Effects of phosphorus-containing additives on carbon transformation during pig manure composting

Abstract

The effects of two typical phosphorus-containing additives (i.e. phosphogypsum and superphosphate) on carbon transformation during pig manure composting were investigated. Three addition strategies, including 10% phosphogypsum as well as 2.5% and 10% superphosphate (based on dry mass) were designed with same dosage or phosphorus content. Results showed that all strategies could alter organic biotransformation to reduce carbon loss during composting. Adding 10% superphosphate and phosphogypsum could restrain microbial activities to retard organic biodegradation, which thus reduced carbon dioxide and methane emission as well as humic acid (HA) formation. Compared to these strategies with high dosage additives, addition of 2.5% superphosphate could promote the conversion of unstable fulvic acid (FA) to stable HA with high aromaticity for humification. In addition, 2.5% superphosphate was more favorable to reduce CH4 emission given its low dosage to maintain suitable thermophilic period. Thus, addition of 2.5% superphosphate was recommended to accelerate humification and reduce carbon loss during pig manure composting in practice.