How Do Engineers Dispose of Chemical Weapons?

October 17, 2013

vxcanWithin the last few decades, with commendable success, engineers have eliminated 88.5% of the chemical weapons produced and stockpiled by the United States.

With mounting concerns over the feasibility of destroying Syria’s banned weapons, a review of the processes we’ve employed will help inform public debate and analysis of this seemingly intractable problem.


US Chemical Weapon Disposal Efforts

Richard Nixon halted production of chemical weapons in the United States in the 1960s. Soon after, a number of laws were enacted to prevent the further development, testing, or transport of chemical agents, especially within the borders of the United States. The first, Public Law 91-121 (pdf), forbade the use of funds allotted to the Department of Defense to test, deploy, or even transport chemical weapons or delivery systems without jumping through a series of hoops in both the Executive and Legislative branches – including the personal approval of the Surgeon General. If the SG vetoed any such proposal, only the President himself could directly override his decision.

This left the Department of Defense with millions of pounds of munitions and delivery systems which they could not use in theater, could not test in the open air, and could not even load into a truck and drive down the street without months of planning and the approval of multiple agencies. Chemical agents were worse than useless, they were an albatross.


The Department of Defense began studying the problem of safe disposal in 1979, guided by further legislation dictating specific oversight mechanisms for its transport and disposal operations. Public Law 99-145 (pdf) directed the DoD to pursue on-site disposal of existing stockpiles, in cooperation with FEMA and with oversight from the Department of Health and Human Services. (This oversight responsibility would eventually pass to the CDC.)

The 1979 pilot program set the stage for serious disposal efforts, which themselves began in 1990. Incineration was selected in 1982 as the DoD’s disposal method of choice; after review of the pilot program and resulting emissions, incineration was further endorsed by the National Research Council in 1984.

In accordance with Public Law 99-145, the DoD began on-site disposal at all nine of its chemical weapons stockpile locations. Five sites destroyed their agents and delivery systems through incineration, while chemical neutralization was selected for the remaining four.

As of this writing, seven out of nine stockpiles have been completely eliminated, accounting for 88.5% of the US chemical weapons arsenal.

Disposal of Chemical Weapons by Incineration

Five of the nine US stockpiles destroyed their chemical weapons through incineration:

  • Johnston Atoll, 1390km SW of Hawaii (Completed 2004)
  • Pine Bluff, Arkansas (Completed 2010)
  • Anniston, Alabama (Completed 2011)
  • Umatilla, Oregon (Completed 2011)
  • Tooele, Utah (Completed 2012)

WMD_Chemical_Weapon_Disposal_Unloading_lgThe incineration process exposes chemical agents to 1,093 degree C temperatures in a controlled-emission furnace, rendering them down to water vapor, CO2, ash, and combustion byproducts. Delivery systems, after disassembly, are melted down in a separate furnace at 812 degrees C.

To ensure safe operation, a number of internal operating monitors are keyed to a system-wide interlock mechanism. Operating pressure, furnace temperature, and emissions are carefully controlled and observed throughout the incineration process; any deviation from the ideal range for set safety parameters will automatically prevent the introduction of further chemical agents or delivery devices into the system. This allows engineers and technicians to correct operating errors or malfunctions immediately, before any unsafe condition is created.

According to the CDC, which operated in an oversight role during disposal at each of the five locations, no hazardous exposure incidents occurred either in the area surrounding the plant or involving members of the local community. With dioxins, for example – a concern for any incineration plant, regardless of inputs – the CDC reported that these Army-operated chemical weapons disposal plants output some of the lowest levels they’d ever seen.

All of the incineration-based chemical weapons disposal plants have completed operations. In this video, a crew at the Deseret Chemical Depot in Tooele, Utah completes the destruction of one of the last of their stored munitions.

Disposal of Chemical Weapons through Neutralization

Neutralization was the disposal process for the remaining four chemical weapons stockpiles. Two have completed operations, while two more – using robotic disassembly and processing equipment for (almost) fully automated disposal – are set to open within the next seven years.

The four stockpiles employing neutralization disposal are:

  • Aberdeen, Maryland (Completed 2005)
  • Newport, Indiana (Completed 2010)
  • Pueblo, Colorado (Beginning 2017)
  • Blue Grass, Kentucky (Beginning 2020)

neutralization flowchart 1Neutralization is a hydrolysis process, where water or water and sodium hydroxide are mixed with the chemical agent in order to form a toxic, but far less dangerous, hydrolyslate. This hydrolysate can be disposed of through conventional means.

techs disposingThe Aberdeen, Maryland site contained both mustard gas, which was neutralized on site in a heavy industrial reactor by the addition of hot water. The neutralization byproducts were removed to the DuPont Secure Environmental Treatment Facility in Deepwater, NJ, for additional treatment and final disposal.

Newport’s stockpile contained tons of VX nerve agent, which required the addition of sodium hydroxide for complete hydolysis. Mixing VX, water, and sodium hydroxide at 93 degrees C produces a stable hydrolysate, which was processed and safely disposed of by the Veolia Environmental Services company of Port Arthur, Texas.

Only two chemical weapons stockpiles remain: the Blue Grass Army Depot in Kentucky (1.6% of total arsenal, mostly nerve agents and munitions) and the Pueblo Chemical Depot in Colorado (9.9%, predominantly mustard gas). Each is pursuing innovative processing strategies to improve our hazardous material handling capability for future applications.

The Blue Grass Army Depot

The Blue Grass Army depot’s chemical weapons disposal process is unique both in its use of robotics and the neutralization process, itself.

Unlike hot water or water/sodium hydroxide hydrolysis, the pilot plant at Blue Grass employs supercritical water oxidation. Water at a temperature of 374 degrees C and under 3,205 psi of pressure is 90% less dense than normal, mixing more effectively with the organic components of chemical agents while preventing it from bonding with the salts. With the addition of heat and caustic agents, the chemical agents can be efficiently destroyed through oxidation and broken down into safe material.

The ACWA has prepared a video tour of the mechanical and chemical processes employed at the Blue Grass Pilot Plant.

Chemical agent disposal at the Blue Grass plant is slated to begin in 2020.

Pueblo Chemical Agent Destruction Plant

The Pueblo stockpile, consisting of mustard gas and assembled munitions, will employ a similarly advanced robotic disassembly process. Scott Susman, a mechanical engineer with the ACWA, walks us through the automated projectile mortar disassembly system.

The Pueblo plant is also notable for being the first chemical weapons disposal operation to employ biotreament of mustard gas neutralization byproducts. After hydrolysis, an array of living organisms will consume and transform the hydrolysate into harmless material. This results in a cleaner, cheaper, and more environmentally considerate disposal process.

Waste water will be recovered to reuse in further rounds of neutralization, while the processed sludge is removed for final treatment and disposal off-site.

Operations at the Pueblo Pilot Plant are scheduled to begin in 2017.

Featured image credit: jenspie3