Waste-derived polyferric sulphate for landfill leachate treatment: life cycle assessment, environmental trade-offs, and policy implementation framework

The graphical abstract comparing the life cycle environmental impacts of a waste-derived coagulant (PFS) against conventional aluminum coagulants for landfill leachate treatment. It shows that while PFS lowers carbon emissions and resource depletion, it increases human toxicity and ecotoxicity. It also details high pollutant removal rates (above 89%) and concludes that sustainable technology selection requires a balanced policy approach rather than looking at a single environmental indicator. In tropical developing countries, landfill leachate presents a long-term environmental hazard, and the choice of coagulant chemicals have lifecycle impacts to be considered that are seldom tackled by traditional procurement strategies. In this work, a life cycle assessment (LCA) of waste-derived polyferric sulphate (PFS) and aluminium-based coagulants to treat landfill leachate was conducted based on the ReCiPe methodology (2016), where a functional unit was 1 m3 of the leachate treated to the regulatory limits of discharge. Primary inventory data were collected in an industrial PFS production facility in Teluk Kalung, Malaysia based on waste copperas (FeSO4·7H2O) provided by Venator Materials whereas the secondary data on conventional coagulants was sourced with Ecoinvent v3.8 and in peer-reviewed journals. Eighteen midpoint categories and three endpoints were considered and uncertainty was characterised by a Monte Carlo simulation (200 iterations). The findings reveal that PFS has a 14.9% lower global warming potential (7.53 versus 8.85 kg CO2) and an 18.1% lower fossil resource depletion, although its human carcinogenic toxicity (0.386 versus 0.279 kg 1,4-DCB) and freshwater ecotoxicity are 38.4 higher and 25.0 higher respectively due to trace metal contamination in the waste feedstock. The performance data on treatment also validated removal efficiencies of 89.1–96.0% of BOD, TSS, turbidity and phosphate. What makes the study novel is the combination of an LCA of a waste-derived coagulant with a systematic trade-off analysis, and a policy implementation framework that is adjusted to the institutional realities of the tropical developing countries. The results indicate that single-indicator optimisation cannot be effective at selecting sustainable technology and that there is a need to use coordinated regulatory, economic and informational tools to convert environmental superiority to real-life application.