SO2-catalyzed steam pretreatment enhances the strength and stability of softwood pellets

► The grinding step can be replaced by a SO2-catalyzed steam treatment for pelleting. ► The treated pellets were denser and twice stronger than the untreated ones. ► The energy input decreased for production of SO2-catalyzed steam treated pellets. ► Having higher water affinity, treated pellets did not disintegrate at high humidity.