Triflate-catalyzed (trans)esterification of lipids within carbonized algal biomass

► Biodiesel was produced from wet, lipid-rich microalgae paste. ► Wet algae paste was pre-treated through hydrothermal carbonization. ► Rare-earth metal triflate catalysts were effective for (trans)esterification. ► Lipids within hydrochars were (trans)esterified without prior extraction. ► Triflate catalysts are water tolerant.