Steps for reducing farms’ ammonia emissions
WITH the agricultural industry challenged to meet targets for reducing Greenhouse Gas emissions, one aspect is to manage slurry and livestock buildings.
By managing some routine activities on farm, ammonia emissions can be reduced.
In this article, Martin Kirk, a CAFRE Technologist based at Greenmount Campus, explains the various methods farmers can implement to reduce ammonia emissions linked to livestock buildings, slurry management, and also how tree planting can reduce ammonia emissions.
Ammonia is a naturally occurring gas containing nitrogen and hydrogen, with the chemical formula NH3. Some agricultural practices and activities encourage the loss of nitrogen into the atmosphere in the form of ammonia.
When faeces (containing the enzyme urease) and urine (containing urea) mix, ammonia is produced and released.
Ammonia is a key air pollutant having a significant effect on the environment and indirectly affecting human health. Ammonia is released from livestock buildings through the breakdown of urea (in urine) by the enzyme urease (in faeces).
Most of Northern Ireland’s ammonia emissions (96 per cent) come from the housing of livestock and subsequent storage and spreading of livestock manures, particularly cattle (64 per cent).
“Within livestock buildings, it is a challenge to keep both urine and faeces separated and therefore reduce ammonia emissions.
“Where these are not regularly removed to storage, or urine is allowed to pool across large areas, significant volumes of ammonia are released.
Even after scraping, the remaining film of urine and faeces will continue to release ammonia, but to a much lesser extent,” said Mr. Kirk.
An important mitigation strategy that could be implemented on farms across Northern Ireland is the frequent scraping of slurry-covered floors.
The optimum scraping frequency, to reduce ammonia emissions, is every two hours.
Scraping systems will reduce ammonia emissions further when installed in combination with low-emissions floor designs.
“For other areas soiled by slurry outside of livestock pens, areas such as collecting yards and handling facilities, further emission reductions can be achieved through frequent washing,” said Mr. Kirk.
Emissions from external slurry storage can be reduced by limiting the airflow across the surface of the slurry.
This can be achieved by installing impermeable or semi-permeable covers, or by increasing the depth of stores to reduce the ratio of surface area to volume of the stores.
Another novel mitigation method is the use of site-specific tree planting to capture ammonia emissions.
Air from nearby livestock buildings is naturally directed into a relatively open tree canopy. The movement and turbulence of the air, through the trees, encourages ammonia gases to be deposited on the tree and leaf surface.
While most farms will have multiple ammonia emission sources, management techniques and equipment are available to reduce emissions from livestock buildings and slurry management.
The retention of nitrogen within the farm system will benefit both the farmer and the surrounding environment.