Novel bulking agent from clay residue for food waste composting

New granular material from clay residue was investigated as a bulking agent for food waste composting. Five mixing ratios of granule were conducted in a laboratory scale reactor at the desired low rate of air (0.05 l min−1). The evolution of temperature and the accumulative CO2 emissions were monitored. Physical and chemical changes, N loss, and organic matter degradation of compost were also examined. Adoption of granules of 15% V/V (FAS 31.6%) enhanced the thermophilic composting and CO2 emissions; thus satisfying the Process to Further Reduce Pathogens (PFRP, USEPA) as well as obtaining the highest rate constant of organic matter degradation (k = 0.005 day−1). As the amount of granules was doubled (35% V/V), the temperature was not only cooled, but also promoted the substantial N loss (54%). It was suggested that bulking agent from clay residue can be used beneficially as reusable media for microbial inoculation as analyzed by SEM.