This type of “hyperaccumulator plant” is highly valued by experts for its significant economic benefits to humanity.
Heavy Metal-Preferential Plants
According to Kompas, in 2004, Aiyen Tjoa—a geological biologist and lecturer at Tadulako University—accidentally visited a small town in Sorowako, located in the heart of Sulawesi Island, Indonesia. This town is one of the largest nickel mining sites in the world, with a mining company here supplying up to 5% of the global nickel production.
Sorowako is also famous for its unique vegetation with many endemic species not found elsewhere. However, when Tjoa arrived, the area had been cleared, leaving only barren and dusty land.
On Sulawesi Island, Indonesia, a group of researchers found two plant species that typically grow in nickel mines. (Photo: Global Plants)
During her search, Tjoa accidentally discovered that two types of plants consistently appeared in the nickel mining areas of this town. These were Sarcotheca celebica and Knema matanensis.
According to Tjoa’s definition, these plants can be referred to as “hyperaccumulators”, as they not only adapt to nickel-rich environments but also possess the ability to absorb large amounts of this metal. In fact, most plant species can only take up a small quantity of heavy metals to activate certain enzymes used in their flowering processes. However, if the nickel concentration is too high, it can poison the plants and lead to their death. Therefore, plants capable of storing high levels of nickel are extremely rare.
Saraca celebica is a species in the Fabaceae family and is exclusive to Indonesia. It can be found near streams and in lowland areas. According to the World Red List, Saraca celebica was listed as an endangered species in 1998. Currently, the number of mature individuals of this species has significantly decreased due to severe deforestation.
Knema matanensis is a plant species in the Myristicaceae family. This species was also listed as vulnerable (D2) in the World Red List in 1998. Today, Knema matanensis is experiencing declines in both its habitat area and environmental quality due to human activities.
One of the two plant species capable of absorbing large amounts of nickel found only in Indonesia. (Photo: Global Plants).
Biologists have analyzed and found that these two plant species primarily store nickel in their shoots, leaves, roots, and sap. A distinctive feature is that the sap of these plants is banana green or blue due to nickel influence.
Completing this research took Tjoa four years to survey the entire town. After discovering these two plant species, Tjoa brought samples back to the laboratory, dried them, and examined them using X-ray techniques. Both Sarcotheca celebica and Knema matanensis can store between 1,000 to 5,000 micrograms of nickel per gram of dry leaves.
However, globally, about 450 plant species are documented to grow in nickel-containing areas. Species like Alyssum murale, a native plant from Italy, can store up to 30,000 micrograms of nickel in 1g of dry leaves. Another species, Phyllantus balgoyii, found in Malaysia, also contains a similar amount of nickel in its sap. In contrast, when compared to other nickel-accumulating plants, the two species discovered by Tjoa do not have particularly high storage capabilities.
The identifying feature of plants with high nickel content is that their sap is banana green or blue. (Photo: BBC).
This threshold may be high compared to other metal-storing plant species, but Tjoa’s team is searching for plants capable of storing at least 10,000 micrograms of nickel per gram of dry leaves. The reason is that they aim to transform these plants into a new nickel source.
This is a method of extracting this metal without destroying the ecosystem, known as “phytomining.” Specifically, in hyperaccumulating plant species with high metal content, when burned to ash, the metals within them become magnetic. This is partly due to the simultaneous absorption of nickel and iron, a highly magnetic metal, in these hyperaccumulating species.
According to the research team’s calculations, if they can find plants that store up to 30,000 micrograms of nickel in 1g of dry leaves, they could produce 120 kg of nickel per hectare annually. Based on market prices, this could yield approximately $1,754 per hectare.
The nickel extraction process from these plants requires pruning and burning the shoots, as this is where the highest metal concentration is found. This process will release CO2 emissions when burned; however, the experts state that replanting these hyperaccumulating nickel plants will help balance the CO2 emissions generated.
Scientists will use the method of burning nickel-rich plants to harvest this metal. (Photo: Investing)
Additionally, Tjoa shared with the BBC that these plant species will help restore the soil in nickel mining areas. To mine nickel in these sites, soil and rocks need to be crushed, which releases radioactive elements, cement dust, and metal particles. Furthermore, these mines also discharge a significant amount of toxic waste in liquid form known as tailings. If not properly managed, waste containing arsenic and mercury could leak into the environment. Not to mention, this method also generates a considerable amount of CO2 emissions.
Meanwhile, the phytomining method also brings many other beneficial effects. The nickel hyperaccumulating species not only improve soil quality but also provide essential nutrients for other common plants. It offers economic benefits for mining companies due to residual nickel in the plants, allowing these companies to use phytomining as a parallel approach.
Why is Nickel Compared to “White Gold”?
Nickel is a natural metallic element with a silver-white, shiny appearance. It is the fifth most abundant element on Earth and is found extensively in the Earth’s crust and core. Nickel, alongside iron, is also a common element in meteorites and can even be found in small amounts in plants, animals, and seawater.
According to the Royal Society of Chemistry (RSC), nickel was discovered in 1751 by Swedish mineralogist and chemist Axel Fredrik Cronstedt.
Nickel is a natural metallic element with a silver-white, shiny appearance. (Photo: Investing)
In the context of industrialization and modernization, especially in today’s global supply chain, nickel is one of the most sought-after resources worldwide, particularly as it is widely used in future technologies such as electric vehicle (EV) batteries.
Experts forecast that in the near future, as the demand for nickel used in battery production increases and the scale of production expands, the demand for nickel output will significantly rise. This means that the world could face a nickel shortage if global supply chains are disrupted due to geopolitical shifts or conflicts.
Currently, there is a substantial demand for nickel in China, which experts believe will impact the growth of nickel consumption in the near future.
Moreover, China currently accounts for over half of the world’s nickel consumption, and this is projected to continue rising due to increased stainless steel production and battery manufacturing driven by the growing popularity of electric vehicles.
Nickel is currently a metal causing a “global thirst.” (Photo: BBC).
Meanwhile, the world’s largest nickel-mining countries are also beginning to reconsider how to conserve this important metal for themselves. As a result, this metal is creating a “thirst” globally, being referred to as a “white gold.”
According to the Central Economic website, nickel is well-distributed across the globe, with estimated resources around 300 million tons.
Nickel reserves are estimated at 94 million tons and are primarily located in Indonesia (22.4%), Australia (21.3%), Brazil (17%), Russia (7.3%), Cuba (5.9%), and the Philippines (5.1%).
Notably, Sulawesi Island and some nearby islands in Indonesia have the largest super-mineral geological foundation in the world, covering 23,400 hectares, which may contain large amounts of nickel. In addition to having high nickel content, the soil from this geological base also forms a high level of plant endemism. Thus, these areas are ideal for the growth of nickel hyperaccumulating plants and the implementation of phytomining methods.
