Effects of woody peat and superphosphate on compost maturity and gaseous emissions during pig manure composting

This study investigated the effect of calcium superphosphate on compost maturity and gaseous emissions during pig manure composting with woody peat as the bulking agent. Two treatments were conducted with or without the addition of calcium superphosphate (10% dry weight of the composting mass), which were denoted as the control and superphosphate-amended treatment, respectively. Results show that the composting temperature of both treatments was higher than 50°C for more than 5days, which is typically required for pathogen destruction during manure composting. Compared to the control treatment, the superphosphate-amended treatment increased the emission of nitrogen oxide, but reduced the emission of methane, ammonia and hydrogen sulfide by approximately 35.5%, 37.9% and 65.5%, respectively. As a result, the total greenhouse gas (GHG) emission during manure composting was reduced by nearly 34.7% with the addition of calcium superphosphate. The addition of calcium superphosphate increased the content of humic acid (indicated by E₄/E₆ ratio). Nevertheless, the superphosphate-amended treatment postponed the biological degradation of organic matter and produced the mature compost with a higher electrical conductivity in comparison with the control treatment.