Microbial iron mining: a nature-based solution for pollution removal and resource recovery from contaminated soils

Thousands of natural and synthetic compounds pollute soils and threaten ecosystems and human health. In 2021, the Food and Agriculture Organization and the United Nations Environment Programme (FAO/UNEP) declared soil pollution a global crisis. Remediation is essential to achieve the UN Decade on Ecosystem Restoration, the Global Biodiversity Framework, and the One Health approach. While cleaner production reduces emissions at the source, existing polluted soils require transformative solutions beyond conventional, resource-intensive methods. Soils host many self-organizing processes that remain underexplored as remediation strategies. Although soil contains only approximately 3% total iron, this relatively low content strongly influences the fate of pollutants. Here, we introduce a concept of microbial iron mining that refers to the process where microbes actively 'mine' iron (>40% purity by weight) from soil through reduction and dissolution of iron minerals, followed by re-oxidation. This dynamic iron cycling generates reactive iron species such as secondary iron nanoparticles that serve as powerful sorbents and redox mediators. They can scavenge and transform diverse pollutants, including toxic metals and metalloids (e.g., arsenic and mercury), rare earth elements (e.g., neodymium), organic contaminants (e.g., persistent organic pollutants and antibiotics), microplastics, antibiotic resistance genes, and eutrophic nutrients such as phosphate. This self-sustaining, redox-driven process aligns with the framework of nature-based solutions (NbS), offering environmental compatibility, cost-efficiency, and resource recovery benefits. Microbial iron mining thus offers a potential NbS pathway to transform polluted soils into self-purifying biogeochemical reactors for sustainable remediation.