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

Lime (Ca[OH](2)) and oxygen (O-2) were used to enhance the enzymatic digest ibility of two kinds of high-lignin biomass: poplar wood and newspaper. The recommended pretreatment conditions for poplar wood are 150 degreesC, 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 condition s, 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 m g of eq. glucose/g of raw dry biomass, and the 3-d total sugar (glucose + x ylose) conversion increased from 6 to 77% of raw total sugars. At high cell ulase loadings (e.g., 75 FPU/g of raw dry biomass), the 3-d total sugar con version reached 97%. In a trial run with newspaper, using conditions of 140 degreesC, 3 h, 0.3 g of Ca(OH)(2)/g of dry biomass, 16 mL of water/g of dr y 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 bioma ss, including 78% of lignin and 49% of xylan; no glucan was removed. Ash in creased because calcium was incorporated into biomass during the pretreatme nt. After oxidative lime pretreatment, about 21% of added lime could be rec overed by CO2 carbonation.