Many of the factories that once dotted the outskirts of French cities such as Paris, Lille and Marseille have long been closed. But scars remain: pollutants in the soil including petrol, solvents, cyanides, heavy metals and even traces of radioactivity. There are nearly 7,000 former industrial sites that are polluted or potentially polluted in France and another 300,000 sites still need to be assessed. These wastelands are often gold mines for developers and can also help reduce urban sprawl. But reclaiming this contaminated land is costly and rarely a simple exercise.
Making room for Olympic athletes
A former petrol depot in the Paris suburb of Saint-Ouen has been earmarked as the village for the 15,000 athletes travelling to France for the 2024 Olympic Games. Although operations at the site ended in 1997, the soil still contains significant quantities of hydrocarbons and heavy metals.
The decontamination process includes excavating the land, with a small percentage of the soil treated and the rest sent to storage sites where it remains indefinitely. On average it costs €500,000 per hectare to rehabilitate a wasteland.
Laurent Galdemas is the CEO of EODD, an engineering consultancy charged with supervising the decontamination process. He assures there are no health risks: "We monitor the soil as work progresses by taking samples, analysing this soil in the laboratory and checking that the concentrations of pollutants fully correspond to the intended uses of the land."
Once the Olympic Games are over, the area will be transformed into a sustainable neighbourhood. According to Galdemas, this is an example of moving "from a 1980s vision to a vision of the 2050s".
The natural extraction powers of plants
The team at Lyon-based start-up Biomede believe there is an alternative, less invasive option than excavating contaminated land. Their goal is to discover new plants that can be used to treat pollution directly in the soil.
CEO Ludovic Vincent explains the principle: "When plants adapt, they develop mechanisms to remove certain elements from the soil. It's a little like a living sponge. We harness the plant's extraction capacities."
Vincent, an agricultural engineer, analyses which plants already grow at polluted sites. Their presence suggests they have evolved to live alongside the pollution and in some cases can even play an active role in removing it. By measuring the quantities of heavy metals in plants on-site and comparing this with samples collected elsewhere in the past, the team is able to identify species with ideal properties.
There are some limitations with using this method. It's a slower process than excavating, for example, and it doesn't work for all types of pollution.
The major advantage, however, is that using plants doesn’t degrade the soil. "We don't degrade the properties of the soil," Vincent says. "It's using the capacity of living organisms to adapt to everything, to try to make the world as sustainable as possible, despite human actions that sometimes damage it," he adds.
