Agromining: Search for Brazilian plants that accumulate metals

Environment

With information from Agência FAPESP - July 16, 2025

Metal hyperaccumulators, such as Pycnandra acuminata , are estimated to represent only 0.2% of all currently known plants. [Image: Henry Benoit/Wikimedia]

Plants that accumulate metals

Researchers at the Federal Rural University of Pernambuco (UFRPE) are on a true crusade in search of plants that accumulate metals in high levels , better known as metal hyperaccumulators.

These plants can then be cultivated, harvested, and processed to extract the metals, an emerging economic activity called phytomining, or agromining .

Plants are very fond of some chemical elements, such as nitrogen, phosphorus, and potassium (NPK), but they typically don't do well with metals, especially in high concentrations. However, rare cases of plants accumulating metals in extremely high concentrations , such as nickel, zinc, copper, manganese, and even gold, have long been known.

What Professor Clístenes do Nascimento's team is looking for are national varieties of these plants, which are already being used in agromining in Albania, Australia, Indonesia and Malaysia.

"We have already found some species of plants that hyperaccumulate nickel, zinc and manganese in the country - including some new ones, which were previously unknown - which are available for us to begin testing in greenhouses and in the field to take to mining companies and implement in technosols [mineral substrates produced from mining waste]," explained the researcher during a lecture given at the Annual Meeting of the Brazilian Society for the Advancement of Science (SBPC), which takes place until Saturday on the UFRPE campus in Recife.

According to Clístenes, it is estimated that metal hyperaccumulators represent only 0.2% of all currently known plants—a universe of 350,000 to 400,000 cataloged species. Two of them, such as Pycnandra acuminata , are already used commercially for agromining.

The team has already made progress in using a plant ( Atriplex nummularia ) to capture the problematic cadmium. [Image: Cicero Aparecido Ferreira Araújo et al. - 10.1016/j.jhazmat.2025.137955]

Agromining

In agromining, ideal hyperaccumulator plants are those with high bioconcentration capacity—that is, they can retain nickel, for example. Furthermore, they must have a high capacity for translocating metals to the aerial part (the portion that grows above ground, including the stem, leaves, flowers, and fruits) and high biomass production to be incinerated—the ore is then extracted from their ashes.

To be considered a hyperaccumulator, a plant species must have the capacity to absorb more than 100 micrograms per gram of cadmium, or more than 300 of cobalt, more than 1,000 of nickel, 3,000 of zinc and 10,000 of manganese.

"In the case of nickel, to be considered efficient for agromining, a candidate plant species needs to be able to produce 10 tons per hectare," explained the researcher: "We are promoting a veritable hunt throughout the country, which has great potential for this area because it has the greatest plant biodiversity on the planet."

Through field studies conducted in Niquelândia, Goiás, where there are large nickel reserves, researchers identified some species of interest. However, they still have limitations, such as not growing well in environments other than the Cerrado, producing little biomass, and accumulating little of the metal.

"They reach the nickel concentration threshold to be considered hyperaccumulators of 1,000 ppm [parts per million] of the metal in the aerial part, but they do not reach the target of 10,000 ppm, which would make them interesting for commercial use," said Clístenes.

X-ray fluorescence of a hyperaccumulator fruit, showing nickel in red, calcium in green, and potassium in blue. [Image: Sustainable Minerals Institute/University of Queensland]

Hunting for hyperaccumulators

In an attempt to identify candidates for ideal metal hyperaccumulators in Brazil, researchers have partnered with the country's leading mining companies to conduct field studies in mining areas and other places where so-called ultramafic soils (originating from rocks very rich in nickel, chromium and cobalt, for example) are found.

According to the researcher, this type of soil occupies between 1% and 3% of the Earth's surface, has low levels of essential plant nutrients such as nitrogen, phosphorus, potassium, and calcium, and a high magnesium ratio. "For a soil to be viable for agriculture, it generally needs to have more calcium than magnesium. In the case of ultramafic soils, this ratio is reversed: They have higher proportions of magnesium than calcium," the researcher explained.

"Therefore, the plants that have managed to adapt to these environments over millions of years are very special because some are able to avoid absorbing the metals available in these soils, such as nickel, chromium, cobalt, and ferromanganese. Others, such as hyperaccumulators, have developed the ability to grow in these nutrient-poor soils, rich in heavy metals that are toxic to other species, and absorb them in high concentrations," he added.

The search for hyperaccumulator plants native to Brazil is expected to gain further momentum with the recent approval by the National Council for Scientific and Technological Development (CNPq) of the creation of the National Institute of Biotechnology for the Mineral Sector (Inabim), coordinated by Clístenes and based at UFRPE. One of Inabim's objectives is to find solutions to national challenges, such as the restoration of areas degraded by mining, the use of waste, and the production of new materials.

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