4.6 Syngas Quality

Gasification of biomass produces a gas mixture containing additional constituents such as tars, ash, particulate matter, higher hydrocarbons (e. g., C2H2, C2H4, and C2H6), and gaseous compounds containing sulfur and nitrogen other than CO, H2, and CO2. Many studies highlighted the adverse effects of these impurities on syngas fermentation including process upset, cell dormancies, and inhibition of enzymes. Therefore, syngas should be free from these impurities before entering into the fermenting process. The commonly adopted gas clean-up methods include cyclones, various types of filters and scrubbers, and rotating par­ticle separators. Post gas clean-up operations always contribute to high operational and main­tenance costs. Turn et al. (2003) proposed a pretreatment protocol combining milling and leaching to reduce S, N, and Cl compounds from biomass feedstocks from sugarcane family. Takara and Khanal (2011) reported the elimination of nitrogen compounds from biomass feedstocks by adopting wet or green processing through upfront juicing and clean fiber utili­zation for biofuel production.