Do Hydrates Have a Future?
By Bill Moore
The year is 2031. A fuel cell-powered submarine tug slowly pulls a train of giant rubber bladders each a 100 meters in diameter and 400 meters long just above the gray mud of the Gulf of Mexico. The underwater train's destination is an offshore, natural gas processing facility 20 miles south of Galveston, Texas.
Inside the bladders is a substance some researchers and scientists consider the fuel of the future, an icy compound that burns more cleanly than oil or coal. It is a material that is so abundant that it could power the world for thousands of years. While estimates of the size of methane or gas hydrate deposits worldwide vary dramatically, conservative estimates say there is more of this frozen fuel buried under coastal sea plains and Arctic tundra than all the oil, natural gas and coal in the world combined!
Methane hydrates first captured the attention of the oil industry in the 1970s. As oil and gas exploration moved offshore and into the high Arctic, natural gas pipelines along the seabed and on the tundra began to clog with frozen clumps of water and gas. Oil companies funded research on how to prevent methane hydrate formation in their deep sea and Arctic gas pipelines.
Further exploration of the sea floor along the continental shelf has revealed vast natural deposits of methane hydrates, sometimes just above natural gas vents and often associated with colonies of a little-known species of tube worms, dubbed "Ice Worms."
Methane hydrates are natural gas frozen inside a crystal lattice of water. A combination of intense pressure at 300 meters and/or freezing temperatures naturally forms these curious deposits. There are two types of methane hydrates, those formed above undersea natural gas vents and those formed by bacterial action on organic matter washed into the oceans from coastal rivers and swamps. The bacteria-formed hydrates predominate and are generally the purest.
It is estimated that undersea hydrate deposits along the coasts of America are equal to 200 times the current estimate for conventional, recoverable natural gas in the United States. One deposit off the coast of North and South Carolina could supply the US with enough natural gas to power the entire country for 70 years.
Interest in methane hydrates was rekindled in the late 1990's as a potential energy source to replace dwindling reserves of conventional natural gas in the US. The current shortage of natural gas both in the United States and Canada only serves to highlight the need to find additional sources of this clean fossil fuel. Methane hydrates, if they could be safely tapped and transported, could provide the US Ð and the rest of the world Ð with all the fossil fuel energy it could ever want.
Power with Peril
While there are vast quantities of methane hydrates just offshore and under the Arctic tundra, getting to it and making use of it, is not without significant environmental risk.
Methane (more commonly known as natural gas) is an important greenhouse gas that is produced by biologic and geologic processes. Two of the most important biologic sources of atmospheric methane are termites and ruminants like cattle. Like carbon dioxide, methane in the atmosphere can trap and hold the earth's heat, causing the much-talked-about "greenhouse effect." However, unlike carbon dioxide, methane is 20 times more effective at capturing and holding heat, and herein lies one of the major environmental concerns about its use.
It is now believed by some in the scientific community that it was a massive release of methane some 8,000 years ago which suddenly ended the ice age. Deep craters that pockmark the seafloor off Norway seem to have been caused by gigantic prehistoric eruptions of decomposing methane hydrate deposits.
According to the theory, as the earth gradually warmed near the end of the last Ice Age, the ice cap over the North Atlantic retreated far enough to let in warm Gulf waters, disturbing the sediments, exposing the hydrates and causing them to begin decomposing. Released from its watery prison, it rushed to the surface and entered the atmosphere. Enough methane was added to cause temperatures to rise around the world, greatly accelerating global warming and the release of more methane, until a delicate equilibrium was reached.
Today the fear is that if global warming reaches a point where more methane in the sea beds and the Arctic were to be released, we could see global temperatures rise far faster than through the mechanism of man-made carbon dioxide emissions alone. One projection suggests average global temperatures would rise as much as 12 degrees in only a few years time, not the 3 degrees average projected by 2100. In short, it could get awfully hot, awfully fast.
On the other hand, if we could safely tap this plentiful resource, we could substitute this cleaner-burning fossil fuel in place of far dirtier fuels like oil and coal.
Transport By Submarine
Finding methane hydrate deposits is easy enough, safely tapping into it and then moving it to where it can be used, is an entirely different matter. If you either raise the temperature or lower the pressure under which methane hydrates are formed, it will "melt." It appears you cannot simply drill holes in a deposit and suck up methane like a "Slurpie" (a frozen fruit drink). Injecting a heated fluid into a deposit might set off a catastrophic eruption that could sink the platform or drilling ship. It has been demonstrated both in the laboratory and at sea that an underwater release of methane gas will neutralize a ship or floating drilling rig's buoyancy. Some even speculate that this could be the cause of mysterious ship and aircraft disappearances in the infamous Bermuda Triangle, an area know to have huge deposits of methane hydrate.
Instead, what might make some sense is to find a way to "mine" it and transport it at its ambient temperature and pressure, hence the idea of an undersea train where large amounts of relatively stable and concentrated hydrate can be moved to a processing facility offshore. Here, as the pressure is lowered, it can only do some mechanical work, for example powering electric turbines as it expands, but then when processed into natural gas can be safely distributed through conventional pipelines.
In addition to the technical challenges of extracting methane hydrates, there also is the question of its impact on ocean ecology and "strip mining" the seas. What will such activities do to marine life upon which we also depend?
What is obvious is that many nations have buried relatively close to hand a nearly inexhaustible source of natural gas that could be converted to hydrogen to run fuel cells or highly efficient gas turbines, even our cars, buses and boats.
From a strategic and economic perspective alone, methane hydrates could free many nations, including the US, from dependence on imported energy. This alone makes it worthwhile investigating.... very, very carefully!
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