Sustainable production of methanol using landfill gas via carbon dioxide reforming and hydrogenation: Process development and techno-economic analysis

Aiming at achieving the large-scale CO₂-equivalent reduction in the landfill industry, conceptual design of two sustainable landfill gas-to-methanol process options without the pre-treatment and methanol upgrading sections were implemented via using Aspen Plus simulator. In both proposed options, the optimum syngas ratio (H₂/(2CO + 3CO₂) = 1) is fulfilled by either supplying additional H₂ (option 1) or pre-separating the surplus CO₂ in LFG using membrane (option 2). A comparative techno-economic analysis was carried out to determine the energy efficiency and the CO₂-equivalent reduction rate, as well as the net present value (NPV), the internal rate of return (IRR), and the discounted payback period (DPBP) of both proposed options. It is shown that both options 1 and 2 can be regarded as alternative processes for converting landfill gas to methanol, and option 1 is more energy efficient and eco-friendly, while, option 2 is more economically competitive. Moreover, a sensitivity analysis indicates that the CAPEX, the prices of methanol, CO₂ allowance, and H₂ are the most sensitive factors, and option 1 can be economically comparable with option 2 given that the H₂ price can be lowered down to around 1000 $/Mt. This work provides two candidate process routes for efficient conversion of landfill gas to value-added methanol, which makes the landfill industry become more sustainable and profitable, especially in the event of a future high carbon tax and low H₂ price.