Soon after the Flinstones’ cartoon period, formally called the Stone Age, humans started to use metals for constructing tools, weapons, or ornaments which tremendously boosted human development. Since then, metal utilization has been evolving and nowadays, metals are a central pillar for all kind of routine and technological uses. You can find aluminium in most of your pots and pans; copper as conductive material in wires or as heating sinks in computers, TV sets or disk drives; platinum in car catalysts to reduce air pollution; gold, silver, platinum, palladium, copper, tin, and zinc in cell phones. These are just a few examples of the extensive metal utilization to which society has succumbed. Look around you right now and try to picture your world without metals…difficult, right?
The metal mining industry needs to satisfy this increasing societal demand for metals. However, most of the high quality ores have been mined already. That leaves only ores with lower quality (low content of target metal and high content of undesired metals like arsenic) for future generations. This results in more metal-ores being processed and, therefore, a large amount of solid waste generated, around 20,000-25,000 megatons per year. This mining waste is often contaminated with high amounts of non-recovered metals. This represents a serious threat to the environment because many toxic metals easily mobilize upon contact with water.
Careless management of this solid waste in the past and present has resulted in formation and release of acidic water, contaminated with a wide range of toxic heavy metals, also known as acid mine drainage. This acidic water continuously threatens the health of many life-forms on earth including humans (for example via contamination of drinking water sources). Release of these hazardous waste streams by failure or absence of storage facilities has created big environmental problems in the last century, and continues to do so. We have recently witnessed terrible accidents related with mine waste storage failures. On 5 November 2015, a tailing dam containing iron ore failed, and around 60 million cubic meters of iron and other metals flowed into the Doce River. This destroyed the nearby village of Bento Rodrigues (Minas Gerais), killed 13 people, and caused huge environmental pollution. Additionally, over a hundred other tailing-related accidents took place in the last century. Local communities had to watch metal-coloured waters from mines flow into their pristine mountain streams on which they relied for drinking water and agriculture. Besides mine tailing failures, there were many other critical mine-associated problems all over the world. For instance, in South Africa, acid mine drainage affected the drinking water supply in 2012 with low-pH water contaminated with uranium. This led to an interrupted drinking water supply that lasted for months. With water stress already being a worldwide challenge, the water that still is available should be protected and not polluted with toxic metals.
Surely many factors contributed to these tragedies, but there is a direct connection with the careless mismanagement of governments and companies that often operate in developing countries, far away from their administrative centres. In the Environmental Justice Atlas (filtered by “Mineral Ores and Building Materials Extractions”) we can visualise the amount of conflicts (protest and accidents) related with mine industries. We can also see the “Not In My Back Yard” effect; usually the biggest mining companies are from Australia/UK (BHP Billiton or Rio Tinto) or China (China Shenhua Energy) but most of the problems took place in Central and South America. Even when mining takes place in developed countries, the remoteness of metal affected areas still keeps it away from the top of the political agenda.
We have to face the fact that we need metals if we want to keep our standard of living or increase it in developing countries, so mining is just necessary, now and in the foreseeable future. But what is unacceptable is that our society keeps on ignoring the vast environmental and socio-economic problems that are a direct effect of mining activities. We are still in time to prevent new disasters by raising awareness and taking the right measures; this is the right and the duty that we have as citizens of our society.
Since most of the problems are legacies of past mining activities with huge ongoing impact on environment and society, we should demand that our governments find solutions, even if this means taking over the management of those wastes. Secondly, governmental bodies should force operating mining companies to stop offloading the global environmental costs of their activities. Thirdly, and most importantly, more sustainable mining and recovery of metals should be stimulated where metals get a sustainability certificate, just like hard wood.
It will take time to make the change, and it will require funding and other resources. The positive side about advocating for metal recovery is that it will even be economically beneficial for companies. As mentioned, after mining activities, a leachate with a mixture of heavy metals is generated. Usually, one specific mine focusses on one specific metal and the rest of the ore is considered waste and disposed of as such. But this toxic waste contains many metals that can be recovered and used in a sustainable way. A way to do it is using sulfate-reducing microorganisms, which are able to reduce sulfate and produce sulfide. The sulfide reacts with metals and forms metal sulfides. A peculiarity of metal sulfides is that different metals precipitate at different pH values (copper is very insoluble even at low pH while iron needs higher pH to precipitate). Therefore, if the metal-laden leachate is consequently treated at different pH values using sulfate-reducing microorganisms, we will precipitate selectively different metal sulfides. The metals in the form of sulfides are very stable and dense enough to be separated and reused again in smelters or other applications. Since many metals are valuable resources, the mining companies can use this metal recovery for economic benefit. There are numerous examples in scientific literature and on-going technological applications which have proven the successful implementation of microorganisms for treating metal wastes. In this way, not only do we focus on waste treatment, we also aim to avoid waste generation altogether by turning potential waste into resource. We can change mining practises by using microorganisms and we can decrease the hazards of mining waste storage, thereby respecting the planet where we and future generations have to live.
Since this sustainable technology is available and even economically attractive, we encourage innovation and application by the industry from the beginning of the design of their mines. For the cases where the economic benefit threshold is smaller, governments should implement adequate laws in order to prevent further unnecessary environmental accidents linked to human industrial activities. It is time for a change.
Featured image credit: View of the Tinto River, an acid rock drainage environment. The rust-brown color is due to dissolved ferric iron. The water column has a pH of around 2.3 and contains elevated concentrations of several other transition metals, including copper and zinc. Photo taken by Jose Luis Sanz. Used with permission from the author.