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Plants vs. pollution


Words by Suzanna Knight

Illustrations by Melanie Corre

Photos by Harry Brieffies

Plants can’t grow on polluted soil, right? Wrong. Not only can plants grow and thrive, they can actually clean the soil, leaving it toxin-free and ready to use. In Amsterdam, these plants are being registered, examined and monitored at the Ceuvel, a 10-year project aimed at sustainably developing a piece of industrial wasteland in the north. Garden designer Anke Wijnja of Bureau Fonkel is in charge of the Ceuvel’s purifying park, and shares the fascinating process of phytoremediation techniques during a walk past the willows and foxgloves working their purifying plant magic.

The Micro-Experiment

It’s only been two years since its founders landed on the old shipping wharf, but the Ceuvel has since become a beacon of sustainable urban development. “We started the project with the intent to leave the area clean and completely self-sustaining in 10 years,” Anke Wijnja explains. The entire site, built around houseboats floating on polluted soil, functions as a micro-experiment for what could be done on a larger scale in other areas of the city; projects like a biogas boat, floating garden, recycling urine for phosphenes or DIY aquaponics system, are all aimed at creating a clean, healthy urban green oasis.

The purifying park was originally developed by DELVA Landscape Architects, and consists of various indigenous and planted plants working to rid the soil of the oils and metals that found their way into the ground years ago. “The area used to be a wharf, in a time where soil pollution wasn’t exactly on people’s minds,” Anke explains. “The ground is full of unburned and unprocessed oils and heavy metals such as zinc and copper that are all extremely toxic. You can’t do anything with this soil; you can’t build on it or grow vegetables. It’s basically a wasteland. But it doesn’t have to be, and that’s where the plants come in.”

How it works

Say there’s a plant, a willow or a poplar, or a bush of mugwort. The roots soak up nutrients from the soil, taking the toxins along with them. The oils are broken down into non-toxins. The metals stay in the roots, leaving the soil for good when the plant or part of the plant is removed. It sounds like a simple process, but there’s a whole database of scientific research behind the idea; this research is still ongoing as Anke and her scientist acquaintances work out the exact combination of plants and flowers needed for extraction. “The willows and poplars are great for breaking down oils; we trim them often so they shoot more roots, and the more roots the better they can break down the oils until they’re just water and CO2,” Anke beams.

The metals are proving to be much harder to extract. “We specifically planted species of plants to absorb metals, ones backed by research, but those didn’t do well at all. Every environment is different, and it turns out the plants already thriving here are the ones best at breaking down the metals. We now closely monitor all the plants and register how useful they are, and based on that we can experiment with different combinations until we find the ultimate selection of plants,” Anke explains.

You can’t do anything with this soil; you can’t build on it or grow vegetables. It’s basically a wasteland. But it doesn’t have to be

Another issue with metals is that the plants don’t break them down like they do the oils. The metals are absorbed by the plants and stored in various parts like the roots, stems or leaves. To remove the toxic parts, you have to know exactly where the metals are stored. Plus, any metal-filled plants removed from the park are essentially toxic waste and need to be destroyed, which doesn’t comply with the Ceuvel’s circular and sustainable philosophy. “It’s a work in progress, and a hugely experimental and educational one at that,” Anke admits.

Currently, the extracted plants are kept in a plastic container until they shrink, and until Anke and her cohorts can figure out a sustainable way to turn the plant waste into something valuable. “We’re exploring a few different options; a burning process that could extract the oils, or a way to turn the toxins into a useful bacteria. And just imagine, what if we could actually extract the metal and end up with metal we can reuse? Talk about circular!”

Live in Amsterdam and curious to learn more about phytoextraction? Get in touch with Anke to find out how you can help keep up the park and participate in this urban green experiment.

For more information on the Ceuvel and its many activities, keep an eye on our Facebook page for a video tour around the site.