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Life Cycle Assessment of Two Catalysts Used in the Biofuel Syngas Cleaning Process and Analysis of Variability in Gasification

Jin, Enze
Syngas known also as producer gas is the main product from biomass gasification process. This gas is considered as a renewable energy which can be converted into liquid fuels. Within syngas are significant amount of tars, syngas cannot be used directly as a clean fuel. The current method used in the syngas cleaning process is reforming tars with metal catalysts. Biochar, a co-product of gasfication, has been developed with the function of removing tars from the syngas. Compared to metal catalyst, biochar has a lower price and higher potential sustainability for the environment. Life cycle assessment (LCA) is introduced into this study to analyze the sustainability performance of producing a metal catalyst versus a dedicated biochar catalyst. The comparative LCA results indicate that biochar production has a 93% reduction in GHG emissions and requires 95.7% less energy than the metal catalyst. Biochar production also releases few impacts on human health than metal catalyst. The disadvantage of biochar in ecosystem quality is due mostly to its larger agricultural land occupation impacts. Sensitivity analysis is also carried out for identifying the effects of variability in the two production systems on environmental impacts. In the metal catalyst manufacture, the production of nickel and energy used has significant effects on the environmental impacts. The gasification process using low moisture content (9%) and high yield type (8 tons/acre) of switchgrass is suggested as possibly a more sustainable scenario to produce syngas and biochar.