Hong Kong is a highly urbanized and populated city with limited space available for municipal solid waste (MSW) disposal. At present, Hong Kong relies mainly on landfills for MSW disposal. It is expected that the current three strategic landfills in Hong Kong, namely South East New Territories, North East New Territories, and West New Territories, will reach their maximum capacities one by one by 2020. Among the 9,000 tonnes per day of MSW discarded in these three strategic landfills in Hong Kong in 2013, about 3,600 tonnes is food waste, accounting for 40% of the waste disposed and constituting the highest percentage among other waste components in Hong Kong.
In order to tackle the MSW issue in Hong Kong, landfill extension (LFE) and advanced incineration facility (AIF) have been p...[
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Hong Kong is a highly urbanized and populated city with limited space available for municipal solid waste (MSW) disposal. At present, Hong Kong relies mainly on landfills for MSW disposal. It is expected that the current three strategic landfills in Hong Kong, namely South East New Territories, North East New Territories, and West New Territories, will reach their maximum capacities one by one by 2020. Among the 9,000 tonnes per day of MSW discarded in these three strategic landfills in Hong Kong in 2013, about 3,600 tonnes is food waste, accounting for 40% of the waste disposed and constituting the highest percentage among other waste components in Hong Kong.
In order to tackle the MSW issue in Hong Kong, landfill extension (LFE) and advanced incineration facility (AIF) have been proposed by the HKSAR government. In this study, the environmental and economic aspects of proposed LFE and AIF for MSW disposal in Hong Kong are evaluated using life cycle assessment (LCA) and life cycle costing (LCC) methodologies. On the basis of the data collected, assumptions made, and system boundary defined, the net greenhouse gas emissions from the AIF (i.e., 19.9 kgCO
2e/tonne MSW) are less than the LFE (i.e., 111.6 kgCO
2e/tonne MSW). Using the SimaPro 7.2.4 software, the mid-point results of LCA study show that the LFE performs more poorly than the AIF in view of climate change and respiratory inorganics, but vice versa for carcinogens and respiratory organics. For the AIF, the sub-process that brings most burden to the carcinogens category is the ash disposal and treatment system (i.e., 67.7% for whole category), and 32.3% from the stack discharge system. It is worth noting that the dioxins and furans released from the stack discharge system have insignificant impacts (i.e., 0.48% or 1.2×10
-10 disability adjusted life year (DALY)/tonne MSW of the total impact for the stack discharge system) on human carcinogenicity and should not be a major concern to the public. Considering the human health category (i.e., end-point result), which is obtained by combining the four mid-point results, the AIF (i.e., -8.85×10
-8 DALY/tonne MSW) performs better than the LFE (i.e., 4.71×10
-8 DALY/tonne MSW) in this category.
For the LCC study, with the inclusion of private and external costs, the life cycle costs of AIF and LFE are 1619.2 HKD/tonne MSW and 1782.4 HKD/tonne MSW, respectively. The AIF has a slightly lower life cycle cost (i.e., 163.2 HKD/tonne MSW or 9.2% lower) than the LFE. However, if only private cost is considered, the result is reversed, in which the LFE has a lower life cycle cost than the AIF. A modified eco-efficiency indicator is developed in this study in order to integrate the LCA (with a focus on human health category) and LCC results associated with these two proposed waste disposal facilities. The results reveal that the AIF falls under the fully eco-efficiency category, indicating that the AIF is more eco-efficient relative to the LFE.
Since food waste is the largest constituent of MSW in Hong Kong, turning food waste into a viable renewable source has been proposed as an alternative to conventional energy resources while also addressing the burgeoning problem of food waste management. Using the LCA methodology, the life cycle environmental impacts of valorizing food waste for three types of energy use, namely electricity and heat, city gas, and biogas fuel as a petrol, diesel, and liquefied petroleum gas substitute for vehicle use, are evaluated. The results show that biogas fuel as a petrol substitute for vehicle use is advantageous over other types of energy use for human health (i.e., -3.36×10
-4 DALY/tonne food waste) and ecosystems (i.e., -1.94×10
-6 species.yr/tonne food waste), and it is also the best considering the government’s future emission reduction targets set out for the power and transport sectors in Hong Kong. In sum, it is hoped that the findings of the research can act as an additional view to the decision makers in developing the policy framework for sustainable MSW management in Hong Kong.
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