Reducing ammonia and greenhouse gas emission with adding high levels of superphosphate fertilizer during composting

Previous studies revealed that superphosphate fertilizer (SSP) as an additive in compost can reduce the nitrogen loss and improve the effectiveness of phosphorus during composting. However, few studies have explored the influence of adding SSP with high levels on ammonia and greenhouse gas emission and the suitable amount for SSP addition according to a combined assessment of the composting process and product. The present study aimed to evaluate the impact of SSP with high additive amounts on NH3, CO2, CH4, and N2O emission and organic carbon loss. All piles were mixtures of pig manure and cornstalks with different levels of SSP addition including 10%, 14%, 18%, 22%, 26%, and 30% dry weight basis of raw materials. Compared with the control without SSP, the amount of NH3 cumulative emissions was decreased by 23.8–48.1% for the treatments with 10–30% SSP addition, and the emission of greenhouse gas including CO2, CH4, and N2O by 20.9–35.5% (CO2 equivalent) was reduced by 20.9–35.5%. Adding SSP with the amount exceeding 14% to compost could reduce CO2 emissions by 32.0–38.4% and more than 30% carbon loss at the end of composting but exceeding 26% had an adverse impact on maturity of the composts. Therefore, considering the maturity and safety of compost and gas emission reduction, 14–26% SSP was the optimum amount for composting addition, which is an effective and economical way to increase the nutrient level of carbon, nitrogen, and phosphorus in compost and reduce environmental risks.