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Harvesting invasive plants for fertilizer and fuel

Oct 25, 2016

Researchers who work in wetlands in Michigan are taking a new approach to invasive plants. They’re harvesting them for fertilizer and fuel. 

When you’re in the middle of the Shiawassee National Wildlife Refuge, you don’t realize how massive it is. It’s 10,000 acres of marshes and bogs, forest and farmland. To put the size in perspective, Manhattan is roughly 15,000 acres.

Brendan Carson is a researcher from Loyola University Chicago. He’s working on a project at the wildlife refuge centered around harvesting cattails. The problem species: an invasive European cattail that has crossed with a native cattail to make a hybrid.

“The hybrid’s called Typha. x glauca," he explains. "And the hybrid can become fairly dominant, or extremely dominant in a lot of wetlands, especially where there are excess nutrients like nitrogen and phosphorus.”

Carson says when there are too many cattails in one place, they can crowd out native plants. A wetland can lose its ability to filter water, and birds and fish can suffer from a lack of food and shelter.

Harvesting, then reusing cattails

Most afternoons on the refuge are peaceful, but today is a harvest day.

Eric Dunton, a biologist at the Shiawassee National Wildlife Refuge.
Credit Sam Corden / Interlochen Public Radio

The team fires up the bright red harvester, and it roars forward, spitting out cattails as it moves. It’s specially made for projects where you need to have a low impact on the earth. It seems to glide over the marshland, consuming every cattail in its path.

Carson says the project is designed to let the cattails grow all summer, absorbing the nutrients like a sponge, before the harvesting takes place.

“So as long as you can remove that tissue while it’s still green, you’re going to be removing quite a bit of nitrogen and phosphorus,” he says.

Then, those nutrients can be put to good use elsewhere. The researchers give the shredded cattails to local farmers, and the farmers use them to fertilize crops.

Carson says harvesting invasive plants is more cost effective than spraying them with chemicals.

The invasive plants might also have other uses. One researcher in the Upper Peninsula has started using invasive plants to make fuel pellets. Pellet stoves are similar to wood-burning stoves. They can burn plant matter as a renewable source of home heat.

And at the University of Wisconsin-Oshkosh, Brian Langolf is using a mechanical digester to turn the cattails - and other materials -- into electricity.

“Roughly the capacity to produce up to 10% of our university’s power consumption equivalent, or roughly 220 average American homes year round we can provide heat and power to,” says Langolf.

Using invasive plants in these ways is still pretty new.

But the researchers say farmers and businesses could work together to create markets for them, and that could result in healthier wetlands in the Great Lakes.

Support for this story comes from the Knight Center for Environmental Journalism at Michigan State University.