Japan’s decade-long quest to produce gas from undersea methane hydrate, or "flammable ice," paid off this week with the announcement of a successful extraction from nearly 900 feet below the seabed, the world’s first. The achievement has the potential to unlock a vast new fuel source, as the total amount of carbon in methane hydrate deposits worldwide is conservatively estimated at twice that of all other fossil fuels. The majority of those deposits are located beneath the seabed, and Japan’s Oil, Gas, and Metals National Corporation (JOGMEC) says that it hopes to commercialize the extraction technology within five years.

Methane hydrate is formed when water and methane gas mix under high pressures at low temperatures, freezing the components together. In order to separate the two, the researchers pumped water out from under the seabed, lowering the pressure around the deposits and melting the ice. The gas can also be extracted by heating the methane hydrate solid, but the low pressure technique uses significantly less energy.

The achievement is a big deal for resource-poor Japan, whose energy needs are being satisfied in large part by expensive fossil fuel imports since the 2011 Tohoku earthquake stalled the country’s nuclear energy production. But methane is a powerful greenhouse gas, prompting environmental concerns about its extraction, and detractors are criticizing the government for investing so heavily in fossil fuels at the expense of renewables.