METAL INDICATOR SPECIES, METAL TOLERANCE, METAL UPTAKE
Metallophytes in Latin America / Revista Chilena de Historia Natural / 2004
“…Second, metallophytes endemic to areas of well-defined soil composition have been used historically as geobotanical indicators for mineral exploration. For instance, some of these plants have extensively been used in Europe and central Africa as metal bioindicators as they can be used to delineate metalliferous substrates when prospecting for metal ores (Brooks 1998).
Third, further uses for metallophytes by the mining industry have been promoted in the most recent drive towards sustainable development and responsible mine site closure in Europe and North America (Whiting et al. 2002).
On the one hand, endemic metallophytes can be used in the revegetation and restoration of former mined sites (phytostabilization), and on the other, they can be used in the clean-up of toxic metals from soils (phytoextraction) or in the phytomining of low grade ore that cannot be processed economically by other techniques (Baker et al. 1999, Tordoff et al. 2000).”
The deposition of metal-rich wastes in terrestrial environments by the metal mining industry (e.g. tailings dumps and sterile piles), has generated new habitats for potential micro-evolution and colonization of metal adapted variants of common species and for metalophytes colonization (e.g., Allen & Sheppard 1971, Baker 1984, Bush & Barret 1993, Ginocchio et al. 2002).
Abandoned and naturally recolonized old mine sites can therefore be seen not only as a liability but also a resource base of unique genetic materials. The study of these plants and their colonization behaviour and evolution observable on former mine sites has improved closure and rehabititation strategies in some mined areas of developed countries (e.g., Gunn 1995)…”
AGROMINING METALS with HYPER-ACCUMULATING PLANTS
Hyper-accumulating plants thrive in metallic soil that kills other vegetation, and botanists are testing the potential of phytomining
by Ian Morse / Feb. 26, 2020
“With roots that act practically like magnets, these organisms — about 700 are known — flourish in metal-rich soils that make hundreds of thousands of other plant species flee or die.
Slicing open one of these trees or running the leaves of its bush cousin through a peanut press produces a sap that oozes a neon blue-green. This “juice” is actually one-quarter nickel, far more concentrated than the ore feeding the world’s nickel smelters.
The plants not only collect the soil’s minerals into their bodies but seem to hoard them to “ridiculous” levels, said Alan Baker, a visiting botany professor at the University of Melbourne who has researched the relationship between plants and their soils since the 1970s. This vegetation could be the world’s most efficient, solar-powered mineral smelters. What if, as a partial substitute to traditional, energy-intensive and environmentally costly mining and smelting, the world harvested nickel plants?
Dr. Baker and an international team of colleagues has set its sights on convincing the world the idea is more than just a fun thought experiment. On a plot of land rented from a rural village on the Malaysian side of the island of Borneo, the group has proved it at small scale. Every six to 12 months, a farmer shaves off one foot of growth from these nickel-hyper-accumulating plants and either burns or squeezes the metal out.
After a short purification, farmers could hold in their hands roughly 500 pounds of nickel citrate, potentially worth thousands of dollars on international markets. Now, as the team scales up to the world’s largest trial at nearly 50 acres, their target audience is industry. In a decade, the researchers hope that a sizable portion of insatiable consumer demand for base metals and rare minerals could be filled by the same kind of farming that produces the world’s coconuts and coffee.
Phytomining, or extracting minerals from hyper-accumulating plants, cannot fully replace traditional mining techniques, Dr. Baker says. But the technology has the additional value of enabling areas with toxic soils to be made productive. Smallholding farmers could grow on metal-rich soils, and mining companies might use these plants to clean up their former mines and waste and even collect some revenue. “It’s icing on the cake,” Dr. Baker said. The father of modern mineral smelting, Georgius Agricola, saw this potential 500 years ago. He smelted plants in his free time.
