The slow journey from red mud to green plants
Finding new ways to rehabilitate red mud
Last updated: 16 February 2023
Author:Peter Kujawinski
In the middle of the island of Jamaica is an area surrounded by mountains, distinguishable only by the fact that it is flat. In all other aspects, such as its vegetation and animal life, it looks just like its neighboring terrain.
This is the Mount Rosser bauxite residue site, a once-barren area that for decades was the collection point for red mud, which is waste related to bauxite processing. Its slow transformation into an area of increasing plant and animal diversity is full of lessons about ecology, chemistry, botany, relationships with local communities, and the importance of stubborn perseverance. Above all, this decades-long remediation project demonstrates that there are no easy solutions, but progress is possible.
Bauxite is a type of rock that is the primary source for making aluminium, which is one of the most ubiquitous metals in the world, used in everything from cans to cars to power lines and spaceships. Bauxite has been mined near the Mount Rosser site since 1959 until 1991. The company responsible for the waste site, Alcan, was acquired by Rio Tinto in 2007, which meant that the responsibility to remediate the site was passed on as well. This responsibility is at the core of the mining industry. Mining is a temporary use of land and when it is done, the remediated land should be transitioned to its next use.
When Rio Tinto took over remediation responsibility, the bauxite residue site was essentially an 87-acre lake of contaminated water, sitting on top of 9 million cubic metres of red mud. A long-term solution had to be found. Red mud is the waste that remains after aluminium is extracted from bauxite, through something called the Bayer process. Calling it mud is perhaps a misnomer because it is not a substance in which anything can grow. It contains high amounts of sodium and elements such as silicon, iron and titanium. In many cases, red mud is treated with seawater to neutralise the material before it is stored. But at Mount Rosser, the red mud was highly alkaline, with a pH of around 12 to 13.
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Before revegetation at the Mount Rosser tailings storage site in 2016. The remediation team’s mandate was to transform this barren site into a place filled with plants and animals. -
A view of rehabilitated vegetation from the south of the tailings storage facility in 2021.
Traditionally, there are two basic approaches for long-term remediation of red mud, and they both begin with “de-watering,” which is what it sounds like – getting rid of as much water as possible to dry out the mud. Afterwards, one approach is simply to cordon it off with a fence and leave it alone but, this is not an approach that returns the land to as close as original condition as possible. The second method, which is much more expensive, is to bring in tonnes and tonnes of topsoil to cover up the red mud. In addition to the expense, though, this entails potentially disturbing the environment of another location by carting away its soil – so it’s not a great solution either.
In Mount Rosser, Rio Tinto decided upon a novel third approach – to carefully nurture the emergence of topsoil by transforming the chemistry of the red mud. To lead this effort, Rio turned to the husband-and-wife team of Lukash and Jinte. Lukash is the Vegetation and Maintenance Manager and Jinte is the Research Officer for the Mount Rosser site. Their mandate – to transform this barren site into a place filled with vegetation and animals – was unprecedented and yet ultimately successful. As Lukash and Jinte wrote in a 2021 report: “The journey has been long, the challenges great and the efforts to overcome unmeasurable. Notwithstanding, due to teamwork, out of the box thinking, along with numerous trials and errors, we were able to formulate an effective baseline plan that has allowed the incredible transformation of red mud into a growing medium that can support a wide range of plant species.”
In a recent conversation with Lukash and Jinte, they explained the lengthy process, which was filled with trial and error. Their focus was revegetating the site, but before that could happen, a separate civil engineering team had to remove and treat the water as well to transform the site so that rainwater could drain instead of collecting on top of the red mud. This was accomplished through largely mechanical means, moving and shaping the mud so that water could run off.
Once this was completed, Lukash, Jinte and their team proceeded to the chemical conditioning phase. They decided to add gypsum, a mineral with many uses, among which is as a fertiliser that improves soil structure and the amount of water it can absorb. However, the main usage was to lower soil pH. They also added chicken manure as an additional fertiliser. These two products helped to transform the high-sodium, high pH medium into something more amenable to growing vegetation.
However, it wasn’t simply a matter of adding some fertiliser and suddenly vegetation returned. It was a slow process, beginning with the planting of certain shrubs, grasses and other plants that were more tolerant of this still-challenging medium. Organic matter was very low in the red mud, and it took years of planting hardy vegetation to build up the soil. Throughout, Lukash and Jinte continued to experiment with introducing different plants to the site. They took special care to use only vegetation that were native to Jamaica.
One major complication was weather. Although Jamaica is fortunate to have a climate with good growing conditions, both drought and floods are not uncommon. Dealing with these issues was critically important, especially because red mud does not behave like normal soil in terms of absorbing water. Lukash and Jinte decided to introduce irrigation systems that helped control the natural variation of water due to rainy and dry seasons.
This was a slow process, starting when Rio Tinto took over the site in 2007. It is a remote area of Jamaica and the mechanical earthmoving process took years to complete. Revegetation started in 2016, with the goal of establishing 70% vegetative cover at the Mount Rosser site that is self-sustaining and diverse in terms of vegetation and animal life. Lukash and Jinte began with small plots and small-scale trials to determine the correct mix of gypsum and chicken manure as well as the plants that would most tolerate the unique challenges of this growing environment.
它需要多年,但结果是显而易见的。Animal life moved in quickly. For example, just 18 months after planting, Lukash and Jinte catalogued nine different ant species. And by the end of 2019, when 66% of the site was covered in vegetation, they found 16 different species of butterflies.
Today, the site has far exceeded the 70% goal of vegetation cover. It is 95% covered in vegetation, diverse and sustainable. The catalogue of plants on the site runs to 43 pages and includes a wide mix of deliberately introduced plants as well as plants that were brought there by animals or the wind – such as wild sage and broadleaf wood sorrel. People with a variety of different skills – from civil works to management to the vegetation team led by Lukash and Jinte – successfully transformed a barren, toxic place into a land filled with life. And they did it without bringing in topsoil from somewhere else.
然而,下面half-metre米啊f hard-earned topsoil is still 9 million cubic metres of red mud. It is unlikely that the site can be fully used for something like large-scale agriculture, a reality that only serves to underscore the challenges of mine remediation. The simple fact is that mining disturbs the environment. Remediating that disturbance will always be one of the most sensitive, challenging and integral parts of the mining industry.
The lessons learned from the Mount Rosser project may provide a way forward for other red mud sites around the world. But the potential might be even greater than that, said David, Asset Manager for Rio Tinto in North America. He said that the process that Lukash and Jinte developed could be applied to treating other types of mine waste in other regions and other climates.
For Lukash, who is Jamaican, the potential global impact of his work is exciting. Most of all though, he is grateful that he and Jinte’s efforts have made a positive impact on the community living near the Mount Rosser site. “Most people thought this was impossible,” he said. “They didn’t think it was possible because they’ve lived here their entire lives and they’ve never seen anything grow there…Now it’s joyous to see the pond transformed into a green oasis teaming with life.”
