Hot ice / Lisa Margonelli

Methane hydrates can solve the world's energy problem, or exacerbate its warming

One morning in August 2014, Doc Ricketts, the Monterey Bay Marine Research Institute's deep-water robot, was sent to probe the ocean floor in the very cold waters off the coast of Northern California. At a depth of 1,812 meters, it hovered over a long mound, 60 meters wide and two kilometers long, with thin layers of khaki-colored sediment scattered here and there. In the video taken by the robot's underwater camera suddenly appears something that looks like piles of snow, dirty indeed, but shining in their whiteness. If it weren't for the oysters and the fish around them, they would look like embankments piled up from a level of snow on the side of a road. This bright vein betrays the fact that the mound contains water, or methane hydrate: a lattice structure of frozen water in which molecules of methane gas, CH4, are trapped in molecular ice cages. If you make a snowball out of this material, you can set it on fire.

Such arteries, protruding on the surface, are only the tip of the iceberg, literally. Most of the deposits of methane hydrate are trapped slightly below the sea floor, in cold and deep areas of the ocean. The total size of the deposits is huge, and scientists are discovering them everywhere, along all the continental shelves. According to the latest estimates, worldwide these hydrates contain carbon in an amount equal to that found in all the reserves of coal, oil and natural gas on earth, or even exceeds it. Still, only a few deposits have been studied in detail.
The purpose of the research expedition in August, which lasted 11 days, was to collect samples from this large mound of methane hydrate and from the sediments surrounding it - not an easy operation. The robot equipped with mechanical arms was connected by a cable to the "Western Flyer" research ship and operated by remote control. The institute's senior scientist, marine geologist Charlie Powell, crackled with glee as the images appeared on the 20 screens in the ship's small control room. More than a dozen scientists from the Monterey Bay Institute and the US Geological Survey (USGS) crammed into the small room with Paul, me, and other people sitting on old airplane seats and overturned buckets. All these minds and this equipment prepared to attack the secrets of the mound and decipher them: how was it formed, where did the methane come from and did this vein start to emerge from the bottom ten years ago or has it been growing for a million years?
The researchers were looking for basic information that could help address broader issues. A recent geological survey found that the hydrates found off the coast of the USA (excluding Alaska and Hawaii) store fuel equivalent to supplying natural gas to the USA for 2,000 years, at the current rate of consumption. If it is possible to extract even a little of this fuel commercially it will be very useful; In March 2013, for the first time, natural gas was extracted from methane hydrate in the middle of the sea, aboard the Japanese research ship "Chikyo". But if the warming of the oceans destabilizes the hydrates and causes them to release the methane into the water and from them up into the atmosphere, it could precipitate a climate disaster. The effect of methane as a greenhouse gas, over a century, is greater than that of carbon dioxide (methane stores heat more efficiently than carbon dioxide but breaks down in the atmosphere faster - the editors). So, are methane hydrates going to be the next hit In the field of energy, or the next big trouble in the environmental field? Scientists like Powell are looking for answers.

A frozen black box
Powell, a tall man with a broad white mustache and English with a "flat" Rhode Island accent, began researching the hydrates in the 70s, when they were best known as a stumbling block to the oil industry: their ice crystals clogged pipes in wells dug deep underwater . When asked a question about the hydrates, he almost always opens with an enthusiastic burst of facts and ends with agonized gloom with the list of things he doesn't know. Over the course of his career, hydrates went from a strange and esoteric phenomenon to potentially weighty players in the Earth's carbon system, which made them even more mysterious. Before, every discovery of a new deposit was exciting, but "now the question is where there are no deposits," says Powell.

About one percent of methane hydrates are actually found on land, when they are squeezed between layers of ice-up near the poles. Almost all the other hydrates are found in the places defined as "the stability zone of the hydrates", where low temperature and high pressure prevail, under at least 300 meters of water. In these areas, extensive networks of crystals fill layers of sedimentary rocks that are up to 1,000 meters thick. Deeper the methane is in a gaseous state due to the heat coming from the Earth's interior. Hydrates form all the time, but unexpectedly. They solidify in certain porous spaces between sand grains, while in other spaces they remain in the state of flowing gas. Scientists do not know for sure why they solidify in these places and not in other places.

A careful investigation of the elusive characteristics of the hydrates is necessary for those seeking to utilize the energy stored in them: why they oscillate between gas and solid or how long the methane is kept in one place. These questions have become more urgent following several successful methane production experiments. The ship "Chiquio" drilled into sedimentary rock rich in hydrates, then pumped water from the vicinity of the drilling. The removal of the water reduced the local pressure and caused the methane to break away from its ice lattice that trapped it in the rock. Gas flowed from the well for five and a half days.

