Biomethane from Wastewater Treatment Plants in the State of Minas Gerais: An Analysis of Production Potential and Associated Costs

Biomethane is a renewable fuel obtained by upgrading biogas from anaerobic treatment of organic wastes and municipal wastewater. This study estimates the technical production potential and the levelized cost of biomethane (LCOB) for wastewater treatment plants in Southern Minas Gerais, Brazil, and benchmarks scale effects with a reference set of larger Minas Gerais municipalities operating Upflow Anaerobic Sludge Blanket reactors. The assessment integrates population projections, wastewater generation and service coverage (collection/treatment), a COD-based methane balance with temperature correction, and capacity-parameterized CAPEX/OPEX equations to compute LCOB. In Southern Minas, LCOB spans US$0.49–12.72 per m 3 , Poços de Caldas at the lower bound (US$0.49) and Cambuí at the upper bound (US$12.72). In the expanded set, Uberaba and Contagem achieve US$0.26 per m 3 ; Uberaba is prioritized given its higher biomethane output. The total technical potential for Southern Minas is ≈1.19 million m 3 /year of useful biomethane (assuming 70% upgrading efficiency and 92% availability). A clear inverse relationship between methane flow (m 3 /h) and LCOB confirms economies of scale. Sensitivity tests (± 30% in OPEX, CAPEX, and discount rate) identify OPEX as the dominant driver of LCOB, followed by CAPEX and then the discount rate. The results support strategies focused on operational efficiency (energy management, predictive O&M), standardization/modularity, and scale-capturing arrangements (inter-municipal consortia, co-digestion, and integration with landfill gas). Transport and commercialization costs, excluded here, should be addressed in project-level evaluations.