Measuring agriculture’s contribution to air pollution in the EU

The two main sources of air emissions are greenhouse gases (GHGs) that are responsible for climate change, including carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and F-gases (hydrofluorocarbons), and the main air pollutants that damage human health, the environment and biodiversity, which include as sulphur dioxide (SO₂), nitrogen oxides (NO_x), non-methane volatile organic compounds (NMVOCs), ammonia (NH₃), carbon monoxide (CO), as well as fine particulate matter (PM_2.5 and PM₁₀), total suspended particulates (TSB) and black carbon (BC), together with heavy metals and persistent organic pollutants.

Greenhouse gasses

Based on the data of European Environmental Agency (EEA), in terms of source and sink categories, the energy sector¹ was the largest greenhouse gas emitter (82.2%), while agriculture accounted for 11.7% and industrial processes² for 9.8% for total GHG emissions in 2021 in the EU-27. In addition to the 3.4% emissions from the waste source category, the carbon-absorbing forest and land use sector reduced total GHG emissions by 7.1% (Figure 1). It is important to note that the global warming potential of each greenhouse gas varies. Therefore, to facilitate comparison, the unit of measurement CO₂ equivalent (CO₂eq) is used. This standardises the climate effect of various greenhouse gases by taking into account their global warming potential and how long they remain in the atmosphere.

¹ Energy sector comprises of fuel combustion activities (in energy industry, manufacturing (including food), construction and transport), fugitive emissions from fuels and CO2 transport and storage.

² Mineral, chemical, metal and electronics industries and other sectors

Of the GHGs emitted by agriculture, nitrous oxide and methane are the most significant pollutants. EU agriculture accounted for 73.8% of total N₂O emissions which represented only 4.2% of total GHG emissions expressed in CO₂ equivalent. It predominantly comes from inorganic nitrogen fertilisation of soils, but recycling of stalk residues left on the soil and manure management can also be considered as N₂O sources. Methane emissions are mainly the result of cattle and sheep enteric fermentation and from cattle and pig manure storages. In 2021, the EU's agricultural sector contributed to 56.0% of total CH₄ emissions, equating to 7.2% of all GHG emissions (Figure 2). Direct CO₂ emissions from agriculture were responsible for only 0.3% of total GHG emissions, primarily due to the use of urea fertilisers.

Air pollutants

The primary source of emissions for major air pollutants (SO₂, NO_x, NMVOC, NH₃ and CO) as well as particulate matter (PM), similarly to GHG emissions, was the energy sector (64.0%) in the EU-27 during 2021, whilst agriculture was responsible for 16.3% of the emissions (Figure 3). For agriculture, ammonia is the main contributor, but NMVOC, NOX, TSP and PM₁₀ emissions are also significant. 93.9% of the EU’s NH3 emissions come from agriculture, which represents 7.5% of all air pollutants. NH₃ is mainly released from livestock manure in stables and manure storage facilities. However, it is worth noting that a significant amount of NH₃ is also emitted from inorganic nitrogen fertilisers used in arable crops and from the application of manure (Figure 4). Besides the high concentration of this gas, which is harmful to the lungs and serves as a precursor to secondary particulate matter (PM_2.5), it has the potential to cause damage to both terrestrial and aquatic ecosystems through acidification and eutrophication.

Conclusion

Agriculture accounted for 12% of total GHG emissions and 16% of total air pollutant emissions in the EU in 2021. In the ranking of the 13 source and sink categories, agriculture is the fifth in terms of GHG emissions and second in terms of air pollutant emissions, alongside transport. As regards GHG emissions, it is important to note that CO₂, which is the primary source of long-term warming, is the dominant pollutant in sectors that emit more GHGs than agriculture. In agriculture, however, methane and nitrous oxide are the dominant pollutants.

Of the air pollutants, ammonia is the one that stands out among agricultural emissions. It is the most abundant alkaline gas in the atmosphere and a major component of total reactive nitrogen. NH₃ emissions contribute to environmental issues such as acidification, nitrification, and eutrophication. Additionally, it is a precursor to atmospheric particulate matter, which has public health impacts. Reducing anthropogenic ammonia emissions is a priority of both EU legislation and international air quality legislation (Behera et al, 2013.)

What does this mean?

Air pollution and climate change are interconnected issues that should be addressed together, with a focus on protecting public health. Short-lived climate pollutants should be addressed to achieve dual benefits of improving air quality and health while mitigating climate change globally. To effectively tackle air pollution, it should first be measured and monitored, and the main sources of air pollution identified. Reducing air pollution may require physical investments, policy reforms, or both. It is important to consider the context when selecting interventions, as not every intervention is suitable for every situation. It is crucial to choose interventions that have a net benefit, particularly in terms of improved health (The World Bank, 2022; UNECE, 2023).

In a future article we will introduce EU regulations for reducing and reporting on air pollutants and GHG emissions, a measurement approach, and dsm-firmenich’s Sustell™, a tool specifically tailored for livestock farms to address these challenges.