Torrefaction has become a topic of interest in recent times not only because farmers could increase their income due to more farming activities for biomass feedstock demands but also it promotes opportunities for green job creation, provides alternative fuel source for coal fired plants, and contributes to greenhouse gas emission mitigation. Hence, this thesis explored the torrefaction behaviour of both herbaceous (switchgrass, miscanthus, wheat straw) and short rotation (willow) agricultural energy crops in terms of hydrophobicity, grindability and energy density. The lignocellulosic compositions of raw and treated switchgrass and bulk density of raw and treated miscanthus were also determined. Hence, the outcomes of these experimental investigations facilitated the development of a torrefaction definition. The research also studied the heat transfer mechanisms of torrefaction and developed mathematical models to simulate the heat generation profile due to the internal and spontaneous combustion of a cylindrically-shaped poplar wood. COMSOL modeling software was used to analyze and simulate the heat generation profiles that were closely similar to those from the experiments; hence led to a development of a correction factor to scale treatment inputs.