In Herzog's view, the call for full carbon capture is "a policy of inaction, a policy that won't move forward either new coal plants or the CCS technology." Partial capture could be a viable intermediate step.
The push for full capture (defined as 90 percent of the total) is in part economic: everyone assumed that 90 percent capture would due to economies of scale yield the lowest cost per ton of CO2 removed. Anything less than 90 percent would mean a higher per-ton cost.
To investigate that assumption, Hildebrand and Herzog modeled the technological changes and costs involved in capturing fractions ranging from zero to 90 percent. 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 ton of CO2 removed declines as the number of captured tons increases. Not surprisingly, when the second series is added, cost per ton goes up, but it then quickly levels off. Cost per ton 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 run
|Contact: Elizabeth Thomson|
Massachusetts Institute of Technology