Storage of the CO2 is envisaged either in deep geological formations, in deep ocean masses, or in the form of mineral carbonates. In the case of deep ocean storage, there is a risk of greatly increasing the problem of ocean acidification, a problem that also stems from the excess of carbon dioxide already in the atmosphere and oceans. Geological formations are currently considered the most promising sequestration sites. The National Energy Technology Laboratory (NETL) reported that North America has enough storage capacity at its current rate of production for more than 900 years worth of carbon dioxide.A general problem is that long term predictions about submarine or underground storage security are very difficult and uncertain and CO2 might leak from the storage into the atmosphere.

There are two places we've found to store CO2 -- underground and underwater. In fact, estimates project that the planet can store up to 10 trillion tons of carbon dioxide. This would allow 100 years of storage of all human-created emissions [source: Science Daily]. (Though we'll obviously survive much longer than that.)

First, we'll talk about underground storage. The pressure found deep underground causes CO2 to behave more like a liquid than a gas. Because it can seep into the spaces in porous rocks, a great amount of CO2 can be stored in a relatively small area. Underground storage, also called geological sequestration, is already in use by the oil and gas industries to squeeze out extra oil or gas from depleted reservoirs. Oil and gas reservoirs are well suited to store CO2 as they consist of layers of porous rock formations that have trapped oil and gas for years. Geological sequestration involves injecting CO2 into underground rock formations below the Earth's surface. These natural reservoirs have overlying rocks that form a seal, keeping the gas contained. There can be risks to underground storage, though, and we'll discuss those a bit later.

Basalt formations (volcanic rock) also appear to be suitable for storing CO2. In fact, basalt is one of the most common types of rock in the Earth's crust -- even the ocean floor is made of basalt [source: USGS]. Researchers have found that when they inject CO2 into basalt, it eventually turns into limestone -- essentially converting to rock. The Pacific Northwest National Laboratory in Washington State currently has a team devoted to running a pilot project to test basalt carbon storage [source: MSNBC].

http://science.howstuffworks.com/environmental/green-science/carbon-capture3.htm

http://en.wikipedia.org/wiki/Carbon_capture_and_storage