Australian companies won't be too upset by units trading at a 30th of the current carbon price of $24.15 a tonne. Under the proposed changes, they can meet 6.25 per cent of emissions compliance with the Certified Emissions Reduction units in the first year, and double that amount in later years. Those changes need to survive both the federal election and then probable opposition from the Greens in the Senate.

Unlike Europe, where stagnant economies and over-allocation of permits have sent prices down to about $6 a tonne, the UN market "is a victim of its own success", Rob Fowler, a representative for Australia for the International Emissions Trading Association, said. "The change it stimulated is massive."

About 6900 projects are producing CER credits, for a total supply of 2.2 billion tonnes as of last month, or about four times Australia's annual emissions. Supply will swell to 3.8 billion tonnes by 2020, Bloomberg New Energy Finance (BNEF) says.

Demand, though, is running at just 1.7 billion tonnes. The emergence of new emissions trading markets, such as in Australia, South Korea and China, may stoke demand, as might a global pact among airlines to cut their emissions. Even so, supply will be "far more than total demand", the head of Asia research at BNEF, Milo Sjardin, said.

"You need a large combination of demand centres to make a difference to CER prices," Mr Sjardin said.