Last year, Japan succeeded in extracting an untapped fuel from its ocean floor – methane hydrate, or flammable ice. Proponents argue that it will offset energy crises, but what are the environmental risks?
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.
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Could this humble material solve future energy crises? (Credit: US Department of Energy)
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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.
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(Credit: Nigel Hawtin, data from Renewable and Sustainable Energy Reviews, 41, 884-900)
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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.
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In 2013, the
deep-sea drilling vessel Chikyu succeeded in extracting methane hydrate
from the waters around central Japan.(Credit: Getty Images)
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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.
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| (Credit: Nigel Hawtin, based on data from Reviews of Geophysics, 55(1), 126-168) |
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.
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Flammable ice can
be fragile, and if it crumbles during drilling, it could release a
'methane burp' into the ocean. Some fear that this may unleash a tsunami.(Credit: Alarmy)
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“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.”
As well as the reserves buried
beneath the sea floor, there is another type of methane hydrate deposit
that has been gaining attention from Japanese researchers. Efforts to
research shallower deposits, very close to the seafloor surface, is also
being explored off in the Sea of Japan to the west of the country.
Accessing these shallow reserves poses a very different potential risk.
“These
are very active biological environments,” says Tim Collett, a senior
scientist at the US Geological Survey’s Gas Hydrate Project. “There are
whole communities that live off the methane.”
These environments
are rich in unique organisms, from bacteria to very large tubeworms and
crabs, all specialised to live off the methane as their source of
energy. In other parts of the world where these methane-based
communities live, they are often protected as rare natural environments.
Beneath the permafrost
Japan’s
main efforts in extracting methane hydrate, however are not in the
seafloor at all, but in the only other place that flammable ice can
found – deep in the permafrost, the permanently-frozen layer of rock or
soil that covers the ground at polar regions and high-rise mountains.
Researchers from Japan, which doesn’t have its own permafrost, are
assisting in the most ambitious on-land production test for methane
hydrate so far, in Alaska’s North Slope.
In December, researchers
from Japan’s national research programme are set to start work with the
US Geological Survey and the US’s Department of Energy, to begin what
they hope will be a long-term production test site. While this source of
methane hydrate is very different, the methods used to get to it are
actually very close.
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| Flammable ice appears to smoke as it melts (Credit: Getty Images) |
“The conditions at those reservoirs under the permafrost are pretty
similar pressure and temperature conditions as they are in the Nankai
Trough,” says Collett. “It turns out, to the best of our knowledge, even
though the Arctic and the marine environment are very different, the
physical properties of the deposits and how they occur in the sediments
appears to be very similar.”
The production techniques used in
Alaska could end up being transferrable to the marine environment. But
there are still big challenges. A long-term production of methane
hydrates hasn’t been carried out anywhere yet, on land or under the sea.
“We’re still very much in research mode,” says Collett.
Given
the difficulty of retrieving gas from methane hydrate reserves, and the
concerns around extraction, the stakes have to be high for a nation to
invest heavily in this technology. Having very few other options in
terms of domestic energy makes this hard-to-access source of methane an
appealing prospect. Japan is not a country that has other carbon-based
sources of energy to fall back on.
“Japan imports a lot of natural
gas, but it is very costly. If we have our own domestic resource, [it
could] contribute to the energy security of Japan,” says Yamamoto.
As
an economic resource, it’s easy to see the appeal of methane hydrate.
But, fundamentally, it is just another source of natural gas and burning
it would contribute to climate change.
All the social and environmental issues associated with fossil fuels apply to gas hydrates
“The
most important thing is the recognition and appreciation that gas
hydrates are just another fossil fuel,” says Collett. “All the social
and environmental issues associated with fossil fuels apply to gas
hydrates.”
In this context, methane hydrates – if they are to play
a role in Japan’s energy future – are likely to be used as a bridging
fuel, in the transition towards renewables. Natural gas is the least
carbon-intensive form of fossil fuel, releasing less carbon dioxide per
unit of energy released than coal or oil. But, as a carbon-based fuel,
burning it still contributes to climate change.
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| Japan has been researching the potential of flammable ice for decades,
but it is only within the last few years that extraction has come within
reach.(Credit: Getty Images) |
“We need to shift to renewable energy,” says Koji Yamamoto. “But complete switch to renewable energy [takes] a very long time.”
Even
as a transition fuel, gas hydrates could be hugely important, Ruppel
says. “Were a country able to efficiently produce methane from these
deposits, it could open a new realm in bridge fuels to another energy
future,” she says.
How useful a role it can play in the future
depends on how quickly methane hydrate can be accessed and produced on a
commercial scale. The Japanese government hopes to begin commercial
projects exploring methane hydrate between 2023 and 2027, according to
its
latest Strategic Energy Plan.
This
target could be a bit ambitious. Jun Matsushima, a researcher at the
Frontier Research Center for Energy and Resources at the University of
Tokyo, puts the estimate at around 2030 to 2050. “There is a long way to
commercialise methane hydrate,” says Matsushima.
The
make-or-break moment will be when a long-term production test can be
sustained without technical problems or budget constraints shutting it
down, says Ruppel.
“I would guess there will be a long-term
production test – from months to more than a year – by 2025. But I don’t
have a crystal ball,” Ruppel says.
But at the same time, Japan is
committing to moving towards renewable energies and decarbonisation. As
technologies for harnessing renewable energy become better and cheaper,
the role for fossil fuels – especially experimental and expensive ones
like methane hydrate – decreases. The longer it takes to get methane
from gas hydrate reserves on a commercial scale, the shorter the useful
window for using it may be. The other possibility is that adding in a
new accessible source of fossil fuel could delay the transition to
renewables, says Collett.
This source of carbon, the most abundant
in the world, may be one of the last new forms of fossil fuel to be
extracted on a commercial scale. It is also the only one to be developed
with the end of fossil fuels in sight. The race for methane hydrates is
a unique one, where researchers are working towards a goal that might
be made irrelevant by renewables by the time they reach it.
For
this reason, methane hydrates may well have a shelf life, but it remains
to be seen whether Japan, and other countries pursuing them, will be
able to get to them on a sufficiently large scale before they’ve already
become expendable.
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