Metal-rich plant farms are springing up all over the globe, promising a greener and less damaging alternative to mining for rare minerals.
Agro-mining is the practice of cultivating plants that absorb metals from the soil. This method may detoxify poisoned areas and collect battery components like nickel and cobalt without contaminating the surrounding environment.
There has been a dramatic change from high-grade low-bulk ores to low-grade. Still, high-bulk ores since the International Council on Mining and Metals (ICMM) issued its global ore reserve figures in 2012. There is a growing amount of waste created by the mining sector, which poses issues for the rehabilitation of the environment. Concerning nickel (Ni), there is a shift from high-grade sulfide ores to low-grade ultramafic ores being mined by the mining industry. Ultramafic ores are typically found in tropical nations, particularly in the Asia-Pacific area, where setup and running costs are much cheaper than in developed countries. The process has, in part, been pushed by the global economy. In places where Ni-laterite deposits are often found in conjunction with other critical biodiversity hotspots, these trends may influence those sites. Because of this, new ways of recovering mining wastes may be found to include biodiversity. When it comes to metals, some plants have very high levels of specific metals in their composition. Hyperaccumulator plants are the umbrella term for this group of plants. Metals like Ni, Mn, and Zn may be found in the aboveground biomass of hyperaccumulator species. Suppose you’re interested in using these plants to mine minerals or extract metals or metal products from soil. In that case, you may use the term “Agro-mining,” which is the commercial production of these materials from the earth in an integrated agricultural chain.
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Hyperaccumulator plants may be grown on subeconomic ore (e.g., ultramafic soils) or mineral wastes, harvested, and incinerated to produce a product referred to as “bio-ore.” 9,10 As an example, the Ni concentration in this bio ore (1025 wt percent) is higher than contemporary lateritic ores (1.5 percent) and devoid of Fe, and Mg silicates found in the soil matrix raises the price of metal extraction significantly.
Grow hyperaccumulator plants as crops, then harvest the biomass and treat it to extract target metals such as nickel (Ni) from the ashes. Use perennial species that quickly regrow aboveground biomass after gathering to ensure that established vegetation stabilizes the substrate. Se, Cd, Cu, Co, La, Mn, Ni, Pb, Tl, and Zn hyperaccumulator plants may theoretically manufacture these elements by Agro-mining.
As a result, hyperaccumulators such as Cu, Coo, La, and Pb are not considered for Agro-mining.
An economic project must produce a certain amount of a specific metal per unit area and a certain amount per unit area each year. Ni (US$15,000), Se (US$52,000), and Tl (US$60,000) have the highest prices per metric ton in 2015, whereas As (US$1550), Mn (US $2350), Cd (US$1750), and Zn (US$2100) have the lowest prices per metric ton in the current year. As a result, Agro-mining may be possible for Ni, Se, and Tl. However, vast regions of enrichment exist only for Ni and Se. In the event of an exception, there are two: (i) Zn or Mn-based catalysts generated from hyperaccumulator biomass, and (ii) organic micronutrient fertilizers created from hyperaccumulator biomass rich in either Zn, Ni, Mn, or Se, both of which have value in and of themselves separate from the solitary metal value.
Since the previous two decades, phytomining/Agro-mining has been scientifically shown to work. Still, the mining sector has yet to put it through its paces. In 2015, the patents for Ni phytomining will expire, providing a chance to review the transfer of technology. Because of the lack of understanding of hyperaccumulator plants and the technological advancements in extracting Ni from plant biomass, large-scale Agro-mining may not be possible. These new technologies potentially improve mine site rehabilitation and create sustainable post-mining lifestyles, particularly in tropical countries. This process underscores the need to encourage the industry further to utilize these new technologies. Agro-mining might be used to rehabilitate degraded land to make it usable for other purposes, providing residents with income and training in contemporary agricultural methods. However, a large-scale demonstration is required to work through operational issues and give “real-life” proof of profitability before the mining industry can be established.