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 9. h of fermentation.
Bibliographical noteFunding Information:
The work was funded in a part by an Economic Development Incentive Grant ( 131-5-909511 ) from the University of Wisconsin , Madison, USA. In addition, the Wisconsin Institute for Sustainable Technology receives funding support from the US Department of Agriculture , and National Institute of Food and Agriculture , USA. The authors are grateful to all the staff at the four mills for providing sludge samples and information regarding the filler and additives used in the paper making process. Authors acknowledge Sophie Demchik and Justin Hall for technical assistance.
- Cationic polyelectrolytes
- Enzymatic hydrolysis
- Hydrogen peroxide
- Paper mill sludge