Variations of community structures of ammonia oxidizing and denitrifying bacteria correlated with N 2 O emissions among different composting techniques

BACKGROUND: Composting is a significant source of nitrous oxide (N₂O) emissions. Although numerous studies have correlated quantities of functional genes with N₂O production during composting, information is lacking about the variations of related microbial community structures. This study investigates the responses of ammonia oxidizing and nirK‐type denitrifying bacteria in terms of both community structures and quantities relating with N₂O emissions during pig manure composting with different techniques. RESULTS: The techniques (forced aeration, turn windrow and static pile) significantly affected the N₂O emissions during composting. The forced aeration treatment had the highest cumulative N₂O emission rate which accounted for 2.4% of the initial nitrogen. Terminal‐restriction fragment length polymorphism (T‐RFLP) and clone sequencing analyses of bacterial amoA and nirK genes showed the variations in community structures of ammonia oxidizing and nirK‐type denitrifying bacteria under different composting techniques. Co‐existence of Nitrosomonas spp. with 45‐bp terminal restriction fragment (T‐RF) of the amoA gene and denitrifier with 189‐bp T‐RF of the nirK gene could contribute to the substantial emissions of N₂O in the forced aeration technique. CONCLUSIONS: Results from this study highlight the role of microbial community structure influencing N₂O emissions and provide unique insights for further understanding of the mechanisms of N₂O emissions among different composting techniques. © 2019 Society of Chemical Industry