Devolatilization kinetics for the biomass fuels miscanthus, leached miscanthus, and KCl-doped pinewood were determined at high heating rates (∼105 K s–1), high peak temperatures (1405–1667 K), and short residence times (<70 ms). The particle temperature and residence time distribution were obtained from computational fluid dynamic simulations. The measured devolatilization rates, formulated in terms of single first-order reactions, were significantly faster than data reported in the literature. This difference was attributed partly to the fast heating rate/high-temperature conditions of the present study and partly to a more accurate estimate of the particle temperature. The current results indicate that neither the biomass type nor the alkali content of the biomass has a significant impact on the devolatilization rate under the investigated conditions. The development in the particle morphology was studied by electron microscopy as each fuel underwent partial to full conversion. The char yields ranged from 0.02 (leached miscanthus) to 0.11 (KCl-doped pinewood), indicating that even during fast heating, the biomass alkali content promotes char formation.