Exxon Corporation has been experimenting with carbon sequestration, or pumping the greenhouse CO2 in liquefied form deep underground in Wyoming. The project involves liquefying the gas into a gooey mixture which is pumped down a well into a deep underground rock formation called the Madison formation. Because green energy is being demanded by states like California the scientists at Exxon believe that carbon sequestration underground may be a way to make coal a "green" fuel. If the holy grail of clean coal technology is ever realized something will have to be done with millions of tons of carbon dioxide waste every year and pumping it into places like the Madison formation in Wyoming may be the answer. For more see see the following article...