Researchers at the University of Michigan have found serious flaws in previous statements about the economics of carbon capture and storage.

Previous estimates have put the cost of adding carbon capture and storage to the typical coal-fired power plant at about $29 million a year. The new University of Michigan research calculates the additional cost at close to $126 million.

The reason is that previous studies don’t take account of a feedback effect.

Implementing carbon capture and storage requires a choice between accepting lower useful power output or burning more fuel to keep the power output stable. The $29 million a year figure is based on accepting lower useful power output – decreasing a typical new coal-fired power plant’s efficiency from about 38% to about 26%.

However, if you opt to keep the power output the same as it would be without carbon capture and storage, you have to burn more coal – which means that you have to capture and store store more carbon, which means burning more coal, and so on. The University of Michigan researchers say that this decreases the power plant’s efficiency to about 16% and increases the cost of operating the typical power plant by almost $100 million a year.