Japan has announced a renewed commitment to mining methane hydrate, also known as 'flaming ice' or 'methane clathrate'.
The alternative fuel methane hydrate consists of methane molecules held loosely in a cage of icy water molecules. The mining of methane hydrate provokes concern because methane, which you may also know as natural gas, has a much higher global warming potential than carbon dioxide. Methane hydrate is stable only at low temperatures and high pressures, so some fear that disturbing the naturally occurring flammable ice will trigger the release of large quantities of methane, further spurring the global warming trend.
Of course, there are concerns that methane in the ocean ice already contributes to global warming, and may also suffer from feedback effects by which the warmer atmosphere causes faster release of the methane, which further warms the atmosphere in a vicious and accelerating cycle. Scientists have measured elevated levels of methane bubbling up from under patches of ocean like the one shown below.
From a technological point, the purpose of the mining is to capture the methane; any releases represent production losses. Of course, industry has a long history of gladly suffering huge waste as long as there is still profit in the inefficiency. The dangers of methane offer a better incentive to control release in mining operations: the frozen flammable ice can release large amounts of gas, quickly increasing pressures in confined spaces, and is flammable -- with the risk of an explosive atmosphere forming. In fact, formation of methane hydrate has been blamed for foiling BP's countermeasures after the Deepwater disaster.
The current scope of the project in Japan consists mostly of exploration -- drilling for samples to characterize the amounts and properties of the flammable ice around their island. The Japanese are also involved in a joint project with the U.S. State of Alaska to refine mining methods for the methane hydrate. The flaming ice presents particular difficulties because changes in pressure and temperature can easily destabilize the water cage, releasing the methane gas.
Japan's government included funding for the methane hydrate development in an economic stimulus package approved at the end of 2014, and targets to commercialize methane hydrates as an energy source by 2023.
The technology may even have some hidden benefits. Studies indicate that the clathrate ice may prefer to harbor a CO2 (carbon dioxide) molecule, suggesting that one methane harvesting option might be to incorporate carbon dioxide in the ice, bumping the methane free for collection. This could sequester carbon dioxide and reduce the amounts of methane available at the sea bed to be released as the seas warm. That's a long shot, as the most cost effective technologies usually win the race rather than the ones with benefits not so easily monetized. At any rate, the pursuit of flammable ice will be worth watching as the technology develops.