Replacing mercury & cyanide in gold mining
Artisanal gold mining feeds families, and it runs on two of the most toxic chemicals in industry: mercury and cyanide. Ban either one and the income vanishes; leave them and the mercury reaches the fish, the cyanide reaches the river. The way through isn’t prohibition. It’s better chemistry that recovers more gold, so miners switch because the math tells them to.
The scale of the problem
Roughly 15 to 20 million artisanal and small-scale gold miners work across Sub-Saharan Africa, South America, and Southeast Asia. They produce about 20% of the world’s gold and roughly 37% of all global anthropogenic mercury emissions, about 2,200 tons a year, the single largest source. Mercury used in amalgamation evaporates during smelting, settles into rivers and oceans, and bacteria convert it to methylmercury, which bioaccumulates in the fish hundreds of millions of poor people eat. This is the mechanism that produced Minamata disease. Cyanide leaching, used in larger operations, occasionally fails and releases toxic concentrations straight into drinking-water rivers.
Our stance is that miners are not adversaries. They are people doing dangerous, low-margin work to feed their families. The most durable fix is the one that pays them to adopt it.
Mercury → borax and retorts
The mercury problem has a persuasive answer because the alternative simply recovers more gold.
Borax smelting (the replacement)
Crushed gold-bearing ore is concentrated by gravity (panning, sluicing, or a centrifuge) down to a heavy mineral fraction, then melted with borax flux, which lowers the melting point and dissolves silicate impurities, leaving pure gold behind. No mercury enters the process, so none escapes into the watershed.
Read the top two rows together: the miner who switches to borax roughly doubles their gold yield while eliminating mercury entirely. That is the whole case for switching. Once the math is shown, the conversion is voluntary, permanent, and faster than any enforcement could achieve. The higher yield is what makes the switch last.
Mercury retorts (an occupational safeguard)
A retort is a cheap device that condenses and recaptures mercury vapor when amalgam is burned, instead of letting it drift into the air and the miner’s lungs. It reduces mercury released and protects the person doing the burning. But a retort is occupational protection for miners still using mercury, not a replacement for mercury. The goal is always to move to borax; the retort reduces harm while that transition happens.
Cyanide → a thiosulfate process
Cyanide is harder, because there is no drop-in replacement that simply out-earns it the way borax out-earns mercury. Clean Water Help’s Baguio Gold research is developing a cyanide-free alternative based on thiosulfate, a far less dangerous chemical than cyanide:
The goal is a discharge with no cyanide and with the heavy metals captured instead of released into the watershed. The full-scale pilot planned for early 2027 will run the new process side by side with the normal cyanide process, so gold recovery, cost and discharge quality can be compared directly. Operating details stay private until the pilot results are reviewed.
The cost is complexity. The process needs trained, careful operation, which is why it fits operations where cyanide is already in use and a supervised chemistry transition is feasible.
The thiosulfate cyanide-replacement is Clean Water Help’s own Baguio Gold research and is still being validated. It is not yet a proven turnkey product. Costs and performance shown here are early estimates from our field work, consistent with the detoxifying-communities solution table. Borax and retort figures are drawn from established ASGM practice (UNEP, planetGOLD).
Where each fits
| Mining context | Intervention | Why |
|---|---|---|
| Mercury amalgamation | Borax smelting + sluice/pan | Better gold yield is what persuades miners, and the gain is immediate. |
| Miners still on mercury | Retort (interim) | Cuts vapor exposure while the switch to borax happens. |
| Cyanide leaching, small-scale | Thiosulfate process | Removes cyanide; designed to precipitate heavy metals and sharply cut discharge toxicity. |
You don’t win this by banning the chemical. You win it by handing the miner a process that recovers more gold and happens to poison no one.
The economic case
Stopping a toxin at the source costs a fraction of chasing it downstream. It costs roughly $1,500 to prevent a kilogram of mercury from entering a river by helping a miner switch to safer chemistry, and roughly $50,000 to remove that same kilogram once it has dispersed into sediment, fish, and people. Mercury and lead source control show ROIs above 100:1 in the public health literature. Because the payoff is large but takes years, and early research carries some risk, foundations and sustainable-development funders pay for most of this work. Gifts to a specific project, such as Baguio or Ghana, help too.
Stage 1: founder & volunteer funded. Field chemistry, lab analysis, and small research trials (like Baguio Gold) are paid for by our founders and volunteer scientists, a small board-approved research budget, and gifts made to the project. We make the case before we ask for capital.
Stage 2: grant & foundation funded. Validation, deployment, and scaling of a de-risked intervention, backed by $10K–$1M+ commitments from foundations, agencies, and sustainable-development organizations with the right risk tolerance and time horizon.
Clean Water Help in the field
This brief is grounded in our Baguio Gold project in the Philippines, where the thiosulfate research is being developed, and in Ghana’s artisanal gold-mining belt, where our sequence with Nyankonton Aid Foundation is filters first, then behavior change: community-made heavy-metal filters to cut exposure, then education and mercury-use intervention to reduce and ultimately replace mercury at the source. If you fund this kind of work, both projects have proposals ready.
Sources & notes
- Chemistry, costs, and recovery figures: Clean Water Help field research (Baguio Gold), summarized in the detoxifying-communities solution table, cross-checked with UNEP Global Mercury Assessment and Minamata Convention reporting.
- Field examples: Baguio Gold research and Ghana mining-belt program.
- The thiosulfate cyanide-replacement is research-stage; borax and retort routes are established ASGM practice. Figures are approximate and context-dependent.
Common questions
Why do miners switch away from mercury voluntarily?
Money. Borax recovers ~80% of fine gold versus mercury’s 30–40%. More gold per gram of ore, no mercury. Once the economics are shown, the conversion is voluntary and durable.
What is a mercury retort?
A cheap device that condenses and recaptures mercury vapor when amalgam is burned. It cuts exposure but is an occupational safeguard for miners still using mercury, not a replacement for mercury.
What replaces cyanide leaching?
Our Baguio Gold research is developing a thiosulfate-based process that uses no cyanide. It is designed to capture heavy metals and cut the toxicity of the discharge. A full-scale pilot in early 2027 will test it side by side with cyanide.
Related
Partner with us on source control
Source control shows ROIs above 100:1 for neurotoxins like mercury. Our Baguio pilot has a validated proposal, with equipment and partners ready once the chemicals are purchased. Our Ghana work has district government and partner approval and starts with community filters built from 100% locally sourced materials.