Full carbon upcycling of landfill gas into methanol by integrating CO2 hydrogenation and methane reforming: Process development and techno-economic analysis

This study proposes an innovative methanol production process from landfill gas (LFG) through direct CO2 hydrogenation and methane (CH4) reforming. The integration of two methanol production routes from CO2 and CH4 enables the full upcycling of carbon sources in the LFG into methanol, as compared to conventional processes that utilize only CH4 as a carbon source. The optimal process configurations and operating conditions of two LFG-to-methanol processes (L2M), stand-alone (L2M-SA) and with hydrogen supply (L2M-HS), are proposed by developing rigorous process models with the aid of sequential quadratic programming optimization. The capability of the processes is analyzed using four evaluation metrics: carbon and energy efficiencies, net CO2 emission, and unit production cost (UPC). It was observed that the carbon and energy efficiencies of both the L2M processes could reach up to 92% and 69%, respectively. The methanol UPC is estimated in the range of 392-440 USD/ton, which is competitive against other renewable and conventional methanol production options. In addition, the CO2 emission (0.83 and 1.29 kg of CO2 per kg of MeOH of the L2M-HS and -SA, respectively) implies that the full upcycling of LFG to methanol is not only economically viable but also an environmentally clean strategy. (C) 2020 Elsevier Ltd. All rights reserved.