(3 , N ₂ O, CH ₄ NH _{) Preservation And Nitrogen Emissions Of Harmful Gases In The Composting Process}

It is of great concern for the suitable disposal of swine manure and sewage sludge due to the increasing production in China. The discard of swine manure and sewage sludge has an immeasurable damage to the environmental hygiene and the unsuitable disposal process also results in labor health risk. According to recommendation of technical requirements for non-hazardous treatment of animal manure issued by Department of Agriculture of China in2006, composting of animal manure has been applied widely in China recently. While during the composting process, the release of toxic gases has been increasingly paid more attention to by researchers and government. The emission of toxic gases not only leads to labor health risk but causes serious nitrogen loss. What is more, the incomplete mature process of composting increases environmental hygiene risk. In this study, a swine manure windrow composting plant and a sludge composting plant were selected to investigate emission of toxic gases including NH3, CH4and N2O through on-site observation, as well as optimize of operational parameters for nitrogen saving and improving labor’s sanitation. Major results were listed as following:1) Turning frequency had significant impacts on emission of toxic gases, not only increased emission of methane, nitrogen dioxide and ammonia, but also increased the percentage of total nitrogen loss due to NH3emission (42.2%at turning once a week and70.05%at twice a week, respectively). The average pile temperature of the test group was lower due to the frequent turning. As far as the labor and environmental hygiene was concern, turning once a week was better than twice a week.2) Though low C/N ratio might increase higher ammonia emission slightly (8.68%higher than the control group), it was helpful to reduce methane and nitrogen dioxide emission (1.70g eCO2/kg DC for the test group and2.85g eCO2/kg DC for the control group, respectively) and total nitrogen loss (16.1%and21.8%for the test and control groups, respectively). Through applying an aeration strategy in which the airflow rate was lower in the beginning and higher in the end of sludge composting, a higher methane and nitrogen dioxide emission and a lower ammonia emission were observed in the test group, e.g.,55.1%higher of methane and nitrogen dioxide emission than the control, and66.86g·m-2and72.04g·m-2of ammonia emission in the test and the control, respectively. And a good conversation of total nitrogen thus occurred in the test caused by such aeration strategy, e.g.,51.34%of TN loss in the control.