The early buzz around emissions trading has been little more than a faint hum in recent years. New cap-and-trade schemes have been launched in places such as California, Quebec and South Korea, but liquidity is patchy and hopes of a global market have so far been dashed. Meanwhile, the world's biggest carbon market – the European Union Emissions Trading System (ETS) – has seen a mass retreat of market-makers, particularly investment banks.

But while the market has languished, the withdrawal of