How storage conditions shape greenhouse gas emissions, physical-chemical characteristics, and pathogen fate in cattle manure.

Given the large amounts of manure generated in livestock farming, evaluating the effects of aerobic and anaerobic storage on emissions and pathogen fate is essential. Accordingly,six batches of fresh cattle manure were collected over 12 months and stored for 28 days under aerobic and anaerobic conditions in 2.1-L gas-tight bottles. The emissions of greenhouse gases (GHG) (CO2, CH4, N2O) and H2S, as well as the variations of the physical-chemical characteristics and pathogen fate were assessed during storage. Aerobic storage promoted a higher production of CO2 (70 - 80 mgCO2/g) compared to anaerobic conditions (7 - 9 mgCO2/g). CH4 and H2S emissions tended to be higher under anaerobic storage conditions, although some manure batches exhibited comparable CH4 production under aerobic storage. Maximum cumulative emissions reached 0.45 mgCH4/g and 0.2 mgH2S/g under anaerobic conditions. Within the experimental campaign, some manure batches exhibited the highest cumulative N2O emissions (0.8 - 1.3 mgN2O/g) under aerobic storage. These emissions significantly contributed to the overall global warming potential, with peak values reaching 33000 kg CO2-eq/100 m3. In addition, aerobic storage of manure reduced Campylobacter and showed variable Escherichia coli removal among manure batches. Finally, principal component analysis (PCA) grouped manure samples according to their physical-chemical characteristics and GHG emissions, explaining a total variance of 70% and 68% for aerobic and anaerobic storage conditions, respectively. Complementary ANOVA confirmed significant differences in GHG emissions among manure batches collected at different periods of the year, providing additional insight into the combined influence of manure characteristics and storage conditions on emission behavior.