Resumo:
Biomethane is a renewable fuel obtained by upgrading biogas produced in anaerobic reactors that treat organic residues and wastewater. Its production valorizes waste while contributing to greenhouse-gas mitigation, energy transition, and environmental sustainability. This study estimates the production potential and the levelized cost of biomethane (LCOB) for wastewater treatment plants (WWTPs) in Southern Minas Gerais (Brazil), combining population projections, wastewater generation, biogas/biomethane yields, and capacity-parameterized cost equations. Given the low flow rates observed in part of Southern Minas, a reference set of larger Minas Gerais municipalities operating UASB (RAFA) reactors was included to evidence scale effects. LCOB values in Southern Minas ranged from US$ 0.49/m³ to US$ 12.72/m³, with Poços de Caldas at the lower bound (US$ 0.49/m³) and Cambuí at the upper bound (US$ 12.72/m³). In the expanded set, the range was US$ 0.26/m³ to US$ 12.72/m³, with Uberaba and Contagem achieving the lowest costs (US$ 0.26/m³); Uberaba is prioritized in the final comparison due to its higher estimated biomethane output. The total technical potential for Southern Minas is approximately 1.19 million m³/year of useful biomethane, accounting for 70% upgrading efficiency and 92% availability. A negative relationship between methane flow rate (m³/h) and LCOB confirms economies of scale. The economic analysis focused on investment (CAPEX), operation (OPEX), and the levelized production cost, excluding transport and commercialization expenses. To test result robustness, a sensitivity analysis varied ±30% in three levers—OPEX, CAPEX, and discount rate. OPEX emerged as the dominant driver of LCOB, followed by CAPEX and, lastly, the discount rate. These findings support strategies centered on operational efficiency (energy management, predictive O&M), standardization/modularity, and scale-capturing arrangements (inter-municipal consortia, co-digestion, integration with landfill gas) to reduce costs and enhance project viability.
