This paper reports the diagnosis of bed agglomeration during biomass fast pyrolysis in a fluidized-bed reactor at a wide range of temperatures (200-700 degrees C). The results show that under all conditions, bed agglomeration can be modelled using sand loading (S-L), which is the mass of sand that directly interacts with the incoming biomass feed normalised to the total mass of biomass fed into the reactor. The values of sand loading S-L during pyrolysis is greatly influenced by the ethanol-soluble extractive contained within the raw biomass. For the pyrolysis of the raw biomass, at temperatures <310 degrees C, S-L follows an endothermic reaction pathway (E-a = 28 kJ/mole) during which its values increases with increasing temperature. However, at higher temperatures >350 degrees C, S-L follows an exothermic reaction pathway (E-a =-45 kJ/mole) during which its values decrease with increasing temperature. (C) 2016 Elsevier Ltd. All rights reserved.