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CYANIDE REGULATIONS The Current Status of Cyanide Regulations By Professor Jan G. Laitos Cyanide heap leaching is an integral part of most modern gold mining operations.
The use of low-cost cyanide heap leaching techniques to recover metal from ores has allowed miners to profitably extract gold deposits. The chemical compound has on occasion been mishandled, and in some locations releases have created environmen- tal problems. However, worldwide, the min- ing industry has shown it can work with cyanide responsibly. In part this basically good record is due to an evolving regulatory landscape, and a realization by the mining industry that cyanide spills are to be avoid- ed. Nonetheless, despite a voluntary polic- ing effort by the industry, and the adoption of strict regulations by governments where the mines are located, certain environmen- tal groups have attacked the use of cyanide. These groups often rally the support of local citizens (voters) by conjuring the memories of those disasters. While there have been notable past problems with cyanide, for the most part its use by the mining industry has not resulted in environmental catastrophe. More than 90% of all gold extracted worldwide relies upon the use of cyanide. Of the 1.1 million tons of hydrogen cyanide (HCN) produced annually, only 6% is con- verted into sodium cyanide for use in the mining industry. The remaining 94% of hydrogen cyanide is used to produce a wide variety of products, such as adhesives, com- puter electronics, fire retardants and nylon. With more than 150 gold mines, Nevada is the hub of the U.S. gold mining industry, accounting for the most explo-
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ration and mining activity on federal lands. The State of Nevada alone annually con- tributes approximately 75% to national U.S. gold production. States that currently use cyanide leaching to recover metals from ore are: Arizona, California, Colorado, Idaho, Montana, Nevada, Utah, South Carolina, South Dakota and Washington. Cyanide solution can be used for both heap leaching and vat leaching applica- tions. Heap leaching is by far the widest application and the most controversial. Mines contain the cyanide solution by placing multiple "impermeable" liners at the base of heap leaching stockpiles and along the bottom of leachate collection ponds. During operations, the cyanide solution is collected and processed. When the mine is closed, there is a short- and long-term cleanup plan to detoxify the solution so that no residual cyanide remains to harm the environment. The detoxification and neutralization process converts cyanide into a less toxic cyanate, before combining it with the mine tailings. Some operations may also use water treat- ment facilities to treat and neutralize efflu- ent discharge. Any remaining cyanide decomposes naturally as sunlight breaks the compound into carbon and nitrogen. Cyanide is a naturally occurring com- pound that bonds with gold, allowing it to be brought into solution. It can easily be separated from gold for collection. It is a simple, cost effective process. No suitable
alternatives exist. In other words, banning the use of cyanide in effect bans the extraction and production of gold. Gravity separation works well with lodes or veins, but there are few of those types of deposits to be found. Froth flotation is not efficient enough to process low grade gold deposits. Amalgamation, which is used extensively by artisanal miners, requires the use of even more toxic mercury in solution. Cyanide releases into the environment do represent potential environmental and health hazards. The adverse effects caused by cyanide releases, however, are normally acute and short-term in nature, lasting only hours or days. As a result of rapid decompo- sition, cyanide releases are not generally associated with continued long-term effects. Despite this biological reality and the bene- fits of its use, it is a substance which has become the target of much regulation.
Limits on Cyanide Use in Mines
There are currently four ways by which the use cyanide can be banned, regulated, lim- ited and conditioned. These methods include voluntary initiatives, state and local regulations, including outright bans, federal international laws and treaties, and multi- national agreements. The International Cyanide Management Code is a
best practices code of regulations. It was prompted in response to a cyanide spill in Romania in January 2000. A tailings dam ruptured at a mine operated by Aural S.A., releasing about 100,000 m3 of liquid and suspended waste. The tragedy was blamed on a combination of design defects, unex- pected operating conditions, and bad weath- er conditions. A plume of cyanide solution worked its way through Hungary and Yugoslavia on the Danube River all the way to the Black Sea. Prior to the Fukushima dis- aster in Japan last year, the Baia Mare spill has often been referred to as the worst envi- ronmental disaster since Chernobyl. In the U.S., state and local cyanide
are typically based on the U.S. Bureau of Land Management's (BLM) national cyanide policy. The mine must have the ability to contain any process using cyanide so that it
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Memories of past disasters reinforce present-day fears
voluntary
reg- ulations withstands the run-off
