In a sealed room behind a gantlet of armed guards and three rows of high barbed wire at the Army’s Pueblo Chemical Depot in Colorado, a team of robotic arms was disassembling some of the last of the US’ vast and ghastly stockpile of chemical weapons.In went artillery shells filled with deadly mustard agent that the Army had been storing for over 70 years. The robots pierced, drained and washed each shell, baked it at 1,500o Fahrenheit. Out came inert and harmless scrap metal, falling into a dumpster with a clank. “That’s the sound of a chemical weapon dying,” said Kingston Reif, deputy assistant secretary of defence for threat reduction and arms control.The destruction of the stockpile has taken decades, and the Army says the work is just about finished. The depot near Pueblo destroyed its last weapon in June; the remaining handful at another depot in Kentucky will be destroyed in the next few days. And when they are gone, all of the world’s publicly declared chemical weapons will have been eliminated.The US stockpile, built upover generations, was shocking in its scale. They were a class of weapons deemed so inhumane that their use was condemned after World War I, but even so, the US and other powers continued to develop and amass them. The US once also had a sprawling germ warfare and biological weapons programme; those weapons were destroyed in the 1970s. The US and the Soviet Union agreed in principle in 1989 to destroy their chemical weapons stockpiles, and when the Senate ratified the Chemical Weapons Convention in 1997, the US andother signatories committed to getting rid of chemical weapons once and for all.Other powers have also destroyed their declared stockpiles: Britain in 2007, India in 2009, Russia in 2017. But a few nations never signed the treaty, and some that did, notably Russia, appear to have retained undeclared stocks. But destroying them has not been easy. Defence department once projected that the job could be done in a few years at a cost of $1. 4 billion. It is now wrapping up decades behind schedule, at a cost of $42 billion — 2,900%over budget. But it’s done.The decades-long effort to dispose of the stockpile took so long as citizens and lawmakers insisted that the work be done without endangering surrounding communities. At Pueblo, each shell is pierced by a robot arm, the mustard agent inside is sucked out. The shell is washed and baked to destroy any remaining traces. The mustard agent is diluted in hot water, then broken down by bacteria. It yields a residue that is mostly ordinary table salt, said Walton Levi, a chemical engineer at Pueblo depot.
