Effects of Superphosphate as an Additive on Nutrient Characteristics and NH3, CO2, CH4, and N2O Emissions during Pig Manure Composting

Nutrient conservation and greenhouse gas emission control during composting have attracted much attention. This study investigated the effects of different amounts of superphosphate (SSP) on greenhouse gas emissions and the dynamic changes in nutrients during pig manure composting. Six treatments were used: pig manure + straw (S1), pig manure + straw + 3% SSP (S2), pig manure + straw + 6% SSP (S3), pig manure (M1), pig manure + 3% SSP (M2), and pig manure + 6% SSP (M3). The results showed that the addition of SSP had no negative effect on organic matter composting, and all treatments met the requirement of being harmless. The contents of TN, TP, and TK increased during the composting process, but the content of organic matter decreased gradually. At the end of composting, the total nutrient content of the pig manure + straw + 6% SSP treatment was the highest (6.39%), while that of the pig manure treatment was the lowest (4.47%). The NH3 emission reductions with additions of 3% and 6% SSP were 37.13 similar to 56.80% and 45.63 similar to 77.04%, respectively, compared with the pig manure treatment. The treatment addition of 6% SSP reduced CO2 emissions by 10.3 similar to 20.1% compared with the pig manure treatment. The pig manure + 6% SSP treatment resulted in the lowest cumulative emission of N2O, which was 79.75% lower than that of the pig manure treatment. For the cumulative emission of CH4, the treatment of pig manure + 6% SSP was at least 23.14 mg.kg(-1) and had the lowest global warming potential. In conclusion, adding 6% SSP to pig manure compost effectively reduces NH3 and CO2 emissions and improves compost quality.