Recent advances in biomass pretreatment – Torrefaction fundamentals and technology

Biomass and its utilization have been intimately associated to renewable energy in the recent years. However, the undesirable properties of biomass such as high moisture content and its heterogeneous nature pose a barrier to its competitiveness in the energy generation market. A viable option to overcome the issues associated with biomass feedstock is to carry out a pretreatment process called torrefaction. Torrefaction is a mild pyrolysis process carried out at 200–300 °C under inert condition. In this review, a survey of the recent research work on torrefaction is presented. The properties of biomass before and after torrefaction are discussed. Literature data are tabulated for various types of biomass utilized in the torrefaction study. A brief account on the kinetic study is outlined in the present paper. Some aspects of recent commercial development in the torrefaction process are reviewed and cited.