Sugarcane Bagasse Fly Ash as a No-Cost Adsorbent for Removal of Phenolic Inhibitors and Improvement of Biomass Saccharification

Abstract

The phenolic compounds generated during the pretreatment of lignocellulosic biomass have inhibitory effects on the enzymatic hydrolysis and fermentation steps in biorefineries employing the biochemical platform. This work proposes the use of sugarcane bagasse fly ash as a no-cost adsorbent for removal of the phenolics generated by the liquid hot water (LHW) pretreatment of sugarcane bagasse. Physical–chemical characterization revealed that the sugarcane bagasse fly ash was mesoporous and possessed a surface charge that promoted the adsorption of monomeric (vanillin) as well as oligomeric (tannic acid) phenolic compounds, under different conditions of pH and temperature. Adsorption isotherms for the fly ash revealed similar maximum capacities for both types of phenolic compound. The potential use of the fly ash as an adsorbent for biomass pretreatment inhibitors was demonstrated by the removal of 80% of the phenolics from the LHW liquor, which resulted in a remarkable 52% increase in the glucose released in the enzymatic hydrolysis of sugarcane bagasse. The findings demonstrated that the use of sugarcane bagasse fly ash to remove phenolic compounds could effectively increase the efficiency of enzymatic hydrolysis of lignocellulosic biomass, with performance similar to that of commercial activated carbon. In addition, there is no cost for the acquisition of the fly ash, making the process highly economically attractive for implementation in future large-scale biorefineries.