Assessment of the environmental sustainability of municipal solid waste valorization by anaerobic digestion and by composting in Sri Lanka.

Municipal solid waste management (MSWM) remains a major concern in Sri Lanka, and various treatment methods have been deployed. Though both composting and anaerobic digestion have been effective in environmental decontamination, there are other environmental issues that should be assessed. This study aimed to evaluate the environmental impacts of a full-scale composting plant and an anaerobic digestion plant for managing the organic fraction of municipal solid waste (OFMSW) in Sri Lanka using life cycle assessment (LCA). The results show that OFMSW composting causes unfavourable environmental impacts on damage categories such as human health (6.77 × 10 disability-adjusted life years (DALY) tonne OFMSW), ecosystem quality (1.90 × 10 species.year tonne OFMSW), and resource scarcity (3.66 × 10 United States Dollar (USD) tonne OFMSW). Anaerobic digestion also leads to unfavourable impacts on human health (2.13 × 10 DALY tonne OFMSW) and ecosystem quality (6.46 × 10 species.year tonne OFMSW). However, the impact on resource scarcity (-3.85 × 10 USD tonne OFMSW) was avoided due to electricity production via anaerobic digestion. Specifically, the treatment of OFMSW by anaerobic digestion resulted in a reduction by 68.3% in the total environmental load as compared to composting. It can be concluded that out of the two existing systems investigated, anaerobic digestion has a more favourable environmental impact than composting.