Daniel Ciolkosz, The Pennsylvania State University Department of Agricultural and Biological Engineering, 249 Ag Engineering Building, University Park, PA 16802, USA.
The torrefaction of biomass is a thermochemical decomposition process in which hemicellulose degradation is the dominant reaction, with the cellulose and lignin fractions largely unaffected. The primary product is a solid material that retains 75–95% of the original energy content. Properties of the torrefied solid include improved grindability, hydrophobicity, and energy density. Torrefied biomass has been processed successfully in batchâ€mode and continuous process devices; net thermal efficiencies of the process as high as 90% have been reported. Torrefied biomass has been proposed as a feedstock for coal coâ€combustion, as well as for gasificationâ€combustion and Fischerâ€Tropsch fuel production. Analyses of supply chain impacts indicate that, in some scenarios, torrefaction can be the lowest cost and most energy efficient option for supplying fuel, especially when combined with pelletization of the material.