For years, power generators and industrial companies in the European Union have had to pay little attention to the vagaries of the Emissions Trading System (ETS). Due to the global financial crisis and Europe's subsequent economic woes, the cost of emissions plummeted and remained at relatively low levels. And in any case, many owners of industrial installations – also known as direct participants in the ETS – were simply handed the carbon allowances they needed for free.

Now, things are about