Japan is leading the international race, which is small in scope but very important, to produce energy from methane hydrates. In 2013, Japan spent 120 million US dollars on research. In 2010, the USA invested about 20 million dollars on the subject, but in 2013 the amount dropped to only 5 million. Germany, Taiwan, Korea, China and India operate small research programs, as well as the oil companies Shell and Statoil. While these expenses are not negligible, they are dwarfed by the billions of dollars the global oil industry spent on research and development in 2011 alone.

Japan, struggling with the need to import energy, and still dealing with the aftermath of the Fukushima nuclear disaster, may be able to benefit greatly from the large and tempting amount of methane lying off its shores. The US has less incentive to explore energy production from hydrates because it has an abundance of shale gas that is much cheaper to produce than methane hydrate production. Canada is also rich in hydrates, but abandoned its research program for similar reasons.

A "winning method" for mining hydrates of methane, if such a one existed, should stabilize the structure of the hydrates, bury in the ground the greenhouse gases that may be released during mining, and of course, provide fuel. In 2012, researchers from the USGS, the US Department of Energy, ConocoPhillips, Japan and Norway tried to do exactly that. They pumped a mixture of carbon dioxide and nitrogen (to prevent freezing) into the ice-covered hydrate in northern Alaska and hoped that the CO2 would push the methane out, take its place in the lattice and thus preserve the hydrate's structure.

Methane flowed from such an experimental well for a month, but the researchers were not sure that the CO2 actually replaced the methane. "The idea is simple, but nature is more complicated," says Ray Boswell, director of hydrate technology at the US Department of Energy's National Energy Technology Laboratory. Boswell says the test data points to a "messy black box below the surface." Despite the relative success of the experiment, ConocoPhillips sent its employees who were involved in the research to other tasks. The Ministry of Energy is looking for another partner in the industry to continue the experiments.
To Powell, this experiment demonstrates how limited our understanding of hydrate behavior is. In 2010, he chaired a committee of the US National Academy of Sciences that reviewed the Ministry of Energy's tests regarding the production of energy from hydrate methane. The group of experts came to the conclusion that the engineers can most likely overcome the technical challenges involved in producing fuel from hydrates, but many more scientific, environmental and engineering issues must be clarified before an informed decision is possible whether to continue with this or not. Unlike oil deposits, hydrates are difficult to map and are inherently unstable. Moreover, their effect on the ecosystems in their environment is almost unknown. "I think we don't have enough knowledge about the consequences of using them in an environmentally reasonable way," says Powell.
Stuck in a frozen airport waiting room
Understanding the elusive and unpredictable nature of hydrates is at the core of being able to determine if they can be reliably mined and if they could increase global warming.
Touching a hydrate, for example, is enough to make it go from solid to gas and ruin an experiment. That's why Paul instructed the "Western Flyer" team not to touch and dig in the piece of ice protruding from the mound until the end of the dive. The robot hovered over the murky, greenish bottom, and the mound rose in front of him like a giant blister with holes scattered here and there, as if it had been hit by tiny meteorites. Powell believes that the holes are places where bits of hydrate have broken off and fallen out due to tiny shocks like a fish hitting. Wherever there are deposits in the sea, you can see snowflakes of hydrate floating up in the wake of gas bubbles, like tiny comets being pulled in their wake to the surface of the water.
Hydrates are formed and decomposed constantly throughout the stability zone. During one of the dives, the sonar of "Doc Ricketts" detected a stream of gas bubbles emanating from the mound. Paul wanted to know if this gas was created in a hot "kitchen" deep in the earth's crust, similar to oil and natural gas, or if it was created in a biological process during which different types of bacteria process particles of organic matter that sinks and accumulates in the sediment layer. Almost all deposits contain gas from biogenic sources, and some of them also contain gas from thermal sources. Understanding this mix may help answer the question of how the mound was formed and what is beneath it. Paul asked the operator to lower the robot to the source of the bubbles: a dim fissure, surrounded by clams that feed on bacteria that sustain themselves from chemosynthesis, the conversion of methane into energy.
The team landed "Doc Ricketts" on the exposed hydrate, and the cameras immediately picked up a crab settling on the bubbles as he frantically tries to scoop them into his mouth with his pincers. Since the water temperature was only two degrees and the pressure was enormous, the gas quickly formed small hydrate crystals and decorated the crab's mouthparts with a ridiculous-looking white beard, thwarting its attempts to eat the bubbles. A biologist who was on board said that crabs trying to swallow methane bubbles are a common sight, although apparently they are not deriving any nutritional value from it.
To avoid the same trouble that befell cancer, the institute's engineers connected a heating unit to the tubes that fill the sample bottles, all of which the robot controls. And yet it was necessary to make several additional dives in the following days in order to collect a sufficient amount of sample to determine the ratio between the thermogenic gases and the biogenic gases in the mixture.
Paul also asked to know the age of the mound in order to understand how long it took to form. The team landed "Doc Ricketts" on the edge of the mound and with the help of his arms he attached special tubes to it to sample its contents. There were places where the pipes stuck easily in the frozen and dirty sediment, and there were places where they encountered resistance from hard material, ice or calcium carbonate for example.
In the middle of the job, strange light blue bubbles appeared in front of the robot's headlights. In the control room, the USGS geologist hypothesized that these were oil bubbles. Natural oil spills, where oil seeps out of underwater oil and gas reservoirs, occur all the time on the sea floor. A report by the US National Academy of Sciences published in 2003 estimated that every year about 680 million liters of oil seep up into the waters of the world's oceans. These oozes, on which large communities of clams, worms and other organisms exist, demonstrate how difficult it is to determine what a healthy environment is if they derive energy from hydrates.
After the two-meter-long drill samples were loaded onto Doc Ricketts, it took the crew another hour to get the robot and its cargo onto the ship. When the vessel entered through the sliding doors of the airlock in the ship's hull, it smelled strongly of oil and boiled eggs. The researchers stored some of the samples in freezers for later analysis and began processing some of them on the ship. The muddy drill cores resembled brownie batter. They are bubbling from a lot of gas dissolved in them.
Powell and his team rushed to process the smaller samples. They took the cores out of the tubes and placed them on trays to measure every centimeter of sediment and determine when it sank. The rotting mud in front of me contained the scene of a wild bacterial party: this cold sediment contains many types of single-celled organisms that produce methane, consume methane, and exchange sulfur molecules for oxygen molecules. The hydrate crystals, however large they may be, are only transit stations where methane passes from the sediment below the sea floor and between the water above. Lawrenson compares this space to "an airport waiting room," where everyone waits for their turn to take off.
Gerald Dickens, an earth scientist from Rice University, describes the world's hydrates as a huge storehouse of methane that rises into the sediments from below or is formed in them. The warehouse holds the gas, then slowly releases it into the seawater and possibly into the atmosphere as well. What is not known is the speed of operation of this storage, i.e. how long the methane waits before it is emitted. The gas waits there for perhaps seven million years and may be released relatively quickly, which could worsen global warming.
The fact that the researchers do not know for sure how much methane is actually waiting in these warehouses in the depths of the sea, adds to the uncertainty. In 2011, Dickens, based on many studies, reached an estimate of 170 to 12,700 billion tons of carbon, a very wide range that shows the magnitude of the uncertainty. The upper end of the estimate range suggests that methane hydrate deposits may store more than three times the total carbon in all quantified fossil fuel reserves, a total estimated at 4,000 billion tons of carbon.

