In many coal combustion simulations, only one mixture fraction is used to model the coal-off gases. This assumption, however, is not accurate because the coal char and coal volatiles have considerable differences in composition. In the case of a coal:manure blend combustion, the use of one mixture fraction to describe the off gases from the coal and the manure yields inaccurate predictions. The inaccuracy is due to the fact that coal and manure have substantially different compositions and heating values. In the present work three mixture fractions are used separately to account for primary air, secondary air, coal off-gas and manure off-gas in a numerical simulation of blend combustion in a swirl burner. In the near burner region, significant differences in gas temperature and burnout are predicted when compared with a coal only base case. Secondary air and fuel flow rates are changed to keep the same equivalence ratio. The effects of these changes on the gas temperatures and burnout are determined.