Mapping plastic waste flows and leakage in Bacolod City using the waste flow diagram

Plastic waste leakage poses a major environmental challenge in lower-middle-income countries (LMICs), where limited waste management infrastructure contributes to environmental contamination. This study applies the Waste Flow Diagram (WFD) tool to map municipal solid waste (MSW) flows, quantify plastic leakage, and identify systemic inefficiencies in Bacolod City, Philippines. Secondary data from the Waste Analysis and Characterization Study (WACS), conducted by the Bacolod City Environment and Natural Resources Office (BENRO) in collaboration with the Solid Waste Management Association of the Philippines (SWAPP), were integrated with field observations across selected barangays, collection routes, recovery facilities, and disposal sites. Field observations were used to validate waste flow pathways, assess operational practices, and identify leakage hotspots within the municipal solid waste system. The results indicate substantial inefficiencies across the waste management chain. Approximately 3,700 tonnes of plastic waste remained uncollected annually, while total unmanaged plastic waste was estimated at 6,684 tonnes in 2023. Uncollected plastics represented the largest source of unmanaged waste, accounting for approximately 55% of total unmanaged plastics. Overall, an estimated 2,678 tonnes of plastic waste leaked into water bodies annually, equivalent to 4.25 kg/person/year. Leakage hotspots were identified across collection, transport, recovery, and disposal stages, driven by limited infrastructure capacity, inconsistent collection coverage, and informal handling of recyclable materials. The findings demonstrate that the WFD is a practical and data-efficient tool for quantifying plastic leakage and identifying priority intervention points in data-constrained urban contexts. Strengthening collection systems, improving recovery infrastructure, and enhancing disposal site management are critical to reducing environmental leakage and improving urban waste management performance.