Unfortunately the article doesn't offer any other suggestions for storage. Given that the U.S. alone emitted 5.8 billion tons of CO2 in 2003, storing the gas will likely prove far more challenging than capturing it.
Engineers are working on methods for capturing the carbon emitted when coal is burned. They have considered options as diverse as freezing the gases as they come out of smokestacks, and binding them to a liquid chemical after combustion. Two other possibilities are to modify the coal before it is burned, or to change the air it is burned with.
Capturing the gas, though, is just one part of the equation. Finding a way to store it is likely to prove equally challenging. The leading possibility is old oil fields, where the carbon dioxide could be injected to force more oil to existing wells. But the total capacity of all the old oil fields in the world is much too small for this purpose. In addition, the oil fields are punctured by wells that could provide escape routes for the carbon dioxide to leak into.
(As a comparison, the U.S. generated approximately 240 million tons of garbage in 2005. Much of that waste will decompose or can be recycled, meaning the total mass stored will reduce over time. CO2, on the other hand, is completely stable. The entire mass must be stored in perpetuity.)
(Hat tip Instapundit.)