Conversion of paper sludge to ethanol by separate hydrolysis and fermentation (SHF) using Saccharomyces cerevisiae

: ► Bio-ethanol production from paper sludge is feasible without complex pre-treatment. ► Cellulase dosage and time had obvious effects on the degree of saccharification. ► The optimal degree of saccharification of 82.1% can be achieved using the RSM. ► The highest ethanol yield reached to 190 g kg−1 of dry paper sludge by the SHF.