# Ethanol Production from Waste of Cassava Processing
## 3 Results and Discussion
### Potential for Ethanol Production
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Sample** & **Humidity** & **\% Total** & **g/Total** & **Initial** & **Final** & **Mass** & **Volume before** & **Volume after** \\  & **(\%)** & **Solids** & **Solids** & **pH** & **pH** & **(\%)** & **Hydrolysis (mL)** & **Hydrolysis (mL)** \\ \hline A1 & 64.19 & 35.81 & 7.16 & 6.15 & 5.14 & 27.13 & 150 & 130.67 \\ A2 & 68.88 & 31.12 & 6.22 & 5.98 & 5.23 & 29.52 & 150 & 124.00 \\ A3 & 68.59 & 31.41 & 6.28 & 5.94 & 5.37 & 29.24 & 150 & 132.67 \\ A4 & 75.90 &The solutions of A1, A2, and A4 have baselines close to the standard solutions and can be analyzed using the adjusted straight-line method, providing the concentrations of A1 as 12.6%, A2 as 48.5%, and A4 as 53.3%. The A3 solution had a very different baseline from the standard solution; therefore, its analysis was difficult. However, by spectral comparison between the solutions of A3 and A1, the concentrations are expected to be close to each other, obtaining a value of approximately 12% for A3. The ethanol values obtained were found to be directly related to the amount of starch present in the sample, as can be seen in Table 3. It is noteworthy that A2 presented greater efficiency in ethanol production compared with A1 and A3, considering the starch percentage. The A4 had higher conversion of ethanol at 53%, slightly below the values reported by other authors, such as [16]. wherein the ethanol production obtained from cassava pulp was 78.6%. This oscillation in values in relation to ethanol production is directly related to the different process conditions that the samples have been subjected to, from the efficiency of the centrifuges to the storage model. In Table 4, we can observe the comparison between ethanol production potential from different substrates. These variables make it possible to miss a part of starch, as the samples showed acidity, concluding therefore that part of the starch was converted to organic acids. From the values described in Table 4, about 251 mL/kg, that is, 0.25 m\({}^{3}\) of ethanol per ton of cassava bagasse, were obtained. The concentration of ethanol was 31% in average. [21] obtained \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Substrates** & **Starch Concentration (\%)** & **Ethanol Production (g/g)** & **Authors** \\ \hline Cassava bagasse & 64 & 0.21 & - \\ Corn & 69 [17] & 0.32 [18] & [17, 18] \\ Wheat & 66 [17] & 0.31 [18] & [17, 18] \\ Cane bagasse & 15 [19] & 0.11 [12] & [12, 19] \\ Corn stover & 64 & 0.26 [20] & [20] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Potential of ethanol production from different substrates. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Treatment** & **Starch** & **Ethanol** & **Ethanol** & **Ethanol** & **Fibrous** & **Reducing** & **Reducing** \\  & **(\%)** & **(\%)** & **(mL/kg)** & **Yield (\%)** & **Resolute (\%)** & **Sugars (g/100 g)** & **Sugars (\%)** \\ \hline A1 & 64.80 & 12.60 & 103.48 & 12.06 & 27.13 & 2.43 & 0.02 \\ A2 & 59.90 & 48.50 & 368.21 & 48.50 & 29.52 & 2.27 & 0.02 \\ A3 & 64.10 & 12.00 & 97.49 & 12.00 & 29.24 & 2.35 & 0.02 \\ A4 & 68.30 & 53.30 & 461.39 & 53.00 & 32.52 & 3.65 & 0.04 \\ Mean & 64.28 & 31.60 & 251.45 & 31.00 & 29.60 & 2.68 & 0.03 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values after distillation. Figure 2: Chart showing absorption spectra of the solutions A, B, C, and D to the solutions distilled to 10% by volume. by distilling 16 mL of cassava residue, about 32.4% ethanol at a temperature of 32 \({}^{\circ}\)C. The ethanol yield obtained was 31% on average, according to [22] who carried out research using two strains of Saccharomyces cerevisiae of non-manioc.