Study On The Effect Of Conditioner Addition On Compost Air-Immobile Region And Greenhouse Gas Emissions

Aerobic composting is a significant way to recycle municipal sludge,making it harmless,of reduced volume,and resourceful.However,this process suffers from various issues such as low organic matter conversion efficiency,nitrogen loss,and greenhouse gas（GHG）emissions,which reduce its environmental benefits.Many measures have been implemented to decrease GHG emissions during the composting process,such as regulating the basic physicochemical properties of composting materials,optimizing composting ventilation strategies,and adding conditioning agents.However,there is still limited understanding about how the conditioner affects the air-immobile region of the pile and its O₂ consumption during composting,and the effect of the presence of the air-immobile region on the emission of GHGs CH₄and N₂O during aerobic composting.Thus,in this study,aerobic composting tests and hyperoxic composting tests were performed using municipal sludge as the research object.Different conditioners including zeolites,wood chips,and rice brans were added in the aerobic composting process of sludge.The material of the pile was collected at each stage and compared with the treatment of adding rice bran only.The study investigated the effects of conditioner addition on the compost air-immobile region,compost DOM decay,nitrogen loss,and reduction of GHGs CH₄ and N₂O.We constructed emission models of CH₄ and N₂O of granular scale sludge under the conditions of adding different conditioners to provide theoretical support for future research on reasonable emission reduction processes.The results of the study showed that:（1）The addition of zeolite can promote the process of sludge composting and improve the oxygen supply environment;while the addition of wood chips can prolong the high temperature period of sludge aerobic composting,but the effect of improving the oxygen supply environment is not significant.In conventional composting,the addition of zeolite can increase the oxygen consumption rate and air-immobile region in the warming and maturation period,while decreasing the oxygen consumption rate in the maturation period.In hyperoxic composting,the addition of wood chips reduces the oxygen consumption rate in the air-immobile region,warming-up period,and maturation period,whereas the addition of zeolite increases the oxygen consumption rate and air-immobile region in the warming-up and high temperature periods,while decreasing the oxygen consumption rate in the maturation period.（2）In conventional composting,adding zeolite can significantly reduce the emissions of CH₄ and N₂O,and the cumulative emissions of CH₄ and N₂O are reduced by 34.28%and 9.08%,respectively;in hyperoxic composting,adding wood chips and zeolite can reduce the emissions of CH₄,and the cumulative emissions of CH₄ with wood chips and zeolite added are reduced by 37.89%and 32.43%,respectively.However,it cannot reduce the emissions of N₂O,and the cumulative emissions of N₂O with wood chips and zeolite added are increased by 9.22%and 67.61%,respectively.