Pretreatment of yellow poplar sawdust by pressure cooking in water

The chemistry involved in the steam treatment of lignocellulosic materials

“…Hydrothermolysis is a pretreatment method in which the raw material is cooked in liquid water at high temperatures and pressures but no steam is generated in the process 3,64 . Amonia freeze explosion (AFEX) applies liquid ammonia at high pressure and moderate temperatures to pretreat lignocellulosics with the advantage that the pretreatment catalyst (ammonia) can be easily recycled or alternatively used as as a source of nitrogen for the subsequent fermentation step 65,66 . Finally, wet oxidation is carried out under alkaline conditions in the presence of oxygen and takes place at lower temperatures than steaming 67 .…”

“…Finally, wet oxidation is carried out under alkaline conditions in the presence of oxygen and takes place at lower temperatures than steaming 67 . All of these methods are aimed at pretreating lignocellulosics at lower severities to avoid the generation of growth inhibitors and have been primarily used to pretreated agricultural and/or municipal solid wastes including newspaper, poplar sawdust, corn residues, sugarcane bagasse, wheat straw, among others 3,[64][65][66][67] . Hence, the applicability of these methods to the bioconversion of more recalcitrant wood residues including softwoods is yet to be proven 3 .…”

An examination of biorefining processes, catalysts and challenges

“…This pre-treatment process is still at the lab-scale but offers the potential for high xylose recovery from hemicellulose (88-98% [24]) and a reduction in cellulose recalcitrance to enzymatic hydrolysis [40], and with minimal/no comminution of the biomass necessary [41]. It involves superheated water o C) that is kept in the liquid state through high pressures and put in contact with the biomass via various pathways [22]: Co-current pretreatments involve the biomass and water being held in a slurry which is warmed and then cooled; counter-current pretreatments move the biomass and water in opposite directions; and flow-through pre-treatments involve the water passing over the stationary biomass.…”

Extracting value-added products before pulping: Hemicellulosic ethanol from Eucalyptus globulus wood

“…When performed under suitable conditions, autohydrolysis leads to xylan breakdown (yielding soluble saccharides), whereas the remaining solid can still be suitable for pulping (Vila et al 2011 ). When autohydrolysis is performed under harsh conditions, solids can be subjected to aqueous processing, which yields cellulose-containing solids suitable as substrates for enzymatic hydrolysis; therefore, the production of glucose solutions suitable as media for ethanol fermentation is possible (Weil et al 1997 ;Kirsch et al 2011 ). Operation in a percolation reaction at 200 -230 ° C with residence times of up to 15 min enabled the recovery of more than 90 % of hemicelluloses as soluble saccharides, with similar behavior for different types of lignocellulosic substrates (including both woody and non-woody materials) (Mok and Antal 1992 ).…”