If you knew what to look for in a leaf, he wrote in the 16th century, you could deduce which metals lay in the ground below. Rufus Chaney, an agronomist at the U.S. Department of Agriculture for 47 years, invented the word “phytomining” in 1983 and with Dr. Baker helped begin the first trial in Oregon in 1996. His name is immortalized in one of the nickel-sucking plants used in the Malaysian plot. Now, after decades behind the lock and key of patents, Dr. Baker said, “the brakes are off the system.”
With patents no longer an issue, the scientists hope the technology can benefit small farmers in Malaysia and Indonesia. “The hope is that we can show it off and have proof of concept and show people how it works, and that it works,” added Antony van der Ent, a plant scientist at the Sustainable Minerals Institute at the University of Queensland in Australia. His dissertation began the Malaysian project.
Nickel is a crucial element in stainless steel. Its chemical compounds are increasingly used in batteries for electric vehicles and renewable energies. It is toxic to plants, just as it is to humans in high doses. Where nickel is mined and refined, it destroys land and leaves waste. In areas where soils are naturally rich in nickel, typically in the tropics and Mediterranean basin, plants have either adapted or died off.
In New Caledonia, a New Jersey-size French territory in the South Pacific that has been a major source of nickel, botanists know of at least 65 nickel-loving plants. Such plants are the most common metal-craving vegetation; others suck up cobalt, zinc and similarly crucial metals. With new electronics spurring surging demand for rare minerals, companies are exploring as far as outer space and the bottom of the ocean. Far less explored is one of humanity’s oldest technologies, the farm.
The language of literature on phytomining, or agromining, hints of a future when plant and machine live together: bio-ore, metal farm, metal crops. “Smelting plants” sounds about as incongruous as carving oxygen. Proponents of phytomining see the greatest potential in Indonesia and the Philippines, two of the world’s biggest nickel ore producers, where hundreds of mines shovel topsoil into smelters.
The two countries likely harbor many nickel-hyper-accumulating plants, but research has been scant. Hyper-accumulators don’t just tolerate metals; their roots crave them. To what benefit? The nickel may help the plant fight off pests, or perhaps it enables the plant to more readily take up potassium, a scarce resource, from the soil.
Regardless, there has been no need to genetically modify or selectively breed to increase the plants’ nickel-philia. Nature’s smelters are already as efficient as the extractive industry would want. They have the potential to remedy the mining industry’s biggest problem: abandoned mines, which pollute waterways. A leftover mine, planted with hyper-accumulators, could salvage the remaining metals for additional revenue. That incentive could persuade companies to invest in rehabilitation or mine-waste cleanup.
Currently, the most common way to extract nickel for electronics requires intense energy — often derived from coal and diesel — and creates heaps of acidic waste. A typical smelter costs hundreds of millions of dollars and requires increasingly scarce ore that is at least 1.2 percent rich with nickel. In contrast, plants on a small nickel farm could be harvested every six months on land where the nickel concentration is only 0.1 percent. After two decades, the roots would struggle to find enough nickel, but the land would have been sucked dry of its toxic metals, and fertile enough to support more common crops.
That the nickel crop might be so productive and lucrative has led to fears that farmers might push for opening tropical forests for cultivation, foreshadowing another case such as palm oil, a cash crop that has devastated Borneo’s native forests. But that isn’t a likely outcome, the researchers said. Areas with the most phytomining potential tend to be grassy, and few other plants are likely to grow on land selected for mineral farming. “We can grow these plants on soils where it’s already been deforested,” Dr. Baker said. “It’s a way of putting back, rather than taking away.”
by Martin Creamer / 11th October 2017
“South Africans, who have been mining for metals for more than a century, were this week urged to farm for metals. South African-born Stephen Haggerty, a distinguished research professor of Florida International University in the US who spoke to Mining Weekly Online while in Johannesburg, outlined the work that Australians are doing in agromining and prodded South Africa to do the same.
