Compost supplementation with nitrogen loss and greenhouse gas emissions during pig manure composting

This research investigated the influence of biochar (B) and bean dregs (BD) amendments on carbon and nitrogen losses through greenhouse gas (GHG) emissions during pig manure (PM) composting. The treatments included 15% BD, 10% B and 15% BD + 10% B (w/w dry basis of PM) amendments in the compost, whereas the CK (control) lacked any additives. The NH4+-N, C/N and germination index (GI) of the end products ensured compost maturity. Compared with the CK, the 15% BD amendment increased the total nitrogen content (TKN) of the final product by 8.05% but also increased NH3 (54.98%) and GHG emissions (40.35%) as well as nitrogen loss (25.62%). Furthermore, the combined treatment of 15% BD + 10% B improved the TKN (2.83%) of the end product and controlled NH3 emissions (33.71%), GHG emissions (29.56%) and nitrogen loss (24.26%) while increasing CO2 only with the 15% BD amendment. Therefore, the combination of BD + B was recommended.