Cyanide Usage

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Industrial Cyanide Usage

Although the quantity varies from year to year and from source to source, the range of global hydrogen cyanide production is about 1-3 million tonnes with an average of 1 million tonnes produced annually in the Western world, with about 750,000 tonnes produced in the US. Exact numbers are unknown due to poor reporting of data from some countries. All of the cyanide is produced as HCN gas, the most dangerous form, at chemical plants worldwide. Of the total and depending upon the year, about 6-15% is converted to solid sodium cyanide (NaCN). In the most recent year about 6% was converted to solid NaCN, 90% of it used by the mining industry (Figure 1).

Cyanide Usage - Figure 1

Figure 1. Percentage of cyanide used by the mining industry and other industries.

About 40% of HCN is converted into adiponitrile which in turn is converted into nylon. About 28% or so is used in the synthesis of various plastics while about 9% is converted into various chelating reagents such as EDTA.

Interestingly, many opponents of gold mining have used cyanide as the issue to stop this industry claiming it is too dangerous, when in reality many more worker and environmental incidents occur due to other industrial accidents and natural disasters. Elimination of gold mining does not eliminate the use of cyanide or its risks.

The photos in the Figure 1 show proper methods for transporting liquid and solid cyanide. Liquid cyanide is transported in multiple hull tanker trucks certified along with the drivers for hazardous waste materials, the shipment of which are tracked with GPS systems. Solid sodium cyanide is transported as briquettes in steel containers. Transportation accidents are one of the three most common with respect to cyanide incidents and spills in the environment.

Reported Cyanide Bans

There has been considerable discussion related to banning the use of cyanide in the world. Often NGOs and the news media report these so-called bans to suggest there is a widespread negative view of cyanide by the public throughout the world and their resistance to gold mining.

After an extensive review of the alleged bans this graphic was prepared (Figure 2). One or two municipalities in Argentina have banned either the use or transport of cyanide through them.

Cyanide Usage - Figure 2

Figure 2. Actual and reported cyanide bans.

In Australia in the State of New South Wales there was an effort to ban cyanide but it failed. Although reported otherwise there are no country-wide bans in either Greece, Turkey or Germany but there is one in the Czech Republic.

There is a short term moratorium on open pit mining in Costa Rica pending an environmental impact assessment (EIA) and another one in one municipality in Ecuador. These temporary bans are directed more toward mining in general than cyanide specifically.

In the U.S., there is a partial ban on cyanide use in Montana based on an environmental group's attempt to stop one heap leach project. There is no ban on underground mines using tailings impoundments and conventional cyanidation. Interestingly, the most serious environmental incidents, about 2/3 to 3/4 of them, occur due to tailings mishaps.

In Wisconsin there is a ban on mines processing sulfide-containing ores, not cyanide, due to concerns related to acid mine drainage and acid rock drainage. As many gold ore bodies contain sulfide, the ban on gold mining is often inappropriately associated with a ban on cyanide use.