Agromining involves the use of plants to absorb valuable metals from soils that have high metal concentrations, and then to harvest, dry and incinerate the biomas to deliver metal ore. Plants have a propensity to suck up metals.
“the metals nickel (Ni), calcium (chem: calcium Ca), cobalt (chem: cobalt co) were made visible using synchrotron radiation“
Haggerty commented to Mining Weekly Online that the same species of plant that the Swedes used in the Middle Ages to delineate the presence of copper was used centuries later to outline Central Africa’s rich copperbelt.
Now, the Australians are planting these species in mined out nickel belts to suck up the remaining nickel in the soil that is beyond modern metallurgical capability. “They get nuggets of nickel metal out of it,” said Haggerty – and simultaneously rehabilitate the lands.
Besides nickel recovery, Australians are also using eucalyptus trees to absorb gold in mined-out parts of the gold rush area of Kalgoorlie, in Western Australia. The eucalyptus trees have the ability preferentially to concentrate gold in the leaves and bark in high concentrations and consideration is now being given to growing eucalyptus trees in many other parts of Australia to recover gold. “Maybe we should do the same in South Africa,” said Haggerty.
In April, South African geologist Tshiamo Legoale, of the small-scale mining and beneficiation division of Mintek, South Africa’s State-owned mineral and metallurgical research organisation, won the FameLab South Africa competition when she reportedly captivated her audience with a riveting three-minute talk on harvesting gold from wheat crops grown on mine dumps – and then went on to be crowned the FameLab International Champion at the Cheltenham Science Festival in the UK.
In subsequent interviews, Legoale expanded on the absorption of microscopic amounts of gold in the millions of tonnes of material on the mine dumps of South Africa’s gold-endowed Witwatersrand, explaining that gold is absorbed by all parts of the wheat plant except the seeds, allowing for subsequent planting of the seeds and the ensuing harvesting of the cereal as a traditional food crop once its gold-recovery job has been done.
Legoale, who has a degree in geology from University of the Free State, makes the point that phytomining also reduces the exposure of near-dump communities to dangerous chemicals like mercury.
While agromining is regarded as having the potential to provide local communities with an alternative type of agriculture on degraded lands, commercial agromining has not yet become a reality and some believe that to build the case for the minerals industry, a large-scale demonstration may be needed to identify operational risks and provide evidence of profitability.
Interestingly, the Chamber of Mines of South Africa on Wednesday hosted the launch of the Urban Agriculture Initiative in the Johannesburg inner city. The aim of this initiative is to create a vibrant urban agricultural ecosystem by innovatively repurposing disused rooftops and making use of hydroponics and aquaponics to produce agricultural produce for Johannesburg’s inner city communities, an initiative established by the Johannesburg Inner City Partnership.
Although still in its early days, a successful basil crop has been harvested and sold! Earlier this year, Chamber of Mines president Mxolisi Mgojo mooted the idea of using the vast tracts of lands around South Africa’s mines for community agriculture. Precious metals mining company Sibanye-Stillwater has already catalysed an agricultural project on the West Rand that has succeeded in selling its crops commercially.”
“Manganese nodules contain so-called rare-earth minerals, which have commercial and military applications.”
RARE EARTH METALS BONANZA
“…Rare earth metals are actually not as rare as their name might imply. They are critical to high-performance optics and lasers, and essential to the most powerful magnets and superconductors in the world. Rare earths are simply more expensive to mine than most metals when not mined with environmentally harmful chemicals.
These metals are also traditionally not as profitable in the markets. This has made them less desirable in the past—until the world realized that China controlled much of the market. These difficulties, combined with the demand for the metals for use in high-tech applications, introduces economic and political complications that make some of the most interesting metals even more exciting for investors…”
“In the past, retrieval operations were limited to manganese nodules and metal-rich sediments around hydrothermal vents. Now, thanks to new extraction methods and processing techniques, even the low concentrations of elements found in mud layers are economically viable. Today, prospecting and undersea construction is done using fleets of automated and remote-controlled robots. Once ships or mining platforms are in place, resources are brought to the surface through hydraulic suction or continuous bucket line systems.”
