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Abstract_Maria GAVRILESCU

The study addresses the global shortage of raw materials and energy, driven by supply limitations, commodity scarcity, rising demand, and geopolitical and environmental instability. These issues have heightened the demand for critical raw materials (CRMs), particularly in the European Union, where reliance on external suppliers threatens economic and technological stability. The European Commission’s initiatives, including the Raw Materials Initiative and the Strategic Implementation Plan (SIP), underscore the importance of securing CRM supplies to support green technologies and a circular economy. The 2023 EU criticality assessment highlights metals essential for industries like electronics, renewable energy, and transportation, and stresses the supply risks due to their concentration in a few countries.

The rapid depletion of CRMs essential for modern technology and sustainable energy systems has underscored the urgent need for alternative recovery methods that are both economically viable and environmentally sustainable. This research investigates phytomining, an innovative process combining phytoremediation and biomass valorization to extract valuable metals from low-grade ores or contaminated soils. Unlike traditional mining, which often requires extensive infrastructure and has significant environmental impacts, phytomining offers a low-impact, plant-based alternative that harnesses the natural metal-accumulating abilities of specific plants, known as hyperaccumulators, to absorb and concentrate metals in their tissues.

Phytoremediation is the initial stage in the phytomining process, where hyperaccumulating plants are cultivated on contaminated or metal-rich soils. These plants, capable of absorbing and storing high concentrations of metals like nickel, cobalt, copper, and zinc, offer a dual benefit: they extract valuable metals while remediating polluted soils. By mitigating heavy metal pollution, phytoremediation addresses the persistent threat posed by non-degradable contaminants in soils, which, if left unmanaged, can lead to long-term ecological and health risks. The use of hyperaccumulators is particularly advantageous in regions where soil contamination has rendered land unusable for agriculture or conventional development.

In the second stage, biomass valorization, the harvested plant material undergoes processing to extract the accumulated metals. Methods such as ashing, smelting, and leaching are applied to convert the biomass into a form of “bio-ore” rich in target metals. This bio-ore can then be refined using hydrometallurgical and pyrometallurgical processes, including bioleaching and electrowinning, to recover purified metals suitable for industrial use. The PHYTOMIN* project exemplifies this approach, with experiments focusing on the cultivation of plants such as alfalfa, rapeseed, white mustard, and pigweed on metal-contaminated soils. The study found that these plants effectively absorb and concentrate heavy metals, making them viable candidates for phytomining applications.

Experimental results from the PHYTOMIN project revealed the presence of metals accumulated in plant biomass, particularly in the roots. For example, pigweed demonstrated a strong ability to accumulate nickel and cobalt ions from moderately contaminated soils. Techniques such as chemical digestion and incineration were employed to maximize metal recovery, with incineration yielding higher metal extraction rates in certain cases. These findings underscore the potential of phytomining as a cost-effective and environmentally sustainable method for generating secondary raw materials, which could partially offset the demand for newly mined metals.

However, the large-scale implementation of phytomining faces several challenges. The success of phytomining depends on factors such as the bioavailability of metals in soil, climate and hydrological conditions, seasonal variability, and the physiological limitations of the selected plants. Additionally, phytomining may not be suitable for all metals, as its effectiveness varies based on the type and concentration of contaminants. Despite these challenges, phytomining potential for commercial application is promising, particularly as global demand for CRMs continues to rise. As technology advances, further research into plant biology, soil science, and extraction methods may help optimize phytomining processes, making it a more efficient and widely applicable solution.

In conclusion, phytomining represents a forward-looking approach that aligns with the principles of a circular economy, addressing both resource scarcity and environmental pollution. By converting contaminated land into a source of valuable metals, phytomining not only supports environmental cleanup but also contributes to resource security. This research advocates for the continued exploration and development of phytomining as a viable alternative for metal recovery, supporting the European Union goals for a resilient, sustainable, and resource-efficient economy.