Other goals stated by the U.S. DOE have been more comprehensive, including developing the potential to remove 1 GtC/year of U.S. power plant emissions by 2025 and 4 GtC/year by 2050 (75) in order to stabilize atmospheric carbon dioxide levels at 550 ppmv by 2050. The assumption here is that other countries would employ similar technologies and achieve similar reductions in emissions. The present goal (in 2003) appears based on the 18% reduction in emissions intensity (GHG emissions/$ of GDP) by 2012 (78).
Whatever the goal is, no one knows what the real cost is or will be, since no power station has ever had all of its carbon dioxide removed from its flue gas and it is likely that the costs of retrofitting existing stations are probably great enough to not warrant any attempts to install control devices, no matter what technology they are based on.
This means that the only attempts to control carbon dioxide emissions may be at newly constructed power stations when the technology becomes available and is cost effective. From a practical standpoint, the operating life of a power station is about 35 years, meaning that one complete cycle of power stations built today would not be retired before almost 2040 and the next before 2075. It also takes 10-30 years for energy technologies to move from research to commercial use (79). This gives engineers few opportunities to implement new technologies that reduce or eliminate altogether GHG emissions from these sources on a scale large enough to be meaningful in this century.
Thus, it will take many decades for enough conventional power stations to be outfitted to remove the carbon dioxide in their emissions to have any real impact on GHG emissions. By that time, it may be that other solutions will have been found such as decarbonization of the fuel and use of the remaining hydrogen as the energy source. In this case, the carbon dioxide waste stream will be more concentrated and thus, less expensive to capture. Some economic analyses have found that widespread introduction of carbon capture and disposal technologies in the U.S. will be unlikely before 2035-2050 (83).
Another problem with carbon management, even with fuel decarbonization, is what to do with the waste carbon dioxide. Although some work has been done to identify beneficial uses for this material, e.g. its use in enhanced oil recovery operations, the massive quantities produced preclude any significant use as a feedstock for other reactions. Instead, it will have to be “sequestered” or locked up for hundreds of years either in the deep ocean, in underground geologic formations like depleted oil fields, saline aquifers and deep coal beds or in rocks via a chemical reaction, the latter being the least likely due to energy costs (52, 78).
Ocean disposal seems unlikely due to the difficulty and costs of running pipelines from land-based power stations across the continental shelf as well as uncertainty as to whether the waste carbon dioxide will stay there and concerns about the effect on sea life (54, 84). Disposal in depleted oil fields or saline aquifers seems the most likely choice given that sufficient capacity exists in the central U.S. and elsewhere, although leak rates of 1% per year will negate the value of the disposal process (78). One large-scale disposal project is already underway in Norway involving disposal in an aquifer of carbon dioxide extracted from natural gas, although much work remains to be done to ensure that this strategy will work as planned (85).
Even if carbon management from power stations is found to be feasible, it can only solve at most 20% of the global warming problem (5% if only the U.S. is considered), not enough to make any difference if the other contributors are not equally addressed (17). However, if carbon management is applied to all stationary and mobile GHG emission sources as a result of the near complete conversion to a hydrogen economy, then it can significantly reduce global warming forcing due to carbon dioxide, nitrous oxide and ozone.
