Increasing slurry storage capacity on Irish farms to improve water quality should not significantly impact livestock-related greenhouse gas emissions, a leading Teagasc scientist has maintained.

This is despite a recent British research study which claimed that methane emissions from stored slurry could be 2.8 times greater than previously assumed.

Teagasc researcher Shaun Connolly said that additional slurry storage would primarily result in “better manure management” and enable farmers to optimise when slurry is spread and maximise its value as a fertiliser.

“This is simply making sure farmers have enough [slurry] capacity and can spread in the right conditions, rather than making them spread further out in the year,” Connolly claimed.

“I don’t believe increasing storage capacity is really going to have an effect on emissions.

“Because, unless something major happens on someone’s farm, they’re not really going to change their slurry spreading practices,” Connolly maintained.

If a farmer has the same animal numbers but increases storage capacity then this won’t increase the emissions unless they change their normal spreading patterns, he added.

Rainfall and temperatures not taken account of

Connolly accepted that emissions from slurry increased the longer it was stored, but he said other factors also had to be taken into consideration.

“In general, the longer slurry is stored, the more greenhouse gas and ammonia emissions are produced,” he said.

Past Teagasc studies on stored slurry have put methane emissions over a three-month period at 801g/m2 from 7% dry matter slurry.

“Extrapolating this over a five- or six-month period suggests methane emissions of approximately 1,335–1,602 g/m²,” Connolly said.

Other factors

However, this estimate doesn’t take into consideration factors such as dilution from heavy rainfall, which could reduce emissions, or higher temperatures later in the year which could increase them, he said, adding that further research on emissions from stored slurry is needed.

A study by University of East Anglia scientists, based on data from two Cornish livestock farms over 51 weeks during 2022-2023, found that emissions from manure management could be significantly under-estimated.