Estimating the Carbon Footprint of Landfill Methane: Boundary Effects and Method Variability

This article presents a systematic literature review on methane (CH4) emissions from municipal solid waste (MSW) disposal sites and their implications for footprint outcomes. This review followed a PRISMA 2020 screening logic using Scopus and ScienceDirect (2019–2024); English and Spanish; subject areas: engineering and environmental, earth sciences), yielding a final sample of 30 studies for qualitative synthesis. This review focuses on how landfill CH4 is quantified and how system boundaries and functional units shape reported CO2 results. Evidence indicates that reported CH4 estimates are sensitive to methodological choices and key assumptions and site-context drivers (degradable organic carbon (DOC)/model first-order decay (FOD) and constant k, the methane correction factor (MCF), gas collection, oxidation, waste composition, landfill age/type, and climate), limiting direct comparability between studies. Mitigation and waste-to-energy pathways (capture/utilization, anaerobic digestion, and incineration) are summarized in terms of the reported climate benefits. Finally, reporting gaps are identified, and the minimum information set is outlined to improve the reproducibility of landfill-related carbon footprint estimates for planning and future research.