The effect of enzyme addition on the anaerobic digestion of foodwaste

Abstract

Due to increase in the amount of food waste, the proper method to dispose food waste has become a concern. Anaerobic digestion has received increasing attention because of its advantages such as reducing waste pollution and producing clean energy. Hydrolysis, the first step in anaerobic digestion, has been identified as rate-limiting step in this process. Enzyme addition during hydrolysis of a substrate has been reported as a promising alternative to stimulate waste degradation, thus improving the efficiency of the anaerobic digestion system. In this work, Candida Antarctica Lipase B (CALB) was used to facilitate the anaerobic digestion of food waste for 40 days. The effects of lipase addition on the total organic carbon (TOC), biogas production, pH, electrical conductivity and moisture content were studied. The finding showed that the food waste digestion with lipase achieved higher reduction in pH at a shorter time, indicating a higher degradation rate when lipase was added into the system. However, lipase addition had no effect on the final values of both pH and conductivity after 40 days of digestion. It was also found that the usage of lipase in this study did not help in increasing the biogas production due to acidification of food waste during digestion that inhibited the biogas production. On the other hand, it was found that the final moisture content of 88% achieved by food waste with lipase was higher as compared to the control sample. The finding also showed that higher reduction in TOC value was achieved when lipase was added into the digestion system, showing higher degradation rate by microorganisms. The complex molecule in food waste was hydrolysed to a simple molecule assisted by the enzyme added so that it can be easily utilised by the microorganisms.