CH4, NH3, N2O and NO emissions from stored biogas digester effluent of pig manure at different temperatures

•Temperature affects gas emission from biogas digester effluent (BDE) of pig manure.•All gas emissions were extremely low for BDE stored at 5, 10 and 15 °C.•The critical temperature for N2O and NO emissions of BDE storage was 25 °C.•N loss increased from 9% to 42% with temperature increasing from 5 °C to 25 °C.•NH3 was the main form of nitrogen loss, accounting for 4.4–34.9% of the TN.

Emissions of ammonia (NH3) and greenhouse gases (GHG) from digested pig manure storage have negative agronomic and environmental implications. The study was undertaken to evaluate how temperature affects NH3, GHG (i.e., methane (CH4) and nitrous oxide (N2O)) and nitric oxide (NO) emitted from a pig manure based biogas digester effluent (BDE) storage system. Six groups of 125 L of BDE were stored in triplicate for 99 days at 5, 10, 15, 20, 25 °C and uncontrolled temperature condition (UT: temperature ranged from 32 °C to 20 °C) for gas monitoring using the dynamic emission vessel method. BDE characteristics were analyzed weekly during the storage. The results showed that all gas emissions were extremely low for the 5, 10 and 15 °C regimens. The critical temperature for N2O and NO emissions from BDE storage was 25 °C. As the temperature increased from 5 °C to 25 °C, the N loss ratio increased from 8.9% to 41.9%, and NH3 was the main nitrogen loss form, accounting for 4.4–34.9% of the TN. The overall GHG emissions were dominated by N2O, which accounted for more than 53% of the CO2-eq emissions for all of the regimens. The CH4 emission factor was 0.001–0.019 L g−1 VS; the N2O emission factor was in the range of 0.0003–0.0007 kg N2O–N kg−1 N for 5, 10, 15 and 20 °C regimens, while being 0.0038 and 0.0016 kg N2O–N kg−1 N for 25 °C and UT regimens, respectively. The results indicate that NH3 and N2O are the two major gas emissions from BDE storage, and the future research on mitigation for BDE storage should focus more on N2O and NH3.