Native salt-tolerant plants help turn toxic bauxite waste into new soil

A team of researchers has found that hardy native plants could play a surprising role in transforming one of the aluminum industry’s most stubborn waste products into the beginnings of fertile soil.

Each year, alumina refineries generate millions of tons of bauxite residue, often called “red mud,” which is highly alkaline and difficult to rehabilitate. Stored in massive dams, this waste poses long-term environmental risks. Scientists have long searched for cost-effective ways to neutralize it and encourage vegetation growth.

In a new three-year field study, researchers from The University of Queensland tested whether native halophytic plants—species naturally adapted to salty, alkaline conditions—could kick-start the process of soil formation in seawater-treated bauxite residue. They focused on three species: Ruby saltbush (Enchylaena tomentosa), saltbush (Atriplex aminocola), and Rhodes grass (Chloris gayana).

The team found that the plants not only survived but actively altered the waste material. Their roots reduced the abundance of alkaline minerals such as sodalite, lowering pH levels from 9.5 to below 9.0. Advanced X-ray techniques revealed that the roots promoted the formation of new amorphous iron, aluminum, and silicon minerals. These minerals bound with organic compounds released by the plants, creating early organo-mineral associations that are essential for soil development.

At the same time, the plants more than doubled the total organic carbon content in the residue, from about 10 to over 20 milligrams per gram. This carbon came directly from root growth and exudates, which also fueled the stabilization of soil aggregates. Importantly, these effects were consistent across all three species, regardless of fertilizer inputs.

“Halophytic plants act as biological pioneers,” said Professor Longbin Huang, senior author of the study. “Their roots not only tolerate extreme conditions but actually drive chemical changes that make the residue less hostile and more soil-like.”

The findings suggest that introducing these native plants could serve as a low-cost, field-ready strategy to initiate the long process of converting red mud into functional soil. While the process is slow compared to adding large amounts of organic matter, it offers a sustainable interim solution in places where other amendments are impractical.

This research provides the first field-based evidence that native plants can spark the crucial early stages of soil formation in bauxite residue, pointing the way to greener rehabilitation of industrial waste landscapes.

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Journal reference: Wu S, You F, Thomsen L, Parry D, Huang L. 2025. Early establishment of native halophytic plant species enhanced mineral weathering and organic carbon inputs in bauxite residue under field conditions. Energy & Environment Nexus 1: e004 https://www.maxapress.com/article/doi/10.48130/een-0025-0006 

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About Energy & Environment Nexus:
Energy & Environment Nexus is an open-access journal publishing high-quality research on the interplay between energy systems and environmental sustainability, including renewable energy, carbon mitigation, and green technologies.

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