Plastic waste and residual waste management: a case study of the Pathum Thani dumpsite in Thailand

Abstract

Most developing countries commonly dispose of solid waste fractions in open dumps and landfills. This study analysed the composition of municipal solid waste (MSW) at a dumpsite in Thailand, where plastic waste constituted 35%–62% of excavated waste across different sampling depths. Excavated plastic waste was classified by resin codes, with low-density polyethylene (LDPE) dominating 86% of plastic waste from 2012 to 2014 and decreasing to 43% in 2019. The analysis revealed that unbranded single-layer packaging predominated, with branded plastics increasing from 4% to 6% (2012, 2013, and 2014) to 17% (2019). Dumpsite mining operations at the Pathum Thani site produced approximately 100 t of refuse-derived fuel (RDF) per day, generating revenue of 800–1200 THB per ton. However, the process also generated 40–50 t of residual waste daily, consisting of soil-like material mixed with plastic waste (20% plastics, 35% combustible fractions, and the remaining mainly soil type materials). These residues failed Thai compost standards due to high electrical conductivity (8.2 dS/cm vs. standard ≤3.5 dS/cm) and low germination index (4.43% vs. standard ≥80.00%). Recommendations include adjusting the moisture content of input waste and modifying sieve sizes to improve output quality, with approximately 50% of soil fractions potentially recoverable through screening at <12.5 mm. The study estimates total plastic waste in the dumpsite to be 36559.79 t, with a potential revenue of 35 million THB if fully processed. The implementation of site-specific management studies, promotion of dumpsite mining, reduction of unbranded plastics consumption, and extended producer responsibility (EPR) policies are crucial for achieving circularity of plastic waste fractions.