Polar solvents enhance the efficiency of microwave pre-treatment of woody biomass

Microwave pre-treatment of woody biomass may be the key to unlocking an energy efficient process for the production of renewable chemicals and fuels. Here we investigated the dipolar polarisation mechanism of polar solvents, ranging from dilute aqueous solutions of ethylene glycol, isopropyl alcohol, formaldehyde and wateronly, to improve the efficiency of MW pre-treatment of woody biomass. The optimal conditions were 3.7 wt% FA solution for 10 min at 180 degrees C, where heating rate was accelerated by 50%, saccharification of biomass increased by 56% and stabilised lignin monomers were produced compared to water-only. Autoclave pre-treatment of woody biomass released 3 to 6 times less sugar yield in the presence of water-only and 3.7 wt% FA compared to MW irradiation. Our efficient method can potentially produce three streams of building blocks - cellulose fibres, solvated hemicellulose and stabilised lignin - for transformation into renewable products.

Automated summary

The experiment showed that microwave pre-treatment using 3.7 wt% formaldehyde solution is an efficient method, accelerating the heating rate of woody biomass, increasing saccharification efficiency, and producing stable lignin monomers. Compared to traditional autoclave treatment, microwave pre-treatment with formaldehyde solution released a higher sugar yield, potentially generating various basic materials for renewable products.