New Automated Means to Neutralize Old Chemical Weapons

chemical weapons

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The U.S. Army is using two state-of-the-art pilot plants, based on robots, in order to dispose of what remains of the more than 30,000 tons of chemical weapons the U.S. produced in the 20th century. And if all goes according to plan, the plants won’t be needed once they finish the job.

The two plants are “unique, first-of-a-kind facilities,” according to Joe Novad, acting head of the Army’s Assembled Chemical Weapons Alternatives (ACWA) that runs the plants, and will utilize processes that are more environmentally friendly than previous technologies.

About 90% of the U.S. stockpile has been disposed of since 1997, mostly through incineration, but some 2,600 tons of munitions and chemical agents remain at the Pueblo Chemical Depot in Colorado, and another 523 tons are at the Blue Grass Army Depot in Kentucky.

According to, the Pueblo Chemical Agent-Destruction Pilot Plant, or PCAPP, as it’s known, entered a testing phase last September, and will ramp up to capacity sometime this summer. It has already begun processing rounds of mustard gas contained in projectiles and mortar shells, and will slowly ramp up to capacity over the coming months.

To get at the deadly materials within, each shell must be carefully disassembled, and in many cases explosive “bursters” designed to assist in the spread of lethal chemicals must be removed before the “agent cavity” can be accessed.

Fortunately, no one need come in harm’s way to do this work. “Once you start the process, there is no human interaction,” says Novad. Instead, robots are used to “pick and place” the munitions to the various stations throughout the plant. Repurposed from the automobile

industry, PCAPP’s robots are monitored by human staff but operate autonomously, having first gone through a learning process to handle the shells that must either be disassembled or “punched and drained” before the chemical agent can be neutralized separately.

That neutralization process involves mixing the mustard agent with a caustic solution to produce a hydrolysate containing mostly water and a common industrial chemical known as thiodiglycol. This is then biodegraded by combining it with a bacteria-rich sludge from wastewater treatment plant sewage. The water goes through a brine-reduction process before being recycled back into the plant, and the salts and other “organics” that are left over go into a hazardous waste landfill. In the case of nerve agent, a process called “supercritical water oxidization” is used to heat the materials above 700 degrees Fahrenheit at more than 200 atmospheres of pressure, in order to quickly “mineralize” the toxic materials.

The empty shells themselves are also recycled to capture the carbon steel they contain.

The U.S. produced chemical weapons for more than 70 years, ceasing in 1989. Many of the remaining munitions have been damaged in storage or contain chemical agents that have solidified over time and cannot be processed in the main plants. For these, the Army has developed solutions that are literally more explosive.