There is a need for the right catalyst and the right preprocessing step. Lackner suggested using a weak acid to first dissolve this material, making the magnesium salt, and then switching it to the carbonate to recover the acid. The weaker the acid, the easier it is to recover, but it also corresponds to a smaller reaction rate. Determining how to gain another factor of three to five, perhaps even ten, in this process would make all the difference between success and disaster, Lackner said. From a policy point of view, it is absolutely critical because it signals an open door. “The only one of the methods which… opens the door to the next 100 to 200 years is this dramatic step of forming carbonates,” Lackner stressed. There is plenty of peridotite rock, which contains olivine, serpentine, and magnesium silicates. Oman alone has more serpentine than would be needed to deal with all the carbon reserves in the world, but it is highly distributed all over the world, Lackner said.

The obvious place to store CO2 is in power plants, Lackner said, which could also be hydrogen plants. Since hydrogen is likely to come from fossil fuels for a long time. Lackner estimated a price range in gigajoules of energy for various fuels to back this prediction. At a gigajoule, coal on average usually costs less than a dollar. Oil is $6 per gigajoule at $30 per barrel, and electricity, at five cents, is $14 a gigajoule. If hydrogen is to be made from electricity, the cost will be at least $20 a gigajoule for hydrogen. From natural gas or coal at today’s prices, it is $6. The obvious prediction is that hydrogen will be made from the cheapest source—coal. Hydrogen can also be derived from tar, coal, shale, or biomass, but it is very unlikely in the foreseeable future to come from wind, photo well tanks, or nuclear energy. “Unless you put on your burner one cent a third kilowatt hour, which I think is an achievable goal for photo well tanks in the long term, you cannot make hydrogen from it,” Lackner said.

Bypassing the CO2 problem by using windmills may not be possible. The energy that feeds the wind is about 20 times the energy the world consumes today. It is not clear how much wind energy can be harvested without having an impact on the wind field and thus perhaps on climate. Furthermore, a windmill would require at least 80 square meters of rotor-swept area in order to supply enough energy for a single person in the United States. In comparison, the CO2 output per person would flow through an opening the size of a television screen. Therefore, a device to capture the CO2 produced per person would be a factor of several hundred times smaller than one to collect wind energy for that same person. With the ability to capture CO2 from the air comes the option of either making hydrogen from fossil fuels and collecting the CO2 at the hydrogen plant or running your cars on gasoline and capturing an amount of CO2 from the air that compensates for the emission. In addition, if renewable energy



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