Biomass such as torrefied wood or wheat straw are of increasing interest as fuel but are difficult to pelletize. Torrefaction is a thermo-chemical conversion process for biomass that is of interest as a pretreatment prior to producing fuel pellets. The resulting pellets are resistant to moisture uptake and microbiological decay and also have higher physical and energy density relative to untreated biomass. FPL scientists are part of a collaborative team investigating the softening behavior of difficult-to-pelletize biomass and its effect on pelletizing. Dynamic mechanical thermal analysis (DMTA) is used to investigate the effects of composition and moisture on key thermal transitions. A single pellet press simulates the pelletization process and measures key processing variables such as frictional and compaction forces. Once material behavior is better understood, material and process variables can then be optimized.