Improving the conversion efficiency of waste cotton to bioethanol by microwave hydrolysis technology

With the shortage of traditional fossil fuels and global climate change worsening, the recycling and conversion of various types of waste biomass resources into bioethanol has received increasing interests around the world. This study used waste cotton as the biomass resource and applied microwave technology to improve the hydrolysis rate and efficiency. The effects of different parameters on the hydrolysis efficiency were investigated. Experimental results show that waste cotton has the highest cellulose content among common lignocellulosic biomass but it is difficult to convert waste cotton into reducing sugars by conventional hydrolysis methods. The hydrolysis efficiencies of waste cotton were all lower than 0.6% at room temperature (without microwave) even with different acid/alkali reagents and concentrations, but it can be greatly improved to 63% with the assistance of microwave technology. The optimal hydrolysis conditions for waste cotton were achieved with 30% HCl and 110 °C (microwave power 195 W) for 10 min. The hydrolysates were further fermented by the yeast Saccharomyces cerevisiae and the best yield of bioethanol was 2500 mg L -1 .