N2O emissions and nitrogen transformation during windrow composting of dairy manure

• DOI: 10.1016/j.jenvman.2015.06.021
• Publication Date: 2015-06-20T01:00:39Z
• Authors: Ruirui Chen; Yiming Wang; Wei Wang; Shiping Wei; Zhongwang Jing; Xiangui Lin
• Keywords: 13. Climate action; 01 natural sciences; 0105 earth and related environmental sciences; 12. Responsible consumption

Abstract Windrow composting involves piling and regularly turning organic wastes in long rows, being in the succession of static standing periods between two consecutive pile turnings as well as a period of pile turning. N 2 O emissions and N transformation were investigated during the processes of windrow composting. In contrast to the conventional understanding, we observed that N 2 O concentrations inside compost materials were significantly higher after pile turning (APT) than before pile turning (BPT). Pile turning triggered a burst of N 2 O production rather than simple gaseous N 2 O escape from the stirred compost. Denitrification was the dominant pathway in pile turning because the observed NO 2 − and NO 3 − concentrations were significantly lower APT compared to BPT. The sudden exposure of O 2 severely inhibited N 2 O reductase, which can block the transformation of N 2 O to N 2 and thus caused an increase of N 2 O emission. As the NO 2 − and NO 3 − concentrations rose during the following 48 standing hours, nitrification dominated N transformation and did not cause an increase of surface N 2 O emissions. Thus, pile turning resulted in a dramatic conversion of N transformation and strongly influenced its flux size. It was also found that high NO 2 − was accumulated in the compost and had a strong correlation with N 2 O emissions. Practical methods regulating nitrite and the frequency of pile turning would be useful to mitigate N 2 O emissions in manure composting.