Reducing greenhouse gas emissions from agriculture: Does it matter?

By Gary Lanigan from Teagasc’s Soils, Environment and Land-Use Programme, Johnstown Castle, Co. Wexford.

The facts are simple, but the solutions are more complicated. The undeniable fact is that the earth is warming up; the average global temperature has increased by 0.85° between 1880 and 2012.

The Intergovernmental Panel on Climate Change (IPCC), a United Nations (UN) body comprised 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); this 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). These gases contribute 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 has 25 times the warming potential of CO2. Meanwhile, N2O is 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 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. This agreement seeks to limit the rise in global average temperature, this century, to below 2° above pre-industrial levels.

The EU has also set emission reduction targets; Ireland has been allocated a 20% reduction in emissions by 2020 and a 30% reduction by 2030.

Recently the Department of Communications, Climate Action and Environment published the National Mitigation Plan consultation, which aims to set out Ireland’s road map to reducing emissions.

Teagasc has submitted a response to this consultation. It outlined both the challenges and options available for emission reduction in the agriculture and land-use sector.

Why are these climate targets a challenge to Irish agriculture? Well firstly, agriculture accounts for a third of national GHG emissions.

Secondly, agricultural production – particularly in the dairy sector – is increasing, following the removal of quotas and with Foodwise 2025 setting ambitious targets for primary production, exports and jobs.

The footprint

Projections suggest that increases in global population, as well as 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. Therefore, there is currently a strong focus to reduce the carbon footprint across commodities.

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

The footprint of Irish produce was amongst the lowest in Europe. Recent Teagasc data showed that the carbon footprint of Irish produce has been reduced by approximately 15% since 1990. Similarly, the ‘nitrogen-footprint’ of Irish produce has been reduced by close to 25%.

The solutions

Methods to reduce agricultural emissions, according to a Teagasc strategy, include:
  • Stabilising GHG emissions, particularly methane, by enhanced efficiency measures
  • To further reduce emissions, particularly nitrous oxide;
  • To offset GHG emissions with carbon sequestration from afforestation and agricultural land management;
  • Displacing fossil fuel emissions with wood fuel and biogas.

Over the last number of years, Teagasc’s GHG research group has been working to develop solutions.

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

This will be achieved through the adoption of measures such as the Economic Breeding Index within the dairy herd, beef genomics, improved animal health and extending the grazing season. These efficiencies will reduce the carbon footprint of the dairy and beef sectors, while also stabilising methane emissions.

Improved nutrient management planning, in combination with the optimal use of slurry and legumes, will help increase nitrogen efficiency and reduce N20 emissions.

Other strategies can reduce GHG 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;
  • 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.

‘The whole sector must work together’

As both the 2020 and 2030 GHG reduction targets are multi-year targets, the total GHG reduction will be highly dependent on rates of uptake. This means that the role of knowledge transfer (KT) programmes and education will be more important than ever.

Research alone will not lead to emissions reductions without a strong linkage to advisory and education, as well as the involvement of farmers.

In summary, CO2, methane and N20 all contribute to climate change. There is the potential to reduce N20 and CO2, whilst stabilising methane in the short term.

Ultimately, achieving timely and substantial levels of mitigation will require the whole sector to work together. Effective large-scale mitigation will only occur if best-practice can be communicated on the ground.

This will involve the development of closer links between research/analysis, the development of relevant policies and the effective translation of these policies on the ground via knowledge transfer.