Tsunami waves of methane
Being storage, the hydrates can also release large amounts of energy at once, which worries researchers from both the climate and resource aspects. Since hydrates have high buoyancy, they can be dangerous if disturbed from their tranquility. When a cubic meter of hydrate is brought to normal ambient temperature and pressure, it swells to 164 cubic meters of methane gas and 0.8 cubic meters of water. When earthquakes shake up hydrates, such swellings can lead to landslides, which can trigger a tsunami. Scientists believe that such a domino effect is to blame for the "Sturga Landslides" that hit the British Isles 8,100 years ago, and also for the "Cissano Tsunami" that killed more than 2,000 people in Papua New Guinea in 1998.
Prevention of such geological disasters is a challenge facing anyone who wishes to mine hydrates for energy purposes. To extract conventional oil and gas, the rock is drilled into closed underground reservoirs. But the methane in the hydrate is in a solid that needs to change its aggregation state to a gas in order to extract the methane from it, which shakes the entire structure.
A broader global concern is what happens to the methane after the hydrate breaks down. If it is released into the atmosphere and does not remain in the sea it could have a dramatic effect on the climate. I happened to see a piece of hydrate rising in the water column. During one of the dives, the robot bit off a melon-sized chunk of hydrate from the exposed section at a depth of 1,800 meters. The floating block was pulled upwards, and the robot had trouble getting it into the mesh bag. One of the researchers who observed the attempt called the frustrating dance "basketball in reverse gravity". From the control room, it appears that in deep water the ball remains more or less intact. But when the robot went above the stability zone, more and more gas was released, and the sack was covered with a mass of bubbles. When the robot finally reached the surface of the water, the volume of the hydrate was reduced to the volume of a few teaspoons.
On board, Lawrenson hastened to submerge the disappearing specimen in liquid nitrogen to preserve it for later testing. He also set fire to a small part of the sample and offered me to taste another morsel of it. The stuff fizzed in the mouth and was nauseating as expected from such a carbonated sorbet, except for an aromatic aftertaste that was almost minty.
This wild rise to the surface of the water can hint at the amount of methane that will be released into the air. Marine chemist Peter Brewer of the Monterey Bay Institute uses laser tomography to examine hydrates floating up. He found that they were falling apart both inside and out. Another experiment showed that the bubbles form sort of thin hydrate shells, like ping-pong balls that bubble and run around as they rise. Figuring out the physics and chemistry of hydrate breakdown, Brewer says, will help researchers determine where it occurs in the water column, how marine microorganisms consume the methane, how much, if any, typically makes it to the surface of the water and how much methane is expected to enter the atmosphere.

