Conceptual assessment of sustainable methane production from oxycombustion CO2 capture in waste-to-energy power plants.

• A detailed techno-economic analysis of the production of sustainable methane is developed. • Green methane production costs range from 73.9 €/MWh to 180.4 €/MWh. • Costs of CO 2 capture from 58.87 €/ton CO 2 to 73.84 €/ton CO 2. • Average SPECCA and efficiency penalty of about 3.5 MJ/kg CO 2 and 6 % points, respectively. The worldwide deployment of renewable energy is growing exponentially. However, its intermittency limits its impact on the yearly energy contribution to the grid. Thus, coal remains the largest source of electricity generation in the world. Developing negative emissions technologies, such as Bioenergy with Carbon Capture and Utilization (BECCU), is a promising pathway. This study focuses on integrating waste biomass oxycombustion and a power-to-methane system. A proton exchange membrane electrolysis driven by photovoltaic solar energy is considered to produce hydrogen and oxygen, which is used for oxy-waste combustion in a sub-critical steam power cycle. Depending on the operation strategy, a certain amount of additional O 2 would be required, produced by a cryogenic distillation air separation process. At the exit of the boiler, the almost pure CO 2 stream is further purified, compressed, and sent to the methanation reactor. A quasi-stationary model of the entire plant is developed to simulate different operation conditions and assess the integration efficiency. The results show an excellent integration of the whole plant, with a yearly average efficiency penalty associated with the CO 2 avoided of 6 % points. Since waste biomass is used as fuel, the system provides −610 kg CO 2 /MWh emissions compared to biomass plants without CO 2 capture. Results from a yearly detailed techno-economic analysis show an average levelized cost of electricity of 199.56 €/MWh and an average green methane production cost of around 110.12 €/MWh. These yearly results involve a CO 2 capture cost of about 65.66 €/ton CO 2 , which justify the potential interest in the proposed system for new and retrofitted biomass power plants. [ABSTRACT FROM AUTHOR]