Reduce Methane Emissions
Methane (CH4) is a colourless, odourless gas occurring abundantly in nature and as a product of certain human activities. Globally, it is the second most important greenhouse gas (GHG). Its contribution to global warming is estimated at 27 times that of carbon dioxide, over a 100 year period. Once produced, methane persists in the atmosphere for around 9-12 years after which it is eventually broken down into carbon dioxide and water.
Biogenic methane (methane produced by animals and plants) is one of the predominant GHG emissions emitted from global agricultural, the majority of which is originates from ruminant livestock as enteric or manure methane. Ruminant livestock have a unique ability to convert grass into high quality sources of dairy and meat protein for human consumption. In the rumen or forestomach of ruminant livestock there is a microbial ecosystem with bacteria, archaea, protozoa and fungi, collectively known as the rumen microbiome. This microbial ecosystem allows ruminant livestock to obtain nutrition from plant matter. Enteric methane is a natural by-product of this process, and is estimated to account for some 90-95% of the methane associated with ruminant livestock.
A 500kg beef animal on a high concentrate diet produces 230 g methane per day and a 550kg dairy cow grazing on pasture emits about 320-330 grams of methane per day.
Biogenic methane cycle: Methane (CH4) is emitted to the atmosphere by ruminant livestock as a by-product of digestion in the rumen (enteric) or from manure. Over the course of 9-12 years, methane is converted to carbon dioxide (CO2) and water (H2O). The carbon dioxide is eventually taken up and used by plants to grow, as part of photosynthesis, which are subsequently consumed by livestock, restarting the ruminant biogenic methane cycle.
In the EPA's national inventory report for 2022, 74% of Irish agricultural GHG emissions were attributed to methane associated ruminant livestock production: 65% from methane produced by the rumen of cattle and sheep and a further 9% from methane associated with the storage of manure and slurry from ruminants, as well as pigs. As a result, reducing the volume of methane produced by ruminant livestock, will be critical to achieving the agricultural sectors 2030 GHG emissions reduction target.
Priority Research Questions
- What are the emission factors and drivers of enteric methane emissions from dairy, beef and sheep under Irish pastoral conditions?
- What is the impact of genetics, feed additives and supplements, grazing management and novel measures on enteric methane output?
- How do management practices to reduce the age of finishing of prime beef cattle impact on enteric methane emissions and meat quality?
- How can manure management/processing strategies and manure additives reduce manure methane emissions?
- Can the rumen microbiome be manipulated to reduce enteric methane emissions?
Anticipated Research Outcomes
- Refined national methane emission factors to reduce inventory uncertainty.
- Enhancing national ruminant breeding indexes to improve efficiency, reduce emissions, and assess the potential for directly breeding livestock with lower methane emissions.
- Development of measures to improve live weights on farm, in turn supporting reduced age of finishing to reduce methane emissions.
- Development of grassland /grazing management systems to reduce methane emissions.
- Quantification of the methane reduction efficacy of feed additives and supplements and novel measures in animals managed under grassland systems.
- Enhancement of manure management technologies, including manure additives, to reduce methane emissions from manure storage.
Methane Green Feeds: Across the entire organisation, Teagasc has some of the most up to-date and advanced research technology for measuring both enteric and manure methane emissions. The Green Feeds monitoring systems measure individual feed intake, which is a critical factor influencing the quantity of enteric methane emitted by ruminant livestock.
Research Snapshots
- Animal breeding - breed animals which emit less methane; this is a long term strategy
- Dietary supplementation/management - feeding of methane reducing supplements
- Improved animal health – a healthy animal will be more productive during its lifetime
- Improving lifetime performance/reducing the age at finishing – finishing prime beef animals at a younger age can reduce the volume of methane produced over the animal’s lifetime.
Please note: All farms are unique and please contact your local Teagasc advisor for your individual enquiries before carrying out any solutions listed above.
Feed additives to reduce methane emissions
The methane mitigating feed additive 3-nitrooxypropanol (3-NOP) has been evaluated across a range of differing scenarios for Irish conditions. 3-NOP is most effective in indoor settings when mixed throughout feed using a mixing
wagon, achieving methane reductions of ~30%. However, in pasture-based dairy systems, grazed grass makes up the majority of an animal’s feed intake. At present, the only practical opportunity to supplement animals with feed additives during grazing is via supplemental feed in the milking parlour twice daily. However, in this scenario, studies have shown a short efficacy period of the additive, due to its rapid metabolism in the rumen once ingested, meaning the cumulative reduction in daily enteric methane was only ~5%. There is a large research programme underway in Teagasc Moorepark to identify anti-methanogenic feed additives that are effective and practical to use in pasture-based systems.
Dr Hazel Costigan from Teagasc Moorepark presenting on methane reducing feed additives at the Signpost General Assembly in November 2024. Paper: Methane Reducing Feed Additives (PDF)
The Impact of Finishing Age on GHG Emissions
Reducing the finishing age of prime beef cattle has been identified as a key greenhouse gas mitigation measure for the Irish agricultural sector. The amount of enteric methane produced by ruminants is largely driven by feed intake. As an animal’s level of feed intake increases, more feed is fermented in the rumen, which increases the supply of energy and protein to the animal, but also elevates the supply of substrates to methanogens (microbes that produce methane), leading to an increased synthesis of methane in the rumen. Based on work conducted by Teagasc Grange, growing beef cattle have been shown to produce 22-27 g of methane for every kg of dry matter intake (DMI). Both rumen size and the voluntary feed intake of an animal increases in order to meet the nutritional demand of an animal as it grows. Thus, at the latter stages of an animal’s life, when it is at its heaviest and thus consuming a greater proportion of feed, the quantity of methane an animal produces on daily basis is at highest. As a result, by reducing the finishing age of an animal, the total quantity of methane associated with bringing that animal to finish, is reduced.
Ongoing research at Teagasc include the BeefQuest project which aims to determine the key animal nutrition, health and on-farm environmental related factors presently constraining growth performance, and subsequently influencing the finishing age of cattle on Irish farms. Research is also underway at Teagasc Grange to assess the impact of early
life nutrition on the lifetime live weight performance of cattle.
Dr Paul Crosson from Teagasc Grange presenting on the Impact of Finishing Age on GHG Emissions at the Signpost General Assembly in November 2024. Paper: Reducing Greenhouse Gas Emissions from Agriculture by Finishing Beef Cattle at Earlier Ages (PDF)
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Current projects on reducing methane emissions