Dec 9, 2008
Partial carbon capture could be stepping stone to full capture and storage
Capture of 45–65% of the carbon emissions from coal-fired power stations would bring them into line with cleaner gas-fired power plants. This partial capture could both enable short-term use of coal, which is cheaper than gas, with fewer emissions and act as a testing and development ground for full-scale capture and storage (CCS) systems, which remove 85–90% of emissions, say researchers at MIT, US.
“While wide-spread deployment of full capture is the clear long-term goal, partial capture makes sense as a near-term transition strategy,” Ashleigh Hildebrand of MIT told environmentalresearchweb. “Basically, we want to make it a little easier to achieve capture now so that we can get the first ‘wave’ of CCS plants running. This will generate the technical and operating knowledge both for capture and for storage (because the carbon dioxide from these partial capture plants could be used for storage tests), which will really stand to expedite large-scale deployment of full capture.”
Increasing electricity demand in the US is creating a need for higher baseload capacity. Renewables lack the steady power generation capacity needed to create baseload power and new nuclear plants take a long time to come on-stream. Which means coal is useful for baseload generation, particularly as, compared to natural gas, in the US it’s cheaper, more stable in price and more readily available.
But Hildebrand says that currently it is expensive and difficult to get a coal-fired power plant built, especially because of the pressure to use CCS, which is, as yet, untested on a large scale. Indeed, the US has experienced “coal paralysis”, with proposals for 70 new coal plants shelved between January 2007 and mid-August 2008. Plans for FutureGen, an integrated gasification combined cycle plant designed to run on coal but produce near-zero carbon emissions, were shelved earlier in the year when the US Department of Energy withdrew its share of the funding.
“There are significant disincentives for ‘first-movers’, so our research is aimed at reducing those disincentives,” explained Hildebrand.
Hildebrand and colleague Howard Herzog say that partial capture of carbon emissions is possible at both pulverized-coal and integrated-gasification combined-cycle power plants. It has the advantage over full capture of requiring less equipment – and so reducing capital costs – and creating a smaller reduction in the output of the power plant. It may also be possible to carry out partial capture without using the non-standard equipment that full capture would require.
“The CCS world conventionally thought that you had to go all the way to full capture (85–90%) to get the lowest price per ton of carbon dioxide, which I tend to think of as ‘economic efficiency’,” said Hildebrand. “Our results show that it’s actually relatively flat once you get past about 30%, and pretty flat especially from 60–90%. This means that a lower capital investment can still achieve significant capture without sacrificing the economic efficiency.”
The researchers reported on their work at the 9th International Conference on Greenhouse Gas Control Technologies in Washington, US, and are set to publish a paper in Energy Procedia.
About the author
Liz Kalaugher is editor of environmentalresearchweb.