A New Methodology to Determine Fire Risk and Its Methane Management Effect in Municipal Solid Waste Disposal Sites: Development, Weighting, and Pilot Validation in Chile and Ghana

Landfill and dumpsite fires are a recurring but structurally under-addressed dimension of municipal solid waste management, releasing toxic compounds and uncontrolled methane emissions while damaging the infrastructure that would otherwise capture that methane. This study aimed to develop and validate a replicable Fire Risk Index (FRI) for landfills and dumpsites, integrating Hazard, Vulnerability, and Exposure across 22 factors weighted using the Rank Order Centroid method. Vulnerability emerged as the dominant component (combined weight of 0.45), ahead of Hazard (0.33) and Exposure (0.22), pointing to site management, rather than climate alone, as the most actionable lever for risk reduction. The methodology was validated at eleven pilot sites in Chile and Ghana (FRI 1.04–2.06, no site below the medium-risk threshold) and subsequently applied to Chile’s complete national inventory of 104 disposal sites using a three-tiered data collection approach. Under the SSP5-8.5 climate scenario, the climate-driven increment in risk is projected to be uneven across Chile, most pronounced in the Northern Macrozone. A dedicated sensitivity analysis found that three methane-related factors, waste composition, leachate control, and gas capture status, jointly account for 18.9% of the FRI’s total weight and can alone shift a site’s risk classification by a full category. These findings position the FRI as an evidence-based tool linking fire risk management to methane mitigation, with direct applications for landfill licensing, incident reporting, and climate adaptation planning across Latin America and Sub-Saharan Africa.