential for 100 years, and cumulative energy demand using the CML 2 baseline 2000 version 2.05 method and the CED version 1.08 method. A cost-benefit analysis was also performed for the studied scenarios. The life cycle assessment results show that food waste-to-energy biodiesel system is favoured for food waste with oil content > 5% and anaerobic digestion for those with oil content ≤ 5%. The cost-benefit analysis results show that anaerobic digestion is the best choice if applicable in the local environment. Otherwise, food waste-to-energy biodiesel is the preferred choice over incineration. In conclusion, this study presents the advantages of anaerobic digestion and food waste-to-energy biodiesel system in comparison with incineration of food waste. The results from this study suggest a need for adaptive strategy based on the food waste type and composition, and provide decision makers in Singapore with insights into the three food waste management strategies and directions to improve the existing system. [ABSTRACT FROM AUTHOR]

Batch and column tests were conducted on untreated incineration bottom ash (IBA) samples from two incineration plants in Singapore, using seawater as the leachant. The main objective of this study was to investigate the change in the leaching behavior of certain elements (i.e. As, Cd, Cr, Cu, Ni, Pb, Sb, Se and Zn) when IBA comes into contact with seawater. Such an investigation using seawater as leachant was not commonly carried out when investigating leaching behavior in IBA. The leaching tests were then carried out on the same IBA samples using DI water, as a comparison. Lower level of leaching was observed for Pb and Zn when seawater was used as the leachant. Cr and Sb showed significant cumulative release at Liquid-to-Solids (L/S) ratio 5 in the seawater column leaching. The influence of Dissolved Organic Carbon (DOC) on Cu leaching seems to decrease after L/S 2 when using seawater in the column test. Although the leaching behavior of IBA was affected when seawater was used, for the column test, there was no significant difference during the initial release when compared to DI water. The initial L/S fractions collected were important as the low L/S ratios represent the pore water concentration and the maximum output in an actual application. The results from this study would be useful for the future study on using IBA in marine applications., (Copyright © 2016 Elsevier Ltd. All rights reserved.)