WASHINGTON: An MIT model can help the US fend off growing power shortages by bringing down costs of reducing down carbon dioxide emissions.

The steep cost involved in capturing such emissions has slowed down construction of new coal-fired power plants in the country.

The 'partial capture' technique of Massachusetts Institute of Technology (MIT) could capture not all but a significant fraction of those emissions with low cost changes in plant design and operation.

"The partial capture technique can get CO2 (carbon dioxide) emissions from coal-burning plants down to emissions levels of natural gas power plants," said Ashleigh Hildebrand, graduate student in chemical engineering of MIT.

Her co-author is Howard J. Herzog, principal research engineer at the MIT Energy Initiative and chair of the conference organising committee.

To investigate whether partial capture could be viable, Hildebrand and Herzog modelled the changes and costs involved in capturing fractions ranging from zero to 90 percent, said an MIT release.

The model takes into account technological breakpoints. For example, carbon capture is achieved by a series of devices that absorb CO2, release it and compress it. Full capture may require two or more parallel series.

The model confirms that the cost per tonne (CPT) of CO2 removed declines as the number of captured tonnes increases. Not surprisingly, when the second series is added, cost per tonne goes up, but it then quickly levels off.

CPT is thus roughly the same at, say, 60 percent capture as it is at 90 percent capture. Since there are no economies of scale to be gained by going to 90 percent, companies can remove less - and significantly reduce their initial capital investment as well as the drop in efficiency once the plant is running.

Hildebrand presented her findings Tuesday at the ninth International Conference on Greenhouse Gas Control Technologies in Washington.