The amount of coal waiting to be mined around the world is thought to be around 900 gigatonnes. Even if the amount were one-third as great, we are still faced with the likelihood that enough will be burned to raise the atmosphere’s carbon dioxide content well above 560 parts per million (more than double the pre-industrial content). Model simulations suggest that this would warm the earth by about 3.5 degrees Celsius. As a consequence, the focussing of rainfall on the tropics will be strengthened and the adjacent dry lands will become more arid. Sea level will undergo a slow but expensive rise. All natural flora and their accompanying fauna will be forced to migrate.
While the world’s rich nations could perhaps accomplish a major shift to alternate fuels and hence avoid large-scale coal use, developing nations will very likely follow China’s lead and power their standard-of-living rise largely with coal. Hence, we must be prepared to deal with the consequences. As shown by Klaus Lackner and his associates at General Research Technologies (GRT) in Tucson, Arizona, it is economically and environmentally feasible to capture CO2 directly from the atmosphere. This opens the means for rich nations to “compensate” for the use of coal by developing nations. As the atmosphere mixes very rapidly, it does not matter where CO2 is removed. So, for example, the European Union could pay for the sequestration of the CO2 produced by nations in central Africa, while the actual removal and burial of the CO2 could be done in Chile’s Atacama Desert.
GRT’s plan is to absorb CO2 on fibres of a plastic with ligands (charged molecular sites). The CO2 would then be removed by exchange with steam. They have shown that the plastic’s CO2 to H2O exchange cycle can be repeated hundreds of times without loss of capacity. The plastic also withstands punishment by the wind and by the impurities it carries. GRT plans to have a commercial prototype in production by the end of 2010. Each modular unit will remove one tonne of CO2 a day and can be shipped in a standard container. The goal is that capture and storage of CO2 by this method will raise fossil-fuel energy costs by no more than 20%.
Of course, even with such a capability, many hurdles stand in the way of its deployment. How will CO2 capture and storage be paid for? Where will it be stored? Can the necessary global agreements be negotiated?
Regardless of how the CO2 problem is dealt with, when all is said and done, the consequences of coming greenhouse warming will be sufficiently uncomfortable and expensive that there will be a strong plea to bring the atmosphere’s CO2 content back down. Only one means will be available: direct capture from the atmosphere.
Wallace Broecker is Newberry Professor at Lamont-Doherty Earth Observatory at Columbia University.
Backgrounder: Lackner’s trees
Martin Bunzl spoke to Klaus Lackner about his vision of direct carbon capture.
Klaus Lackner and his associates have been working on a model to capture carbon from the air rather than the smokestacks of coal-fired power plants. This would have many advantages, if it can work and be cost effective:
* Much CO2 comes from places other than coal-fired power plants, on which most work on carbon capture is currently focussed;
* Capturing CO2 from coal plants will be extremely difficult;
* Not everyone running a coal-fired power plant is actually going to capture the CO2, given the additional costs of doing so, even if they say they are;
* Separating out who produces CO2, where it is (or was) produced and where and when it is captured allows the developed world to clean up some of its historic output.
I spoke to Lackner recently, and he cited figures of US$200 a tonne going down to $30 a tonne for the operational costs of such a system at scale. This includes the cost of manufacture and the power needs of the system, but excludes the costs of sequestration. He envisages deploying small units the size of shipping containers, which each remove one tonne of CO2 a day. Like all carbon capture, this approach uses power, so unless you use renewable energy as a source, it adds to the problem as it works to solve it. Cleaning up the CO2 that a coal-fired power plant produces requires burning 30% more coal to produce the energy for the clean up.
However, with an ambient system one could locate Lackner’s units in a desert and run them with solar power. How many would be needed? If each extracts one tonne of CO2 a day, three would take out roughly 1,000 tonnes a year. The world currently puts out about 27 gigatonnes of CO2 annually and we need to reduce to 18 gigatonnes to stabilize atmospheric CO2 at 450 ppm. Lackner is about to publish data on his work, which has been eagerly awaited by the scientific community. If it holds up, the real fly in the ointment of the whole scheme may be the sequestration of the carbon. But one way or another, there is no getting around the urgent need to test sequestration for safety on land or in deep sea locations. There is just too much coal available to burn.
Martin Bunzl directs the Initiative on Climate Change and Social Policy at Rutgers University.
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