Second-Generation Bioethanol from Residual Woody Biomass

Abstract

Olive tree trimmings (OTT) were subjected to sequential stages of autohydrolysis (with hot compressed water) and ethanolÀwater mixtures (organosolv pulping), to obtain three separate streams containing hemicellulose-derived products (autohydrolysis liquors), lignin fragments (pulping liquors), and autohydrolyzed, delignified solids (denoted ADOTT) mainly made up of cellulose. Up to 42% of the polysaccharides contained in the raw material (accounting for about 25% of the OTT dry mass) were recovered in autohydrolysis liquors as valuable compounds, whereas ADOTT showed high susceptibility toward enzymatic hydrolysis and allowed the formulation of media in which saccharification and ethanol fermentation were carried out simultaneously at a high product yield. Ethanol conversions higher than 90% of the theoretical value (calculated from the ADOTT content of cellulose) were achieved, whereas the ethanol concentration of fermented media reached values up to 39 g/L.

Sustainable Production of Levulinic Acid from the Cellulosic Fraction ofPinus PinasterWood: Operation in Aqueous Media Under Microwave Irradiation

“…Studies in this field have considered a number of raw materials, including woods and woody materials, [6][7][8] bamboo, [9] straw, [10] and industrial byproducts. [11] The various fractions from autohydrolysis pulping can be used in a wide spectrum of applications.…”

Two‐step fractionation of Pinus radiata by autohydrolysis and organosolv delignification for enzymatic hydrolysis

“…For the second step (ORG), autohydrolyzed wood (15 g) was loaded in the reactor with an ethanol/water mixture (50:50, w/w) at a wood/solvent ratio of 1:8 (w/v) . This pretreatment was carried out under autocatalyzed conditions (ORG 200 ) and acid‐catalyzed conditions (ORG A,185 ).…”

“…The liquid stream with solubilized hemicelluloses can be employed to obtain value‐added products such as furans or levulinic acid . The main product of the organosolv step is a pretreated solid rich in cellulose, which can be subjected to a step of enzymatic hydrolysis or simultaneous saccharification and fermentation (SSF) for glucose obtainment or bioethanol production, respectively . Furthermore, this delignification with an organic solvent allows the production of lignin with high purity and high chemical reactivity, which is considered as a valuable byproduct in the development of bio‐based materials and chemicals .…”

“…13 The main product of the organosolv step is a pretreated solid rich in cellulose, which can be subjected to a step of enzymatic hydrolysis or simultaneous saccharification and fermentation (SSF) for glucose obtainment or bioethanol production, respectively. 14,15 Furthermore, this delignification with an organic solvent allows the production of lignin with high purity and high chemical reactivity, which is considered as a valuable byproduct in the development of bio-based materials and chemicals. 16,17 For instance, organosolv wheat straw lignin has been applied as a substitute for phenol in a phenol-formaldehyde-resol resin.…”

“…2,22 This pretreatment can be performed without or with catalyst, either acidic (sulfuric or hydrochloric acid), basic (sodium hydroxide) or neutral (magnesium chloride). [22][23][24] This sequential pretreatment has been studied for different lignocellulosic materials such as E. globulus wood, 25 olive tree trimmings, 15 Miscanthus switchgrass, 20 corn stover, 26 Eucommia ulmoides wood, 16 elm, 17 rice straw, 17,19 barley straw, 27 wheat straw, [28][29][30] and sugarcane bagasse. 14,[31][32][33] These works show the current interest in this pretreatment to achieve the fractionation of agricultural wastes and woody materials and allow the utilization of the separated fractions in subsequent steps, such as enzymatic hydrolysis.…”