Spotlight On Mercury

Mercury 18 May , 2020

Mercury (Hg) is a potent yet toxic element that allows people around the world to extract and concentrate gold during what is called the amalgamation process. Use of Mercury by artisanal and small-scale gold miners accounts for 37% of global mercury emissions (IUCN, 2020), exposing workers to toxic fumes with often detrimental health impacts.

Around the world, governments have become signatories of the so-called Minamata Convention – an international agreement banning the use of mercury. But looking at ASM, there are few, if any, viable alternatives to mercury use, putting artisanal miners in a tough position.

The Impact Facility has committed to contributing to this challenge by providing technical solutions to the problem. In practice, this resulted in the provision of gravity-based concentration equipment to various mines across East Africa. In full transparency, adoption of the provided technology has been slow, for various reasons that we shall explore in a future blog post. You can learn more about alternatives to mercury during our upcoming webinar; “Mercury matters: How soon can we eradicate mercury in artisanal and small-scale gold processing?” – taking place on June 3rd, 2020 you can register here. One fundamental critique of existing technological solutions is the price tag attached to it, making it inaccessible for most artisanal miners. A lot of innovation is happening to develop more efficient and more affordable solutions. Meanwhile, mercury uses continuous at thousands of mines across Africa.

Why do gold miners use mercury?

Mercury acts as a binding agent central to the gold amalgamation process. The liquid separates gold and metals with similar characteristics, from non-metal content such as crushed orepowder, forming a mercury amalgam. During the gold washing process, as the application of mercury is often referred to, mostly female workers mix a slurry of ore concentrate with mercury. Using their bare hands, workers expose themselves directly to the poisonous substance

The resulting amalgam – a matt, silvery mix of mercury, gold and associated metals – is then burnt off using hot coals or a gas flame, evaporating mercury into the air. What is left behind is called a gold doré. During the evaporation process, mercury is emitted to the air, creating toxic fumes exposure to which can have crippling effects on human health.

The key to mercury reduction

Most artisanal miners in East Africa currently depend on this toxic yet straightforward, processing method. A process primarily executed by women using their bare hands, often making less than 3-4 dollars a day. While most adult workers won’t experience health impacts for years, mercury poisoning directly affects unborn babies, leading to miscarriages or severe disability.

Various national and international stakeholders are trying to sensitise miners regarding the dangers of mercury. Still, given the lack of easily accessible alternatives, the practice has been slow to change.

In the absence of more advanced alternatives to mercury, mercury retorts are the next best solution. With the support of ethical jeweller MAKAL, The Impact Facility is sensitising women washers at eight mining groups based in Kakamega and Migori, Kenya. The programme aims at providing professionally fabricated mining retorts and gas burners to each of the mining group, a programme supported by the EPRM and designed to help in reducing toxic fume exposure from mercury during the burning process.

What is a retort, and how does it work?

A retort is a small piece of equipment that can easily be fabricated by local welders. A retorts purpose is to ensure that the amalgamation process is conducted in a ‘closed environment’ – preventing mercury from vaporising and escaping into the atmosphere.

A retort is a closed-loop mercury recycling system, capturing mercury fumes and channelling them into cooler-water instead of emitting them into the air. Rather than using an open fire or hot coals to burn amalgam (commonly balanced on a spoon), the amalgam is inserted into a closed burning porch. Mercury fumes are directed through a pipe, flowing condensing when reaching a coolant, before being collected into a separate container. If executed correctly, this method cuts mercury emissions by 90-95%, minimising human exposure to the toxic fumes as much as possible.

Availability of retorts

In many places across East Africa, it is difficult to get ahold of a good retort. Retorts, however, are simple devices and can easily be fabricated locally. Its efficiency depends on its technical design, the use of high-quality materials and trained execution.

One of the most important factors is that the heat source allows the users to reach temperatures of roughly 1,300°Celsius within just a few minutes. This means rather than relying on coals or a small open fire, the retort relies on heating from a Bunsen burner connected to a gas cylinder.

The benefit of using mercury retorts

90-95% reduction of mercury emissions;
Reduction of operating costs as mercury gets recycled;
legal compliance – a growing number of countries has made the use of retorts obligatory.

Challenges of this practice

Retorts are nothing new; this technology has been promoted heavily in many countries with varying degrees of success. Some of the reasons why it might be challenging to establish regular use of retorts are:

Retort use is less convenient than the current practice and slightly more time consuming
Investing in a retort is costly (USD 50-100 in East Africa), especially given average daily incomes of less than USD 5 a day.
Cultivating trust in new technologies is difficult. Miners frequently voice concerns placing their gold in a non-see-through apparatus, worrying that they might lose some of their gold in the process.
Literacy around the negative health impacts of mercury is often still lacking.

What we do to drive retort use

Last year the Impact Facility helped organise a miner exchange visit, showing miners how improved practices can help grow their business. During this presentation they were also introduced to retorts.

Cognisant of all these challenges, we have set up a training curriculum as part of our ongoing EPRM-funded engagement with mines in Migori and Kakamega country. Engaging miners regularly, our goal is to repeatedly highlight the dangers associated with mercury exposure, while building the technical capacity too confidentially utilising retorts. This includes the promotion of adequate PPE use (gloves and moth protection) during the gold washing process.
We further incentivise the timely adoption of this technology, as retort use is a condition for the mines to access equipment leasing services through the Impact Facility.
To do away with the cost barrier, preventing adoption by the mostly female workforce, we are pleased to announce the generous support of ethical jeweller MAKAL.

As we proceed with the retort training, Cyrus will keep reporting about progress made and challenges along the way. Special thanks to MAKAL for sponsoring the fabrication of retorts for eight mining groups in Kenya! Learn more about MAKAL and their beautiful gold nugget jewellery visit their website.

David Sturmes

View Profile