Thermo-carbide slag pretreatment of energy plants for enhancing enzymatic hydrolysis

Abstract Energy plants have several advantages, such as, low lignin, fast growth, large production and perenniality, and present great potential for biofuel production. To enhance its biodegradability, in this study, carbide slag as a novel pretreatment agent was employed to pretreat four typical energy plants, namely Medicago sativa, Panicum virgatum, Triarrhena lutarioriparia, and Arundo donax. These energy plants were all pretreated in 1.75% (w/v) carbide slag solution at 120 °C for 1 h, and then were hydrolyzed to produce reducing sugar within 72 h by an enzymes loading of 30 FPU/g substrate. The results showed that thermo-carbide slag remarkably disrupted the surface microstructure from a high compact and tight structure to a poly-ravine and distorted structure of four energy plants. Thermo-carbide slag pretreatment significantly facilitated the removal of hemicellulose and lignin, and increased the crystallinity indexes. After thermo-carbide slag pretreatment, four energy plants yielded more than 220 mg/g of reducing sugar. The maximum reducing sugar yield of 297.87 mg/g was produced from pretreated Panicum virgatum , which is 7.9 times higher compared with that of raw Panicum virgatum . The significant improvement of enzymatic hydrolysis may be attributed to the low lignin content, higher retention of cellulose, and low crystallinity after the thermo-carbide slag pretreatment. Thermo-carbide slag pretreatment is a promising pretreatment method, especially for Panicum virgatum . Carbide slag, as the abundant and cheap alkaline waste, can reduce the processing cost of energy plant bioconversion for further biofuel production. The study provides a novel research direction for further biofuel production through waste treating waste.