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Biogas Digester Hydraulic Retention Time Affects Oxygen Consumption Patterns and Greenhouse Gas Emissions after Application of Digestate to Soil
Author(s) -
Van Nguyen Quan,
Jensen Lars Stoumann,
Bol Roland,
Wu Di,
Triolo Jin Mi,
Vazifehkhoran Ali Heidarzadeh,
Bruun Sander
Publication year - 2017
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2017.03.0117
Subject(s) - digestate , denitrification , biogas , anoxic waters , soil water , environmental science , woodchips , hydraulic retention time , anaerobic digestion , nitrification , greenhouse gas , environmental chemistry , environmental engineering , chemistry , pulp and paper industry , waste management , nitrogen , soil science , methane , wastewater , ecology , organic chemistry , engineering , biology
Knowledge about environmental impacts associated with the application of anaerobic digestion residue to agricultural land is of interest owing to the rapid proliferation of biogas plants worldwide. However, virtually no information exists concerning how soil‐emitted N 2 O is affected by the feedstock hydraulic retention time (HRT) in the biogas digester. Here, the O 2 planar optode technique was used to visualize soil O 2 dynamics following the surface application of digestates of the codigestion of pig slurry and agro‐industrial waste. We also used N 2 O isotopomer analysis of soil‐emitted N 2 O to determine the N 2 O production pathways, i.e., nitrification or denitrification. Two‐dimensional images of soil O 2 indicated that anoxic and hypoxic conditions developed at 2.0‐ and 1.5‐cm soil depth for soil amended with the digestate produced with 15‐d (PO15) and 30‐d (PO30) retention time, respectively. Total N 2 O emissions were significantly lower for PO15 than PO30 due to the greater expansion of the anoxic zone, which enhanced N 2 O reduction via complete denitrification. However, cumulative CO 2 emissions were not significantly different between PO15 and PO30 for the entire incubation period. During incubation, N 2 O emissions came from both nitrification and denitrification in amended soils. Increasing the HRT of the biogas digester appears to induce significant N 2 O emissions, but it is unlikely to affect the N 2 O production pathways after application to soil. Core Ideas O 2 planar optode images system and N 2 O isotopomer analysis were deployed. O 2 consumption was greater for digestate with a hydraulic retention time of 15 d than 30 d. N 2 O production was smaller for digestate with a 15‐d hydraulic retention time. Lower N 2 O emission for 15‐d retention time digestate was due to higher complete denitrification.