Bioethanol Production from Chemically Obtained Cassava Hydrolysates: Effect of Nature of the Acid

Ethanol production from corn and sugarcane is well established; however, reliance on these feedstocks raises concerns related to food security, highlighting the need to explore alternative raw materials such as cassava. This study evaluates bioethanol production from different cassava root fractions—peeled cassava, starch, and peel—assessed individually within a unified experimental framework. Chemical hydrolysis using HCl or H2SO4 was employed as a cost-effective alternative to enzymatic saccharification. Hydrolysis efficiencies above 95% were achieved for both cassava and starch, regardless of the acid used, although HCl promoted higher glucose release in all samples. Chemical hydrolysis induced noticeable increases in surface roughness and porosity across all fractions. Fermentation efficiencies for cassava (93.1 ± 1.1% vs. 77.8 ± 4.9%) and peel (85.7 ± 2.8% vs. 69.8 ± 7.4%) were higher when HCl was used during hydrolysis, whereas starch showed no significant differences between acids. In contrast, the highest ethanol yields on a dry raw material basis were obtained from cassava hydrolyzed with H2SO4 (up to 0.37 ± 0.002 g/g), corresponding to a 73% ethanol recovery efficiency. The highest volumetric ethanol production rates were achieved with HCl hydrolysates, reaching up to 1.85 g/L/h for peel-derived hydrolysates.