Carbon Footprint and Energetics of a 25-kW Direct Combustion Waste-to-Energy System for Municipal Solid Waste

Abstract

 The Philippines faces dual challenges of a mounting energy crisis and an increasing volume of municipal solid waste (MSW). Waste-to-energy (WTE) technologies have emerged as a potential solution to address these issues. One related initiative is the government-funded project on the establishment of a 25-kW WTE facility utilizing a direct combustion process for the treatment of MSW located at the University of the Philippines Los Baños (UPLB) in Laguna, Philippines. To evaluate the technology’s potential as a sustainable and environmentally sound alternative for waste disposal in the country, the carbon footprint and energetics performance of the WTE system using life cycle assessment (LCA) approach were evaluated. The assessment was conducted using Aspen Plus® for process simulation and SimaPro® for LCA. The system boundary included the MSW transportation, sorting, and processing. The carbon footprint analysis was based on the functional unit- disposal of 1 kg of MSW, enabling comparative analysis with landfilling as the business-as-usual scenario. The modeled facility generated approximately 27 kW gross power for a feed rate of 50 kg h-1 of combustible MSW, achieving a plant capacity factor of 84%. The total greenhouse gas (GHG) emissions of the WTE system was 1.55 kg carbon dioxide equivalent (CO2e) kg-1 MSW, significantly lower than the 3.11 kg CO2e kg-1 MSW associated with landfilling. This translates to a GHG reduction of approximately 1.56 kg CO2e kg-1 MSW, or about 50%. Accounting for avoided emissions due to electricity generation and by-products like precipitated calcium carbonate, the net carbon footprint of the WTE system could be reduced to -0.24 kg CO2e kg-1 MSW. The carbon debt from facility fabrication and installation was calculated at 1.40 × 105 kg CO2e, which could be offset in approximately 0.20 years based on the system’s carbon savings. The system achieved an operational power efficiency of 0.54 kWhr kg-1 MSW, comparable to the typical range of 0.30-0.70 kWh kg-1 MSW which was reported as the overall power generation rate in a WTE plant. These findings underscore the potential of the WTE system to contribute to sustainable solid waste management and energy generation in the Philippines. Future studies are recommended to explore commercial-scale feasibility to further strengthen the country’s drive toward sustainability and energy independence.

Keywords: bioenergy, biomass, carbon footprint, direct combustion, energetics, incineration, life cycle assessment, municipal solid waste, thermochemical conversion, waste-to-energy