[Impacts of different aeration modes on nutrients conservation during swine manure composting with magnesium salt...

Experiments were carried out to investigate the effect of two aeration modes on nutrients conservation in the thermophilic stage of swine manure composting with adding magnesium chloride. These results indicated that in the end of thermophilic stage of composting, the ammonia nitrogen losses of the piles with the intermittent aeration and with continuous aeration, were 23.56 g and 56.98 g, respectively, which means the loss of ammonia nitrogen of swine composting by the intermittent aeration was just 41.35% of that by the continuous aeration. Such loss of ammonia nitrogen resulted in 9.8% higher of the total kjeldahl nitrogen (TKN) concentration in the pile with the intermittent aeration than that with the continuous aeration. No significant difference occurred between two piles in orthophosphate, sequential extraction phosphorus and the total phosphorus (TP). However, in the pile with intermittent aeration, the percentage of the easily dissolved phosphorous forms such as H2O-P and NaHCO3-P was increased from 27.6% of TP to 66.5%, and the other pile from 27.6% to 64.9%. The TP concentrations in both piles were 17.2 g/kg in the end of thermophilic composting stage. The mixed crystals containing magnesium and phosphorus were formed in both piles of swine composting.