Relationship between Torrefaction Parameters and Physicochemical Properties of Torrefied Products Obtained from Selected Plant Biomass

Waste biomass from plant production is an important raw material for producing energy from renewable sources. Capabilities and technologies of processing are still being improved and modernized in order to achieve the highest energy efficiency. This study assesses energetic properties of wheat straw, rapeseed, and willow. The material was subjected to heat treatment, i.e., torrefaction process at temperatures of 220, 260, and 300 °C for the duration of 60, 75, and 90 min. Measurements were performed to compare parameters of raw biomass and the torrefied products. The materials were examined and compared for the contents of moisture; biogenic elements N, C, and H; as well as calorific value, ash, and volatiles. Measurements were also performed to assess the composition of biomass in terms of particle sizes. Analysis of the results made it possible to determine optimal parameters for carrying out the torrefaction process. The use of the torrefaction process made it possible to obtain a material with an increased calorific value by more than 20%, and a 2–3 times higher content of elements in the powdered material, as well as to improve the grinding of the material. This information will enable the development of biomass thermal treatment technologies towards the use of waste biomass from agricultural production