In the updraft gasifier, the material is fed from the top of the reactor and the air is introduced from the bottom of the reactor through a
grate. Material and air move in opposite direction in the gasifier [3]. The “combustion” zone is essentially in the lowest part of the gasifier. In
this zone, biomass is combusted and char is formed. During the process of combusting, the temperature of the lower part of the gasifier
raises to about 750 C. The hot gases pyrolyze the biomass and dry it in further in the upper part of the gasifier. Pyrolysis of biomass results in
release of volatiles and formation of a sizeable amount of tar [4]. Some of the tar may be released with the outgoing gases. The humidity of
the air used in the gasification plays an important role in controlling the temperature [5]. A schematic of the updraft gasifier is shown in