The first phase of the multifaceted plan to relieve Syria of its chemical weapons went surprisingly smoothly: the regime of Bashar al-Assad not only dismantled its manufacturing facilities, it did so slightly ahead of schedule. This was regarded by the United Nations and the Organisation for the Prohibition of Chemical Weapons, which recently won the Nobel Peace Prize, as a sign of Syria’s willingness to live up to the rest of its promises. But a document leaked last week revealed that the original mid-2014 deadline for destroying all of Syria’s chemical weapons—thought to consist of over a thousand metric tons of mustard, sarin, and VX gases and their precursors—will likely be missed. A final plan detailing the elimination process is due on Friday, but the next steps for Syria’s stockpile will likely involve moving its chemicals to another country, where the O.P.C.W. will oversee use of a new U.S.-developed, semi-mobile facility to neutralize the chemicals.

Chemical weapons can be destroyed easily or safely, but not both. According to the Chemical Weapons Convention (C.W.C.), signed by a hundred and ninety nations, including Syria, any toxic chemical or precursor that can cause death, injury, temporary incapacitation, or sensory irritation is a chemical weapon. (“Precursors” are substances that can aid the production of chemical weapons, and may themselves be harmful.) Munitions and other delivery devices are also considered chemical weapons. First signed in 1993, the convention mandates that signatories physically destroy their chemical-weapons stockpiles. Before then, many nations destroyed their chemical weapons by burning, burying, or dumping them in the sea, where they remain threats to health and safety. After the Second World War, for instance, some forty thousand metric tons of chemical munitions, containing around thirteen thousand metric tons of chemical-warfare agents, were dumped into the Baltic Sea; several thousand metric tons have resurfaced over the last several decades, either by floating ashore, as they did in 1955, when lumps of solidified mustard gas washed up on Polish beaches, injuring more than a hundred people, or by being caught by fishing vessels. Even the U.S. buried its decommissioned chemical weapons, interring them at two hundred and fifty sites across forty states, after President Nixon renounced their use in November, 1969.

The O.P.C.W. suggests destroying chemical weapons in one of two ways: closed incineration or neutralization. Incineration, which is used by the U.S. Department of Defense, utilizes extremely hot furnaces, in which temperatures can reach up to twenty-seven hundred degrees in the primary chamber and two thousand degrees in a secondary chamber. The high temperature is supposed to break down any toxic chemicals into harmless—or, at least, controllable—end products. But there’s always the possibility that not every single component will be roasted until it’s a harmless residue. According to Paul Walker, the director of environmental security and sustainability for Green Cross International, an N.G.O. that helps to facilitate the destruction of chemical weapons, while the effluents do get “a thorough scrubbing” in a pollution-abatement system before the exhaust is vented, incineration “has released small amounts of live agents out of the stack from time to time.”

For that and other reasons, the environmental community favors the neutralization of chemical weapons, which confers a greater capacity to control, test, and manage toxic effluents. During neutralization, another chemical, or a combination of them, is added to the toxic agent in a weapon, causing a chemical reaction that renders it harmless. Typically, Walker said, “the liquid agent is drained from the munitions and mixed in tanks with a hot and caustic reagent.” While hot water alone is sufficient to neutralize mustard gas, for instance, hot water and sodium hydroxide together work as a reagent for the nerve gas VX. After one of these mixtures ripens for a few months, allowing the reagent to thoroughly react with the chemical, the resulting effluent is referred to as “hydrolysate”—mustard hydrolysate, VX hydrolysate, and so on. These hydrolysates are not harmless; though no longer “weaponized”—they won’t kill you immediately—they remain caustic, with a pH in the range of ten to thirteen, or somewhere around bleach or oven cleaner. As such, they remain classified as hazardous wastes.

At this point, the chemical effluent undergoes a second process. In some facilities, it is bioremediation, in which the hydrolysate is broken down into simpler and non-toxic compounds by a mix of microorganisms, not unlike sewage treatment. (A microorganism that could degrade nerve-gas effluents like organophosphates, which are neurotoxic—toxic to the nervous system—was first isolated in 1973. Since then, other microorganisms that can consume organophosphates have been discovered, and researchers have worked to engineer other microorganisms with the organophosphate-eating gene.) This much cleaner effluent is then sent to a brine-reduction system, where the water is evaporated, leaving behind metallic salt. In other plants, the waste is treated by supercritical water oxidation, in which extremely hot, pressurized water is added to the hydrolysate to decompose the liquid waste into its basic components of water, carbon dioxide, heavy metals, and salts. The heavy metals and salts are then disposed of like other industrial waste; they’re sent either to a hazardous-waste treatment and disposal facility, or to a commercial disposal facility, depending on their contents.

According to Walker, all of the unfilled chemical munitions in Syria—shells and rockets armed with explosives, but not with chemical weapons—must also be destroyed, to remove the temptation to fill them again. Munitions that have never held chemical agents can be destroyed by either compaction or detonation. Those that have held chemical agents will be washed, and the metal parts will then be heated to a thousand degrees Fahrenheit for fifteen minutes, after which the metal can be recycled.

After the destruction of Syria’s chemical weapons, just a handful of countries will have known, remaining stockpiles of chemical weapons, with the largest belonging to Russia and the United States. While Russians hope to dispose of their chemical weapons by 2015, the U.S. does not expect to eliminate its stockpile until 2023.

Photograph by Philipp Guelland/AFP/Getty.