Buried below the seabed around Japan, there are beds of methane, trapped in molecular cages of ice. In some places, the sediment covering these deposits of frozen water and methane has been eroded away, leaving whitish mounts of what looks like dirty ice rearing up out of the seafloor.
Put a match to this sea ice and it doesn’t just melt, it ignites
Take a chunk of this stuff up to the surface and it looks and feels much like ice, except for a give-away fizzing sensation in the palm of your hand, but put a match to it and it doesn’t just melt, it ignites. Large international research programmes and companies in Japan, among other countries, are racing to retrieve this strange, counter-intuitive substance – known as fiery ice – from beneath the seafloor to use its methane for fuel. If all goes to plan, they may even start extraction by the end of the next decade. But the journey so far has been far from smooth.
There’s no doubt that methane hydrates could offer a major source of fuel, with recent estimates suggesting they constitute about a third of the total carbon held in other fossil fuels such as oil, gas and coal. Several nations, notably Japan, want to extract it. It is not hard to find, often leaving a characteristic seismic signature that can be detected by research vessels. The problem is retrieving that gas and bringing it to the surface.
“One thing that’s clear is that we’re never going to go down and mine these ice-like deposits,” says Carolyn Ruppel, who leads the US Geological Survey’s Gas Hydrates Project.
It all comes down to physics. Methane hydrates are simply too sensitive to pressure and temperature to simply dig up and haul to land. They form at typically several hundred metres beneath the seafloor at water depths of about 500 metres, where pressures are much higher than at the surface, and temperatures are close to 0C. Take them out of these conditions, and they begin to break down before the methane can be harnessed. But there are other ways to do it.
“Instead, you have to force those deposits to release the methane from the formation in the seafloor. Then you can extract the gas that comes off,” says Ruppel.
A Japanese government funded research programme is trying to do just that. Its initial mission, after several years of preliminary research scoping out likely spots for methane hydrates, was in 2013. “It was a world-first,” says Koji Yamamoto, director general of the methane hydrate research and development group at the Japan Oil, Gas and Metals National Corporation, and one of the leading researchers in Japan’s national gas hydrates research programme.
The team managed to produce gas from the methane hydrate reserves by drilling a borehole down into the seabed of the Nankai Trough, off the eastern coast of Japan’s main island. By lowering the pressure on the reserves, they were able to release and collect the gas. The test ran for six days, before sand entered the well and blocked the supply.
A second test in 2017 ran in the Nankai Trough. This time the researchers used two test wells. The first encountered the same problem as before and became blocked with sand after several days. But the second of the well ran for 24 days without technical problems, Yamamoto says.
In general, people just feel really scared to do anything to the ocean floor. The place is known to be unstable and earthquakes happen – Ai Oyama
Even though the tests ran for a short time, they showed that there was a glimmer of potential that Japan might have usable carbon-based natural resources. The public reaction, however, was mixed, says Ai Oyama, a technical translator and former research analyst working on methane hydrates at the Hawai’i Natural Energy Institute. Some welcomed the idea that Japan may have energy independence. Others were very wary about any technique that disturbed the seafloor near tectonic plate boundaries.
“In general, people just feel really scared to do anything to the ocean floor. The place is known to be unstable and earthquakes happen,” Oyama says.
The fear is that depressurising one part of the methane hydrate deposit might make the whole reserve become unstable.
“People worry that we’ll start extracting methane from the gas hydrates and get into a runaway breakdown where we can’t stop it,” says Ruppel.
The problem with this would be two-fold. First, a lot of methane gas would suddenly be released into the ocean – which could potentially add vast amounts of the greenhouse gas to the atmosphere.
Second, methane hydrate releases a lot of water as well as a lot of methane when it destabilises, which would introduce a lot more liquid into the sediment below the ocean floor. In a steeply sloping environment, a lot of excess water could lead to landslips. Some environmentalists even fear that it could lead to a tsunami.
However, the physical properties of methane hydrate put a natural brake on this chain of events, says Ruppel. To release methane from a deposit, you have to put energy into the system. Without working hard to release the gas – through lowering the pressure or raising the temperature of the deposit – it simply stays put in its stable form of methane hydrate.
“So the problem is actually the opposite. You may start the process of getting the gas to come off, but to keep that process going, you have to introduce more energy to make it happen,” says Ruppel.
While a runaway reaction isn’t likely, the Japanese programme is still carrying out extensive environmental studies to test the safety of the methane hydrate production. The data gathered at the first test in 2013, and at a second longer test in 2017, so far hasn’t suggested that the technique will destabilise the ocean floor, Yamamoto says. But given Japan’s history of natural disasters – around 24,000 people are still under evacuation order since the 2011 Tōhoku earthquake and tsunami – the public is highly risk-averse.
“We feel that gas hydrate production is environmentally safe,” says Yamamoto. “But still, [the public] have a concern about negative effects of gas hydrate production.”