Anaerobic digestion of biorefinery lignin: Effect of different wet explosion pretreatment conditions.

ABSTRACT

This study examine ways to make biorefinery lignin accessible for anaerobic digestion. The raw material was the residue after removing carbohydrates by Wet Explosion pretreatment at 190 °C and 7.5% O2 followed by enzymatic hydrolysis. The residual solid was mainly composed of lignin and was the raw material for a second WEx pretreatment operated at 220 °C with 4% oxygen and variable concentrations of NaOH (0-2%). Lignin B was the residue after pretreated without NaOH, Lignin C was pretreated at 1% NaOH, and Lignin E at 2% NaOH. Anaerobic digestion was carried out on all lignin fractions (Lignin A, B, C and E) at thermophilic conditions (52 °C) by mixing 70% of each lignin fractions with 30% clarified manure. The results showed that the lignin samples were demethoxylated as part of the biodegradation and that the highest severity pretreatment (with oxygen and 2% NaOH) resulted in the highest methane yield.