A zero-emission sustainable landfill-gas-to-wire oxyfuel process: Bioenergy with carbon capture and sequestration

Abstract

Landfill-gas basically consists of methane and carbon dioxide and its reclamation is mandatory for better waste utilization and low greenhouse-gas emissions to transition towards renewable-energy matrices. Power generation or landfill-gas-to-wire is a solution for landfill-gas utilization with electricity-supply benefits skipping complex purification/transportation steps. As municipal solid-waste is rich in biomass, landfill-gas-fired power generation, with carbon capture and sequestration, leads to negative emissions and, consequently, climate-change mitigation. This work investigates the feasibility of zero-emission landfill-gas-to-wire concepts with oxyfuel carbon sequestration against conventional landfill-gas-fired plant facing carbon charges. Economic analysis is supported by Aspen-HYSYS simulation assuming large-scale landfill-gas supply. Different gas-turbine pressure-ratios are economically sought for both conventional and oxyfuel power plants to establish most profitable configurations. The greatest net values of conventional and oxyfuel plants are respectively attained for combustion pressures around 8 and 20 bar. This indicates investment and compression costs pulling down gas-turbine pressure-ratio in the landfill-gas combined-cycle plant. At such conditions, carbon dioxide is captured at 0.875 kg/kWh entailing oxyfuel efficiency penalty of 9.2% based on landfill-gas lower heating value, and increasing the long-term break-even electricity price from US$36/MWh to US$104/MWh. Economic superiority of zero-emission oxyfuel-combined-cycle over conventional plant occurs for carbon taxes above US$95/t.