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 NO_x emissions, corrosion, and ash deposition.   Biomass generally has relatively low sulfur compared to coal.