The Effect of Different C/N Ratios on the Composting of Pig Manure and Edible Fungus Residue with Rice Bran

The aim of this study was to determine the effects of initial C/N ratio (16.3, 19.1, 24.1, and 29.6) on decomposition rate and nitrogen loss during the composting of pig manure and edible fungus residue with rice bran. The results showed that all composting piles reached a temperature greater than 55°C for at least 7 days (which meets the requirements for destroying pathogens), and the maturity times of composts with low initial C/N ratios were shorter than in composts with high initial C/N ratios. The nitrogen loss in the composting pile with initial C/N of 16.3 was significantly higher than the other treatments. Furthermore, the statistics analysis showed that the initial C/N ratios of the composts, which varied from 16.3 to 29.6, had a significant negative linear correlation with the loss of total organic matter (R = −0.9661) and loss of total nitrogen (R = −0.9365). Therefore, for treating more agricultural wastes and achieving high-quality final product as well as the reduction of nitrogen losses, this study recommends that initial C/N ratios ranging from 20 to 25 are suitable for composting pig manure and edible fungus residue.Highlight:Various agricultural wastes can be successfully composted with initial C/N ratios 16:1–30:1.Nitrogen loss had a significant linear negative correlation with the initial C/N ratio.Compost with a low C/N ratio was beneficial to dispose of more pig manure since reducing the addition of carbon materials.