Effects of Superphosphate on Greenhouse Gas Emissions and Compost Quality During Industrial Scale In-Vessel Swine Manure Composting

Composting is an environmentally friendly method for transforming the nutrients present in livestock manure into organic fertilizer. In this study, the compost quality-enhancing and N 2 O and CH 4 emissions-reducing effects of superphosphate were investigated during industrial-scale in-vessel composting of swine manure. Alongside a control group, three different doses of superphosphate were tested: 5% (SSP5), 10% (SSP10), and 15% (SSP15). The results revealed that the superphosphate reduced the N 2 O and CH 4 emissions by 18.5–26.3% and 15.8–25.1%, respectively. In addition, the superphosphate enhanced both the N and P contents of the compost. However, it had an adverse impact on compost maturity, with the SSP15 dose showing the lowest germination index (GI) at 70.4% and the highest electrical conductivity (EC) at 9.04 mS·cm −1 . These findings suggest that superphosphate has potential for greenhouse gas mitigation and nutrient augmentation in industrial composting. Although the economic benefits of superphosphate addition for GHG reduction are limited, the technology holds considerable economic potential for nitrogen conservation. Further investigations should focus on combining superphosphate addition with other improvements, considering both compost quality and economic viability.