Bacteria mining in Finland produced 1.2% of the world nickel supply in 2020

What bioleaching is

Bioleaching is a way of pulling metal out of rock using living bacteria instead of a chemical plant or a furnace. Many metals sit locked inside sulfide minerals, rock where the metal is chemically bonded to sulfur. A conventional processing plant breaks that bond with heat or with acid brought in from outside. Bioleaching instead stacks crushed ore in an outdoor pile called a heap, pumps air through it, and waters it so that naturally occurring bacteria can feed on the sulfur. The bacteria produce their own acid as they feed, and that acid dissolves the metal so it can be collected afterward. Terrafame, a mining company in Sotkamo, Finland, runs one of the biggest bioleaching operations in the world this way. Its ore sits in a primary heap for around 15 months, then moves to a second heap, with the whole bioleaching stage lasting about 5 years.

Small, but real and counted

Bioleaching remains a small part of world mining, but it is not a pilot project. Frank F. Roberto and Axel Schippers, 2 academics who reviewed the industry in a peer reviewed journal, counted how much of each metal the world produced this way in 2020. Copper, 1.2% of world production. Gold, 1.9%, from the general bacterial process called biooxidation, which frees gold trapped inside sulfide rock instead of the roasting or high pressure treatment a mine would otherwise need. Nickel, 1.2%. Cobalt, 0.4%. Zinc, 0.4%. Copper bioleaching is shrinking, the review found, as mining shifts to other methods. BIOX, the named gold process inside biooxidation, has produced more than 30 million ounces of gold over 30 years, and one mine in Russia, Olimpiada, produced 965,000 ounces of it in 2020 alone.

The Finnish operation behind the nickel share

Of that 1.2% nickel share, the same review found, all of it came from Terrafame on its own, 29,600 tonnes of nickel in 2020. Terrafame is now expanding, building a fifth heap under a program it calls LEACHMAX, with earthworks starting in the summer of 2026 and production targeted for early 2027. The company applied for 18.3 million euros from the European Union Innovation Fund toward the cost, alongside selling and leasing back its internal electricity network.

I am very pleased that we can launch the LEACHMAX investment programme, which is an important part of our future growth plans.

Antti Koulumies, chief executive officer of Terrafame. Source 2.

An independent life cycle analysis, a study that adds up the emissions created by every step of making something, cited in the same review, not produced by Terrafame itself, found that a kilogram of Terrafame nickel sulphate carries only 32% of the carbon dioxide that conventional processing produces, a cut of 68%, credited with preventing 620,000 tonnes of carbon dioxide a year.

Not yet how a dead battery gets recycled

Bioleaching cannot yet do the same job on a used electric vehicle battery. Bijayananda Kumar Biswal and Ramaraj Balasubramanian, 2 academics who reviewed the technique specifically for spent lithium ion batteries, found lab tests recovering as much as 100% of the lithium and up to 99.95% of the cobalt and nickel inside old battery cells, using bacteria or fungi, a mold like microorganism, to do it. The review states plainly that for batteries the technique is still explored only at lab scale, not run as a working plant, unlike the ore examples above. A typical bacterial test takes 3 to 14 days, and a fungal one 21 days or more.