Bioconversion of paper mill sludge to bioethanol in the presence of accelerants or hydrogen peroxide pretreatment

Abstract

In this study we investigated the technical feasibility of convert paper mill sludge into fuel ethanol. This involved the removal of mineral fillers by using either chemical pretreatment or mechanical fractionation to determine their effects on cellulose hydrolysis and fermentation to ethanol. In addition, we studied the effect of cationic polyelectrolyte (as accelerant) addition and hydrogen peroxide pretreatment on enzymatic hydrolysis and fermentation. We present results showing that removing the fillers content (ash and calcium carbonate) from the paper mill sludge increases the enzymatic hydrolysis performance dramatically with higher cellulose conversion at faster rates. The addition of accelerant and hydrogen peroxide pretreatment further improved the hydrolysis yields by 16% and 25% (g glucose / g cellulose), respectively with the de-ashed sludge. The fermentation process of produced sugars achieved up to 95% of the maximum theoretical ethanol yield and higher ethanol productivities within 9h of fermentation.

Optimization and Scale-Up of Enzymatic Hydrolysis of Wood Pulp for Cellulosic Sugar Production

“…To make cellulosic ethanol feasible in the market, ethanol production must be at least 76.5 g/L, which requires an initial sugar concentration higher than 150 g/L (Gurram et al 2015). In this experiment, pulp concentrations of 10%, 15%, and 20% were compared; sugar production increased Hu et al (2016).…”

Integrated bioconversion of pulp and paper primary sludge to second generation bioethanol using Saccharomyces cerevisiae ATCC 26602

“…CaCO 3 increases pH value of primary sludge (8-10), which is higher than the optimum pH for cellulase activity ($5). Acid pretreatments have been used, in SHF and SSF processes, to neutralize CaCO 3 (Fan and Lynd, 2007;Marques et al, 2008;Li et al, 2009;Kang et al, 2010;Wang et al, 2011;Mendes et al, 2014;Gurram et al, 2015). However, the chemical pretreatment with acids releases CO 2 , an environmental inconvenience in the process.…”

Second Generation Bioethanol Production: On the Use of Pulp and Paper Industry Wastes as Feedstock

“…The major challenge of using PPMS for bioethanol production is the high content in ash, namely CaCO 3 , which adsorbs to the enzymes and increases de pH of the sludge, hindering enzymatic hydrolysis. In order to surpass this limitation, acidic treatments are frequently used to neutralize CaCO 3 [161,[167][168][169]. Moreover, the high ash content limits solid loading, leading to bigger reaction vessels, and, consequently, to increased costs.…”

“…Also, the sludge with higher ash content led to better fermentation results [170]. Gurram et al (2015) tested chemical, with HCl, and mechanical de-ashing of primary sludge, and found that the enzymatic hydrolysis performance improved in de-ashed sludges. The authors also investigated batch SHF of different primary sludges, either chemically de-ashed or without de-ashing, when two different accelerants or H 2 O 2 pretreatment were applied to enzymatic hydrolysis.…”