Enhanced microbial activity for moisture removal in biodrying with the assistance of stacked MFCs

Low microbial activity affected the organics degradation and limited the improvement of matrix temperature, leading to inefficient drying performance in conventional biordying (CB). In this study, two microbial fuel cells (MFCs) connected in series were applied on biodrying to facilitate water removal. Compared with CB process, moisture content (MC) of organic waste for stacked MFCs assisted biodrying (MB) process was rapidly decreased by 36.7 % within 6 days (CB: 13.8 %). Meanwhile, the assist of MFCs reshaped microbial communities and enriched electroactive bacteria Bacillus, 1.5 times and 3.4 times higher than those in CB during thermophilic and cooling phase, respectively. It could facilitate extracellular electron transfer and thus improving the reaction with O₂. The analysis of O₂ content also proved that electric field provided by stacked MFCs boosted O₂ utilization and stimulated microbial metabolism. Therefore, organics biodegradation was greatly increased by 50.0 % and high-temperature duration was prolonged from 1.4 d to 2.3 d, which were essential driving forces for water removal. The dried product of MB was identified to be a satisfactory refuse-derived fuel (RDF) with low heating value of 9.35 MJ/kg, which was about 1.57-fold higher than that of CB. These results suggested that stacked MFCs assisted biodrying is an effective technology to ameliorate conventional biodrying, achieving rapid drying of municipal solid wastes with high MC and helping to improve the resource utilization of wastes. In particular, the integration of MFCs using reality organic wastewater as substrate and biodrying system could provide a feasible reference for the development of circular economy.