Producing biofuels from renewable biomass resources is considered to be an effective way to reduce carbon emissions and is helpful for establishing sustainable society[1].Biomethane(CH_(4))is a promising and available clean energy in the future owing to its properties such as high calorific values,low carbon emissions and full miscibility and interchangeability with natural gas or shale gas.Therefore,the production of methane directly from waste biomass resources like straw is highly attractive.However,because of the robustness and variety of C-C bonds and C-O bonds existing in biomass molecules,it is very difficult to achieve high-selective methanation of biomass resources under relatively mild conditions.Several processes including high-temperature gasification followed by methanation and anaerobic digestion have been developed for biomass methanation.In the traditional chemical process,biomethane is produced via multiple steps,and harsh conditions(temperature>400℃)and multiple reactors are required,limiting widespread applications of this technology[2,3].For the anaerobic digestion process,the produced biogas usually contains 45%-70%methane together with 24%-40%of carbon dioxide[4].The carbon dioxide(CO_(2))produced not only reduces the calorific value of the biogas but also causes corrosion problem to the gas pipeline.Thus,the biogas produced from the anaerobic digestion process needs further undergoing separation or methanation process to increase the content of methane[5].Consequently,direct and selective methanation of biomass resources under mild conditions is a highly attractive but challenging process.
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