Reducing greenhouse gas emissions from agriculture

The problem

The facts are simple, the solutions are more complicated. The undeniable fact is that Earth is warming up, with the average global temperatures having increased by 0.85°C between 1880 and 2012.

The Intergovernmental Panel on Climate Change (IPCC), a UN body of hundreds of expert scientists who assess the science of climate change, has stated that man-made greenhouse gases (GHG) are the primary cause of this warming.

The main man-made gas is carbon dioxide (CO2), which accounts for 76% of global emissions. However, agricultural emissions are dominated by methane (from ruminants and manures) and nitrous oxide (N2O from fertiliser and animal deposition) and contribute to 16% and 6% respectively towards man-made warming.

While there is much less methane and N2O in the atmosphere, as outlined in IPCC reports, these gases have different capacities to trap heat. As a result, they are assessed using global warming potential, which compares the ability of 1kg of each gas to trap heat over a 100-year time horizon.

Using this measure, methane (CH4) has 25 times the warming potential of CO2 and N2O 298 times higher than CO2. These gases also remain in the atmosphere for different lengths of time. CO2 does not break down easily and it remains in the atmosphere for several centuries. N2O also has a lifetime of 121 years. In contrast, the atmospheric lifetime of methane is much shorter at 12.4 years.

The challenge

In order to address climate change, 197 countries signed up to the Paris Agreement which seeks to limit global temperature rise this century to below 2°C above pre-industrial levels.

The EU has also set emissions reduction targets, with Ireland allocated a 20% reduction in emissions to 2020 and 30% to 2030.

Why are these climate targets a challenge to Irish agriculture? Well, firstly agriculture accounts for one-third of national GHG emissions. Secondly, agricultural production, particularly in the dairy sector, is increasing post-quota removal and Foodwise 2025 has set ambitious targets for primary production, exports and jobs.

The footprint

Projections suggest that increases in global population and changing patterns of wealth will increase demand for dairy and meat by more than 50% to 80% by 2050. As a result, there are significant concerns that increasing food production will lead to increased global GHG emissions, so there is currently a strong focus to reduce the carbon footprint across commodities.

Comparisons of the carbon footprint of international livestock production by Food and Agriculture Organisation (FAO) and the EU Joint Research Council have demonstrated that the carbon footprint of dairy and beef production was the lowest in temperate grass-based systems, with the footprint of Irish produce amongst the lowest in Europe.

Recent Teagasc data showed that the carbon footprint of Irish produce has been reduced by c. 15% since 1990. Similarly, the ‘Nitrogen-footprint’ of Irish produce has been reduced by c. 25%.

The solutions

Teagasc’s strategy for reducing agricultural emissions is a) to stabilise GHG emissions, particularly methane, by enhanced efficiency measures, b) to further reduce emissions, particularly nitrous oxide, c) to offset GHG emissions with carbon sequestration from afforestation and agricultural land management and d) displace fossil fuel emissions with wood fuel and biogas.

Much of the answer lies in farm efficiency: so if we can produce food with fewer inputs, then this reduces emissions to the atmosphere and costs to the farmer.

This will be achieved through adoption of measures such as better breeding, improved animal health, and extending the grazing season.

These efficiencies will reduce the carbon footprint of dairy and beef and stabilise methane emissions via increased product per head.

Other strategies can reduce greenhouse gas emissions even further. Examples include the development of novel, low-emission fertilisers, reducing crude protein in bovine and pig diets, fatty acid supplementation to reduce methane, drainage of poorly drained mineral soils and adding amendments to manures during storage.

In addition, enhancing carbon sequestration and/or reducing soil carbon losses are key strategies to reducing sectoral emissions. This will principally be achieved through increased afforestation, reducing losses on organic soils and enhancing pasture sequestration.

In summary, CO2, methane and nitrous oxide all contribute to climate change. There is potential to reduce the more long-lived nitrous oxide and CO2, while stabilising methane in the short term.

Ultimately, achieving timely and substantial levels of mitigation will require the whole sector, including farmers, industry, research, advisory/education and policymakers working in concert.

Read more

Scientific opinions on climate change

The Earth is in the midst of a CO2 famine – Princeton professor

MEPs pass stricter climate targets estimated to cost Ireland €1bn

Editorial: idealism trumps reality in climate change vote

Letter: false accusation – climate debate