Plans to build the world's biggest biomass power station fuelled by wood chips have been given the go-ahead by the UK government.
The £400m plant with 150 jobs in Port Talbot will have the capacity to power half the homes in Wales.
When completed it will produce about 70% of the Welsh Assembly Government's 2010 renewable energy target.
But critics are worried about the impact the plant would have on health and the local environment.
London-based Prenergy Power Ltd will build the plant in the town's docks area after being given the go-ahead by Business Secretary John Hutton of the Department for Business, Enterprise and Regulatory Reform, formerly the Department of Trade and Industry.
The station will burn about 3m tonnes of chippings shipped in each year.
Prenergy said the use of wood chip as a fuel for electricity generation was recognised as being carbon-free.
It said the carbon dioxide (CO2) released was equal to that absorbed during the growth of the tree, and replanting the trees ensured sustainability.
The power station would also create around 150 permanent jobs.
But there has been a local campaign against the proposal, with public meetings, 7,000 signatures in a petition, and protesters marched through the town centre.
Campaigners have also called for a public inquiry.
Councillor Ted Latham, whose ward overlooks the power station site, said campaigners were "extremely disappointed" at the decision and would meet later in the week to discuss their next move.
"Ever since the application was lodged, we have had severe reservations in terms of the impact that it would have on health and the local environment for people here," he said.
"Port Talbot is the most polluted area in Wales and is already exceeding EU pollution levels on an all too-regular basis.
"In this particular case, we believe that enough is enough and that there are still too many questions that need answering."
A council report which went before a Port Talbot planning meeting in March predicted emissions from the plant "would not have a significant effect on air quality" for surrounding areas and the visual impact was in keeping with the surrounding industrial area.
Kevin Mowbray from the Welsh Energy Research Centre said running a biomass plant was a balancing act.
"If you burn wood you are still producing carbon, but what we have got to do is balance that out by actually growing the wood that will suck the carbon back in," he said.
"I am sure that the plant will be putting in a robust filtering system to keep the ash down but the health issues will be local."
In announcing the plant, Mr Hutton also indicated support for the Severn Barrage at a select committee hearing on Tuesday.
This was despite concerns from conservation and environmental groups of the impact on the eco-system in the Severn Estuary.
Mr Hutton said the low carbon benefits of the barrage, which could provide 5% of the UK's electricity, were enormous.