Towards standardised measurement of ammonia emissions from naturally ventilated dairy barns: Progress and perspectives

Measuring ammonia (NH3) emissions from naturally ventilated dairy barns (NVBs) is a significant challenge due to their structural heterogeneity, dynamic and variable airflow, and complex pollutant dispersion. However, these emissions contribute to air pollution, ecosystem acidification, and eutrophication. Accurate quantification is essential for complying with regulations and implementing effective mitigation strategies, but it is complicated by variable climate conditions and the lack of shared international measurement standards. The study critically analyses progress in measuring NH3 emissions from NVBs through a critical review based on a systematic literature search in recent years, assessing the state of method consolidation, identifying emerging approaches, investigating critical issues related to measurement uncertainty, and highlighting the growing interest in advanced tools to support data interpretation. The review was conducted using the Scopus and Web of Science databases, and the final dataset was subjected to critical analysis, including categorising the methods, objectives, and main topics, and examining emission factors, uncertainty, and modelling. The results highlight a progressive methodological convergence on CO2 mass balance and direct airflow measurements as the most common strategies for quantifying emissions. The analysis of emission factors (EFs) showed values ranging from 0 to 2.4 g h−1 LU-1, with variability across studies. Clear seasonal differences were observed, with higher EF values consistently reported during summer, while additional variability was associated with differences in sampling strategies. Despite the inherent complexity of NVBs, methodological advances in recent years have improved the ability to quantify, predict, and correct uncertainties in NH3 emissions.