Pellets produced from mechanical processing residues of Pinus taeda: quality assessment against the EN PLUS standard

Brazilian sawmills generate 27–37% of their raw material as residues, bark, shavings, chips and sawdust, frequently underused or improperly discarded. Compaction into pellets converts this heterogeneous, low-density lignocellulosic waste into a standardised, high-energy-density solid biofuel. This study evaluated four residue streams from a high-technology Pinus taeda mechanical-processing facility and benchmarked the resulting pellets against the EN PLUS quality standard. Bark, shavings, chips, sawdust and a commercial reference were collected at a sawmill in Guarapuava (Paraná, Brazil), air-dried, hammer-milled (3 mm screen) and pelletised in an Amandus Kahl 14-175 ring-die pelletiser (6 mm channel, 95–100 °C, 1500 rpm). Pellets (1.5 kg per treatment) were characterised for dimensions, unit and bulk density, moisture, mechanical durability, fines, gross calorific value and proximate composition (volatiles, ash, fixed carbon) following the relevant BS EN ISO standards. A completely randomised design with three replicates was analysed by ANOVA and Tukey's test (α = 0.05) in R. All pellets met EN PLUS Class A1 thresholds for bulk density (659–731 kg m⁻³), calorific value (19.3–20.9 MJ kg⁻¹) and fines (< 0.31%). Chips and sawdust most closely approached the commercial reference. Bark pellets failed the moisture (13.7%) and ash (1.69%) limits; shavings exceeded the Class A1 ash threshold (1.35%). Mechanical durability fell below the EN PLUS Class B threshold (97.5%) in all laboratory treatments (95.5–96.9%), attributable to characteristic limitations of laboratory-scale pelletisation, particularly the low die compression ratio (L/d = 3.33) and the absence of steam conditioning. Chips and sawdust from Pinus taeda mechanical processing are the most promising feedstocks for high-quality industrial pellet production. Process optimisation, particularly an increased die compression ratio and the introduction of steam conditioning, is expected to bring mechanical durability into EN PLUS compliance, supporting the valorisation of sawmill residues within a circular forest bioeconomy.