Conversion of Rice Straw into Methane Gas using Zeolites

In Japan, there is a large amount of biomass waste from agriculture to be used as resources. In this study, we examined the conversion of rice straw into methane gas by thermal decomposition using zeolite catalysts. Four types of zeolites, NaA, NaX, NaY and HY, with different properties, crystal structure, exchangeable cation and Si/Al ratio were used as catalysts. The mixture of rice straw and zeolite was added into the reactor, and the reactor was heated 400 oC for 1 h in nitrogen atmosphere. The amount and composition of the gas generated during the heating, and the weight of residue were examined. The results show the conversion of rice straw into methane gas can be improved using zeolites, and faujasite zeolites having Na cation, NaX and NaY, could convert rice straw into the largest amount of methane gas in this experiment. With increasing the heating temperature, production of methane gas promotes due to the promotion of decomposition reaction. The valuable gas including methane can be obtained from rice straw by heating at higher than 600 oC for 30 min with NaY addition of same weight to rice straw.