oa South African Journal of Chemical Engineering - Bio ethanol from sewage sludge : a bio fuel alternative - research

Volume 25 Number 1
  • ISSN : 1026-9185



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 (4.0e7.0), temperature (15e45 °C), incubation time (10e70 h) and yeast concentrations (2e10% (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.

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