Producing platform molecules from sawdust – paving the way toward the biorefinery concept.

A jointly supervised PhD project between the University of Oulu (Finland) and the LRP laboratory at Université Grenoble Alpes (UGA) has successfully converted sawdust into platform molecules — furfural and 5-hydroxymethylfurfural (HMF) — using green chemistry approaches, such as ultrasound or microwave-assisted reactions in recyclable green solvents like deep eutectic solvents (DES).

Low-frequency ultrasound-assisted treatment of birch sawdust in hot water, either neutral or with a few percent formic acid, was investigated for the first time under high-pressure and high-temperature conditions. Under these conditions, furfural production increased significantly, highlighting the direct hydrolysis of hemicellulose. The highest furfural yield (43–44%) was obtained using 5% formic acid.

In the experiments involving diluted acid, the remaining solid fraction — composed mainly of cellulose and lignin — had a completely different morphology compared to the raw material. This resulted in a sort of “wood pulp” with reduced particle size, enabling ultrafast preparation of hydrolyzed wood. Additional pressure had a notable effect. Overall, the combination of ultrasound, hot water treatment, and diluted acid shows great potential for the efficient valorization of birch sawdust into platform chemicals.