Energy-efficient co-biodrying of dewatered sludge and food waste: Synergistic enhancement and variables investigation

• Synergistic enhancement was observed in co-biodrying of food waste and dewatered sludge.
• Small size (<3 mm) of bulking agent (corncob) was beneficial for biodrying performance.
• A moderate air-flow rate of 0.04 m3 h−1 kg−1 presented efficient water removal for biodrying.
• The initial 62.68% was preferable for co-biodrying among the three tested conditions.

In this study, dewatered sludge (DS) and food waste (FW) were co-biodried by balancing substrate’s property and microbial aspect. A series of experiments were conducted to explore the effects of mixing ratio, particle size of bulking agent, air-flow rate and initial moisture content (MC). A synergistic enhancement of co-biodrying of FW and DS was observed in terms of a stable temperature profile and long high-temperature duration. The biodrying index (water removal/VS consumption) indicated that the co-biodrying had a high efficiency for water removal with less organics consumption, especially for DS/FW = 2/2. The small size (<3 mm) of bulking agent and initial MC of 62.68% was preferable for the biodrying process by providing adequate free air space and extra carbon source. A moderate air-flow rate of 0.04 m3 h−1 kg−1 showed the best water carrying capacity. This finding suggests that the co-biodrying strategy could be a promising approach to treating different organic wastes with synergistic enhancement.

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