Bio ethanol from sewage sludge: A bio fuel alternative

M. M. Manyuchi, P. Chiutsi, C. Mbohwa, E. Muzenda, T. Mutusva

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


In this study, the potential to fully exploit sewage sludge as a raw material for bio ethanol a source of bio fuel is investigated. Sewage sludge hydrolysate was first made by introducing Bacillus flexus in order for saccharification to take place before fermenting to bio ethanol using yeast. The hydrolysate was then prepared for fermentation by introducing 10 g/L of peptone, 2 g/L of KH2PO4 and 1 g/L of MgSO4. Afterwards, fermentation was allowed to take place at varying pH (4.0–7.0), temperature (15–45 °C), incubation time (10–70 h) and yeast concentrations (2–10% (v/v). Bio ethanol concentrations were characterized through spectrophotometry and its physicochemical properties analyzed by standard methods. Pearson Correlations Coefficients in MATLAB 13.0 were used to determine the coefficients of interaction between the various parameters in bio ethanol production at 95% confidence interval. Highest bio ethanol yields of greater than 40 mL/L were achieved at an incubation period of 10 days, with an operating temperature of 30 °C and pH of 6.5 with yeast concentration of 6% wt. The interactions between incubation temperature and pH had the best interaction coefficient of 0.9759 being achieved for optimal bio ethanol yield. The bio ethanol produced had a flash point of 19.2 °C, pour point of 4.9 °C, cloud point of 20 °C and viscosity of 1.30 cP.

Original languageEnglish
Pages (from-to)123-127
Number of pages5
JournalSouth African Journal of Chemical Engineering
Publication statusPublished - Jun 2018


  • Bio ethanol
  • Biomass
  • Fermentation
  • Hydrolysis
  • Process conditions
  • Sewage sludge

ASJC Scopus subject areas

  • Catalysis
  • Education
  • Energy (miscellaneous)
  • Process Chemistry and Technology
  • Fluid Flow and Transfer Processes
  • Filtration and Separation


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