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Energy & Environment

These Texas State students are turning invasive plants from the San Marcos River into menstrual pads

A person in a canoe holds a water hyacinth on the banks of the San Marcos River.
Patricia Lim
/
KUT
Wren Vogel holds a water hyacinth on the banks of the San Marcos River. The invasive species crowds out native plants and blocks sunlight — and ultimately oxygen — from getting into the water below.

Texas State University student Jamie Hand leans over the edge of her canoe and yanks out a thick, shiny-green plant from the bank of the San Marcos River.

From springtime to early fall, vast swaths of the river are chock-full of this multifaceted and trouble-making plant: the water hyacinth.

Here, it's an invasive species, crowding out native plants and disturbing the balance of the ecosystem. It multiplies quickly, creating a messy thicket of leaves that blocks sunlight — and ultimately oxygen — from getting into the cool water below.

"It’s just like wine. One glass of wine is good, but two boxes of wine ain’t going to make anything good," says Sanchul Hwang, an assistant professor of civil engineering at the Ingram School of Engineering.

Two people in a canoe on the river
Patricia Lim
/
KUT
Sangchul Hwang and Texas State student Jamie Hand extract water hyacinth from the San Marcos River.

In some places, the aquatic plant has a different reputation. When it's not busy overcrowding waterways, the plant can act as a natural water purifier, absorbing heavy metals and other pollutants through its roots. Some Asian countries are even cultivating it for this purpose, Hwang says.

"So that’s the thing. Water hyacinth [are] actually good and beautiful," he says. "But when they grow a lot, that is [the] environmental disaster.”

Hwang and his students have spent the last few months extracting and harvesting the water hyacinth as part of their work with HEDGE, a research team Hwang started that upcycles invasive species into sustainable and functional materials.

One of their main projects is turning the water hyacinth into a menstrual pad.

The idea came to Hwang after his first encounters with the river — abundant in people, businesses, and of course, water hyacinth. At the time, his teenage daughter started talking to him about global inequalities related to menstrual hygiene and "period poverty."

He combined what he had seen along the river with what he heard from his daughter.

"She is actually [the] initiator or, you know, kind of made me think of this project," he says.

All-natural protection

In the HEDGE office, menstrual pads are tacked on the walls, almost like artwork. With the pad's wings spread open, Wren Vogel jokingly calls them "airplane decorations."

"Sometimes we’ll just grab them off the wall if we’re thinking about like layers and things like that," says Vogel, a graduate student involved with HEDGE. "We'll cut it open and just kinda see, like get an idea of how manufacturers do it."

hyacinthstem_PL_101721
Patricia Lim
/
KUT
The inside of a hyacinth stem is fluffy and fibrous.

Inside the lab next door, she cracks open the stem of a dried up water hyacinth.

"Whenever the water hyacinth is dried, the inside turns very fluffy and you can see, like, the cellular structure," Vogel says. "You see the little, it kinda looks like hexagons?"

That fluffy, fibrous material is part of what makes the plant so absorptive — and ideal for a plant-based pad.

hyacinthpad.jpg
Riane Roldan
/
KUT
The fibrous material inside the stem of the hyacinth is mixed with raw cotton and water to make the pad.

After they're harvested, the plants are cleaned and dried in industrial-sized ovens. The crunchy stems are then blended into a fine powder (which Vogel says smells just like apples) and mixed with raw cotton and water.

The result is a prototype that roughly resembles a panty liner, one that's speckled brown instead of bright white. And this is just one layer — the final product will have a few more.

"[The] overall main thing is ensuring it is natural, user-friendly and biodegradable," Vogel says.

Removing an invasive species from a treasured waterway like the San Marcos River is a win in and of itself, she says. But HEDGE is trying to do more than just win.

"The idea is, let’s upcycle them instead of just harvest them and then dump to landfill," Hwang says. "It’s — Hey, let's make something out of it. Especially something, some product, which can be utilized or used for vulnerable communities."

Finding good in the bad

Though there are fewer water hyacinths along the banks of the San Marcos River this time of year, there are a number of other invasive species: elephant ears, water lettuce, alligator weed and hydrilla, to name a few.

"In the San Marcos area, there's so many invasives," Vogel says. "It was invasive plants that were the first global travelers, and they are among the top five threats to biodiversity."

The challenge lies in finding ways to work with all of them — honoring their natural capabilities while still keeping a close eye to make sure they don't wreak havoc on the natural balance of the ecosystem.

"There's so much you can do with the plants," Vogel says.

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