Optimization of bio-drying of kitchen waste: inoculation, initial moisture content and bulking agents

Bio-drying has been proved to be a promising method for treatment of MSW (municipal solid waste) and sewage sludge due to its high energy efficiency and low operating cost. In this study, bio-drying was adopted to treat kitchen waste, which has quite different features from MSW and sewage sludge. The main operating factors of bio-drying, including sludge inoculation, initial moisture content, and different bulking agents, were systematically investigated. The trial with a high inoculation ratio showed a shorter lag phase and better temperature profile, thus resulting in a better drying performance with higher evaporation efficiency. Furthermore, 71.7 % of initial moisture content, which is relatively higher than the values reported in other studies, was found to be favorable for microbial activity, which could save the operating cost by reducing bulking agent in bio-drying of kitchen waste. Among the tested bulking agents (i.e., corncob, sawdust, and straw), straw was found to be the best in terms of better temperature profile and water removal efficiency due to its high water absorption capacity and the proper FAS. These results will provide some valuable information for efficient bio-drying of the kitchen waste.