The Globe and Mail has sought out columns from thought leaders in Western Canada, people whose influence is shaping debate, but whose names may not be widely recognized.
Metals to support our way of life are extracted by mining and processing large quantities of rock. The basic extraction paradigm is “drill, blast, load, haul, dump, crush, grind, separate, process.” There are many variations, but fundamentally, the paradigm has not changed since ancient times.
Innovations have made operations in the paradigm safer, more efficient, automated and even autonomous. Rock containing very small quantities of metal can be economically mined and processed and it is tempting to think that further innovations will allow mining and processing of rock containing even smaller amounts of metal.
However, some constraints are having a significant effect on the feasibility of mining. First, economic metal deposits are very difficult to find. Some deposits exist at depths of one kilometre or more, but heat and rock-mass stability at these depths make their exploitation difficult. Also, the waste-rock dumps and tailings generated by mining and mineral processing pose significant engineering challenges, environmental concerns and financial liabilities.
For almost every proposed mine, there are associated social and political issues which, if not understood and managed, can stop mine development faster than any technical issue will.
These constraints cannot be avoided by innovations within the current paradigm. A radical shift is needed, starting with seeking alternatives to handling and processing large amounts of rock.
There is at least one alternative – microbes, small organisms that interact with minerals and metals in an enormous variety of ways and have been doing so for a few billion years. Bacteria (single-celled microbes) will influence or control mineral precipitation or dissolve minerals to suit their needs for energy and carbon. One current application is the use of particular bacteria to dissolve minerals that contain gold in order to release the gold.
Complex microbial communities exist in mineral deposits even at large depths. The reason is they derive energy and carbon from interacting with the minerals. Within a coal seam, the growth of naturally occurring microbes that consume coal and produce methane can be enhanced resulting in economic quantities of methane. Microbial communities also exist in oil sands and in other mineral deposits and their characteristics are just beginning to be understood.
Some bacteria sequester nano-sized metal particles within or on the surface of their cell walls as a means of protection against metal toxicity. It has been suggested that such bacteria-metal interactions could be the basis of metal extraction processes.
Biotechnologies that do not involve microbes are possible. For example, plants called hyper-accumulators absorb metals through their root system and accumulate them in their leaves. Phyto-mining is the practice of growing hyper-accumulators in soils having sufficient metal concentration and then processing the plants to extract the metals.
It is also possible to use biochemical methods to construct molecules that contain a binder to a mineral of economic interest and chemicals that dissolve the mineral. Once the molecule binds to the mineral, the chemicals are released and the mineral is dissolved releasing the desired metal. This idea is the result of shameless borrowing of technologies associated with targeted drug delivery to diseased cells in humans.
Although metal extraction can be done using existing biotechnologies or by adaptations developed through further research, the technologies involve nano-sized “machines” and the sources of metals are in large unstructured environments. The question is how to deliver these technologies to the sources.
Large numbers or swarms of small robots offer a possible means of delivery.
Swarms can perform complex tasks and can adapt to environmental changes, much like what occurs in ant or bee colonies.
It is possible to conceive of thousands of small robots each delivering extractive biotechnologies to a metal source.
An article in The Globe and Mail on Aug. 15 entitled “This horde of tiny robots swarms toward artificial intelligence,” described the potential capabilities of a swarm of 1,024 small robots.
What would result if these ideas were implemented? The “mine” would be a combination of sources such as mineralized rock, scrap metal, mine waste, or metal-contaminated wastewater. Only small diameter drill holes would be necessary for access to mineralized rock.
Little to no waste would be produced. A mining company would be a metal-supply company managing linkages from sources to consumers.
Canada has the expertise to pursue these ideas or similar ones.
It should do so to remain a leader in resource extraction.
Scott Dunbar is the head of the Department of Mining Engineering at the University of British Columbia. Prior to joining UBC, he worked in consulting engineering. In addition to teaching topics in mining, he works with other researchers on ideas and concepts for metal extraction that might be used later this century.
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