Converting textile waste into value-added chemicals:An integrated bio-refinery process

The rate of textile waste generation worldwide has increased dramatically due to a rise in clothing consumption and production.Here,conversion of cotton-based,colored cotton-based,and blended cotton-polyethylene terephthalate(PET)textile waste materials into value-added chemicals(bioethanol,sorbitol,lactic acid,terephthalic acid(TPA),and ethylene glycol(EG))via enzymatic hydrolysis and fermentation was investigated.In order to enhance the efficiency of enzymatic saccharification,effective pretreatment methods for each type of textile waste were developed,respectively.A high glucose yield of 99.1%was obtained from white cotton-based textile waste after NaOH pretreatment.Furthermore,the digestibility of the cellulose in colored cotton-based textile wastes was increased 1.38e1.75 times because of the removal of dye materials by HPAC-NaOH pretreatment.The blended cotton
PET samples showed good hydrolysis efficiency following PET removal via NaOHeethanol pretreatment,with a glucose yield of 92.49%.The sugar content produced via enzymatic hydrolysis was then converted into key platform chemicals(bioethanol,sorbitol,and lactic acid)via fermentation or hydrogenation.The maximum ethanol yield was achieved with the white T-shirt sample(537 mL/kg substrate),which was 3.2,2.1,and 2.6 times higher than those obtained with rice straw,pine wood,and oak wood,respectively.Glucose was selectively converted into sorbitol and LA at a yield of 70%and 83.67%,respectively.TPA and EG were produced from blended cotton
PET via NaOHeethanol pretreatment.The integrated biorefinery process proposed here demonstrates significant potential for valorization of textile waste.

Wet oxidation of activated carbon for enhanced adsorptive removal of lignin from the prehydrolysis liquor of kraft-based dissolving pulp production in an integrated forest biorefinery

Prehydrolysis is a key step for the production of kraft-based dissolving pulp.The pre-hydrolysis liquor mainly contains hemicellulosic components.Lignin can also be released into the pre-hydrolysis liquor,which hinders the purification and utilization of these hemicellulosic components.In this work,wet oxidation of activated carbon with nitric acid was employed to enhance the adsorptive removal of lignin from the pre-hydrolysis liquor.Under mild oxidation conditions(2%nitric acid solution),the oxidization of activated carbon resulted in significant enhancement of lignin removal.Adsorption isotherms showed that the specific surface area and the amount of carboxyl groups were affected by the oxidation treatment.The selective removal of lignin fitted well with the pseudo-second order kinetics model.

Implementation of a Forest Biomass-Based Biofuel Industry： A Canadian Experience

The forest biomass is an abundant renewable resource from which biofuels can be derived. In the Kraft process, the cellulose is extracted from the wood to form the paper pulp while the other organic components, primarily hemicelluloses and lignin, are burnt to produce steam. It is possible to divert part of the hemicelluloses or lignin to produce fuels on site, a mode of operation referred to as the integrated forest biorefinery. Hemicelluloses can be hydrolysed into sugars which in turn are converted into ethanol or butanol, while lignin can be extracted from a residual process stream, the black liquor, by acid precipitation, de-ionized, dried and directly used as a fuel or further processed into value added chemicals. Biorefinery processes have been proposed and analysed by simulation on Aspen Plus. Intensive integration of thermal energy, water and material systems is of paramount importance to the sustainability of the global site; the increased energy load on the utility systems could cause rising dependency of the global site on fossil fuels. To avoid this consequence, a new original energy efficiency analysis and enhancement methodology has been developed and validated on actual Canadian Kraft mills before being applied to the integrated biorefinery and, has produced remarkable results far superior to the current engineering practice. This has led to the concept of the GIFBR （green integrated forest biorefinery）, i.e., an industrial site with zero fossil fuel consumption and reduced GHG （greenhouse gases） emissions vs. the Kraft process and biorefinery plant alone. The GIFBR incorporates a woody biomass gasifier producing syngas as a fuel for the integrated biorefinery and for steam production or sale. It can also include a CHP （combined heat and power） unit driven by steam made available by liberated production capacity from the installed power plant.