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is a leading geoscientist of his generation, venture capitalist, and a significant figure in the politics of Colorado. In this article he reviews some inconvenient truths about the timely implementation of CCS projects in the US, some of which may resonate in other countries seeking CO 2 reduction measures.T he greatest challenge to carbon capture and storage (CCS) is likely to be economic rather than technical. A September 2008 McKinsey report estimated that the first commercial scale CCS projects, potentially to be built soon after 2020, would cost €35-50 per metric ton of CO 2 abated. They assume that if 500+ projects were built by 2030, the cost might fall to €25-40 per ton. About two-thirds of that cost is for CO 2 capture.It is interesting to consider those costs on a global scale. A study by Pacala and Socolow implies that we need to cut a cumulative 25 Gton of CO 2 over the next 50 years just to cap the CO 2 concentration in the atmosphere at a modest 500 ppm (we are now at 390 ppm). If all of our solutions cost €25 per ton, the economic impact would be €625 billion ($833 billion) over the next 50 years.Reducing CO 2 is a global issue, but the US creates 20% of the problem. It also offers an interesting case study on the difficulty of finding practical solutions in a challenging political and economic environment. Hopefully along the way the reader will discover opportunities as well as pitfalls to avoid.According to the US Department of Energy's Energy Information Administration (DOE-EIA), 98% of America's human-generated CO 2 comes from energy use, with 40% of that from electricity (coal and natural gas) and 33% from transportation (mostly petroleum). Coal produces 45% of America's electricity and natural gas produces 23% (see Figure 1).McKinsey's study notes that 'Retrofitting of existing power plants is likely to be more expensive than new installations, and economically feasible only for relatively new plants (with high efficiencies).' But according to the DOE-EIA, over the past 20 years coal contributed only 3.7% of total added US capacity while natural gas accounted for 88%. Few modern, efficient US coal plants have been added in the past 20 years.'Efficiency' is a term used to define the conversion of the theoretical energy content of a fuel into electricity. The McKinsey report notes that the energy required for the CCS CO 2 capture process increases the amount of coal that must be burned per MW-hour delivered, and estimates a CCS 'efficiency penalty' of 10%. This means that if a future coal plant could be built to achieve a 50% thermal efficiency, CCS would decrease that efficiency to 40%. Such a plant would be burning 50/40=1.25 times as much coal per MW-hour. And burning 25% more coal would also increase harmful emissions since CCS captures only about 90% of CO 2 and none of the other pollutants.CCS also faces storage challenges, such as site selection, CO 2 transportation costs, pipeline and CCS site permits, and uncertainties in monitoring CO 2 sequestration. Leakage of just 0.5% per year w...

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