The gasifier is essentially a chemical reactor, where several thermo-chemical process such as pyrolysis, combustion and reduction take place. Most biomass materials can be converted into a gaseous fuel known as producer gas, which comprises of carbon monoxide, hydrogen, carbon dioxide, metheane and nitrogen. This gas has a lower calorific value (1000-1200 kcal/nm3) compared to natural gas or liquified petroleum gas, but can be burnt with high efficiency and good degree of control without emitting smoke. The producer gas flame temperature can be as high as 1100°C. Each kilogram of air-dry biomass (10% moisture content) yields about 2.5 nm3 of producer gas. In energy terms, the conversion efficiency of the gasification process is in the range of 80-90%. For thermal applications, the technology is well proven and gasifier systems are already working in the field with capacities ranging from 100 kWth to 3000kWth.