Detailed material balance and ethanol yield calculations for the biomass-to-ethanol conversion process

  • Christos Hatzis
  • Cynthia Riley
  • George P. Philippidis
Session 3 Bioprocessing Research


Applying material balance calculations to the evaluation and optimization of lignocellulosic biomass conversion processes is fundamentally important. The lack of a general framework for material balance calculations and inconsistent compositional analysis data have made it difficult to compare results from different research groups. Material balance templates have been developed to follow accurately the distribution of carbon in lignocellulosic substrates through the pretreatment and simultaneous saccharification and fermentation (SSF) processes, and provide information on overall carbon recovery, recovery of individual sugars, and solubilization of biomass components. Based on material balance considerations, we developed equations that allow us to compute overall ethanol yields for biochemical conversion of biomass correctly.

Index Entries

Carbon balance dilute-acid pretreatment simultaneous saccharification and fermentation enzymatic conversion overall yield 



amount (mass) of a substance containing 1 mol of the element carbon (g)


concentration of pentose sugars in hydrolysate (g / L)


concentration of hexose sugars in hydrolysate (g/L)


density of liquor (SSF or hydrolysate) (g/L)


ethanol concentration (g/L)


fraction of insoluble solids (g insoluble solids / g slurry)


mass-loss factor of insoluble solids from pretreatment (g pretreated solids/g raw solids)


mass of whole slurry (g)


mass of liquid phase (g)


mass of insoluble solids (g)


mass fraction of pentose sugars in raw substrate (g/g dry mass)


mass fraction of hexose sugars in raw substrate (g/g dry mass)


ethanol yield (g/100 g hexose sugar)



liquid-phase composition or mass


maximal potential yield


raw substrate or beginning of SSF (t = 0)


substrate or solids compositions after pretreatment


solids composition or mass.


  1. 1.
    Philippidis, G. P. and Wyman, C. E. (1992), inRecent Advances in Biotechnology, Vardar-Sukan, F. and Sukan, S. S., eds., Kluwer Academic, Dordrecht, The Netherlands, pp. 405–411.Google Scholar
  2. 2.
    Grohmann, K., Torget, R., and Himmel, M. (1985),Biotechnol. Bioeng. Symp. 15, 59–80.Google Scholar
  3. 3.
    Philippidis, G. P. (1994), inEnzymatic Conversion of Biomass for fuels Production, Himmel, M., Baker, J. O., and Overand, R. P., eds., American Chemical Society, Washington, DC, pp. 188–217.Google Scholar
  4. 4.
    Hinman, N. D., Schell, D. J., Riely, C. J., Bergeron, P., and Wyman, C. E. (1992),Appl. Biochem. Biotechnol. 34/35, 639–649.CrossRefGoogle Scholar
  5. 5.
    Torget, R., Hatzis, C., Hayward, T. K., Hsu, T., and Philippidis, G. P. (1996),Appl. Biochem. Biotech. 57/58, 85–101.CrossRefGoogle Scholar
  6. 6.
    Ghose, T. K. (1987),Pure Appl. Chem. 59, 257–268.CrossRefGoogle Scholar
  7. 7.
    McMillan, J. D. (1994), inEnzymatic Conversion of Biomass for Fuels Production, Himmel, M., Baker, J. O., and Overand, R. P., eds., American Chemical Society, Washington, DC, pp. 411–437.Google Scholar
  8. 8.
    Spindler, D. D., Wyman, C. E., Grohman, K., and Philippidis, G. P. (1992),Biotechnol. Lett. 14, 403–407.CrossRefGoogle Scholar
  9. 9.
    Ehrman, C. I. and Himmel, M. E. (1994),Biotechnol. Technique 8, 99–104.CrossRefGoogle Scholar
  10. 10.
    Chum. H. L., Douglas, L. J., Feinberg, D. A., and Schroeder, H. A. (1984),Evaluation of Pretreatments of Biomass for Enzymatic Hydrolysis of Cellulose. Solar Energy Research Institute, SERI/TR-231-2183.Google Scholar
  11. 11.
    Dale, B. E. (1985),Ann. Rep. Fermentation Proc. 8, 299–323.Google Scholar
  12. 12.
    Chum, H. L. and Gellerstedt, G. (1991), Modern Methods of Analysis of Wood, Annual Plants and Lignins. Proc. IEA Pre-Symposium, New Orleans, LA.Google Scholar
  13. 13.
    Hsu, T. and Nguyen, Q. (1995),Biotechnol. Techniques 9, 25–28.CrossRefGoogle Scholar
  14. 14.
    Fan, L. T., Lee, Y.-H., and Gharpuray, M. M. (1982),Adv. Biochem. Eng. 23, 157–187.Google Scholar
  15. 25.
    Saeman, J. F. (1945),Ind. Eng. Chem. 37, 43–52.CrossRefGoogle Scholar
  16. 26.
    Dunlop, A. P. (1948),Ind. Eng. Chem. 40, 204–209.CrossRefGoogle Scholar
  17. 27.
    McKibbins, S. W., Harris, J. F., Saeman, J. F., and Neill, W. K. (1962),Forest Prod. J. 12, 17–23.Google Scholar
  18. 18.
    Williams, D. L. and Dunlop, A. P. (1948),Ind. Eng. Chem. 40, 239–241.CrossRefGoogle Scholar
  19. 19.
    Sarkanen, K. V. and Ludwig, C. H. (1971),Lignins: Occurrence, Formation, Structure and Reactions. Wiley-Interscience, New York.Google Scholar
  20. 20.
    Feather, M. S. and Harris, J. F. (1973),Adv. Carbohydr. Chem. Biochem. 28, 161–224.CrossRefGoogle Scholar
  21. 21.
    Harris, J. F. (1975),Appl. Polymers Symp. 28, 131–144.Google Scholar
  22. 22.
    Root, D. F., Saeman, J. F., Harris, J. F., and Neill, W. K. (1959),Forest Prod. J. 9, 158–165.Google Scholar
  23. 23.
    Kadam, K. L., Hayward, T. K., and Philippidis, G. P. (1995),Solar Eng. 1, 339–347.Google Scholar
  24. 24.
    Gancedo, C. and Serrano, R. (1989), inThe Yeast, vol. 3, 2nd ed., Rose, A. H. and Harrison, J. S., eds., Academic, London, pp. 205–259.Google Scholar
  25. 25.
    Kennedy, M. J., Thakur, M. S., Wang, D. I. C., and Stephanopoulos, G. (1992),Biotechnol. Prog. 8, 375–381.CrossRefGoogle Scholar
  26. 26.
    Combs, N. and Hatzis, C. (1996),Appl. Biochem. Biotech. 57/58, 649–657.Google Scholar
  27. 27.
    Roels, J. A. (1983),Energetics and Kinetics in Biotechnology, Elsevier Biomedical, Amsterdam, The Netherlands.Google Scholar

Copyright information

© Humana Press Inc. 1996

Authors and Affiliations

  • Christos Hatzis
    • 1
  • Cynthia Riley
    • 2
  • George P. Philippidis
    • 1
  1. 1.Bioprocess Development BranchNational Renewable Energy Laboratory (NREL)Golden
  2. 2.Analysis and Project Management Branch, Alternative Fuels DivisionNational Renewable Energy Laboratory (NREL)Golden

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