Present work examines an important practical aspect of torrefaction that is, the effect of size and shape of biomass on torrefaction. Experiments were conducted on different sizes of Poplar and Oak wood in directly heated torrefaction reactors. Experiments were conducted with 13, 19 and 25mm diameter Poplar wood with lengths varying from 8 to 65mm long. Most of the experiments were conducted at 250 degrees C for 60min in a directly heated convective reactor with limited few in a fluidised bed reactor. Results showed increase in mass and energy yield with increasing particle length but opposite with particle diameter. (c) 2012 Canadian Society for Chemical Engineering