High titer ethanol production from simultaneous enzymatic saccharification and fermentation of aspen at high solids: A comparison between SPORL and dilute acid pretreatments

► High solids SSF using aspen at 18% solids with10 FPU cellulase/g glucan. ► SPORL pretreatment produced ethanol yield 211 L/ton wood at 59 g/L. ► Dilute acid pretreatment produced 133 L/ton wood at 35 g/L.