Improving biodegradability and biogas production of miscanthus using a combination of hydrothermal and alkaline pretreatment

Abstract

To alleviate the energy shortage and greenhouse effect, lignocellulosic biomass has received great attention for its sufficient produced in China rural areas. Miscanthus is a kind of effective energy crop for methane production due to its high organic content and biomass yield. While pretreatment is necessary before anaerobic digestion to improve the biodegradability of feedstock. A combination of hydrothermal and alkaline pretreatments was applied to reduce the recalcitrance of Miscanthus in this paper, and the results showed that the digestion performance was much better than single hydrothermally pretreated material. An 8% NaOH dosage at 175 °C was the best pretreatment condition and resulted in a 56.92% increase in biogas yield and a 45.4% reduction in digestion time compared to the control. Lignin was dissolved during hydrothermal alkaline pretreatment in a short retention time, causing destroyed structure of lignocellulose and high content of cellulose and hemicellulose maintaining. Delignification was examined an important factor for methane yield enhancing. Biodegradability, as measured by enzymatic hydrolysis, was markedly promoted. Under the optimal pretreatment condition, hydrolytic process was no longer a rate-limiting process in anaerobic digestion of Miscanthus.