Comparative Study on Bioethanol Production from Agro-Waste Feedstock via Acid Hydrolysis Method using Two Different Mineral Acids as Catalyst

Abstract

The huge demand for energy derived from non-renewable fossil feedstock is not only unsustainable but also have dire environmental consequences.  Bioethanol produced from biomass is an environmental benign alternative to fossil fuels. This study evaluated the production of bioethanol from the acid  catalysed hydrolysis of cassava and yam peels at different concentrations of HCl and H₂SO₄ respectively. S. cerevisiae (Baker’s yeast) was employed  for the fermentation of the hydrolysates to produce the bioethanol. Bioethanol produced from the hydrolysates of cassava and yam peels increased with  increasing concentrations of the acids (HCl, H₂SO₄) respectively, with 3M acid concentrations giving the highest bioethanol yields. At 3M HCl, yields of  20.56±0.9 % and 24.11±0.44% were obtained for the hydrolysates of cassava and yams peels respectively while, 3M H₂SO₄ afforded 25.5±0.71 and  33.00±0.42% maximum bioethanol yield for cassava and yam peels respectively. Overall, the diprotic H₂SO₄ acid performed better than the monoprotic  HCl in the bioethanol production resulting in higher yields under the conditions employed in this study. Generally, yam peels feedstock produced more  bioethanol than cassava peels. Regardless of the acid employed for the hydrolysis, the boiling points of the bioethanol produced for cassava peels  (81±1.00 - 83±2.00^oC) was found to be closer to that of pure ethanol (78^oC) than those obtained from yam peels (81±2.00 - 86±1.00^oC).