Tuesday, March 20, 2007

GAO Report on LNG Risk

The GAO has released a new report on the risk of liquified natural gas (LNG). It's created by supercooling natural gas to -260 degrees Fahrenheit. This turns it into a liquid and reduces its volume 600 times.

In its liquid state, LNG is not flammable or explosive, so it can be transported in tankers. Since 1959, there have been more than 40,000 shipments, without a major incident. There are concerns about it, though, fueled by two factors:

1. Natural gas demand in the U.S. is expected to grow
2. After Sept. 11 (or perhaps more appropriately, since the attacks on the USS Cole and the French supertanker Limburg), there is concern about how much damage terrorists could do by attacking an LNG tanker or terminal.

examined a number of prior studies and consulted experts about the potential risks. They focused on three potential risks:

1. Leaking LNG forms a pool on the water. As the pool evaporates, it forms a cloud, which drifts onshore as an asphyxiation hazard.
2. The vapors from the LNG pool catch fire. This would burn hotter than oil.
3. The fire spreads to the LNG tanker, risking explosion.

Fortunately, none of these things has ever actually happened, so there are no real-world incidents to study.

Regarding the asphyxiation hazard, GAO found:

Only the Sandia National Laboratories’ study examined asphyxiation, and it concluded that asphyxiation did not pose a hazard to the general public.

Experts agreed that some hazards, such as freeze burns and asphyxiation, do not pose a hazard to the public.
Regarding the burn hazard, GAO found:
[T]he studies’ conclusions about the distance at which 30 seconds of exposure to the heat could burn people ranged from about 500 meters (less than 1/3 of a mile) to more than 2,000 meters (about 1-1/4 miles). The Sandia National Laboratories’ study concluded that the most likely distance for a burn is about 1,600 meters (1 mile).

Experts agreed that the most likely public safety impact of an LNG spill is the heat impact of a fire.
Regarding the explosion hazard, GAO found:
All three studies considered LNG vapor explosions unlikely unless the LNG vapors were in a confined space.

Experts agreed that explosions are not likely to occur in the wake of an LNG spill.
The Council on Foreign Relations also reported on the risk in February 2006, which provides good background and links to more resources on the subject.

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