The methane emissions produced by dairy cows while grazing are currently overestimated, according to Laurence Shalloo from Teagasc.

The comments from the head of the Animal and Grassland Research and Innovation programme come as government negotiations continue on setting an emissions reduction target for the farming sector.

“There was some work done measuring methane at grazing maybe 10-12 years ago that had emission factors that were very low in the spring, and when I say very low, I mean, a lot lower than the national inventory calculations,” Shalloo told Agriland.

The summer results were also substantially lower than the national inventory level, while the autumn figure was higher.

Studying emissions

Teagasc has now followed up on that study using different technology from the US called the ‘GreenFeed’ system.

“What we’re finding is that we’re getting spring numbers as low as we were getting the first time, summer numbers are similar to what we were getting, but our autumn numbers are much lower,” Shalloo said.

“So essentially, what we’re saying is that our emission factors for methane in grazing are probably overestimated. Certainly in the dairy setting, we’re over-estimating how much methane our animals are producing.

“There’s a number of things on the dairy side in terms of grass quality, the type of system, the type of cow that might lend itself to have lower methane at grazing,” he outlined.

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Laurence Shalloo, head of the Animal and Grassland Research and Innovation programme at Teagasc

Shalloo explained that agricultural emissions factors are updated on a regular basis.

Teagasc is currently putting together a scientific paper on the latest findings, which will then be sent for peer review.

“That peer-reviewed paper then will hopefully become the basis for conversation with the Environmental Protection Agency (EPA) to include the new emission factors in the models.”

He explained that the peer review process can take up to eight months, but added that the conversation has already begun with the EPA.

Shalloo said that the beef system will have to be more closely studied when it comes to methane emissions at grazing, while overall grass quality will also have to be looked at.

Along with studying absolute emissions factors, Teagasc is also examining strategies to reduce methane.

Carbon sequestration

Shalloo said that a “massive programme” is underway in Teagasc looking at carbon sequestration in both peat and mineral soils, along with hedgerows.

“The idea here is to look at a whole range of management influences on sequestration, from soil type, to climate effects, to sward variety or species, to fertiliser levels and look at the impact on sequestration.

“So it’s very broad and we need it to be broad. Ultimately, where we want to go with this, and my colleagues in Johnston Castle want to go, is to develop models that we can predict the levels of sequestration,” he outlined.

However, results from this research are not expected for at least 2-3 years.

When asked if the research findings will come too late as sectoral emissions reduction targets are expected to be set in the coming week, Shalloo said:

“We’re 100% conscious of that, and obviously the solutions are needed between now and 2030.

“Obviously, this is going to be a really key part of it and there’s going to be a big ramp up in work in research and there’s going to big ramp up in investment and it’s needed to come up with these solutions by 2030,” he said.