Co-combustion of cellulose pellets with propane gas as an auxiliary fuel is investigated in the University of Illinois fluidized-bed incinerator. The incineration phenomenon is examined as a function of the operating parameters which are the pellet and propane-gas feed rates, bed temperature, superficial gas fluidizing velocity, and fractional excess air. Carbon and thermal combustion efficiencies are computed from the relations which have been developed on the basis of carbon and thermal energy balances together with the knowledge of propane and cellulose pellet feed rates and the composition of the hue gas. Emission of CO for optimum combustion conditions is always found to be well within the limit set by the Illinois Environmental Protection Agency (IEPA). Optimum operating conditions are established for the incineration process.