Alkali Pretreatment for Improvement of Biogas and Ethanol Production from Different Waste Parts of Pine Tree

Abstract

Improvement of biogas, enzymatic hydrolysis, and ethanol production from different pine tree wastes, that is, needle leaves, branches, cones, and bark, were investigated using an alkali pretreatment. The pretreatment was performed with 8.0% w/w NaOH solution either at 0 °C for 60 min or 100 °C for 10 min. Different parts of the tree had dissimilar composition and properties, and effectiveness of the pretreatments was significantly different for each part. Among the untreated parts, the highest amount of biomethane production was obtained from needle leaves, which was 213 mL/(g·VS). The high temperature pretreatment was more effective on enzymatic hydrolysis, especially on needle leaves in which the yield was improved from 25.5 to 85%. Similar to enzymatic hydrolysis, ethanol yields from the wastes were improved more by the pretreatment at high temperature. Structural analyses indicated that crystallinity reduction and lignin removal were the main reasons for the observed improvements.