Greenhouse gas emissions and projections

Environmentally, there are two key benefits to using urease inhibited (or ‘stabilised’) fertiliser products:

1. the reduction of emissions of ammonia, an important air pollutant, when compared to the use of ‘straight’ urea;
2. when used as a replacement for Calcium Ammonium Nitrate (CAN), a reduction in nitrous oxide emissions, a potent greenhouse gas.

As outlined in the international guidelines for national inventories and projections (FAQ: How are national inventories updated with the latest science?), research should be conducted at field scale, covering a range of soil types and environmental conditions so that efficacy of any particular product is demonstrated at field level under the conditions in which it will be used.

The following fertiliser products have met the criteria for inclusion as urease inhibitor products within the national greenhouse gas and air pollutant Inventories and Projections 1990-2022:

• N-(n-butyl)-thiophosphoric triamide (NBPT)
• N-(n-propyl)-thiophosphoric triamide (NPPT)
• N-(n-butyl)-thiophosphoric triamide (NBPT) + N-(n-propyl)-thiophosphoric triamide (NPPT)
• N-(2-nitrophenyl) phosphoric triamide (2NPT)

The most relevant national research demonstrating efficacy at field level (Forrestal et al. 2016 [1]; Harty et al., 2016 [2]; Roche et al., 2016 [3]) provide the evidence base for the inclusion of these products. 2NPT’s mode of action is similar to that of NBPT, however, to date it’s use in Ireland has been minor.

If/when information is provided on new products that meet the criteria specified these products will be added to the list above. The emission or abatement factor is applied from the time the product was placed on the Irish market and retrospectively across the time series in instances where a product has been on the market prior to provision of supporting evidence. In the absence of robust scientific evidence then the emission factor for straight urea is applied.

[1] https://doi.org/10.1111/sum.12232

[2] https://doi.org/10.1016/j.scitotenv.2016.04.120

[3] https://doi.org/10.1016/j.agee.2016.08.031

The EPA incorporates the latest scientific information, including on new technologies, in the National Greenhouse Gas Inventories and Projections. This arises through the adoption of new international guidelines on inventory compilation and from national and international research.

In introducing new science and improvements to the inventories, the EPA follows the principles set out in the emission inventory guidelines set out by the Intergovernmental Panel on Climate Change (greenhouse gas emissions)[1],[2] and European Monitoring and Evaluation Programme/European Environment Agency (air pollutants)[3]. Some of the key principles that the EPA follows include:

• Ensuring measurement data covers a representative sample and that suitable measurements have been used.
• Preferring the use of measurement methods developed by official standards organisations and field-tested to determine their operational characteristics.
• Developing Ireland specific emission factors for key categories, with the goal to improve the accuracy of relevant emissions and removals estimates.
• Verifying that emission factors derived from direct measurement are representative of Irelands circumstances.
• Referencing peer-reviewed, published literature relevant to Irelands circumstances as this should provide the most accurate representation of practices and activities.

As part of both international reporting obligations and continuous improvement processes, Ireland’s national inventories are reviewed annually by both the EU and the UN. Recommendations arising from these reviews [4] allow the identification and prioritisation of national greenhouse gas and air pollutant emission research. Subsequently, research projects funded by both the EPA and other public bodies, with associated national and international technical committee participation by the EPA’s Emission Statistics Team, ensure the increasing robustness of emissions estimation.

[1] https://www.ipcc-nggip.iges.or.jp/public/2019rf/pdf/1_Volume1/19R_V1_Ch02_DataCollection.pdf

[2] https://www.ipcc-nggip.iges.or.jp/public/2019rf/pdf/1_Volume1/19R_V1_Ch04_MethodChoice.pdf

[3] https://www.eea.europa.eu/publications/emep-eea-guidebook-2023/part-a-general-guidance-chapters

[4] Latest UNFCCC review report: https://unfccc.int/process-and-meetings/transparency-and-reporting/reporting-and-review-under-the-convention/greenhouse-gas-inventories-annex-i-parties/inventory-review-reports-2022

A greenhouse gas emission inventory is a compilation of historical greenhouse gas emissions from sources, such as transport, power generation, industry and agriculture, from 1990 to the most recent year for which data is available.

A greenhouse gas emission projection is an estimate of what emission levels are likely to be in the future. They are based on key assumptions such as economic growth, fuel prices and Government policy.

Essentially the inventory data provides a summary of past emissions whereas the projections attempt to estimate the emissions in the future.

National Emission Inventories; The United Nations Framework Convention on Climate Change (UNFCCC) and its Kyoto Protocol provide the basis for international action to address climate change. Parties to the convention and its Kyoto Protocol are committed to developing and publishing the national emission inventories of greenhouse gases (GHGs) which is a key element of assessing progress towards meeting commitments and targets.

The EPA compiles Ireland's national greenhouse gas emission inventory on an annual basis. This inventory is submitted to the European Commission and UNFCCC each year by 15 January and 15 April respectively.

Emissions data for the following gases is reported on an annual basis: carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perflurocarbons (PFCs), sulphur hexafluoride (SF₆), and nitrogen trifluoride (NF₃).

Emissions are classified into the ten following sectors; agriculture, transport, energy industries, residential, manufacturing combustion, industrial processes, F-gases, waste, commercial services and public services.

Greenhouse gases other than CO₂ (i.e. methane, nitrous oxide and F-gases) may be converted to CO₂ equivalent using their global warming potentials (GWPs). The GWP of a gas is a measure of the cumulative warming over a specified time period usually 100 years, by a unit mass of this gas. This is expressed relative to carbon dioxide (CO₂) which has a GWP of 1. The mass emission of any gas multiplied by its GWP gives the equivalent emission of the gas as carbon dioxide. This is known as CO₂ equivalent. This makes it possible to sum up the emissions and contribution of Greenhouse Gas (GHG) to climate change and determine options to address climate change.

These gases comprise HFCs (hydroflurocarbons), PFCs (perfluorcarbons), SF₆ (sulphur hexafluoride) and NF₃ (nitrogen trifluoride). They are much more potent than the naturally occurring greenhouse gas emissions (carbon dioxide, methane and nitrous oxide).

Global warming potential of greenhouse gases in the inventories and projections;

Carbon dioxide (CO2) GWP = 1

Methane (CH4) GWP = 28

Nitrous oxide (N2O) GWP = 265

Hydrofluorocarbons (HFCs) GWP = 4 to 12,400

Perfluorinated compounds (PFCs) GWP = 6630 to >17,400

Sulphur hexafluoride (SF6) GWP = 23,500

Nitrogen trifluoride (NF3) GWP = 16,100

The mass emission of any gas multiplied by its GWP gives the equivalent emission of the gas as carbon dioxide. This is known as CO₂ equivalent. This makes it easier to sum up the emissions and contribution of Greenhouse Gas (GHG) to climate change and determine options to address climate change.