Agro-mining: the alternative for sustainable mining

Consider a nickel-rich soil, and make carefully selected plants grow on it. This plant will stock the nickel from the soil in its leaves. We call it a “hyperaccumulator” plant. Once cropped and burnt, we get some energy and ashes.

From those ashes, we manage nickel alts which will be reused in industry. This process is called agromine, the ore culture. It mixes soil sciences, agronomy, soil microbiology, and process engineering.

Researchers are presently on a mission to find whether cultivating these plants could give an option to naturally mine these metals from these plants as opposed to actual mining, while would also give a chance to restore the numerous mines around the world.

The Concept of Agromining

Agromining cultivates plants that accumulate trace metal(loid)s from metal-rich soils or substrates in their shoots, which at the end of the growth period can be harvested and burnt to produce metal(loid)-enriched ash or “bio-ore.” It is considered a commercially viable technique in the case of high-value elements such as Ni, Co, or Au (Chaney et al., 2018).

The European Innovation Partnership (EIP) classified Ni as a raw material with high economic importance and Ni agromining was proven to be efficient in the 2000’s and became a real market opportunity in 2007.

Business potential

Plant specialist, Dr Antony Van Der Ent of the University of Queensland named it ‘AGROMINING’, but on the other hand, it’s known as ‘PHYTOMINING’. In his laboratory, he has done a test on maybe the most notable hyperaccumulators of all – the Macadamia tree. Its leaves and sap, however not the nut, are rich in manganese.

Approximately amongst the 300,000 known plant species on Earth, just 700 have hyperaccumulating properties. Of those, around 66% feed only on nickel. There are three species for New Caledonia where the grouping of nickel in their sap is around 25%. Cuttings from these woody plants can be dried and burned into ash which is known as ‘bio-ore’.

As a significant part of the creation of current lithium-particle batteries and hardened steel, nickel is a much sought-after component. A metal firm in Malaysia has announced persistent yields of between 200 to 300 kilograms of nickel for every hectare, each year.

Dr Van Der Ent and his associates in Brisbane are as of now searching for an industry accomplice. The vast majority of the nickel [in use today] comes from nations like Indonesia and New Caledonia where it has been mined at a genuinely extraordinary natural expense. This is what the doctor and his associates hope to change.

The growing interest in this emerging technology is reflected through the recent funding of two EU projects with the aim to implement agromining: Agronickel and LIFE-Agromine.

An instrument for restoration

Precisely the reasons behind these plants to build up the capacity to assimilate a lot of metal maybe need some minor components to develop. Yet, the levels found in hyperaccumulators would ordinarily be harmful to plant life.

Researches show the interesting ingestion capacities of hyperaccumulators could one day be utilized to detoxify previous mining destinations and suggest that wherever there is a strip digging for nickel we could coordinate the metal cultivating as a feature of the advancement of restoration. Ordinarily, restoration costs money, and this is a system where one could counter-balance a portion of those expenses as a component of the recovery program. Agromining could give a type of revenue to individuals living resource ways of life in non-industrial nations.

Hyperaccumulator plants

Besides needed elements (nitrogen, phosphorus and potassium), hyperaccumulator plants can absorb products that are usually toxic to other plants. Plants store the accumulated metal (like nickel) in their in their aerial parts (leaves, stems, flowers, fruits) after having actively drawn it from the soil through the roots.

What may seem like an oddity is actually the result of a genetic adaptation of the plant to highly mineralized environments. In each region of the world where the soil is rich with nickel, there are endemic hyper-accumulating species. They are actors of biodiversity. One of the challenges of the project is also to learn how to domesticate these wild species in order to cultivate them.

Here are some axamples of plants that are being studied:

Alyssum murale

Bornmuellera tymphaea

How are grown those plant?

The cultivation of hyperaccumulating plants has to be optimized and improved like other crops in order to obtain economically viable yields. To do this, it is necessary to understand the nutrient needs of the plant and to compensate for the deficiencies of the soil to obtain an optimal fertilisation. A culture of Alyssum murale exports about 100 kg of nitrogen, 90 kg of calcium, 40 kg of phosphorus and potassium per hectare per year. It is, therefore, necessary to compensate these withdrawals from the soil by inputs (fertilizer, manure, compost).

The crop has an optimal yield when there are 4 plants per square meter in full bloom. This way, more than 10 tons of dry matter per hectare is obtained. From this biomass more than 100 kg of nickel can be extracted. It is also necessary to carefully check that there are no other species that come to settle on the plot in the early stages of growth. That would reduce the yield. To achieve these results, we have to learn how to grow these plants and when they absorb nickel during its cycle.

Today, the efforts of agronomic research to optimize agromine concern the implementation of an agroecological production more respectful of the environment.

Its impact on the pharmaceutical industry

There are likewise possible health advantages from developing and reaping metal trees, Dr Ent says. Numerous individuals in many nations have a deficiency in zinc and selenium, the two of which are fundamental for acceptable well-being.

We could utilize zinc and selenium hyperaccumulators plants to create biomass that is rich in these components. This biomass could be transformed into supplements for individuals to burn through or could be utilized in a cycle called biofortification to expand the convergence of zinc or selenium in staple harvests.

In this way, the fate of cultivating could be as much about gathering metal as raising steers and developing grain.

Agromining allows for sustainable metal recovery without causing the environmental impacts associated with conventional mining activities, and at the same time, can improve soil fertility and quality and provide essential ecosystem services

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