The Environmental Protection Agency (EPA) has given the green light to a €10m plan by Irish Cement in Mungret in Co Limerick to change its fuel burning practices, against widespread community opposition.
The company wants to end its practice of burning fossil fuels at its giant kiln in Limerick and change to the burning of alternative fuels, such as used tyres and solid recovered waste.
Irish Cement argued it was necessary for the future competitiveness of the plant, which employs 100 people, and to bring in line with other cement plants across Europe.
Its factory in Mungret is one of the last to still use fossil fuels; the company had already changed the practice at its other plant in Co Meath.
It also claimed there would be no health or environmental impact to the local area from the change of use, as the fuels were being burned at such high temperatures.
However, local action groups - including the Limerick Against Pollution group, politicians, and the representatives of University of Limerick - fought against the plan because of concerns it could impact human health and the environment in a densely populated suburban area, and damage Limerick's reputation as a clean green city.
Limerick against Pollution has said they are "extremely disappointed" by the decision.
In a statement, LAP said they "await reading the conditions which will be available on the EPA website at 11am tomorrow morning before we make a decision on how to proceed."
"Unfortunately the only option now available to us and the other objectors is the High Court and a Judicial Review which is extremely costly," they added.
It was also the subject of an oral hearing earlier this year.
Local Fine Gael Councillor Daniel Butler, who lives in the area, said it was an appalling decision against the wishes of all Limerick citizens.
Irish Cement has moved to reassure the local community that switching fuels "will be positive for the area and not negatively impact on air quality or the local environment".
In a statement this evening, factory manager Pat Robinson said: "The entire workforce in Limerick is delighted that there has been a positive conclusion to this extensive review process.
"The EPA decision today provides us with the opportunity to now switch away from the use of imported fossil fuels and play our part in achieving the 2030 alternative fuel target in the Government's Climate Action Plan.
"Important also is the fact that this decision will help secure the future of the factory and is an endorsement of all the hard work being done by everyone on the team."