The work presented in this book deals with the physico-chemical and thermo-mechanical aspects accompanying the reactions involved in the preparation of activated carbon from lignin by the physical method. Although the physical method only involves carbonisation and gasification, oxidation of lignin carbonisates at low temperatures has been shown to be useful prior to gasification due to the formation of a plastic phase by cracking during the carbonisation of lignin. This phase is revealed by an increase in the volume of the material and by microscopic characterisation. The development of the plastic phase slows down the decomposition of the material and gives the carbonisate a high thermal stability. The latter is reduced by treating the carbonisation residue, before gasification, in air at moderate temperatures. The operating conditions are chosen to oxidise the material without destructuring it.