A new review article systematically compared ammonia monitoring technologies and measurement protocols in pig production, offering a practical decision-support framework to guide researchers, farmers, and policymakers toward reliable, regulation-ready emission monitoring.
Recently, a team of researchers from several Irish institutions, including Teagasc, the University College Dublin, and the Animal & Grassland Research & Innovation Centre explored the current state of ammonia monitoring technologies. This study, which was led by led by Izuchukwu Martin Aroh of the Animal & Grassland Research & Innovation Centre at University College Dublin, was published in the journal Computers and Electronics in Agriculture (1). The findings from this review article highlight the strengths and limitations of the main ammonia monitoring technologies used in pig research and commercial farming.
Ammonia (NH₃) emissions from pig production have become a focal point of global environmental and agricultural policy, driven by their contribution to air pollution, ecosystem acidification, climate-related interactions, and concerns around animal welfare and human health. For example, in South Korea, it has been reported that pig production contributes in 30% of total ammonia emissions in the country (2). In Ireland, although pig production only accounts for 4% of total ammonia emissions, the agricultural sector in the country accounts for 99% of total ammonia emissions (3).
As a result, countries such as Ireland are looking at ways to reduce their overall ammonia levels. Under the National Emissions Ceiling Directive (NECD), Ireland and other EU member states have a directive to reduce ammonia emission levels by 5% below the 2005 levels by 2030 (3).
Ammonia emissions from agriculture often result from undigested protein from livestock diets, which is then excreted from livestock through urine or feces (4). This pollutes the air and results in a loss of nitrogen, which is important for the soil and crops to grow properly.
In their study, the research team compiled approximately 115 rigorously selected studies from Europe, North America, and Asia to evaluate current ammonia detection methods. The goal was to determine what methods are more effective and where the current limitations in these methods arise. Some of the methods evaluated in this study included electrochemical (EC) gas sensors, photoacoustic spectroscopy (PAS) gas sensors, laser absorption spectroscopy (LAS) gas sensors, Fourier transform infrared (FT-IR) spectroscopy gas analyzers, and colorimetric gas detector tubes (1). Importantly, the review does not treat these devices in isolation but situates them within the realities of pig housing design, ventilation systems, feeding practices, and slurry-based emission dynamics.
Monitoring ammonia in pig production presents unique challenges because of other variables that need to be taken into consideration to obtain a highly accurate reading. Most pig facilities contain high stocking densities, slurry-based manure systems, and diverse housing designs ranging from fully slatted floors with mechanical ventilation to naturally ventilated barns (1). Apart from the environment, other variables, such as temperature, humidity, dust, and airflow patterns further influence both ammonia release and sensor performance (1). According to the authors, these complexities are often underrepresented in broader livestock emission reviews, making technology selection difficult for researchers, farmers, and policymakers alike.
“Pig production presents distinct challenges such as slurry-based emissions, high stocking densities, diverse housing designs including mechanical and natural ventilation, and feeding practices that affect emission dynamics and sensor performance,” the authors wrote in their study (1). “These aspects are not comprehensively addressed in existing reviews.”
The researchers evaluated each major class of ammonia monitoring technology, highlighting how performance trade-offs shape their suitability for different applications.
For example, electrochemical gas sensors emerge as the most accessible option for on-farm monitoring. These sensors are relatively inexpensive, compact, and increasingly compatible with Internet of Things (IoT) platforms, making them attractive for continuous monitoring and integration into precision livestock farming systems (1). However, the authors emphasize that EC sensors are not without drawbacks. Calibration drift, saturation at high ammonia concentrations, cross-sensitivity to temperature and humidity, and limited long-term stability remain significant challenges, particularly in harsh pig house environments (1).
Another method used for ammonia detection is photoacoustic spectroscopy gas sensors. These instruments offer high sensitivity, accuracy, and the ability to sample air from multiple locations via switching manifolds (1). These features make them especially valuable for detailed emission studies and mitigation trials. However, their size, cost, and technical complexity restrict their adoption outside research institutions (1).
The third method they looked at were laser absorption spectroscopy gas sensors, including tunable diode laser systems. The benefits of LAS devices are that they provide high temporal resolution and strong selectivity for ammonia, with newer designs becoming more compact and cost-effective (1). Although still less common on commercial farms, there is growing interest in LAS technologies for both research and advanced monitoring applications.
Meanwhile, FT-IR spectroscopic gas analyzers are the most established method, according to the researchers. These systems can simultaneously measure multiple gases with high accuracy, making them indispensable for validation and regulatory benchmarking (1). However, the researchers acknowledge that their operational demands, high capital cost, and general bulkiness are key barriers in its practicality for routine farm deployment (1).
And finally, the researchers examined colorimetric gas detector tubes. The benefits of using them include their low cost and ability to deliver spot measurements. As a result, they are good for quick checks and indicative measurements (1). However, they do sacrifice accuracy for speed and cannot support continuous monitoring, which means that they cannot play an active role in comprehensive emission studies (1).
In the second part of this feature of monitoring ammonia emissions in pig facilities, the measurement protocols are explored, and what future studies on this topic should investigate.
