Abstract
Ground softwood Douglas fir (Pseudotsuga menziesii) was treated with pressurized saturated steam at 200-220 C
(1.6-2.4 MPa) for 5-10 min in a sealed container. The contents of the container were released to the atmosphere for a sudden
decompression. The steam-exploded wood particles were dried to 10% moisture content and pelletized in a single-piston-cylinder
system. The pellets were characterized for their mechanical strength, chemical composition, and moisture sorption. The steamtreated
wood required 12-81% more energy to compact into pellets than the untreated wood. Pellets made from steam-treated
wood had a breaking strength 1.4-3.3 times the strength of pellets made from untreated wood. Steam-treated pellets had a reduced
equilibrium moisture content of 2-4% and a reduced expansion after pelletization. There was a slight increase in the high heating
value from 18.94 to 20.09 MJ/kg for the treated samples. Steam-treated pellets exhibited a higher lengthwise rigidity compared to
untreated pellets.