smoking gun
This knowledge could help settle a heated debate that has been going on among scientists for more than a decade: whether the warming of the oceans could lead to a massive release of methane and whether this release could disrupt the ability of the oceans to absorb this methane. An early theory known as the "clathrate gun hypothesis" (clathrate gun hypothesis, in this context, clathrate is a synonym for hydrate - the editors) claims that hydrate accumulations build up and then release methane in cyclical catastrophic events once every few thousand years. There is no evidence of such cycles in the fossil record, but it is possible that a single release of a large amount of methane 55 million years ago contributed to the rapid warming of the Earth in an event that brought temperatures to a peak, known as the "Thermal Maximum" (PETM).
In contrast, models built by David Archer from the University of Chicago suggest that the hydrates may release methane continuously over thousands of years, a release that could lead to a major change in global warming: the rising temperature will cause some of the hydrates to oxidize in the sea to carbon dioxide, CO2, and extend the trend the warming up.
A more immediate danger may be posed by the terrestrial hydrates, trapped under the ice in the Arctic region, and those found in shallow waters near the coast in these regions. A team led by Natalia Shakhova of the University of Alaska at Fairbanks reported in November 2013 that the East Siberian Ice Shelf emits 17 million tons of methane into the atmosphere each year, twice as many as previously estimated. Shakhova discovered a considerable amount of methane bubbles rising from ice-covered hydrate deposits at a depth of 50 meters below the surface of the water. In storms, which frequent the region, these bubbles seem to be dispersed in the atmosphere directly. Before they investigate further, it is impossible to know if this dynamic characterizes the entire Arctic region and not even if the main source of the methane is in hydrates or in the sea ice. This too is another "black box" in our picture of the world. And the research on our ship only added to the mystery. On my last day at sea, Paul examined some of the small drilling samples in the large "wet lab" of the "Western Flyer", as a prelude to the results of the analysis of the long, frozen samples, which will be conducted at the US Geological Survey. He hypothesized that the sediment we saw at the top of the mound was relatively new, and he could test this hypothesis by looking for traces of DDT in the sample, a substance that appeared only after 1945. But the sediment appeared to have swelled like blisters on the ocean floor, suggesting that it had accumulated over about 10,000 years, still relatively new Geological.
Later, analysis of frozen hydrate fragments that Lawrenceon sent to the Colorado School of Mines revealed that the mound not only contains its own methane, but also encloses a system of reservoirs beneath it. The Colorado researchers found several different ratios of carbon isotopes, and hence the methane in the hydrate comes from two different deep, hot reservoirs and two different types of biogenic gas.

This means that the gas flowed up from a hot and unknown source deep in the Earth's crust. He collected with him another gas from a shallower hot source and then crawled through the sediments and added the biogenic gases to it, including one that produced bacteria that broke down light oil into methane. Lawrenson was surprised: "This shows the complexity of migration [of oil and gas]. We don't understand what all these main players are doing there."

Attempting to measure just one mound, the robot encounters a much larger world lying beneath it. Our mound was nothing more than a small plug sealing off a huge reservoir of methane and oil. It turns out that methane hydrate challenges us with simple questions such as whether it is an energetic blessing or a climatic curse, and poses much bigger puzzles regarding the operation of global systems and the timetables to which they are subject. Scientists need to answer these questions, investing much more in basic Earth science, to understand how this mysterious substance links carbon from life that once lived on Earth and the planet's future.

on the notebook
Lisa Margonelli is the author of Oil on the Brain: Petroleum's Long Strange Trip to Your Tank. She is currently writing a book on termites for Scientific American and Farrar Strauss & Giroux.
in brief
Methane hydrates are large deposits of gas trapped in vast ice structures beneath the seafloor near the coast. More energy may be stored in them than all the oil, coal and natural gas reserves in the world.
Scientists are looking at places where the hydrates protrude to the surface to determine how to extract energy from them. They are also testing whether the methane will be released easily as global warming warms the seawater. In that case, the deposits could emit huge amounts of greenhouse gases.
In another disaster scenario, the deposits could break up quickly due to earthquakes, and the expanding gas could cause tsunami waves.
More on the subject
Methane Hydrates and Contemporary Climate Change. Carolyn D. Ruppel in Nature Education Knowledge, Vol. 3, no. 10, Article No. 29; 2013.
A blog that followed the research expedition described in the articleR:

Methane: A threat emerges from the bottom. By Katie Walter Anthony, Scientific American Israel, April-May 2010.