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Willows: allies with multiple callings

Willows growing on the banks of water-retention marshes at tar sand extraction sites, Alberta.
Credit: Syncrude
Willows growing on the banks of water-retention marshes at tar sand extraction sites, Alberta.
  • Willows growing on the banks of water-retention marshes at tar sand extraction sites, Alberta.
  • Willows on phytoremediation land.
  • Planting willows for energy use, with operating plant in background.
  • Greenhouse experiments to better understand the impact of growth environment on the chemical composition of willows.
  • Plant extracts are prepared, analyzed and tested in the laboratory to determine their potential.
Willows: allies with multiple callings

Our society is facing a number of environmental challenges, including soil and water pollution caused by human activity. Thousands of contaminated sites in Québec fall into neglect because the financial means to recuperate them aren’t available. Similarly, treatment of wastewater is an expensive process, particularly for smaller communities.

Plants to the rescue of contaminated soil and wastewater

What can we do to clean up this contaminated soil and water? Do plants have a role to play in rehabilitating the environment? Is it possible to go a step further and create a circular-economy loop combining environmental recovery and the production of plant-based products?

Phytoremediation, which consists in using plants and their associated germs to decontaminate soil and wastewater, is an effective and inexpensive approach in the context of sustainable development. To make phytoremediation attractive, one of the options is to increase the economic value of the plants being exploited for decontamination purposes. The willow is one of the go-to species used in phytoremediation because of its excellent performance. The tree becomes all the more interesting when we consider that its rapid growth provides a good return as a raw material secondarily.

The second life of plants after decontamination

A number of avenues are being studied with a view to taking advantage of the different portions of a plant. On the one hand, there are substances found naturally in plants – phenolic compounds, terpenes, alkaloids, fatty acids and so on – that we’re acquainted with in common forms such as tannins, essential oils and resins. Even though these are produced in very small quantities by the plant, they possess special chemical properties that industry might benefit from. The thing is to find the maximum added value in these molecules. Targeted characteristics include antioxidant, antimicrobial and immunodefensive properties – and still more. That’s the case with cleaning products containing black spruce bark extract, for instance, or cancer-treating drug substances extracted from certain species of yew. 

The prospects are relevant to various sectors: pharmaceuticals and cosmetics, for example, along with cleaning products or specialty products like adhesives, surface coverings or lubricants.

On the other hand, the development of carbon-neutral biofuels as a replacement solution for less environmentally-friendly energy sources could reduce dependence on fossil fuels and contribute to a reduction in greenhouse gases. This would be a complementary avenue to the first one that this time benefits from the structuring compounds of the plant.

So, different development scenarios in this new bioeconomy are currently under study with the goal of identifying the ones that are economically most beneficial. Down the road, the implementation of a circular-economy loop bringing together phytoremediation and green chemistry should stimulate adoption of these green technologies – and make our environment that much cleaner!

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