Assessment of municipal solid waste disposal options using analytical hierarchy process and life cycle analysis

Abstract

Disposal of municipal solid waste (MSW) generated in the city of Johor Bahru has been one of the challenges to the authorities and the public. Population sizes and MSW generation rates are increasing every year. The two existing landfills which are located at Seelong and Tanjung Langsat, can no longer cope with the amount of the MSW. This imposes more negative burden on the environment and public health; thus calling for better MSW disposal alternatives. However, local authorities are confronted with problems, protests and resistance as well as financial constraints in choosing and implementing waste disposals facilities. Solving the problem involves a complex evaluation procedure because compromises and tradeoffs among stakeholders and other interest groups are difficult to reach. In the current study, two concepts, analytical hierarchy process (AHP) and life cycle assessment (LCA) were used. The objectives are to identify stakeholders’ opinion on MSW disposal (through visits, meetings, conferences and symposia sessions) and use AHP to structure those opinions in proposing disposal alternatives (landfilling, recycling, incineration, composting) along environmental, economic and social implications. LCA was finally conducted to assess environmental impacts of the disposals so that informed and sustained disposal decisions can be implemented. AHP results showed that habitat depletion, land use, stream ecology, air quality and flora & fauna dominated environmental concerns of the stakeholders. Capital cost, operation and maintenance cost, landfill capacity and regulation influence were the most critical criteria in economic factors. Concern for public health and safety, public awareness, cooperation among others were found to dominate the social factors. The four alternative disposal options (i.e. landfilling, recycling, incineration, composting) were assessed and ranked according to the preferences of the stakeholders. Incineration and composting were most preferred to landfilling and recycling. Landfilling was not preferred and was perceived to be most environmentally polluting, economically unsustainable and socially unacceptable by the stakeholders. LCA results showed that Landfill has the highest impacts among the selected environmental impact categories namely, global warming (992 kg Carbon dioxide eq), acidification (0.104 moles of Nitrogen or Sulphur-eq), photochemical ozone formation (0.686 kg Non-Methane Volatile Organic Compounds) (MNVOC) and eutrophication (0.104 moles of Nitrogen or Sulphureq); except for ozone depletion potential having the highest impacts (0.686 kg Chlorofluorocarbon 11-eq) in the incineration plan due to the presence of Chlorofluorocarbon-based chemicals utilized in flue gas purification. Incineration with energy recovery and composting with stable organic compost were found to have least environmental impacts. Finally, views of concerns of stakeholder on MSW disposal in Johor Bahru city were identified and modelled with AHP. Practical environmental performance of the disposal alternatives were demonstrated through the LCA. Combination of the concepts (i.e. AHP and LCA) revealled better information in sustainability of disposing MSW by incineration and composting. This can aid more guided information on selecting better MSW disposal alternatives. Thus it will be possible to avoid misunderstandings on MSW treatments e.g. incineration since the public are involved in the decision making processes.