Résumé
The high crude oil prices, the decline of fossil fuel reserves and the increase of greenhousegas emissions are motivating the development of biorefineries that produce energy fromrenewable resources (i.e. lignocellulosic biomass). However, the key driver for the successfulconversion of biomasses into biofuels is the selection of efficient pretreatments that permit tomaximize the sugars recovery and to minimize the consumption of water, chemicals andenergy. This study proposes the application of “dry” chemo-mechanical pretreatments thatpermit to enhance enzymatic hydrolysis and thereafter bioethanol production fromlignocellulosic biomasses.In a first experiment, wheat straw was pretreated with NH3, NaOH, NaOH-H2O2 and NH3-H2O2 at both high (5 kg L-1) and at low (0.2 kg L-1) biomass concentrations, named “dry” and“diluted” pretreatments. Then, untreated and pretreated samples were subjected to centrifugaland ball milling, followed by enzymatic hydrolysis. Compared to diluted mechano -NaOHpretreatments, dry mechano -NaOH and -NaOH-H2O2 were found to be more effective indecreasing the particle size (up to 55%), increasing the surface area (up to 88%) anddecreasing the total energy requirement (up to 50%). Enzymatic hydrolysis was enhanced bypretreatments, as suggested by higher glucose yields (332, 320, 140, 322, 141 g glucose kg-1biomass for diluted –NaOH, dry – NaOH, dry -NH3, dry -NaOH-H2O2 and dry -NH3-H2O2,respectively), compared to that of untreated wheat straw (118 g glucose kg-1). However, lowerenergy efficiency was obtained for dilute mechano -NaOH treatment, compared to drymechano -NaOH treatments.In a second experiment, sugarcane bagasse was pretreated with NaOH and H3PO4 at highbiomass concentration (5 kg L-1) and then milled by using different methods, such asvibratory milling (VBM), ball milling (BM) and centrifugal milling (CM). Results indicatethat NaOH-BM and NaOH-VBM was preferred to enhance glucose yields and bioethanolproduction (up to 76%), while CM consumed 75% and 58% lesser energy than BM and VBM,respectively. The highest energy efficiency was obtained with NaOH-CM. Therefore, thecombination of dry NaOH and CM appears the most suitable and interesting pretreatment forthe production of bioethanol from SB.