Addition of zeolite and superphosphate to windrow composting of chicken manure improves fertilizer efficiency and reduces greenhouse gas emission

Abstract

This study investigated the impact of adding zeolite (F), superphosphate (G), and ferrous sulfate (L) in various combinations on reducing greenhouse gas (GHG) emission and improving nitrogen conservation during factory-scale chicken manure composting, aimed to identify the combination that optimizes the performance of the process. Chicken manure was mixed with F, G, FL, or FGL and subjected to windrow composting for 46 days. Results showed that global warming potential (GWP) was reduced by 21.9% (F), 22.8% (FL), 36.1% (G), and 39.3% (FGL). Further, the nitrogen content in the final composting product increased by 27.25%, 9.45%, and 21.86% in G, FL, and FGL amendments, respectively. The fertilizer efficiency of the compost product was assessed by measuring the biomass of plants grown in it, and it was consistent with the nitrogen content. N2O emission was negligible during composting, and 98% of the released GHGs comprised CO2 and CH4. Reduction in GHG emission was mainly achieved by reducing CH4 emission. The addition of FL, G, and FGL caused a clear shift in the abundance of dominant methanogens; particularly, the abundance of Methanobrevibacter decreased and that of Methanobacterium and Methanocella increased, which was correlated with CH4 emissions. Meanwhile, the changes in moisture content, NH4+-N content, and pH level also played an important role in the reduction of GHG emission. Based on the effects of nitrogen conservation, fertilizer efficiency improvement, and GHG emission reduction, we conclude that G and FGL are more beneficial than F or FL and suggest these additives for efficient chicken manure composting.