Harvest Cattails To Divert Phosphorus, Says IISD

Phosphorus in run-off water is turning Lake Winnipeg into the “most eutrophic” of all the large lakes on Earth.

But on the other hand, phosphorus is a valuable nutrient that is arguably more strategically important to modern economies than crude oil.

But what if the cattails in Netley Marsh were harvested and pelletized into solid fuel?

According to a new study by the International Institute for Sustainable Development, if nature’s own “nutrient scrubbers” were exploited as a biomass energy source, up to 10 per cent of the phosphorus that pours into the lake could be diverted and used to heat homes and buildings.

What’s more, the leftover ash could be used as fertilizer and returned to phosphorus-deficient soil, because 88 per cent of the nutrient is left over after burning.


Turning an environmental crisis into economic opportunities is the kind of approach that IISD advocates, said Henry Venema, director of the Winnipeg-based organization in a presentation at the recent Agriculture Forum.

“Is this a crisis? Is this something that we should use to further constrain agriculture, or should we view this as an opportunity?” asked Venema.

“We’ve got this interesting paradox. What some regard as a noxious pollutant fouling Lake Winnipeg, is in fact a scarce and strategic resource.”

Economically viable rock phosphate mines exist in only a few places on Earth, and depending on which study one believes, there may be anywhere from 50-200 years’ supply of the mineral left.

Peak phosphorus will make peak oil look like a “walk in the park” because there are no substitutes, he added.

When BHP Billiton, the world largest mining conglomerate, tried to take over PotashCorp last fall, many speculated that they were actually after the Saskatchewan miner’s global phosphorus reserves, not its potash, said Venema.


In the future, the “bioeconomy” will be a big part of the Canadian economy, and agriculture will be producing more than just agri-food.

Using the “biorefinery” concept, farmers will be producing inputs for industry, including fuels, nutraceuticals, and “bioplastics,” while at the same time recapturing more of the nutrients.

“You put biomass feedstocks into a biorefinery and produce a whole range of outputs, in just the same way that a petroleum refinery doesn’t just produce gasoline from crude oil, but also bitumen and kerosene,” said Venema.

The IISD’s five-year study of the biomass potential of harvesting cattails in Netley-Libau Marsh, which it has undertaken along with researchers from the University of Manitoba, takes into account that the marsh lies at the mouth of the Red River.

But before the Red delivers its nutrient load into the lake – roughly 60 per cent of the total – it passes through an extensive system of natural filters at the lake’s south end.


To achieve optimum nutrient capture, the cattails must be harvested in the fall before the plants draw reserves into their roots. To this end, the researchers developed a specialized, heavy-duty sickle mower drawn by an eight-wheel amphibious Argo ATV.

Turning cattails into energy is not a new concept. In fact, researchers in Minnesota looked at the concept 30 years ago, but abandoned the idea after they realized that the cost of fertilizing the plants outweighed the potential gain.

“Here in the Netley Marsh, there’s no shortage of nutrients. Just let them grow, let nature do its thing,” he said. “Work with nature and create new value chains; that’s the essence of the idea.”

The project helps to clean up the lake by intercepting nutrients, creates a new energy source, displaces the need to import coal to fire boilers, and recovers nutrients in the ash.

“It’s not a panacea. We can’t use this everywhere. But it is an example of new thinking that turns what appears to be a problem into a solution,” said Venema.

“Society wants to see two things: prosperous farmers and vibrant ecosystems. There’s no reason why we can’t have both.” daniel. [email protected]


Societywantstosee twothings:prosperous farmersandvibrant ecosystems.There’s noreasonwhywe can’thaveboth.”


About the author



Stories from our other publications