Technologies for Tar Removal from Biomass-Derived Syngas

The concerns on the significant negative environmental impacts of conventional fuels such as coal, oil and natural gas have fostered the shift of energy consumption towards renewable and environment friendly sources like biomass derived energy. Many technologies have been developed to generate energy from biomass; among them gasification is considered one of the most promising technologies, since and the generated syngas has many practical applications, such as a world-wide sustainable energy production or synthesis of fuels and chemicals. Unavoidable produced impurities during gasification can create severe problems in downstream applications; therefore, the cleaning of the produced syngas is essential. A major challenge in commercialization of syngas technology and its valorization is tar removal method. This review organizes the knowledge related to tar generated from biomass-derived syngas, and discusses the recent progress on clean technologies for tar elimination. The advantages and disadvantages of different tar removal methods are critically discussed. Primary treatment is able to optimise the gas composition for the secondary cleaning step but is not sufficient for further syngas applications. Among the secondary treatments, the catalytic cracking is most valued in terms of energy and yield efficiencies for syngas cleaning. This review discusses current technical barriers and future opportunities of technical development.