4.1 Syngas Composition

Gasification of biomass produces a gas mixture consisting of CO, CO2, H2, N2, CH4, trace amounts of NOx and SOx, tar, char, particulate matter, and higher hydrocarbons such as C2H2, C2H4, and C2H6. This gas mixture is sometimes referred to as a producer gas (Datar et al., 2004). The gas composition greatly depends on the type of feedstocks and the operating conditions of gasifier (Klasson et al., 1992). Table 1 summarizes the gas constituents from various types of gasifiers and feedstocks. Datar et al. (2004) used a pro­ducer gas consisting of N2 (56.8%), CO (14.7%), CO2 (16.5%), H2 (4.4%), CH4 (4.2%), C2H4 (2.4%), and C2H6 (0.8%) to determine the effects of the gas composition on cell growth, H2 uptake, and acid and alcohol production. The authors found that there was a process alter­ation due to some trace species in the producer gas. Further, they suggested that the producer gas without purification could inhibit hydrogenase enzyme leading to low prod­uct formation.