Using woody biomass in thermochemical gasification can be a viable alternative for producing renewable energy. The type of biomass and the process parameters influence the producer gas composition and quality. This paper presents research on the composition of the producer gas from the gasification of three woody biomass species: spruce, alder, and pine. The experiments were conducted in a drop-tube reactor at temperatures of 750, 850, and 950 °C, using air as the gasifying agent, with equivalence ratios of 0.38 and 0.19. Gas chromatography with a thermal conductivity detector was used to determine the composition of the producer gas, while the production of total organic compounds was detected using Fourier-transform infrared spectroscopy. All three wood species exhibited very similar producer gas composition. The highest concentration of combustible gases was recorded at 950 °C, with an average of 4.1, 20.5, and 4.6 vol% for H₂, CO, and CH₄, respectively, and a LHV ranging from 4.3–5.1 MJ/m³. The results were in accordance with other gasification studies of woody species. Higher temperatures enhanced the composition of the producer gas by promoting endothermic and exothermic gasification reactions, increasing gas production while lowering solid and tar yields. The highest concentrations of combustible gases were observed with an equivalence ratio of 0.38. Continuous TOC measurement allowed understanding the evolution of the gasification process and the relation between a higher production of TOC and CO as the gasification temperature raised.

The co-pyrolysis of biomass and fossil fuels has been the subject of studies on sustainable energy. Co-feeding oil shale with woody biomass can contribute to a transition into carbon neutrality. The present study analysed the thermal decomposition behaviour of oil shale and biomass blends (0:1, 3:7, 1:1, 7:3, 9:1, and 1:0) through thermogravimetric analysis (TGA) at 80–630 °C with a heating rate of 10 °C/min in CO₂ and N₂ atmospheres. A comparison of theoretical and experimental residual mass yields of oil shale–biomass mixtures indicated no significant interactions between the fuels. The blends contributed to a decrease of up to 34.4 wt% in solid residues compared to individual pyrolysis of oil shale, and the TGA curves were shifted from up to 10 °C to a lower temperature when the biomass ratio increased. The use of a CO₂ atmosphere resulted in the production of solid residues, comparable to the one obtained with the N₂ atmosphere. CO₂ atmosphere can be used in oil shale–biomass co-pyrolysis, without affecting the decomposition process or increasing the yield of residues. A kinetic model method is proposed based on TGA data at 10, 20, and 30 °C/min. The apparent activation energies for a temperature range of 200–520 °C were in the order of 139, 155, 164, 197, 154, and 167 kJ/mol for oil shale–biomass 0:1, 3:7, 1:1, 7:3, 9:1, and 1:0 blends, respectively. From the isoconversional kinetic analysis, a two-stage pyrolysis was observed, which separated biomass and oil shale pyrolysis. A simulation of biomass and oil shale co-pyrolysis was conducted in Aspen Plus^® using TGA-derived kinetic data. The model prediction resulted in a close match with the experimental thermogravimetric data with absolute errors from 1.75 to 3.78%, which highlights the relevance of TGA analysis in simulating co-pyrolysis processes.

The partial replacement of fossil fuels with biomass provides an alternative to producing cleaner and more sustainable energy and fuels. Conventional shale oil production infrastructure can potentially be used in co-pyrolysis with biomass to reduce the use of oil shale and decrease its environmental impact. The effect of adding 10 and 30 wt% woody biomasses (spruce, alder, pine, and birch) into oil shale was studied through intermediate co-pyrolysis. The experiments were carried out in a batch reactor at 520 °C, with a 20 min residence time, in CO₂, CO₂-H₂O 1:1, and Ar gas atmospheres. The solid products were collected and analyzed for elemental composition and surface area, while the composition of the gases was determined through gas chromatography. The difference in experimental and theoretical mass balances of fuel blends was lower than 2.5 wt% in all gas environments, indicating slight interactions between the fuels. CO₂ atmospheres contributed to increased decomposition, with up to 2.6 wt% lower solid products. Biomass increased the production of combustible gases, especially CO yields, from 0.42 to 1.30 vol%. The addition of biomass and the use of alternative atmospheres can improve pyrolysis through increased fuel decomposition and a lower share of residual mass from 74.4 wt% for oil shale to 58–70 wt% for oil shale and biomass blends.