Influence of steam explosion processes on the durability and enzymatic digestibility of wood pellets

- Higher hemicellulose content decreased Higher Heat Value (HHV) of pretreated pellets.
- Neutral sulfonation increased the energy required for drying but reduced the energy required for pelletization.
- Neutral sulfonation is effective for improving the ease of hydrolysis of pellets for biofuel production.
- Auto-catalyzed steam explosion increases both pellet durability and higher heating value.

The use of pelletized feedstock in an enzyme-based “biorefinery” would benefit from economies of scale and be capable of utilizing a greater variety of biomass feedstock types. Ground poplar samples were treated using five steam pretreatment regimes including auto-hydrolysis, SO2 catalysis, deacetylation as well as both acidic and neutral sulfonation, followed by being dried and pelletized to form pellet. Drying showed a negative effect on enzymatic hydrolysis of pretreated poplar, which is also the reason for the low hydrolysability of pellet from poplar pretreated by autohydrolysis. Pellet from poplar pretreated by autohydrolysis and SO2 steam explosion is promising for thermochemical application, which is on par with the commercial pellet. Neutral sulfonation mitigated the negative effect of drying, making the resulting pellet better for hydrolysis. However, the reserved hemicelluloses and increased hydrophilicity compromised both the durability and heat value of produced pellets, making these pellets less desirable as fuel pellet. Pretreatment that is integrated into pellet production cycle should be tailored according to the targeted use of the produced pellet.