Influences of the thermophilic period on biodegradation and nitrogen loss in stimulated vegetable waste composting

Development of thermophilic composting with ultrahigh temperature (over 70 degrees C) would enable the vegetable wastes compost harmless, due to the inactivation of the potential viral pathogens. The present study respectively analyzed the influences of temperature (55 degrees C, 65 degrees C, and 75 degrees C), lasting time of temperature over 70 degrees C (12 h, 24 h, and 48 h), and duration over certain temperature (10 days over 50 degrees C, 5 days over 60 degrees C and 1 day over 70 degrees C), on biodegradation and nitrogen loss in composting, by controlling the temperature condition in stimulated composting system. The results showed that in the simulated condition, high temperature over 75 degrees C affected the microbial degradation of organic matter, but the activity of microorganisms could recover if the duration is no more than 24 h, which implied that the thermophilic stage of high temperature with short duration was able to inactivate the pathogenic organisms without affecting the composting process. More NH3 emission was observed in the stimulated composting of consistent 65 degrees C than 55 degrees C and 75 degrees C, while the TN loss rate was higher in the consistent 55 degrees C treatment. The NH3 emission amount was increased with the increase of the duration of 75 degrees C, while the TN loss rate was the lowest when the duration is 24 h. The results suggested that high temperature did not necessarily promote the emission of ammonia, and the influences on NH3 emission and TN loss rate did not always consistent. Furthermore, even the NH 3 emission and TN loss rate were increased along with the temperature increase, the difference of the TN loss rate between the two treatments, over 60 degrees C 5 days and over 70 degrees C 1 day, was not significant. In conclusion, the thermophilic stage of the temperature over 70 degrees C with a short duration to inactivate the potential viral pathogens will not significantly increase the nitrogen loss and influence the composting process. (C) 2019 The Authors. Published by Elsevier B.V.