This text is part of the special Research section: climate issues
Ahmed Jerbi, researcher at the Plant Biology Research Institute (IRBV) of the University of Montreal, studied the effect of fertigation by wastewater on willow plantations. The results of his research are promising for the biofuel market and for the environment.
For his master’s and doctorate, biologist Ahmed Jerbi carried out a series of experiments in Saint-Roch-de-l’Achigan, in Lanaudière. He then studied how to use wastewater from the treatment plant to fertilize and irrigate a willow plantation. This tree, which requires a lot of water and nutrients, grows very quickly, which makes it interesting for various commercial uses, such as insulating chips, organic amendments or plant fences.
His research revealed that wastewater, rich in nitrogen and phosphorus, produces several very desirable effects on the plant itself. First, a very significant increase in biomass, of more than 200%. “You can see with the naked eye that the leaves are three times bigger. And its stomata [les orifices minuscules qui permettent à la feuille de respirer] are also 15% bigger,” explains Ahmed Jerbi.
But the big surprise came from another transformation, of a physicochemical nature: the wood fiber had gained 16% glucose. “This significant increase makes it possible to consider transformation into biofuel,” he explains.
The third observation is that the ecological filtration of wastewater by plants works. At normal flow, the willow root system filtered absolutely all the nitrogen and phosphorus. “And at high speed, of the order of 30,000 m3 per hectare, leaching was certainly higher, but it remained below standards,” explains Ahmed Jerbi.
Serving the environment and promoting
His thesis director, Frédéric Pitre, professor at the University of Montreal and member of the IRBV, explains that Ahmed Jerbi’s work is part of an effort by the Institute to link the treatment of wastewater by phytotechnology and the valorization of biomass, to increase the productivity of irrigated plants.
“Ahmed carried out long-term innovative work, which involved a lot of field measurements, and which required as much climbing in trees as working under a microscope. And its very interesting results are transferable to future applications. »
For 20 years, the development of the corn-based biofuel sector – also called first generation biofuel – has sparked controversy. “Are we using agricultural land for food or for fuel? Second generation biofuels, from wood or forest residues, get us out of this dilemma, explains Frédéric Pitre. For Quebec, which has decided not to produce corn-based biofuel, it is a developing sector. »
“A 16% increase in the quantity of glucose opens interesting prospects, but the industry will still have to take several steps,” agrees Ahmed Jerbi. “But despite the desire to electrify transport, we may still need biofuels for high-power uses and processes for a long time to come. »
“But whatever happens to the biofuel sector, the very significant increase in biomass observed by Ahmed Jerbi makes it possible to show that it is possible to considerably increase the yield of a willow grove while providing a real environmental service by filtration,” says Frédéric Pitre.
Ahmed Jerbi highlights some statistics that make you shudder: Quebec annually produces a third of the 6 trillion liters of wastewater in Canada. Enough to cover the island of Montreal five times under a meter of smelly liquid. “When we know that 60% of this wastewater is released into nature without biological treatment, Quebec should consider phytotechnologies on a large scale. »
Quebec strategy for saving drinking water
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