Reusing Alkaline Solution in Lignocellulose Pretreatment to Save Consumable Chemicals without Losing Efficiency

Abstract

High production costs are biggest obstacles for the commercialization of the lignocellulosic bioethanol. For an attempt to reduce the chemical consumption of the alkaline pretreatment process, the waste solution with high basicity was investigated to be re-used. In respect to the pretreatment efficiency, a minimum addition of NaOH was calculated and the calculation philosophy was presented. The efficiency is defined as the change in the ratio of lignin/cellulose, which leads to cellulose-enriched material after pretreatment. Rubber wood saw dust was employed as the lignocellulose biomass feedstock. HPLC was used to analyze the chemical contents of the starting and pretreated material samples instead of the poor evaluation of the pretreatment efficiency based on only mass loss as that done in the previous study. The experimental results showed that with an alkaline solution of NaOH 2.0 wt% treating the woody material for 24 hours, the cellulose content increased from 41.2 % to 53.52 %, while reusing the wasted alkaline solution with a minimum addition of NaOH gives an almost-equal increase of 41.2% to 52.83 %. This method was shown to cut 30.3 % NaOH and 41.2 % fresh water consumption, implying an impressive saving of chemicals and fresh water while lignin removal efficiency of the process was well reserved.