|Artisanal and Small Scale Gold Mining|
|Friday, 23 September 2011 15:14|
Artisanal Small Scale Gold mining (ASGM)
Artisanal and small scale gold mining (ASGM) is a complex global development issue.
ASGM uses substantial amounts of mercury in mineral processing usually in highly unsafe and environmentally hazardous conditions. Mercury is used to bind the gold to form an amalgam, which helps separate it from the rock, sand and other materials. The amalgam is then heated to vaporize the mercury leaving the gold behind.
The use of mercury in ASGM continues to rise especially in developing countries mainly because it is considered simple and inexpensive. It is believed that ASGM produces 20 – 30 % of the world’s gold or approximately 500-800 tonnes per annum.
An estimated 10-15 million artisanal and small scale gold miners globally in approximately 70 countries are involved and eventually exposed to mercury.
ASGM is the largest demand sector for mercury globally (estimated at 650-1000 tonnes in 2005).
The amount mercury released within ASGM is dependent on the technique applied. The existing techniques include:
1. Whole Ore amalgamation
In this process, mercury is added to all the ore being processes during crushing, grinding and sluicing. This is the most polluting way to use mercury. In many cases, only 10% of the mercury added to an amalgamating barrel or pan combines with gold to produce the amalgam. The rest (90%) is excess and must be recycled or released into the environment. This subsequently leads to widespread mercury levels in the surrounding environment and the most severe health exposure to the miners as well as non-miners.
2. Gravity concentration (Panning)
This very common process involves concentrating gold with the heavier particles in the pan, while the lighter particles are sluiced away. Mercury is then added to the concentrates in order to amalgamate or gather the fine gold particles. About 10-15% of mercury releases from the ASGM are as a result of this process.
3. Burning amalgam
Gold is also recovered from heating the amalgam through burning it in a metal pan over an open fire.When this is done without the use of a retort, mercury vapours are released into the air and inhaled by the miners.This practice produces atmospheric mercury emissions of about 300 metric tones per year worldwide. (GMP, 2006). The use of retorts to collect the mercury vapour can prevent mercury release into the atmosphere therefore reducing exposure to miners and the surrounding communities. With the use of retorts, about 95% of the mercury is recycled and can be re-used.
Low mercury and mercury free solutions are available.
Relevant legislation and NGO policy work
In the EU
In the EU no ASGM takes place, apart from the French territories ofGuiana- where officially mercury use is prohibited under French law.
A relevant piece of legislation however is the EU Mercury Export Ban Regulation
Several projects and initiatives have been and taking place globally, to reduce emissions from the sector.
The Global Mercury Project (UNIDO/UNDP/GEF) began in 2002 with a vision to address the environmental issue of mercury contamination from artisanal and small-scale gold mining (ASGM) and to demonstrate ways of overcoming barriers to the adoption of best practices and pollution prevention measures that limit the mercury contamination of international waters from this sector. Six countries have been formally participating in the GMP:Brazil, Lao PDR,Indonesia,Sudan,Tanzania andZimbabwe. The GMP aims to introduce cleaner technologies, train miners, develop regulatory mechanisms and capacities within Government, conduct environmental and health assessments (E&HA) and build capacity within participating countries which will continue monitoring Hg pollution after the project.
Important work is currently being carried out under the UNEP Global Mercury Partnership on Reducing Mercury in ASGM. The partnership is lead by UNIDO and NRDC (Member of ZMWG).
Smaller on the ground projects have been taking place in Tanzania , funded by NGOs such as the Swedish Society for Nature Conservation, the European Environmental Bureau/Zero Mercury Working Group and the Artisanal Gold Council.
The ZMWG has been following this issue closely and has been giving respective feedback at the global mercury negotiations. See also the ZMWG fact sheet on Artisanal and Small Scale Gold mining (ASGM) (Jan 2011).