Unusual Fuel for the Future?

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UNUSUAL FUEL FOR THE FUTURE?

Could be basis of new world energy economy, scientists say

SAN FRANCISCO, April 13 -- A material with fuel potential ten times greater than all known coal, gas, and oil reserves on the planet lies deep within the oceans or in the permafrost of the arctic tundra, according to Dr. Timothy S. Collett of the United States Geological Survey (USGS) in Denver. Referring to solids called gas hydrates, Collett says that the USGS has developed for the first time a reliable assessment of the earth's supply of this potential fuel for the future, including both onshore and offshore resources of the United States. Speaking here at a meeting of the American Chemical Society, he says countries with little or no native fuels are quite interested in gas hydrates. This is especially true in Japan, which next year plans to drill a gas hydrate research well in the Mackenzie River Delta in cooperation with the Geological Survey of Canada. By 1999, Collett says, Japan will have a very large drilling program off its own shores to exploit their gas hydrates as a re

Gas hydrates are solid compounds that have gas molecules trapped in "cages" within an ice-like structure, says Laura A. Stern of the USGS in Menlo Park, California. The most common gas hydrate in nature is methane hydrate, which can form when methane and water are juxtaposed at moderate pressures and low temperatures, just the conditions that prevail on the ocean floor or in permafrost environments. But, Stern says, before the tremendous commercial potential of the hydrates can be realized, it would be prudent to have a better understanding of the chemical, physical and material properties of these unusual minerals. Stern and her USGS and Lawrence Livermore Laboratory colleagues developed a new technique to make samples of pure methane hydrate in the laboratory, and made an unexpected discovery along the way. They found that by fabricating methane hydrate from mixtures of ice crystals and pressurized methane gas, that the ice crystals could be warmed up to about 60 o F for many hours without melting, before complete reaction to hydrate was
achieved. Stern says they have concluded that "under hydrate-forming
conditions, it is possible to heat ice well above its ordinary melting point
while maintaiuning its solid form." Eventually all the "superheated" ice in the
sample chamber is converted to methane hydrate, which Stern and her colleagues then use in laboratory experiments to determine its strength characteristics.

But not all hydrates that occur in nature are formed by only by methane, says Dr. Roger Sassen of Texas A&M University. Sitting in the Plexiglas bubble of a research submersible at a depth of 1700 feet in the Gulf of Mexico, Sassen has observed and photographed hydrates formed by different hydrocarbon gases seeping into the water column. He was the first to discover the so- called structure H hydrate in nature. He says this type of hydrate will hold molecules much larger than methane, and is an indicator of sub-surface oil fields. Sassen grew gas hydrates in the deep sea for the first time by using these natural vent gases. Borrowing an idea from an Arthur C. Clarke novel of the 1950s, Sassen envisions manufacturing gas hydrates deep in the Gulf of Mexico using the hydrocarbons leaking into the water column. The solid material would then be towed back to shallower depths, where it could be decomposed into the hydrocarbon fuel and water.

Rather than using natural vent gases, Dr. Peter Brewer of the Monterey Bay Aquarium Research Institute formed methane hydrate in a controlled experiment with a remotely operated vehicle by bubbling methane gas from the surface into sea water at depths of over 1500 feet, and where the temperature was just above freezing. Brewer says that hydrates form easily in sea water or porous sediments which are at temperatures and pressures where hydrates are stable. He says that his experiments show it is possible to form large quantities of hydrates very quickly in a natural setting.

Dr. Michael Max and Dr. Robert E. Pellenbarg of the Naval Research Laboratory (NRL) want to take this manufacturing process one step further. Max says that it should be possible to synthesize this hydrate fuel using water, methane, and a "magical" substance X (as yet unknown) which would allow this material to be stable at sea-level temperatures and pressures. In this form it could be transported and stored quite safely, ready to be turned into water and fuel on demand. "It has," he says, "the potential to be the basis of a new world energy economy." (Disclaimer: Unless otherwise stated, this message should not be construed as representing any policy or view of NRL of the Navy, or any of their personnel.)

FUEL 23, 24, 26, and 27 will be presented from 2:20 to 4:15 p.m., Sun., April 13 in Continental 2, Ballroom Level, San Francisco Hilton; FUEL 65 will be presented at 4:15 p.m., Mon., April 14, in Continental 9, Ballroom Level, San Francisco Hilton. The national meeting of the American Chemical Society will be held in San Francisco April 13-17. This paper is among the 7,700 presentations that will be made.

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