Scrubbing up coal plants a costly exercise

How to burn coal in power stations without adding to global warming is attracting a lot of attention these days - but a solution won't come cheap.

The idea is to capture carbon dioxide at power stations or smokestack industries and, instead of sending it up a chimney into the atmosphere, to pipe it to underground storage sites. These would include depleted oil or gas fields, coal seams too deep to mine, or deep aquifers containing salt water.

"Six or seven years ago, this was a bit of an academic exercise, looking at what the options might be if we had to do something, said Dr John Topper, the International Energy Agency's greenhouse gas programme chief, who was in Wellington yesterday to address the Coal Association.

"That's not the case now. It's right at the top of the policy agenda.

"There is a growing consensus that if we are to stabilise atmospheric concentrations of CO2, we will need a whole suite of technologies, including renewables and carbon capture and storage."

He said governments and big companies were spending serious money on the technological quest.

In January, an agency report said it was not yet possible to pick a winning technology for capturing CO2. Several were likely to be used and all would need to become cheaper and more efficient before they were used on a commercial scale - a process likely to take years.

In a 2001 report, the agency estimated that CO2 capture and storage would increase the cost of electricity from gas-fired generation by about 60 per cent and from coal-burning plants by 90 per cent.

Topper said there was a need to get commercial-scale plants running over the next 10 years in order to advance the technology and drive costs down.

He pointed to the dramatic reduction in the cost of a similar technology, which removes the sulphur dioxide responsible for acid rain. It now costs about 25 per cent of what it did in the 1970s.

The European Union has set a target of reducing the cost of capturing and storing CO2 to between 20 and 30 a tonne ($36 to $54), about three or four times the price for avoided emissions on the carbon market.

"The Americans have a similar target. People think that is do-able over 20 or 30 years," Topper said.

In the longer term, the most promising technological options involve gasifying coal to produce hydrogen fuel and a CO2 stream for storage.

But he said the alternative of capturing CO2 after combustion also had to be developed to service existing plants.