Analysis: research is looking at how to reduce methane emissions from cattle, which accounts for almost 20% of Ireland's greenhouse gas total

By Katie Starsmore and Laurence Shalloo, Teagasc

Methane is the main greenhouse gas in Irish agriculture. According to the 2018 Ireland national inventory report, methane accounts for nearly 58% of Irish agricultural emissions and almost a fifth of the total national emissions. The current target in Ireland is to reduce agricultural emissions to between 17.5 and 19.0 million tonnes by 2030.

A relatively short lived gas compared to carbon dioxide, methane lives in the atmosphere for approximately 12 years and is then converted into carbon dioxide. There is some debate on the global warming potential of methane. However, using the commonly used 100 year global warming potential calculation for every 1kg of methane, this equates to 28kg of carbon dioxide. Ruminant animals such as cattle and sheep are the main producers of methane, with 90-95% of agricultural methane emitted through eructation (burping) and only 5-10% through flatulence and slurry storage.

It is important for researchers to understand the life cycle of methane to be able to reduce emissions. The majority of methane is produced through enteric fermentation, which is the breakdown and fermentation of food in the stomach of the ruminant using a whole range of micro-organisms. Through understanding the process within the rumen we can then begin to understand how to influence the amount of methane produced through diet manipulation, additives etc. There is currently research on-going at Teagasc with VistaMilk SFI Research Centre to explore potential feed supplements that could reduce methane emissions from dairy cows, something which could help the Irish agriculture sector reach their climate targets.

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From RTÉ Radio 1's Morning Ireland, new research is underway aimed at reducing methane gas in Irish cows

Cattle and sheep are the main ruminant animals in Ireland. They are called ruminants because they have 4 compartments to their stomach and the largest is called the rumen. The rumen is responsible for fermenting the food and breaking it down to be more digestible. Food matter is broken down and fermented by microbes in the rumen into volatile fatty acids. As a by-product, carbon dioxide and hydrogen gases are produced from this process.

The toxicity of these gases in the rumen increases as the concentrations increase. To ensure that concentrations do not become toxic, there are bacteria called methanogens, who survive by converting carbon dioxide and hydrogen into methane in the rumen. The majority of this methane produced is burped and the methane levels fluctuate throughout the day depending on grazing behaviour and routine. At times where feeding activity is high, for example after milking, methane production increases as there is an increase in intake. The research that VistaMilk is carrying out is investigating these patterns as well as the impact of feed supplements.

To achieve the targets that have been set, we all need to make a small change to collectively have a big impact. One area researchers are exploring is the potential for feed additives and complementary feed for dairy cows to reduce methane emissions. There is currently research investigating different methane reducing feeds and examining the effects.

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From RTÉ Radio 1's Drivetime, environmental journalist Sean Duke on the links between dairy farming and methane

The methane produced is measured through GreenFeed machines and we are using the first Irish outdoor GreenFeed to measure the methane emissions on a 24/7 basis in Ireland. The cows come to the machines voluntarily (they're given a small portion of concentrate meal as an incentive to use the machines) usually around two or three times a day and their emissions are measured on each visit. When the cows visit ,the air that is expelled is sucked into methane, carbon dioxide and hydrogen gas sensors. The amount of each of these gases is measured and the data is sent onto researchers to analyse.

Each supplement is initially being screened during a 10 week trial period. If a reduction in methane is found, then the product will continue into a two year study for further research. The ultimate aim of the project is to have a range of products for farmers to use that reduce methane and that are recognised within the national inventories.

Some feed additives and supplementary feeds have been shown to reduce methane by 30% per animal, with Australian research showing nearly complete elimination of methane with seaweed based additives. The benefit for Ireland could be huge. If a product is shown to reduce methane by 20% and 50% of dairy farmers use it, the reduction in greenhouse gas emissions is approximately half a million tonnes of CO2.

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From RTÉ Radio 1's Countrywide, Lorna Siggins reports on how seaweed feed for cattle can significantly reduce methane emissions

There are a variety of potential strategies to reduce total agricultural emissions. One of the identified areas that could have a large effect would be increasing the average dairy economic breeding index. This is a tool farmers use to maximise genetic gain in their herd and essentially produce more profitable animals and it has the potential to breed for more efficient animals and also lowering emissions per unit of product.

Another method is for farmers to incorporate clover into their pasture. As clover fixes nitrogen in the soil, there is less need for chemical fertiliser. Slurry application also releases emissions into the atmosphere so changing the method of application to a trailing shoe would reduce these emissions. Farmers would also be able to capture more nutrients rather than losing them to the atmosphere during application. Finally there is a lack of knowledge around soils, and especially around soils under grassland when it comes to soil carbon sequestration, which is now a major focus area within VistaMilk.

There is no silver bullet that can reduce emissions in agriculture to date and Irish farmers would need to incorporate a variety of strategies on their farms to collectively reduce Irish agriculture emissions. But there is a lot of research happening in Ireland at the moment that has the potential have a large impact on agricultural emissions.

Katie Starsmore is a Research Technician with the VistaMilk SFI Research Centre based at Teagasc. Laurence Shalloo is Principle Research Officer in the Livestock Systems Research Department of the Animal and Grassland Research and Innovation Programme and an SFI funded investigator and deputy director of the VistaMilk SFI Research Centre at Teagasc


The views expressed here are those of the author and do not represent or reflect the views of RTÉ