Oxidative lime pretreatment of high-lignin biomass. Poplar wood and newspaper

• Published in: Applied biochemistry and biotechnology 2001-04, Vol.94 (1), p.1-28
• Main Authors: CHANG, Vincent S, NAGWANI, Murlidhar, KIM, Chul-Ho, HOLTZAPPLE, Mark T
• Format: Article
• Language: English
• Subjects: Alkalies; Biofuel production; Biological and medical sciences; Biomass; Biotechnology; Calcium Compounds; calcium oxide; Carbohydrates - analysis; Cellulase; Chemical Engineering; Conservation of Energy Resources; Energy; Energy-Generating Resources; Fundamental and applied biological sciences. Psychology; Glucose; Hydrolysis; Industrial applications and implications. Economical aspects; Lignin; Material balance; Oxidation-Reduction; Oxides; Oxygen; Studies; Sugar; Wood
• ISSN: 0273-2289; 1559-0291; 0273-2289
• DOI: 10.1385/abab:94:1:01

Lime (Ca[OH]2) and oxygen (O2) were used to enhance the enzymatic digestibility of two kinds of high-lignin biomass: poplar wood and newspaper. The recommended pretreatment conditions for poplar wood are 150 degrees C, 6 h, 0.1 g of Ca(OH)2/g of dry biomass, 9 mL of water/g of dry biomass, 14.0 bar absolute oxygen, and a particle size of -10 mesh. Under these conditions, the 3-d reducing sugar yield of poplar wood using a cellulase loading of 5 filter paper units (FPU)/g of raw dry biomass increased from 62 to 565 mg of eq. glucose/g of raw dry biomass, and the 3-d total sugar (glucose + xylose) conversion increased from 6 to 77% of raw total sugars. At high cellulase loadings (e.g., 75 FPU/g of raw dry biomass), the 3-d total sugar conversion reached 97%. In a trial run with newspaper, using conditions of 140 degrees C, 3 h, 0.3 g of Ca(OH)2/g of dry biomass, 16 mL of water/g of dry biomass, and 7.1 bar absolute oxygen, the 3-d reducing sugar yield using a cellulase loading of 5 FPU/g of raw dry biomass increased from 240 to 565 mg of eq. glucose/g of raw dry biomass. A material balance study on poplar wood shows that oxidative lime pretreatment solubilized 38% of total biomass, including 78% of lignin and 49% of xylan; no glucan was removed. Ash increased because calcium was incorporated into biomass during the pretreatment. After oxidative lime pretreatment, about 21% of added lime could be recovered by CO2 carbonation.