The elemental composition differences between coal and biomass are indicated by the ultimate analyses. Coal compositions vary with coal rank and geographic region, with two representative examples of a high-rank eastern coal and a low-rank western coal indicated here. It is difficult to establish a representative biomass due to large property variations, but two examples are included here for comparison. The composition variations among biomass fuels are larger than among coals, but as a class biomass has substantially more oxygen and less carbon than coal. Less obviously, nitrogen, chlorine, and ash vary significantly among biomass fuels. These components are directly related to NOx emissions, corrosion, and ash deposition. Biomass generally has relatively low sulfur compared to coal.