In April, Europe's highest court ruled that such industries had received too many carbon permits under the European Union's Emissions Trading System (ETS), which charges power plants and factories for every tonne of carbon dioxide (CO2) they emit.

It also said the European Commission's calculation for handing out the free permits was flawed and gave the EU executive 10 months to review the policy.

"This scenario is threatening the existence of plants in Germany, but also across Europe," Frank Schulz, the chief executive of ArcelorMittal's German unit told Reuters in an interview.

The permits are part of EU policy to limit greenhouse gas emissions and keep global warming to an internationally agreed target.

Under the new system, steel makers would receive a sharply reduced number of permits from 2021 to 2030, forcing them to purchase the required licences.

"Experts calculate that this would leave the industry with additional costs of ten to 30 euros ($33) per tonne of steel," Schulz said.

Average earnings before interest, taxes, depreciation and amortisation (EBITDA) were 35 to 40 euros per tonne last year, Schulz added.

The industry, which employs around 300,000 workers across Europe and is under added pressure from cheap Chinese steel imports, opposes the reform and says it raises the risk of businesses moving to regions where pollution regulations are less strict.

Schulz said that the new rules would affect roughly six million tonnes of ArcelorMittal's steel in Germany, resulting in additional costs of around 120 million euros per year.

"This is about the amount we invest in plant and equipment and would eat up the bigger part of our EBITDA," Schulz said, adding that the German unit, which last year posted revenues of 5.3 billion euros, invested between 90 and 100 million euros per year.

But he said Germany, where ArcelorMittal employs 9,000 workers at four sites and competes with Thyssenkrupp (>> ThyssenKrupp AG) and Salzgitter (>> Salzgitter AG), remained an important market.

"We have no plans to shut down any furnaces in Germany," he said.

ArcelorMittal, which produces around 40 million tonnes of steel across 20 European sites each year, had shut down a total of four furnaces in France and Belgium in recent years.

($1 = 0.9197 euros)

(Reporting by Tom Kaeckenhoff; Writing by Tina Bellon; Editing by Ruth Pitchford)

By Tom Käckenhoff

Stocks treated in this article : ArcelorMittal, Salzgitter AG, ThyssenKrupp AG