Biodrying with the hot-air aeration system for kitchen food waste

Biodrying is a promising method that produces bio-stabilized output with minimum pretreatment requirements. In this study, a hot-air supply system was added to the traditional biodrying process for kitchen waste, which showed significant reduction in moisture content in 5 days (maximum reduction of 37.45%). A series of experiments was conducted to optimize the hot-air biodrying system utilizing different aeration rates, temperatures, and mixing ratios of feedstock to bulking agents. The results showed that a 65 °C aeration temperature led to the highest water removal rate and low volatile solids consumption rate, with the biodrying index reaching 4.9 g water per gram of volatile solids. On the other hand, evaluation of the overall biodrying efficiency based on the weight loss and bio-stabilization showed that intermittent aeration temperature at 55 °C performed best, offering suitable conditions for water evaporation and bio-degradation. In combination with a flow rate of 0.8 L/kg*min and 1:1 mixing ratio, these conditions resulted in the maximum volatile solids consumption of 26.26% in 5 days. The volatile solids consumption and 34.47% water removal rate of the trial had contributed to a total of 64.13% weight loss. The weight loss was even higher than that of a conventional biodrying system which was conducted for more than 14 days.