Thermal decomposition behavior and synergistic effects of binary biomass blends of pine needles, birch leaves, and sawdust for bioenergy production

The global energy transition requires renewable feedstocks. Lignocellulosic biomasses

from forestry residues and wood-processing byproducts offer significant potential to

replace fossil fuels. Unlike previous studies that typically examine individual biomass types,

this work presents a novel systematic investigation of thermal decomposition behaviors

and synergistic interactions in binary biomass blends. The study investigates three forestderived biomasses: pine needles (PN: Pinus sylvestris L.), birch leaves (BL: Betula pendula

L.), and pine-based sawdust (S). The biomass samples were characterized using proximate

and ultimate analyses, Fourier-transform infrared spectroscopy, and scanning electron

microscopy coupled with energy-dispersive X-ray spectroscopy to evaluate their composition, functional groups, and morphological features. Thermal decomposition behavior was

examined using Thermogravimetric Analysis under nitrogen and air atmospheres for individual samples and binary blends. The findings of proximate analysis showed that the ash

contents of BL, PN, and S are 8.26%, 3.06%, and 0.38%, respectively. The 82.9% volatile

content of S offers the highest reactivity and the easiest ignition, while BL presents the

lowest reactivity with 70.16% volatile content. The heating values of the biomasses were

recorded in decreasing order as 4988 kcal/kg for PN, 4494 kcal/kg for BL, and

4608 kcal/kg for S. Conserved mass loss (98.7%) of PN-S blend and increased experimental mass loss (96.8%) of BL-S combinations exhibited clear synergistic effects during oxidation. The synergy between PN-S and BL-S reveals more balanced degradation

behavior, enhanced combustion efficiency, and improved thermal stability compared to

individual biomasses. The findings provide valuable guidance for biomass-powered

heating systems, biofuel refineries, and small-scale power generation units