Effects of additive superphosphate on NH3, N2O and CH4 emissions during pig manure composting

To study the effects of superphosphate (SP) on NH3, N2O and CH4 emissions, an experiment of pig manure composting for 56 days was carried out. Besides control, four mixtures (1.2 m3 each) were treated with different amount of SP additive of 3.3%, 6.6%, 9.9% and 13.2% (dry matter weight). The results indicated that, during 56 days, SP additives in pig manure composting at 3.3% to 13.2% decreased the ammonia volatilization, total nitrogen and carbon losses significantly. Adding more than 9.9% of SP caused adverse effects on the degradation of organic materials. SP additive at 3.3% and 6.6% reduced total NH3 emission by 24.1% and 43.4%, N2O emission by 22.2% and 27.7%, and CH4 emission by 62.9% and 22.4%, respectively. Compared with the control, the total greenhouse gas emissions (CO2-eq) of three treatments with SP additive at less than 9.9% were decreased by 30%. It is concluded that SP as a cheap phosphorus fertilizer can be used as an additive in pig manure composting to reduce the emissions and improve the value of compost as fertilizer; the feasible addition amount of SP could be about 3.3% to 6.6% of raw materials dry weight.