CAFRE Farm Centres install LECA to reduce ammonia emissions

Lightweight expanded clay aggregate (LECA) added to the uncovered above ground slurry stores at CAFRE Farm Centres.

Lightweight expanded clay aggregate (LECA) has recently been added to the uncovered above ground slurry stores at the CAFRE Beef and Sheep Centre and Hill Farm Centre at Glenwherry. 

Stephen Gilkinson, an Air Technologist at the College of Agriculture, Food and Rural Enterprise (CAFRE) explains:

“LECA is naturally produced clay sphere aggregate that is 1cm in size. The purpose of the product is to reduce ammonia emissions from uncovered slurry stores. Applying LECA to uncovered slurry storage at Greenmount Campus will lessen the likelihood of ammonia deposition on nearby sensitive environmental sites.” 

LECA product comes in large 2.2m3 bags. It is applied to a store with a long reach telescopic handler and emptied with via a pull cord from ground level. The LECA spheres find their own level with a recommended application depth of 10 cm.

In calculating the amount of product needed, take the square metres of the store and multiply by 0.1 to give 10cm layer volume. This value is then divided by the volume of the bags (2.2m3) to give the number of bags required for the store. On installation the tank held a 300mm minimum depth of slurry and was thoroughly agitated with no surface crust.

Stephen Gilkinson, Air Technologist at the College of Agriculture, Food and Rural Enterprise (CAFRE)

“The use of LECA as a store cover is estimated to reduce ammonia emissions by 60% compared to a store with no cover,” commented Mr Gilkinson. 

A naturally occurring crust can reduce ammonia emissions, but this is largely dependent on thickness and may not readily form due to tanks being mixed.

“Therefore, using a low-cost option of LECA, which is designed to float on the surface is a constant ammonia mitigation measure.”

As a naturally occurring product about 10% of the spheres will lose their buoyancy and need to be replaced annually. 

Research on LECA as an ammonia mitigation option for slurry stores is taking place at AFBI Hillsborough. Preliminary results are very positive.  

There are other options to mitigate ammonia emissions from stores, such as impermeable covers, (mandatory on new stores), floating covers and hexa tiles are available. These alternatives are considerably more expensive than LECA. The cost of LECA will vary depending on the surface area of the store; however, a rough guide is £330/bag based on CAFRE’s installation amounts.  

When using LECA do not agitate the tank during extraction to avoid any spheres being drawn into the pump system. When extracting ensure that a vortex does not develop above the outlet (which can be 200 mm to 450 mm above the outlet but can be more), as this will draw LECA product into your pumping system.

CAFRE Technologists are continually investigating innovative systems and technologies to help farmers improve sustainability and profitability. These innovations are demonstrated across the CAFRE Farms and form an integral part of CAFRE Knowledge Transfer Programmes.

More information on Sustainable Land Management innovations can be found on the CAFRE website.