High-pressure carbon dioxide/water pre-treatment of sugarcane bagasse and elephant grass: Assessment of the effect of biomass composition on process efficiency

•High-pressure CO2/H2O proved to be an efficient pre-treatment technology.•Biomass composition is the most important factor on pre-treatment efficiency.•The conditions for maximal C5-sugar recovery yield were different for each biomass.•Maximal saccharification yield for both biomasses was obtained at similar conditions.•CO2/H2O mixture showed to be a greener alternative to conventional pre-treatments. The performance of two lignocellulosic biomasses was studied in high-pressure carbon dioxide/water pre-treatment. Sugarcane bagasse and elephant grass were used to produce C5-sugars from hemicellulose and, simultaneously, to promote cellulose digestibility for enzymatic saccharification. Different pre-treatment conditions, with combined severity factor ranging from −1.17 to −0.04, were evaluated and maximal total xylan to xylose yields of 59.2wt.% (34.4wt.% xylooligomers) and 46.4wt.% (34.9wt.% xylooligomers) were attained for sugarcane bagasse and elephant grass, respectively. Furthermore, pre-treated biomasses were highly digestible, with glucan to glucose yields of 77.2mol% and 72.4mol% for sugarcane bagasse and elephant grass, respectively. High-pressure carbon dioxide/water pre-treatment provides high total C5-sugars and glucose recovery from both lignocellulosic biomasses; however it is highly influenced by composition and intrinsic features of each biomass. The obtained results confirm this approach as an effective and greener alternative to conventional pre-treatment processes.