Assessments of sustainable chemicals and bioenergy potentials of selected lignocellulosic biomass feedstocks in Poland via physicochemical characterisation and pyrolysis

Abstract

The varied physicochemical properties of biomass feedstocks influence their behaviour during thermochemical conversion to produce carbon-based fuels and chemicals. In this study, five common Poland-based lignocellulosic biomass feedstocks - oxytree trimmings, pinewood sawdust, vegetal sorghum, coffee waste, and mixed forestry residues were selected for detailed characterisation and intermediate pyrolysis to assess their sustainable chemicals and bioenergy potentials. Proximate analysis showed volatile matter contents ranging from 67.9 wt% (forestry residues) to 79.4 wt% (pinewood), with fixed carbon showing the opposite trend. Intermediate pyrolysis was conducted between 400 and 600 °C in a fixed-bed reactor using fast heating rates (200–300 °C/s) and a vapour residence time of ∼2.2 min. Gas yields increased with temperature, while liquid and biochar yields decreased. Pinewood gave the highest gas yield across all temperatures, reaching 26.9 wt% at 600 °C, while forestry residues yielded the most solid products (40.6 wt% at 400 °C). Thermogravimetric analyses of the feedstocks and their biochars showed progressive devolatilisation and increasing fixed carbon, reaching 80.8 wt% for pinewood biochar at 600 °C. Liquid yields followed the trend: coffee waste > pinewood > oxytree > forestry residues > sorghum. Woody biomass gave biochars with high fixed carbon and thermal stability, suitable for carbon sequestration, soil enhancement, or use as solid fuels. Coffee waste produced nitrogen-rich biochar with potential for fertiliser use, and fatty acid-rich oils suitable for biofuel upgrading. Phenol- and sugar-rich liquids from woody feedstocks have potential uses in resins, biochemicals, and fermentation. These results support tailored pyrolysis strategies to enable the strategic valorisation of Poland's biomass resources.