Quality Enhancement of Torrefied Biopellets Prepared by Unused Forest Biomass and Wood Chip Residues in Pulp Mills

Abstract

The effects of torrefaction of the biopellets made from hardwood chip residue (HW), camellia oilseed cake (CO), and pruning remnants of the toothache tree (TA) and mulberry tree (MT) were evaluated. Torrefaction of the biopellets reduced the volatile matter content of biopellets by 18-58% and increased their heating value by 18-58% without negatively impacting durability or fines content. Torrefaction also reduced the initial ignition time of biopellets by 50-59% and prolonged their combustion duration by 15-24%. Regardless of the type of feedstock, all biopellets exhibited mass yields in the range of 60-80% and energy yields ranging from 80-95%. The novelty of this study lies in the application of torrefaction to already-formed biopellets, which enhances pellet quality without the need for binders, and the use of unused forest biomass and wood chip residue from pulp mills. The use of unused forest biomass and wood chip residue from pulp mills for biopellet production not only provides a sustainable and efficient method for waste utilization but also contributes to environmental conservation by reducing the reliance on fossil fuels. Overall, the torrefaction of biopellets represents a promising technology for producing high-quality solid biofuel from a variety of woody biomass feedstocks without compromising pelletizing efficiency.