Impact of anaerobic digestion on reactive nitrogen gas emissions from dairy slurry storage

Yue Wang; Lina Liang; Jingyi Liu; Dongpo Guo; Zhiping Zhu; Hongmin Dong

doi:10.1016/j.jenvman.2022.115306

Impact of anaerobic digestion on reactive nitrogen gas emissions from dairy slurry storage

J Environ Manage. 2022 Aug 15:316:115306. doi: 10.1016/j.jenvman.2022.115306. Epub 2022 May 17.

Authors

Yue Wang¹, Lina Liang², Jingyi Liu², Dongpo Guo³, Zhiping Zhu⁴, Hongmin Dong⁴

Affiliations

¹ Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, 100081, China; Institute of Plant Nutrition and Resources, Beijing Academy of Agriculture and Forestry Sciences, Beijing, 100087, China. Electronic address: yuewang2008@126.com.
² Institute of Plant Nutrition and Resources, Beijing Academy of Agriculture and Forestry Sciences, Beijing, 100087, China.
³ Asia Dairy Fab. Ltd, Beijing, 100085, China.
⁴ Institute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.

PMID: 35594822
DOI: 10.1016/j.jenvman.2022.115306

Abstract

Biogas digesters are commonly used to treat animal manure/slurry, and abundant digested slurry is generated during the digestion process. Gas emissions from digested and raw slurry may vary with the change in slurry parameters after digestion, but the mechanism is not well understood. Gas emissions from raw dairy slurry (RS) and digested dairy slurry (BS) during 98 days of storage were investigated in this study to evaluate the effects of anaerobic digestion on reactive nitrogen emissions from slurry storage. Results showed that much higher N₂O and NO emission and lower NH₃ emission was achieved in BS than in RS. The mean gaseous emission of RS and BS accounted for 27.8% ± 6.9% and 17.1% ± 2.3% of the initial TN for NH₃, 0.1% ± 0.1% and 3.5% ± 1.6% of the initial TN for N₂O, and 0.0% ± 0.0% and 0.2% ± 0.0% of the initial TN for NO, respectively. Among all detected N₂O-forming and reducing microbial genes, the abundance of amoA genes was the most closely related to N₂O flux (r = 0.54, p < 0.01). More aerobic conditions occurred in BS, and dissolved oxygen (DO) increased to 0.4-1.6 mg L^-1 after 35 days because the low organic matter of BS resulted in good infiltration of surface air into the slurry. The increased DO stimulated the growth of Nitrosomonas and the increase in amoA gene copies and contributed to the high N₂O and NO emissions in BS through the nitrification process. Vulcanibacillus, Thauera, Castellaniella, and Thermomonas were the major denitrifying bacteria that occurred in BS and caused an incomplete denitrification process, which could be another reason for the increase in N₂O and NO emissions from BS. Our study indicated that anaerobic digestion reduced the organic matter content of the slurry and caused an active microbial environment that facilitated the transformation of slurry N to N₂O in BS storage, thus lowering the NH₃ emission compared with RS storage. Therefore, aside from NH₃, N₂O should also be preferentially mitigated during BS storage because N₂O is a greenhouse gas with high global warming potential.

Keywords: Functional genes; Microbial community; N balance; Nitrogen transformation; Reactive nitrogen gas.

MeSH terms

Anaerobiosis
Animals
Gases
Greenhouse Gases*
Manure*
Nitrogen
Nitrous Oxide / analysis

Substances

Gases
Greenhouse Gases
Manure
Nitrous Oxide
Nitrogen