Soy-based Mulch, Playground Surfacing Wins Soybean Competition

From a humble soybean, a team of Boilermakers has sprouted the idea for “Smulch.” Comprised of Indiana soybeans, the rubber-like material could be used to make gardening mulch or soft playground surfacing, eliminating potentially toxic materials used in the traditional versions of both products, says Team Smulch. The student trio captured the $20,000 top prize at the annual Student Soybean Innovation Competition, where students harvest new ideas to drive consumption of the crop.

Many conventional mulch products—both for landscaping and gardening—contain chopped pieces of rubber from recycled tires. The soft, buoyant surfacing used on playgrounds also contains “crumb rubber” made from grinding recycled tires, which is causing alarm.

The U.S. Consumer Product Safety Commission is currently assessing the risk to children from playground surfaces containing tire crumb, as they may get the surfacing in their mouth or on their hands. Additionally, the Centers for Disease Control and Environmental Protection Agency are studying the chemical characteristics of recycled tire materials related to exposures on artificial turf athletic fields.

“[Tires] are made from really bad plastic and can eventually cause a carcinogen effect,” says Zuhal Cakir, a Purdue University chemical engineering PhD student on Team Smulch. “It’s really bad, especially for kids playing on the playground, or even garden settings where [the toxins] can transfer [from mulch] to the vegetables and eventually affect our health. We need healthier and non-cancer related products on the market that we can use in these settings.”

The team’s winning Smulch product could replace tire rubber with a healthy, natural alternative: soybeans.

“We knew we could make a rubbery material. We did a ton of trial and error in the lab, and we found the perfect mixture,” says Ethan Miller, a Purdue biochemistry student on Team Smulch. “We poured it out—it was very rubbery, almost like a sheet—then it would cure, and we would cut it up into mulch bits.”

Smulch contains only three ingredients: soy flour, silicone and a dye to color the final product. Especially notable for the gardening and landscaping applications, Smulch is biodegradable and beneficial to plants. The team discovered that adding soy oil to the mixture made the sheet even more “squishy,” and the second idea for playground surfacing was born.

“Soy is environmentally friendly, and we tried to keep the soy percentage really high—almost 50% in both of our products,” says Cakir. “And [Smulch] is basically 100% environmentally friendly.”

The team says both products could be easily and economically manufactured in sheets; the material could remain in sheet form for playground surfacing or chopped to create the mulch product. The team developed Smulch over the course of six months, and it performed well in lab testing for heat and water resistance, indicating it would work well in outdoor environments.

“When we were deciding what to make [for the competition], the first thing we considered was, ‘Does this solve a real-world problem?’ This product does,” says Libby Plassard, a Purdue business management and finance student on Team Smulch. “It has a great opportunity to fit a niche market of people who are concerned about their health and safety and also want products that are good for the environment.”

The competition is sponsored by the Indiana Soybean Alliance (ISA); the organization is now working to further develop Smulch and evaluate its long-term feasibility and commercial potential. Smulch could follow in the footsteps of previous winners, such as a student who developed soy candles—setting the industry standard for the now wildly popular product. It was ISA’s first major commercialized product, and the organization now holds six patents on soy wax in candles.

The competition awarded the second place $10,000 prize to Team Brilliant Bean, which developed a soy-based ink for markers that can be used on dry-erase boards.

Cakir and Plassard will take part in Purdue Foundry’s ASPIRE Internship this summer, an exclusive opportunity for competition winners to forward their commercial ideas. It’s just one program ISA and Purdue have created to encourage student inventors to remain involved in their inventions—taking advantage of two Hoosier commodities: soybeans and innovative Purdue students capable of engineering big ideas from a little bean.