WASHINGTON — Buried beneath the world’s oceans and the Arctic permafrost lies a global energy source that many think might dwarf today’s fracking revolution: huge reservoirs of natural gas trapped in ice crystals.They’re called methane hydrates, sometimes known as “flammable ice.” If tapping them ever becomes feasible, they would change the geopolitical map. Nations like Japan and India that lack conventional oil and gas resources could suddenly become power players.The Energy Department says “methane hydrates may exceed the energy content of all other fossil fuels combined” and “could ensure decades of affordable natural gas and cut America’s foreign oil dependence.”But the possibility that fossil fuels could drive the world’s economies indefinitely — even the most conservative forecasts describe methane hydrates as a bounty greater than all other sources of natural gas combined — dismays many. For decades, that group has hoped that scarcity would eventually wean the globe from its dependence on greenhouse-gas-producing technologies.“Then you get into the question, ‘Are we going to stick with fossil fuels until we completely fry the atmosphere?’” said Richard Charter, a senior fellow at the environmental group The Ocean Foundation and a member of the Energy Department’s methane hydrates advisory committee.The International Energy Agency said in a November report that the viability of methane hydrates as a fuel source will depend on technological advances as well as climate change policies. Meeting goals to reduce carbon dioxide emissions will require cutting back on all fossil fuels, even those derived from ice. Methane is also a potent greenhouse gas when released into the atmosphere, the energy agency noted, and great care is needed in harvesting it.Producing natural gas from methane hydrates poses huge challenges. But Japan hopes to devise ways to develop the untapped resource in five to 10 years, and other nations are also pressing ahead on research, including the United States, which has vast amounts beneath the permafrost of the Alaskan Arctic and deep in the Gulf of Mexico.Methane hydrates form at crushingly high pressure and frozen temperatures, a condition found at the bottom of the otherwise warm Gulf of Mexico. The ice crystals caused problems for BP’s equipment as it tried to contain the 2010 Deepwater Horizon oil spill in the Gulf. Oil companies are aware of their potential as an energy resource, but so far they’ve mostly been something to avoid while drilling.The potential of hydrates even caught the eye of the producers of the Dallas television show on TNT, who worked it into the plot of last year’s series.Anthony Cugini, director of the National Energy Technology Laboratory, said at this year’s Deloitte Energy Conference that whoever has his job in the coming decades could be talking about a hydrate energy revolution.“These methane hydrates really create an opportunity that can move shale gas to the back page if you believe that. The resource is so large,” Cugini said.But as with the decades-long development of hydraulic fracturing techniques that led to the shale boom, many question whether methane hydrates will ever become an economical energy source.“The technical issues are not the biggest challenge right now. I think the biggest challenge is related to the economics of the situation. Is it really viable to be getting gas from methane hydrates when there are lots of other sources of gas out there?” said Carolyn Ruppel, who is working on the matter at the U.S. Geological Survey.The challenges include the cost of producing and transporting energy that comes from the Arctic and the deep, Ruppel said. It’s not like America’s shale gas, which is found all over the country.America has a glut of cheap natural gas from shale and no immediate need to develop methane hydrates. Other nations, however, have far different energy needs and are pushing harder to develop methane hydrates.Japan a big playerThe Japanese are paying so much to import natural gas that the cost of methane hydrates could make sense for them, said Tim Collette of the Geological Survey’s energy resources team. Some cost estimates for methane hydrates are 10 times as high as those of conventional natural gas. The Japanese hope to lower the production cost and make it more competitive with other energy sources.Japan is also urgently looking for new energy as it moves away from nuclear after the Fukushima disaster, when three reactors melted down and radioactive material leaked out after an earthquake and tsunami in March 2011.The energy consulting firm IHS Cera said it’s plausible to expect Japan to be using methane hydrates within 15 years.South Korea could be next. Like Japan, it’s a developed and wealthy nation without its own oil and gas.Asia could be the cradle of methane hydrates, as “necessity is often the mother of invention,” IHS analysts concluded in a recent report.BreakthroughsA pair of methane hydrate breakthroughs happened in the past year. Researchers on the North Slope of Alaska released natural gas from ice crystals within the permafrost by injecting them with nitrogen and carbon dioxide. The hydrate formation took in the carbon dioxide and released the methane, essentially exchanging molecules, while the research team lowered the pressure in the well to get the gas out.Then Japan produced a flow from deep-water deposits off its shores through a depressurization technique. That involves drilling a well into a formation and pumping out the water. That causes the gas to break free as a result of the difference in pressure between the underground hydrate deposit and the well.Charter, of The Ocean Foundation, said the risks of developing methane hydrates include blowouts and subsea landslides that release planet-warming methane into the atmosphere.“I would say right now they are at a similar development stage to that of the early Edison light bulbs, where half of them blew up,” he said.