A mathematical model was developed to describe the gasification of biomass in a fluid-bed reactor. The model was simplified, applied to the gasification of feedlot manure, and a preliminary attempt was made to compute the gas composition and yields of gas, liquid, and solid products assuming that the water-gas shift reaction was the only gas-phase reaction. The governing equations were solved by using a software interface. Although the predicted and experimental values agreed reasonably well, the comparison suggested that cracking and reforming reactions involving the volatiles produced during devolatilization should be included in the model. An approximate calculation of the gas yields and liquid yields incorporating the thermal cracking reactions of the heavy volatiles compared more favorably with the data. 22 refs.