Pretreatment of Agricultural Crop Wastes for Biofuels Production

Crop straw is an abundant but still underutilized renewable resource. Most of agricultural crop wastes contain about 70% fermentable components. Pretreatment technology aims to expose the fermentable carbohydrates for hydrolytic enzymes and microbes in downstream biofuels production process. An ideal pretreatment method satisfies following criteria: greatly enhancing the enzymatic efficiency of cellulose, minimizing the loss of fermentable carbohydrates, minimizing the formation of inhibitors, and high cost effectiveness. The most studied pretreatment methods include acid pretreatment, alkaline pretreatment, steam explosion, biological pretreatment, and so on. The effects of pretreatment methods on increasing the biodigestibility include increase of surface areas, reduce of cellulose crystallinity, hemicellulose solubilization, delignification, inhibitors production. Different pretreatment method offers its advantages, and also have its own shortcomings. When selecting a pretreatment method and optimizing operation conditions, not only the characteristics of lignocellulosic feedstock but also the target product and fermentation process need to be considered.