Transforming biomass forest residues into transport fuels part 1: Fast pyrolysis and catalytic hydrotreatment

This study investigates the transformation of Douglas-fir (DF) ( Pseudotsuga menziesii ) and Red alder (RA) ( Alnus rubra ) forest residues into fuel-range fractions suitable for transportation applications through pyrolysis and catalytic hydrotreatment. Both feedstocks ground to 0.5 mm or 2 mm particle size were processed in a custom-designed fluidized bed reactor at 500 °C to evaluate the yield of bio-oil, biochar, and non-condensable gases. The bio-oil was subsequently upgraded via hydrotreatment using a sulfided NiMo/γ-Al 2 O 3 catalyst and distilled into gasoline, kerosene, and diesel fractions. The biomass, bio-oil, and upgraded products were characterized using proximate and elemental analyses, HPLC, FTIR, Py-GC-MS, GC-MS, HHV, and Karl Fischer titration. Results show that smaller particle sizes (0.5 mm) increased bio-oil yields by 10 to 15% compared to 2 mm particles. After upgrading, DF bio-oil produced 25% of fuel-range hydrocarbon fractions (gasoline-, kerosene-, and diesel-range), while RA bio-oil yielded 22%. The upgraded bio-oil was distilled into 42-49% diesel, 20-21% kerosene, and 11-19% gasoline, respectively. For every kilogram of DF and RA biomass processed, approximately 100 g of total hydrocarbon fuel were obtained. A techno-economic analysis estimated the minimum fuel selling prices for DF and RA derived fuels, which were aviation fuel ($2.08/L and $ 2.32/L), diesel ($2.12/L and $2.37/L), gasoline ($1.91/L and $2.13/L), and bunker fuel ($2.04/L and $2.28/L). The global mass balance revealed biochar and aqueous fractions (acetic acid) as valuable by-products, supporting a circular bioeconomy. These findings highlight the potential of forest residues for sustainable fuel production.