Methane, locked in frozen deposits, can be released with the injection of the needlessly dreaded carbon dioxide. A 3000 year supply is the conservative estimate. This defines the word “sustainable”.
“The U.S. now produces 21 trillion cubic feet (tcf) of natural gas a year. But it possesses 330,000 tcf of natural gas in its methane hydrate resource – theoretically enough to supply the country for 3,000 years (give or take). Using less conservative numbers (for example, a methane hydrate resource of 670,000 tcf), the U.S. is good to go for 6,000 years (give or take).”