Study of a valorisation process for biomass industrial waste involving acid cooking and enzymatic hydrolysis
Abstract: Lignocellulosic biomass has potential to chip in the chemical and biofuels supplies in future societies,even though lignocellulose is a recalcitrant structure that has to be treated in several steps. After theirproper life cycle, wood-derived materials such as particleboards have few outcomes today apart fromenergy recovery for heat production. Then, they may be used as lignocellulosic biomass sources in theproduction of molecules of interest. Fermentation from wood-derived monosaccharides imposespreliminary sugar retrieval, for instance through pre-treatment and enzymatic hydrolysis. This studyfocuses on the potential of particleboards waste for chemical and biofuel production by comparingsaccharification through simulated steam explosion pre-treatment and enzymatic hydrolysis betweennative and particleboard-derived wood, with an insight in subsequent fermentation by Saccharomycescerevisiae. Urea-Formaldehyde bound particleboard was investigated, as well as some aspects ofMelamine-Urea-Formaldehyde bound particleboard. Pre-treatment resulted in apparition of lignocellulosic degraded compounds in a much larger extent innative wood than in particleboard, which seemed to be only superficially impacted. Formation ofdegraded compounds from sugars – furfural and 5-hydroxymethylfurfural – was enhanced when pretreatmentwas prolonged. Removal of a substantial fraction of the adhesive contained in theparticleboards was observed, leading to comparable concentrations in free urea, its degradedproducts, and formaldehyde between native wood and particleboards during enzymatic hydrolysis.Enzymatic hydrolysis with cellulases and hemicellulases highlighted a critical role of pre-treatment toenhance final yields, both in native wood and in Urea-Formaldehyde particleboard. Adding 20 minutessteam-explosion type pre-treatment at 160 °C resulted in glucose yields increase from 18.5 % to 32.8% for native wood and from 15.6 % to 37.4 % for particleboard. Prolonging pre-treatment residencetime to 35 minutes resulted in much better glucose extraction for native wood but only slight progressfor the particleboard, as glucose yields reached 64.5 % and 41.1 % respectively. Maximalconcentrations achieved were 277 and 184 mg/gbiomass respectively. Fermentation brought to light high inhibition from both native wood and particleboard sources ofmedia, which were attributed to components or degraded products of lignocellulose that were notanalysed in this project. Ethanol was formed during fermentation, with reduced productivity butincreased yields as compared with the control sample. Inhibition was so strong that no difference couldbe given between native and particleboard wood. In this situation, no inhibition potential of resin orits degradation products could be proved.
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