Bioprocess and Biosystems Engineering

, Volume 26, Issue 2, pp 93–101 | Cite as

Conversion of paper sludge to ethanol in a semicontinuous solids-fed reactor

  • Zhiliang Fan
  • Colin South
  • Kimberly Lyford
  • Jeffery Munsie
  • Peter van Walsum
  • Lee R. Lynd
Original Paper

Abstract

Conversion of paper sludge to ethanol was investigated with the objective of operating under conditions approaching those expected of an industrial process. Major components of the bleached Kraft sludge studied were glucan (62 wt.%, dry basis), xylan (11.5%), and minerals (17%). Complete recovery of glucose during compositional analysis required two acid hydrolysis treatments rather than one. To avoid the difficulty of mixing unreacted paper sludge, a semicontinuous solids-fed laboratory bioreactor system was developed. The system featured feeding at 12-h intervals, a residence time of 4 days, and cellulase loading of 15 to 20 FPU/g cellulose. Sludge was converted to ethanol using simultaneous saccharification and fermentation (SSF) featuring a β-glucosidase-supplemented commercial cellulase preparation and glucose fermentation by Saccharomyces cerevisiea. SSF was carried out for a period of 4 months in a first-generation system, resulting in an average ethanol concentration of 35 g/L. However, steady state was not achieved and operational difficulties were encountered. These difficulties were avoided in a retrofitted design that was operated for two 1-month runs, achieving steady state with good material balance closure. Run 1 with the retrofitted reactor produced 50 g/L ethanol at a cellulose conversion of 74%. Run 2 produced 42 g/L ethanol at a conversion of 92%. For run 2, the ethanol yield was 0.466 g ethanol/g glucose equivalent fermented and >94% of the xylan fed to the reactor was solubilized to a mixture of xylan oligomers and xylose.

Keywords

Paper sludge Ethanol Semicontinuous bioreactor 

Notes

Acknowledgements

This study was partially supported by the Consortium for Plant Biotechnology Research (grant no. OR22072-111) and the State of New Hampshire Governor’s Office of Energy and Community Services (grant no. 622188).

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Copyright information

© Springer-Verlag 2003

Authors and Affiliations

  • Zhiliang Fan
    • 1
  • Colin South
    • 1
    • 2
  • Kimberly Lyford
    • 1
  • Jeffery Munsie
    • 1
  • Peter van Walsum
    • 1
    • 3
  • Lee R. Lynd
    • 1
  1. 1.Chemical and Biochemical Engineering Program, Thayer School of EngineeringDartmouth CollegeHanoverUSA
  2. 2.ViaLactia BiosciencesAucklandNew Zealand
  3. 3.Department of Environmental StudiesBaylor UniversityWacoUSA

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