Emissions of carbon dioxide (CO2) accounted for 61.0% of the national total GHG emissions (excluding LULUCF) of 55,006.6 kt CO2 equivalent in 2023, with CH4 and N2O contributing 28.9% and 8.8%, respectively. The combined emissions of HFC, PFC, SF6 and NF3 accounted for 1.3% of total GHG emissions in 2023. In 1990 emissions of CO2 accounted for 59.2%, CH4 29.7% , N2O 11.1% and the combined emissions of HFCs, PFCs, SF6 and NF3 were less than 0.1%, of total emissions of 55,680.3 kt CO2 equivalent.
Carbon dioxide CO2 is the most significant contributor to the greenhouse gas emissions. The energy industries and transport sectors are responsible for 22.8% and 34.7% of total CO2 emissions (excluding LULUCF) in 2023, respectively. The residential sector has a 15.6% share, manufacturing combustion has a 12.3% share and the remainder of CO2 emissions (14.6% share) fall into other categories. Emissions of CO2 increased from 32,945.3 kt in 1990 to 33,563.7 kt in 2023, which equates to an increase of 1.9%. The main driver behind this increase in emissions is fuel combustion in the transport sector (+132%) over the period 1990-2023.
Methane CH4 is the second most significant contributor to greenhouse gas emissions in Ireland and is due to the large population of cattle.
In 2023 estimated emissions of CH4 were 15,914.6 kt CO2eq, indicating an decrease of 3.7% on the 1990 level of 16,534.2 kt CO2 equivalent. Emissions of CH4 increased progressively from 1990, reaching a peak in 1998 of 17,585.9 kt CO2eq. This reflects an increase in livestock numbers and therefore increased emissions from source categories, enteric fermentation and manure management. Between 1998 and 2011 CH4 emissions decreased due to falling livestock numbers from reforms of the Common Agricultural Policy (CAP). The main contributor to the CH4 trend has been the agriculture sector and in 2023 this sector accounted for 94.2% of the total CH4 emissions (compared to 86.5% share in 1990 when emissions from waste sector had a larger share in the level). The sectoral CH4 emissions from agriculture increased by 4.8% between 1990 (14,296.6 kt CO2 equivalent) and 2023 (14,987.9 kt CO2 equivalent).
Another significant source of CH4 emissions is the waste sector, especially from landfill gas in the sector solid waste disposal on land. CH4 emissions from waste decreased from 9.3% share of total methane emissions (1,545.85 kt CO2eq) in 1990 to 4.3% share (691.2 kt CO2eq) in 2023. This decrease is a result of improved management of landfill facilities, including increased recovery of landfill gas utilised for electricity generation and flaring.
Nitrous oxide N2O emissions decreased by 21.7% from their 1990 level of 6,165.2 kt CO2eq to 4,829.4 kt CO2eq in 2023. Like CH4, emissions of N2O increased during the 1990s to reach peak level of 6,897.2 kt CO2eq in 1998 reflecting increased use of synthetic fertilisers and increased amounts of animal manures associated with increasing animal numbers over that period. Emissions of N2O subsequently show a clear downward trend following reductions in synthetic fertiliser use and organic nitrogen applications on land because of CAP reform on animal numbers as well as the closure of Ireland’s only nitric acid plant in 2002. However, in six of the last ten years of the GHG inventory (2013-2023) N2O emissions increased, as the dairy sector expanded, and nitrogenous fertiliser use increased.
The largest contributor to the trend is the agriculture sector with 91.6% share of the total N2O emissions (4,424.3 kt CO2eq) in 2023. This reflects an increase from 81.4% share (5,020.5 kt CO2eq) in 1990. Emissions from the industrial processes chemical industry used to be the second largest contributor to the trend. They contributed 14.8% to the total N2O emissions in 1990 and an average of 11.8% share to the trend between 1990 and 2000, before falling to a 4.9% share in 2002 – the year the nitric acid plant closed. Thereafter, the average share equated to 0.6% of total national emissions.
