Studies On Pretreatment And Enzymatic Saccharification For Ethanol Conversion From Rice Straw

Utilization of agricultural straw fiber to produce fuel ethanol offers a great potential for reducing the raw material cost and increasing the alternatives of raw material. Unlike crops which can be easily hydrolyze into the monomeric sugar, pretreatment is required for the utilization of lignocellulosic materials to attain relatively high enzymatic saccharification.This thesis focuses on the effects of chemical composition and enzymatic saccharification of rice straw pretreated by acid, alkali and sulfite with the use of pulping technics and equipments. The results showed that, compared with other pretreatment methods, the green liquor and sodium carbonate pretreatment are desirable pretreatment methods for conversion ethanol from rice straw, which provide a potential way for the repurpose of pulping mill and diversification of products. The enzymatic hydrolysis sugar yield of green liquor pretreatment is higher than sodium carbonate pretreatment. Rice straw pretreated by 4% GL at 140 oC, the enzymatic hydrolysis sugar yield about 42.1% on the basis of original rice straw, or a sugar conversion ratio close to 80% could be expected. In this condition, the removal of lignin occupied 39.2%, ash 26.6%, SiO2 8.4% and saccharification degradation 12.8% (all based on the components in rice straw). Na2SO3-HCHO pretreatment is another choice for enhancing sugar recovery for bioethanol production if the lignin in enzymatic hydrolysis residue could be used. The total sugar recovery in enzymatic hydrolysis is close to 80% while rice straw pretreated by Na2SO3-HCHO.Based on this experiment, other pretreatment method such as oxygen deligninfication, refining and so on also can be applied to enhance the effect of enzymatic sacchrification. Moreover, other methods like optimizing enzyme combinations, twice enzymatic sacchrification and adding surfactant also can raise sugar yield.