| Biogas digester plant is widely used in livestock industry as an efficient energy saving and emission reduction measure, but little research has been done about the carbonaceous and nitrogenous gas emissions from biogas digester effluent（BDE） storage. The gas emissions from pig manure based BDE storage is studied with dynamic chamber method, to elucidate the influence of key impact factors such as slurry properties, environment parameter（storage temperature）, management parameters（storage depth, storage period） on the characteristics of CH4、N2O、NH3、NO、CO2 gas emissions from BDE storage. The bio-mechanism of gas emissions were investigated by using PCR, DGGE, Illumina MiSeq Platform. The main findings obtained are as follows:（1） Under the specific storage environment with high storage temperature and high slurry DO level, high N2 O emission occurred in BDE may trigger the greenhouse gas（GHG） emissions from BDE storage to be higher than that from raw liquid manure（RLM） storage. With the storage temperature of 30℃, DO level of 2.2-6.3 mg L-1, the CH4 and NH3 emissions from BDE storage were 98.9% and 45.5% lower than RLM, but the N2 O emissions was 360.7% higher than RLM, causing the GHG emission from BDE to be 5.1% higher than RLM. The low COD/TN ratio of the BDE（1.6:1） was the key factor for its high N2 O emission. Differences in CH4 emission characteristics between RLM and BDE were attributed to the differences in methanogen species, while differences in N2 O emission characteristics were attributed to the population of ammonia-oxidizing bacteria（AOB）.（2） With storage depth lower than 2.0m, storage depth showed no significant influence on GHG emissions from BDE storage. The cumulative GHG emissions per unit volume slurry were 15.1 ±2.2, 16.6 ±1.9, 16.6 ±1.2 kg CO2-eq m-3 for BDE stored at 1.0m, 1.5m and 2.0m, respectively. The higher the storage depth was, the lower the CO2, NH3, and N2 O emissions would be, indicating that the storage depth of 2.0m was the priority for gas mitigation. Under the specific storage environment, the storage depth showed no influence on methanogen diversity of BDE, while the relative abundance of methanogen was highest with the storage depth of 2.0m.（3） Temperature showed a significant influence on carbonaceous and nitrogenous gas emissions from BDE storage; 15 °C was the critical temperature for gas emissions. CH4, N2 O, NH3 and NO emissions were extremely low for the 5, 10 and 15 °C regimens, and no significant difference occurred for these gases among the three regimens. The N2 O and NO emissions increased significantly when temperature reached 25 °C. The N2 O emission factor was in the range of 0.0003-0.0006 kg N2O-N kg-1 N for 5, 10, 15 and 20 °C regimens, while being 0.0035 kg N2O-N kg-1 N for 25 °C. No significant difference occurred for NH3 emissions under 20 and 25 °C. As the temperature increased from 5 °C to 25 °C, the TN loss ratio increased from 8.9% to 41.9%, and NH3-N losses accounted for 25% of the TN with storage temperature of 20 and 25 °C.（4） The Illumina MiSeq indicated that the methanogen community in BDE storage was different from that of biogas fermentation process. Nitrosomonas was the key bacteria influencing the N2 O emissions from BDE storage. Vulcanibacillus, Castellaniella and Thermomonas would be the important denitrifying bacteria leading N2 O emissions. Methanobrevibacter and Methanosaeta were two major methanogens from BDE storage. The high CH4 emission during the initial storage period may be triggered by the decomposition of acetic acid by Methanosaeta. Enterobacter plays a key role in mthanogenesis for providing hydrogen for hydrogenotrophic methanogens.（5） Synthesis analysis showed that, controlling BDE storage temperature lower than 25°C and storage depth at 2.0m can achieve a good GHG controlling effect. The results presented in this study can serve as a reference for compiling national gas emission inventory, also being as a basis for gas mitigation measures design for BDE storage. |
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