A discussion paper by researchers from Harvard's Energy Technology Innovation Policy program titled Realistic costs of Carbon Capture found it would cost $US100-150 per tonne of carbon dioxide (CO2) emissions avoided, based on 2008 prices.

By 2030, they say, these costs would have fallen by 65 per cent as the technology is developed and economies of scale take effect, to about $US30-50 per tonne of CO2 avoided.

The cost estimates exclude the costs associated with transporting and storing captured CO2 so the paper takes $US20 per tonne as an illustrative additional cost - as well as any benefit from enhanced oil recovery when CO2 is injected into depleted oil reservoirs.

The paper finds the range of estimated costs is within the range of plausible future carbon prices, implying that mature technology would be competitive with conventional fossil fuel plants at prevailing carbon prices.

The cost premium for generating low-carbon electricity with carbon capture and storage is found to be broadly similar to the cost premiums for generating low-carbon electricity by other means, where mid-case estimates for cost premiums over conventional power generation at present are mainly in the range of about US10c-25c per kilowatt hour.

Comparing carbon capture and storage with other forms of low-carbon electricity generation, the paper found onshore wind at a good site was the lowest cost option. Carbon capture and storage costs were comparable with those of nuclear plants and offshore wind. The top end of carbon capture and storage's cost range was comparable with the cost of concentrated solar thermal, but had a likely cost below that of solar photovoltaics.

Rupert Posner, director at the non-profit Climate Group, said the Harvard findings were consistent with previous research but cost comparisons depended on the location and there was a large degree of uncertainty about long-range cost estimates.

"With [carbon capture and storage], as with a whole lot of other technologies, we don't really know what the costs are going to come down to in the years ahead, but what we have to do is invest in them and find out," he said.

"We actually have to get our hands dirty" to find out.