Why temperature matters for ammonia emissions in pig houses

Diet is often the focus when discussing ammonia emissions from pig farms, but it is only part of the story. House temperature and slurry storage and management can also have a major influence on ammonia losses. Izuchukwu Martin Aroh explains.

Ammonia is produced when nitrogen in pig manure breaks down. Most of this nitrogen comes from the portion of feed protein that pigs do not use up or metabolise, which is excreted in urine and faeces and eventually forms slurry in the manure tank. However, the presence of nitrogen and microorganisms alone does not automatically lead to high ammonia emissions. Temperature in the storage tank plays an important role in driving these processes. As the temperatures increase, microbial activity in the slurry becomes more active, increasing the conversion of nitrogen compounds into ammonia. This is why in new houses it is encouraged, and is becoming a requirement, to store slurry away from directly underneath the pigs – to reduce the storage temperature and reduce microbial activity.

Work carried out in research finishing pig facilities at Moorepark, as well as findings from other pig production studies, has shown that ammonia emissions are generally higher during warmer periods of the year, as seen in Table 1. As a result, pig farms often experience greater ammonia losses during late spring and summer than during cooler months.

Temperature can also indirectly affect emissions through ventilation. During warm weather, ventilation systems in pig farms work harder to keep pigs comfortable. While increased airflow is essential for animal welfare, it can also carry more ammonia out of the building and into the atmosphere. This shows the importance of good environmental management. Maintaining appropriate house temperatures, ensuring ventilation systems are correctly adjusted and regularly managing manure or slurry can all help to reduce ammonia losses.

While temperature cannot be controlled outdoors during slurry spreading, understanding its impact can help farmers make informed management decisions throughout the year. Small improvements in housing and manure management practices can contribute to lower ammonia emissions, improved air quality and better environmental performance on pig farms. The use of Low Emission Slurry Spreading systems helps reduce the ammonia losses at spreading time. Even when pig diets remain the same, warmer temperatures can increase ammonia emissions from pig houses through a process known as volatilisation, where ammonia escapes from slurry into the air.

To help protect our environment and maintain the quality of our air, soil and water, it is important to understand the factors that influence these emissions. Good housing management and effective manure handling can help reduce ammonia losses, improve nitrogen use efficiency on the farm and reduce the environmental impacts associated with ammonia, such as acidification of soils and ecosystems.

Table 1 shows the temperatures recorded in several research studies, including work carried out at Moorepark. Higher temperatures mean higher ammonia emissions, thus this work highlights the importance of maintaining appropriate house temperatures, especially during the warmer Summer months.

Table 1: Indoor temperature of finishing pig farms across seasons.