h i g h l i g h t sARGs could be effectively removed through the thermophilic composting process. The main contributor of reducing ARGs abundance was pile temperature. Bacterial community was the main driver to reduction of ARGs abundance. Swine manure has been considered as the reservoir of antibiotic resistance genes (ARGs). Composting is one of the most suitable technologies for treating livestock manures, and red mud was proved to have a positive effect on nitrogen conservation during composting. This study investigated the abundance of eight tetracycline and three copper resistance genes, the bacterial community during the full scale swine manure composting with or without addition of red mud. The results showed that ARGs in swine manure could be effectively removed through composting (reduced by 2.4 log copies/g TS), especially during the thermophilic phase (reduced by 1.5 log copies/g TS), which the main contributor might be temperature. Additionally, evolution of bacterial community could also have a great influence on ARGs. Although addition of red mud could enhance nitrogen conservation, it obviously hindered removal of ARGs (reduced by 1.7 log copies/g TS) and affected shaping of bacterial community during composting.
It is of great concern to reduce greenhouse gases (GHG) and ammonia (NH3) emissions from animal manure composting in China. The purpose of this study was to investigate effects of adding red mud on emissions of GHG (methane (CH4), nitrous oxide (N2O)) and NH3 in full-scale swine manure windrow composting. Two full-scale swine manure windrow composting experiments were carried out to compare emission of GHG and NH3 with and without addition of red mud. Results showed that the addition of modified red mud reduced N2O emissions by 4.03%, however, it did not help reduce CH4 emissions (51.65% higher than that of the control test). Ammonia emission from both the experimental and the control tests were similar. The addition of modified red mud was useful to conserve nitrogen and phosphorus because the contents of total nitrogen and total phosphorus in the compost of the experiment test were higher than the control test. It was also found that turning was useful to reduce CH4 emissions, i.e. 51.72% reduction of CH4 emission after turning compared to before turning. However, turning resulted in an increased N2O emission flux by 23.15 times in the experiment test and 15.31 times in the control test, respectively.
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