Microbial Load, Physical–Chemical Characteristics, Ammonia, and GHG Emissions from Fresh Dairy Manure and Digestates According to Different Environmental Temperatures

Eleonora Buoio, Elena Ighina and Annamaria Costa ()
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Eleonora Buoio: Department of Veterinary Medicine and Animal Science, Università degli Studi di Milano, Via dell’Università 6, 26900 Lodi, Italy
Elena Ighina: Department of Veterinary Medicine and Animal Science, Università degli Studi di Milano, Via dell’Università 6, 26900 Lodi, Italy
Annamaria Costa: Department of Veterinary Medicine and Animal Science, Università degli Studi di Milano, Via dell’Università 6, 26900 Lodi, Italy

Agriculture, 2025, vol. 15, issue 18, 1-15

Abstract: This study evaluated chemical and physical parameters, volatile fatty acids (VFAs), pathogens indicators, ammonia, and greenhouse gas (GHG: CO 2 , CH 4 , N 2 O) emissions from fresh and digested dairy manure under controlled laboratory conditions, simulating storage at 18 °C and 28 °C. Manure and digestate samples were collected during summer 2023 from three dairy farms in Northern Italy, all operating similar mono-substrate, mesophilic anaerobic digesters at 42 °C with short hydraulic retention times (HRT) of ~30 days, instead of the longer HRTs commonly used (up to 90 days). Gas emissions were measured using a static chamber method over 40 min sessions, and cumulative GHG losses were converted to CO 2 equivalents. Anaerobic digestion significantly increased ammonia emissions ( p < 0.001), in comparison with fresh manure samples. Anaerobic digestion affected pH variations, while reducing CH 4 and N 2 O emissions by up to 67% and 50%, respectively. Storage at 28 °C increased total GHG fluxes by 74% for fresh manure and 66% for digestate. Residual methane emissions suggest incomplete digestion, likely due to short HRT and low digestion temperatures. Among pathogens, only clostridia showed significant reduction post-digestion. Overall, anaerobic digestion effectively lowers the global warming potential (GWP) of dairy manure, but higher environmental temperatures exacerbate ammonia and GHG emissions during storage, highlighting the need for optimized post-digestion handling in warm climates.

Keywords: ammonia; GHG; emissions; storage; anaerobic digestion; global warming (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2025
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