Hydrolysis Optimization of By-Products from the Potato Processing Industry and Biomethane Production from Starch Hydrolysates

Abstract

This study aims to investigate the use of Fenton reagents for the efficient hydrolysis of starch, an industrial by-product obtained from the potato processing industry. A full factorial design experiment (FFD) was conducted and a statistical model was developed for simulating the hydrolysis process. The most important factors were the hydrolysis temperature and the amount of H2O2 followed by the interaction of FeSO4·7H2O and temperature. At maximum levels of FeSO4·7H2O (1.00g/L), H2O2 (0.51 g/L), and temperature (70.0 °C), a 99.5% hydrolysis yield was achieved, with a carbohydrate content of 28.65 g/L. Furthermore, analysis of hydrolysis kinetics demonstrated that an increased concentration of FeSO4·7H2O results in a decelerated rate of starch hydrolysis. Moreover, biodegradability tests were carried out to estimate the methane production potential from the produced hydrolysates. The specific methanogenic activity (SMA) was reached at 0.669 ± 0.014 g CH4-COD g−1 VSS day−1 proving the effectiveness of the hydrolysis process and highlighting the potential of industrial starch for bioenergy production. A preliminary cost analysis showed that a small investment for utilizing the starch in an existing wastewater treatment facility of a potato processing company becomes profitable before the end of the 3rd year, obtaining a net present value (NPV) 37.5% higher than that of the current utilization scenario.