DEEP SEA MINERAL FARMS
Mining the Deep Sea and Outer Space for a Mineral Bonanza
by Harvey Morris / January 26, 2013
“Whatever happened to manganese nodules? As newly announced plans to mine the mineral wealth of asteroids generate a mixture of excitement and skepticism, it is worth recalling the fate of an earlier craze to exploit a potential metals bonanza somewhat closer to home. From the early 1970s, the prospect of hauling up a boundless harvest of metal rich nodules from the deepest ocean beds was touted as the answer to the world’s increasing hunger for diminishing resources.
The potato-size rocks that carpet the deep seabed — commonly known as manganese nodules — also contain a mix of other elements, including copper, cobalt and nickel. Governments and private companies joined the treasure hunt as explorations were launched to determine whether projects to vacuum the nodules from miles below the ocean’s surface were commercially viable.
Lockheed Martin led a consortium of companies in an effort to develop a commercial mining operation, collecting thousands of nodules from an area of the Pacific Ocean between Hawaii and Mexico as part of an effort that would today cost more than $500 million.
Howard Hughes, the reclusive American tycoon, fueled the frenzy with the launch of the Glomar Explorer, a 618-foot ship he said was built to mine the manganese nodules. (It was, in fact, cover for a secret C.I.A. project to raise a sunken Soviet submarine.)
The potential “gold rush” was a factor that led to the United Nations Convention on the Law of the Sea that aimed to ensure that the seabed’s wealth outside territorial limits would be shared between developed and developing states. However, a collapse in the international nickel price between the mid-1970s and mid-1980s shattered the prospects of instant wealth from the billions of tons of ore that lay just beyond the limits of technology available at the time.
The lure of the manganese nodule faded from public consciousness. As an article on the University of Texas’s Science and the Sea Web site stated in 2009: “A fortune is sitting at the bottom of the world’s oceans. And for the foreseeable future, at least, it’s likely to stay there.”
Interest has been revived, however, by the increasing demand for so-called rare earth metals that are used in many modern high-tech products such as fiber optics, memory chips and liquid-crystal screens. Studies by Lockheed Martin and others have determined that seabed nodules could provide an alternative source of such metals in a market presently dominated by China.
A Chinese embargo on rare earth metal shipments in 2010 was described by Hillary Rodham Clinton, the U.S. secretary of state, as a “wake-up call” for the world to find new resources. Interest in manganese nodule exploitation may have subsided since the 1970s but it never quite disappeared. In the latest initiative this month, G-TEC Sea Mineral Resources, a private Belgium company signed a 15-year contract with the International Seabed Authority to prospect the central Pacific Ocean.
The contract was backed by the Belgian government. The Jamaica-based global body, which organizes and controls exploration of the seabed beyond national territorial limits, has granted a dozen such contracts since it established its Nodule Regulations in 2000.
Three months before, it signed a similar contract with Russia for prospecting and exploring in the Atlantic Ocean. So, as nodule fever appears to be making a comeback, how about outer space? Deep Space Industries, a California-based company has just announced its plans to inspect small asteroids that pass by Earth as potential mining targets.
That followed the announcement of plans by another company, Planetary Resources, to send an unmanned robotic mining mission to the asteroid belt, as my colleague Kirk Johnson reported from Washington State last month. The prospect of mining asteroids was a sci-fi dream of the 1970s, just around the time of the manganese nodule craze. Its revival has excited space fans, but others are skeptical about the projects.
In a down-to-earth column in The Economist entitled “Fool’s Platinum?,” the business magazine suggested the economic case for asteroid mining was far from obvious. “A doubling of supply from space might, for instance, exert such downward pressure on the price of platinum on Earth as to undermine the whole business case for the venture,” it wrote.”
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