## 4 Discussion
### Emissions of NH\({}_{3}\) and GHGs  
NH\({}_{3}\) emissions of all treatments quickly peaked at the thermophilic phase due to the intense biodegradation of organic nitrogen to NH\({}_{4}\)+-N [7; 42], forming a positive correlation confirmed by the RDA analysis (Figure 6a-c). High pH altered the solution equilibrium between NH\({}_{4}\)+-N and NH\({}_{3}\) to the benefit of the volatilization of NH\({}_{3}\). Compared with the cumulative NH\({}_{3}\) emissions of C1 treatment, I1 treatment was 24.37% lower, and I2 treatment was 19.27% lower. C1 treatment has the highest cumulative NH\({}_{3}\) emissions due to its continuous plentiful oxygen supply which facilitates the degradation process and leads to increased NH\({}_{4}\)+-N release [19; 43]. Therefore, intermittent aeration can effectively reduce NH\({}_{3}\) volatilization.  
The mechanism of the N\({}_{2}\)O emission is complicated because N\({}_{2}\)O could be produced both during incomplete nitrification processes and also as an intermediate product of denitrification [2; 44; 45; 46]. N\({}_{2}\)O emissions were detected in the first three days of composting, which may be explained denitrification or nitrification had begun before the process of mixing the composting materials [22; 44]. The N\({}_{2}\)O emission pattern was similar to previous studies [15; 47]. However, this result was opposing to the observations of [PERSON] et al. [16], which reported that N\({}_{2}\)O cannot be produced because nitriifying bacteria are unable to thrive at thermophilic temperatures. During the maturation phase, the second peak of N\({}_{2}\)O emissions was observed in all treatments. However, the peak value of C1 treatment was very low because the denitrification process was difficult to carry out with the continuous aeration [19]. Among the three treatments, the cumulative N\({}_{2}\)O emission of C1 treatment was the lowest, because intermittent aeration promoted N\({}_{2}\)O emissions through the alternation of nitrification and denitrification [18].  
CO\({}_{2}\) emissions are a crucial indicator of organic matter (OM) decomposition and microbial activity [2]. CO\({}_{2}\) was mainly emitted during the thermophilic period due to the rapid degradation of OM and increasing temperature with microbial activity [3; 7; 22; 33]. During the maturation phase, low CO\({}_{2}\) emission was observed with the gradual consumption of the OM and decreasing temperature [18]. C1 treatment showed the highest cumulative CO\({}_{2}\) emissions (636.91 g/kg DM), which indicated that enough aeration time promoted the degradation of OM and increased CO\({}_{2}\) emissions at high temperatures [17; 18].  
CH\({}_{4}\) is produced by the deoxidization of CO\({}_{2}\), CO, and VOAs by methanogens under anaerobic conditions [47]. Previous research reported that CH\({}_{4}\) emissions mainly occurred at the thermophilic stage of the composting might be due to composting mass settlement and then anaerobic pockets formed [15; 19; 48; 49]. The intermittent aerated treatments had higher CH\({}_{4}\) emission peaks compared to continuous aerated treatment. The initially large CH\({}_{4}\) emissions for C1 might be due to the mosaic of aerobic and anaerobic microsites within the composting matrix because the high O\({}_{2}\) consumption and CO\({}_{2}\) production rates coincide with moisture evolution limit the O\({}_{2}\) concentration and diffusion rate, and thus decreasing O\({}_{2}\) availability at a local scale [17]. By the end of composting, I2 treatment has the highest CH\({}_{4}\) accumulation may be the insufficient oxygen supply for the intensive degradation caused by the long aeration interval [14].