NH3 and greenhouse gas emissions during co-composting of lignite and poultry wastes and the following amendment of co-composted products in soil

Abstract

Ammonia (NH₃) and greenhouse gas (GHG) emissions are substantial contributors to C and N loss in composting. Lignite can increase N retention by absorbing $N{H}_4^{+}$ and NH₃. However, the effects of co-composting on NH₃ and GHG emissions in view of closing nutrient cycle are still poorly investigated. In the study, poultry litter was composted without (CK) or with lignite (T1) or dewatered lignite (T2), and their respective composts $N{H}_4^{+}$Com_CK, Com_T1, and Com_T2) were tested in a soil incubation to assess NH₃ and GHG emission during composting and following soil utilization. The cumulative NH₃ flux in T1 and T2 were reduced by 39.3% and 50.2%, while N₂O emissions were increased by 7.5 and 15.6 times, relative to CK. The total GHG emission in T2 was reduced by 16.8% compared to CK. Lignite addition significantly increased nitrification and denitrification as evidenced by the increased abundances of amoA, amoB, nirK, and nirS. The increased reduction on NH₃ emission by dewatered lignite could be attributed to reduced pH and enhanced cation exchangeable capacity than lignite. The increased N₂O was related to enhanced nitrification and denitrification. In the soil incubation experiment, compost addition reduced NH₃ emission by 72%∼83% while increased emissions of CO₂ and N₂O by 306%∼740% and 208%∼454%, compared with urea. Com_T2 strongly reduced NH₃ and GHG emissions after soil amendment compared to Com_CK. Overall, dewatered lignite, as an effective additive, exhibits great potential to simultaneously mitigate NH₃ and GHG secondary pollution during composting and subsequent utilization of manure composts.

Keywords: Lignite amendment; carbon dioxide emission; dewatering; methane emission; nitrous oxide emission.