Ireland's carbon pollution from big industries fell by 6.4% in 2020 to the lowest level since 2005.
However, the drop is less than the European average of between 11% and 12%.
Carbon emissions from electricity generation, industry and aviation are included in the EU Emissions Trading Scheme and reported by the Environmental Protection Agency.
It has welcomed the fall, but warns there are some sectors, such as dairy processing and PharmaChem, where emissions rose.
The EPA said that emissions from electricity generation were down 8.4% last year as power from renewable sources increased and use of fossil fuels fell.
But emissions from the ESB coal-fired plant at Moneypoint increased by almost 27%, mainly due to increased demand for balance on the National Grid.
In industry, overall carbon pollution fell by 3.5% and cement industries reported a drop of 5.7%.
But emissions from the PharmaChem industry rose by 10.9% and those from the dairy processing sector by 4%.
A spokesman for the Irish Pharmaceutical Healthcare Association, which represents drugs manufacturers, said: "Manufacturing medicines at scale is energy-intensive so the industry is investing in sustainable practices in a bid to move towards carbon neutrality."
Dairy Industry Ireland said that last year there was a 3% increase in dairy exports delivering €5.2 billion in export value to the economy.
It said the Irish dairy processing industry is committed to achieving cuts in its ETS emissions portfolio and is investing significantly in a range of new energy solutions and capital investment to drive down emissions from processing over the coming years.
The aviation sector saw the biggest drop by far of any industry, with a fall of 63% from 2019 levels to 4.74 million tonnes.
The only airline that reported a rise in emissions specialises in air freight.
Aviation emissions reported to Ireland come mainly from flights in and out of Ireland and also flights anywhere within the European Economic Area (EEA) where the aircraft carrier has an operating licence from the Irish Aviation Authority.
All emissions for 2020 reported by Ireland under the Emissions Trading Scheme added up to a total of 13.28m tonnes.