Making fire from ice: a new fuel for the 21st century

At the bottom of the planet's deepest oceans, and beneath the frozen shallows of our coldest seas, there is gold.

Gas hydrate, an ice-like crystalline solid that exists in the oceanic sediment, is a mixture of water and gas - usually methane. It may become one of the great energy sources of the 21st century, with the power both to enhance our lives, and, if approached without care, to damage our planet irreparably. Last week, 100 scientists from 20 countries convened in Edinburgh to discuss the best way to progress with gas hydrate research, and it will not be their last meeting.

The key to gas hydrate's great power lies both in its content and its volume. The highly concentrated levels of methane found in gas hydrate can yield astonishing energy returns - one litre of methane hydrate solid, for instance, would contain 168 litres of methane gas. But when it comes to the volume of gas hydrate that exists on Earth, opinions are split. Many scientists believe - and this seems to be the consensus from those gathered at Edinburgh - that gas hydrates have the potential to yield twice as much energy as all the world's fossil fuel reserves.

"That amount," says Professor Bahman Tohidi, head of the gas hydrate unit of Heriot-Watt University's Institute for Petroleum Research, "is too big to ignore. Even if we were being conservative, and said that there was only the equivalent amount of gas hydrate as the total amount of fossil fuels, that is still an enormous quantity.

"But what is also interesting about gas hydrate is where one finds it. A lot of countries who do not have conventional reservoirs [of oil or gas], do have hydrate reservoirs. Japan, for instance. India, too. It is strategically very important for them to be self-sufficient from an energy viewpoint.

"And these methane hydrates, because they are mainly methane gas, are regarded as a low-carbon fuel, like natural gas. It's clean - not totally clean like hydrogen - but low-carbon."

So far, so rosy. But this is not, says Professor Tohidi, the entire picture. Gas hydrate, despite its potential as a low-carbon fuel, could wreak untold damage on the atmosphere. Due to the very high methane content in its structure, a dissociation of methane hydrate into its constituent parts, methane and water, could lead to staggering levels of the gas being released into the atmosphere.

With this grim caveat in mind, major countries around the world are now in a race to discover how to produce energy from methane hydrate. But the challenges involved are manifold. "Hydrate reservoirs are different from conventional reservoirs," says Professor Tohidi. "In traditional reservoirs, the energies are freed. Here, the source of energy is solid. Because hydrates are like ice, they are already in formation. So, to produce from them, you have to turn hydrates into water and gas: you have to dissociate them."

How is it done?

"One technique is to decrease pressure, another is to increase temperature, and a third is to introduce alcohol, a little like one would do with antifreeze," says Professor Tohidi. "But the method we are developing involves CO ₂. What you do is inject CO ₂, and produce methane, because CO ₂ can also form a hydrate. And CO ₂ hydrate is more stable, from a thermodynamic viewpoint, than methane hydrate.

"So, you can inject CO ₂, and that CO ₂ will replace the methane, and release it, so the methane can come out. You kill two birds with one stone. You get rid of CO ₂ and you produce the methane."

The technique sounds simple enough. But is only the first step in a battle with an energy source that is buried deep in the sea bed.

"Yes, the challenges are great," says Professor Tohidi. "One major issue arises because these hydrates are basically part of the sediment structure. And if you dissociate the hydrate, there will be emptiness where there was once hydrate. These are shallow sediments - hydrate occurs at about 600m below the sea bed - so [the sediments] are not consolidated. So, if you remove some of the substance from them, they might subside. And, if they subside, the sea bed will collapse. Then, the gas could escape freely, which could be incredibly harmful. This is why we are trying to replace one hydrate with another, but, as I said, there are challenges.

"The most serious of those challenges is the prevention of a sudden release of methane gas, which could have an immediate, disastrous impact on global warming; the sudden release of methane has been fingered as a culprit in past climate change. Scientists attempting to extract gas hydrates do not want another catastrophe on their hands."

If one needed an example of the destructive power of gas hydrate, one need look no further than the Bermuda Triangle. Scientists, including Professor Tohidi, seriously believe that much of the myth surrounding this fatal stretch of water can be explained by the prevalence of dissociating gas hydrate in the sediment, which causes methane to bubble up through the sea.

"If methane is coming through the water," says Professor Tohidi, "the density of water will be reduced. A ship floats only because of the density of the water beneath it, so if you reduce the density, the ship will sink. Also, if planes are crashing in this area, that could be explained, too - methane is highly flammable. Explosions could happen. Even the problem of the radar going all over the place might be explained by those bubbles of methane coming out. They might be causing static electricity, and that can change the magnetic field in the area."

The lesson to be gleaned from this odd tale is that methane's lowering of the density of water can have serious implications for oil rigs, too. And that is just one of the reasons why British businesses - in particular Fugro and BP - are heavily involved in gas hydrate research and exploration right now. But for all our know-how, Britain has no hydrate reservoirs of its own (or very few - there may be some in waters close to the Faroe Islands). Professor Tohidi's research unit, one of the world's oldest, was brought into existence because of the dangers gas hydrates were posing to North Sea oil pipelines, where they were forming due to unique pressure and temperature conditions.

"Yes, I would say Britain's role in the future of gas hydrate can be influential," says Professor Tohidi. "Even without considering the energy potential, Britain has an interest in stopping sub-sea landslides. And Britain certainly has a role to play in climate change. But as far as energy is concerned, British scientists and companies can help with production all over the world - and we already have interest from Taiwan and China, the US and Canada."

If the struggle for oil is the "great game" of the early 21st century, that game may now be acquiring a new set of rules. The world is not far away from the first viable, commercial production of energy from gas hydrates. Japan, for instance, has set the bar - claiming it will start commercial extraction by 2016. China, too, has recently invested $100m in gas hydrate research, starting a new 10-year programme to find and develop the energy source. The US Geological Survey is currently conducting some of the most advanced work on gas-hydrate production. And, with the Gulf of Mexico, Alaska, and Siberia all showing the possibility of viable gas-hydrate reserves, the old sparring partners - the US and Russia - will surely play major roles in the future of gas hydrates.

What no one knows is whether gas hydrates can fulfil their potential. Will the reservoirs be too dispersed? Will the production methods prove too costly? Will monitoring, rather than exploiting hydrates, become the main concern for scientists? What we do know is that decisions that have the power to shape the energy future of the planet will be taken during the next decade, and to understand them, one could do worse than know a little about the frozen booty at the bottom of the ocean.