Now that UN inspectors have identified sarin as the chemical agent used in Damascus last month, the world is turning its attention to how best to destroy Syria's stock of chemical weapons. Here's a primer:
What is sarin?
Sarin is a human-made chemical warfare agent classified as a nerve agent, the most toxic and rapidly acting of the known chemical warfare agents. It is a clear, colourless, tasteless and odourless liquid that can easily evaporate into the air.
Sarin was developed in Germany in 1938 as a pesticide, but it proved much more deadly. Ordered into production as a military weapon, it was never used by the Germans.
It was believed to be among the chemical weapons used in 1988 by the Iraqi regime of Saddam Hussein, first against Iraqi Kurds in the northern town of Halabja, killing about 5,000, then against Iranian troops near the end of the Iran-Iraq War, driving the Iranians out of the al-Faw Peninsula they had captured in southern Iraq.
It was twice used by the Aum Shinrikyo sect in Japan, first in 1994, killing eight people in Nagano, then in 1995, killing 13 people in the Tokyo subway.
Most recently, it was used on Aug. 21 in Syria, killing several hundred people on the outskirts of Damascus.
Effects on the body are almost immediate; even a small amount ingested or inhaled results in loss of consciousness, convulsions, paralysis and likely death from respiratory failure.
Lessons learned about destroying chemical weapons
Foreign ministers of the United States and Russia reached an agreement Saturday on a framework that calls for destruction within nine months of all chemical weapons in Syria. The two agreed that there are about 1,000 tonnes of chemical weapons in Syria's arsenal, most of it sarin. (By way of comparison, the U.S. stockpile reached about 31,500 tonnes and Russia's, 44,000 tonnes.)
"I don't know how they can possibly meet that deadline," said Brian Finlay, a weapons specialist at the Stimson Center, a defence think tank in Washington, D.C. "There's just too much involved in destroying this stuff."
Only the United States and Russia have had experience decommissioning large amounts of sarin weaponry. Under the terms of the Chemical Weapons Convention, signed in 1997, the two Cold War superpowers agreed to destroy their vast arsenals of sarin and VX (an even deadlier nerve agent) by April 29, 2012. They still are years from completion.
The technologies involved to destroy chemical weapons all require massive, sophisticated facilities, the construction of which can take years.
But dealing with a chemical agent that already has been put into bombs, artillery shells or other weapons is an even greater challenge. Robotic systems are usually employed to remove the shells' contents, and separate facilities are needed to destroy the casings and other parts of the munitions.
At Blue Grass, Ky., site of one of the final two U.S. destruction sites, munitions containing some 523 tonnes of sarin and VX are waiting to be decommissioned. The necessary facilities are only about half built and will take until 2017 to be completed. The necessary testing and adjustments will take three more years and the destruction itself of the nerve agents another three years, until 2023.
The Blue Grass stockpile is relatively easy to deal with. It's half the size of Syria's weapons arsenal and it's located in one place, not spread around a war-torn country, notes Mr. Finlay.
The U.S.-Russia framework calls for as much of the chemical weapons as possible to be moved outside Syria for destruction, but this is a highly dubious notion, Mr. Finlay said. "The chemical agents are far too vulnerable to be moved any distance except under the most stable of conditions."
Long gone are the days when chemical weapons can be dumped into the sea or bulldozed into the ground, as Libya did with much of its mustard gas. Today, there are two approaches to destroying sarin or VX that are practical and acceptable under the Chemical Weapons Convention.
The United States, which began its efforts to decommission chemical weapons in 1990, even before the convention, developed incineration technologies that have been used in most of its weapons destruction.
Basically, liquid chemical agents are burned in extremely high-temperature furnaces. This includes the vats of chemical agents as well as the agents that must be drained from individual munitions such as rockets and artillery shells, likely similar to those used in Syria.
The munitions themselves are put through a metal-parts furnace, as are other contaminated materials such as wood pallets, fibreglass cases, etc. Those munitions that include explosives, as many do, must be separated and burned in an explosives furnace, armoured to withstand blasts.
Tonnes of gaseous effluents are then scrubbed by multiple wet and dry filters and released into the atmosphere through a tall smokestack.
2. Neutralization (or hydrolysis)
This is the process preferred by Russia and the four U.S. states that have outlawed incineration.
This approach requires that the chemical weapons container or munitions be drained and the liquid agent placed in a mixing tank with hot water or a caustic reagent such as sodium hydroxide, or with both. The chemical reaction destroys the toxicity of the agent and the liquid effluent can then be further processed in a second stage, using either a liquid industrial incinerator or a bioremediation process similar to sewage treatment.
The metal parts of weapons are processed in a metal-parts furnace.
The Canadian experience
Against the backdrop of the Sept. 11, 2001 terror attacks on the United States, the 2002 G8 summit in Kananaskis, Alta., announced a new Global Partnership Against the Spread of Weapons and Materials of Mass Destruction. The initiative was intended to secure and eliminate such weapons in the former Soviet Union. For its part, Canada pledged up to $1-billion to assist in the decommissioning of chemical weapons.
A destruction facility in Siberia faced an acute problem: transporting a vast number of unstable chemical-weapon containers and weapons to the neutralization tanks and high-temperature furnaces 20 kilometres away over extremely rough terrain.
Even in the smooth U.S. robotic facilities, munitions are moved on belts no faster than three or four kilometres per hour. It was deemed too dangerous to move the volatile Siberian chemical weapons unless some comparable mechanism could be constructed. Canada proposed and funded a rail line to gently transport the 1.9 million chemical-weapon shells to their site of destruction. The total cost was $33-million.
"It was a real Canadian success story," said Brian Finlay of the Stimson Center, a defence think tank in Washington, D.C. "The whole operation had been delayed by all kinds of infighting and technology issues, until Canada stepped in."