The quality of torrefaction pellets depends on the biomass feedstock and the torrefaction and pelletisation production conditions (e.g. temperature, residence time, die type etc.). The quality can be tuned to the requirements set by the logistics chain and the end-user.
Torrefaction can be applied to upgrade all (pre-dried) lignocellulosic biomass as well as biomass mixtures. At ECN (The Energy Centre of the Netherlands), for example, torrefaction tests have been conducted for a wide variety of biomass and waste streams like bagasse, grass seed hay, road side grass, straw, beech, poplar and solid recovered fuel (SRF).The main reason for this is that about all biomass are built from the same polymers. The chemical changes of these polymers during torrefaction are practically similar resulting in the same property changes.
However, at same operating conditions, mass and energy yields will vary for different biomass, as the polymeric composition and reactivity may differ. Consequently, each biomass will have its own set of operating conditions to achieve the same product quality.
Torrefaction has the potential to provide a significant contribution to an enlarged raw material portfolio for the European biomass fuel production, by including both agricultural and forestry biomass. The main focus will be on residual materials, enabling the opening of new feedstock sources worldwide, as well as allowing and increasing importations into Europe in an economically and environmentally sustainable manner.