Mining is big business, but also one of the world’s biggest polluters. A 2019 report estimated that the world’s 3,500 large-scale mining operations produce over 100 billion tonnes of solid waste per year. The ratio of useful materials to waste minerals is staggering; waste mass can be several times that of base metals, and can be millions of times that of rare elements such as gold.

This waste is of particular concern due to its often toxic content, with poisonous materials such as mercury a frequent by-product of mining operations. Recent accidents, such as the collapse of a tailings dam at Vale’s Brazilian operations near the town of Brumadinho, have also shone a spotlight on existing waste storage and treatment facilities, with growing concern that simply collecting vast reserves of solid and liquid waste is both unprofitable and highly dangerous. As demand for minerals, particularly rare earths and other uncommon commodities, grows, this problem is set to only increase.

A promising counter to this growing problem is that of waste recovery. Rather than cutting down on waste itself, companies are investing in new industrial processes to extract and re-use some of the useful materials that are often dumped among tonnes of less useful mining waste. With platinum group metals (PGMs), base metals, and even rare commodities such as gold among these unintended by-products of mining, there are a number of initiatives across the mining industry to improve the reclamation of resources, and push the sector towards a truly circular economy.

Mineworx moves to pilot plant

Canada-based Mineworx has been involved in the mining industry for some time, having entered into the sector in 1975 with the acquisition of the Cehegín iron ore project in Spain, which produced four million tonnes of ore in its first fourteen years of operation. Since then, the company has moved into the development of more advanced technologies, aiming to increase the environmental viability of both its operations in particular and mining in general. The business reached a major milestone in April when it announced an agreement with Tennessee’s Davis Recycling Inc. to construct a pilot plant; the operation will see  platinum group metals (PGMs) recycled from used catalytic converters.

The project will see the miner enter into a PGM recovery business that it values at around $30bn annually, and the move is a critical step in demonstrating the efficacy of the technology, which builds on the work of another partner, EnviroLeach. This third company has developed a water-based process to extract PGMs from catalytic converters, with up to 90% of the precious metals being recovered. The process removes the need for harmful substances, such as cyanide, to be used in the extraction process, which have been an industry standard but pose significant risks to human health and environmental safety.

This collaborative approach could help share information that could be beneficial across the mining industry, a sector which could see an increased demand for innovative waste treatment in the future. EnviroLeach notes that global electronic waste is predicted to increase to 78 million tonnes by 2026 as electronic devices become more widespread, and demand for gadgets increases.

Comstock targets mercury removal

Another mining company targeting a particular mineral is Comstock Mining, a Nevada-based miner that aims to improve the recovery and removal of mercury from mine tailings. The poisonous metal has long been a source of public health concerns in both artisanal mining and large-scale operations. A 2018 report found that over 1,000 tonnes of mercury was produced in the artisanal gold mining sector, due to the metal’s use in separating gold from non-precious ores. Notably, the waste that flooded the town of Brumadinho in the infamous Vale tailings dam collapse was found to contain dangerous quantities of mercury, arsenic, and manganese.

Fonte: Mining Technology