Biomass resources include a wide variety of materials diverse in both physical and chemical properties. Depending on the application, these variations may be critical for the final performance of the system. In particular, some advanced applications require fairly narrow specifications for moisture, ash content, ash composition. Both the physical and chemical characteristics vary significantly within and between the different biomass raw materials.However, biomass feedstocks are more uniform for some of their properties compared with competing feedstocks such as coal or petroleum. For example, coals show gross heating value ranges from 20 to 30 GJ/tonne. However, nearly all kinds of biomass feedstocks destined for combustion fall in the range 15-19 GJ/tonne for their LHV. The values for most woody materials are 18-19 GJ/tonne, while for most agricultural residues, the heating values are in the region of 15-17 GJ/tonne.