Methanation System for Upgrading Landfill Gas into Pipeline Quality Renewable Natural Gas by Thermocatalytic Conversion of CO2

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Renewable natural gas (RNG) can be produced from landfill gas (LFG), a product of the decomposition of an organic material. Since LFG contains large amounts of CO2 (up to 55 vol%), it must be processed prior to use, which is conventionally done by separation using pressure swing adsorption or membrane separation. However, this approach is associated with high capital investment and operating costs and markets for utilization of separated CO2 are limited. An alternative approach is to convert the CO2 contained in LFG into CH4 via the thermocatalytic methanation reaction, by reacting CO2 with hydrogen (H2) over a catalytic bed. Hydrogen can be generated by water electrolysis using carbon emission-free renewable energy sources (wind, solar, hydro) or low-cost surplus electricity. Upgrading LFG to RNG, which is fully interchangeable with the pipeline quality natural gas, is a beneficial alternative to the LFG flaring. The use of clean energy sources for LFG upgrading to RNG as a substitute to fossil natural gas reduces the overall carbon emission resulted from power generation and residential heating. The use of RNG can bolster the existing natural gas supply system, while consuming captured feedstocks rich in greenhouse gases, and can be utilized as part of a power-to-gas infrastructure for surplus energy storage and redistribution.