"In a average year we would need rights (to emit) a couple million tonnes more than we expect to get. In a really bad year we could be short of rights for an additional 5 million tonnes," he said.

Emissions trading is the linchpin in the EU's plan to fight global warming caused by burning fossil fuels and meet obligations under the Kyoto Protocol, an international agreement that aims to reduce heat-trapping greenhouse gases.

It involves thousands of EU factories, power stations, steelmakers and other energy-intensive industries.

Companies exceeding carbon dioxide (CO2) caps can buy emissions -- essentially the right to pollute -- from firms which end up within their targets, thus keeping overall emissions consistent.

Fortum -- currently in the process of splitting its utility and oil operations into separate firms -- emits some 17 million tonnes of carbon dioxide, the main greenhouse gas broadly blamed for global warming.

It is one of the top utilities in a region where the prime source of energy is hydropower. Hydropower has no CO2 emissions but is at the mercy of rain and snowfall, so if reservoir levels are low producers have to turn to alternative energy sources.

Emission rights have been trading in the 8 euro to 9 euro ($10.70-$12.03) range over recent months and Niininen said he does not expect that to rise.