The candy company had a problem. Its products were popular. This meant sales, but it also meant the wrappers were piling up as garbage and litter. Garbage and litter with the company’s name on it.
Concerned by the environmental impact, a researcher from the company reached out to UChicago Pritzker School of Molecular Engineering Founding Dean Matthew Tirrell. Tirrell brought the issue to postdoctoral researcher Pamela Cai.
“It was a piece of plastic that could have been made to last forever, but was meant to be used just once,” Cai said. “It would be so much better to make something that is inherently biodegradable, that can be recyclable and that can break apart and dissolve in the ocean with little to no impact.”
Putting waste to work
The solution wasn’t entirely an obvious one - seaweed and hair.
Due to climate change, the planet’s oceans have seen record levels of seaweed over the last few years. If Cai could find a use for the waste clogging up the world’s beaches, she could solve two environmental problems in one. Similarly, hair and wool are shed and discarded as waste daily. Collecting these materials and extracting the keratin puts that waste to work.
Plastic is a catchall term for long-chain polymers often, but not necessarily, derived from petroleum. Cai knew early on that to be truly sustainable, her plastic needed to come from biopolymers, long-chain molecules made by nature instead of by humans from oil.
“Biopolymers are naturally biodegradable, I don't have to bake in chemical structures to turn non-biodegradable plastics biodegradable,” Cai said.
Putting two polymers in solution – one positively charged, one negatively charged – causes the oppositely charged groups to find each other and form a new material, a phenomenon called polyelectrolyte complexation.
“I am deriving the first polymer from seaweed, that one is called alginate, and then working to derive the second polymer from hair or wool, which is keratin, and modify the charges on each of these so that if I put them in solution, they'll self-assemble into a solid,” Cai said.
After use, the solid naturally biodegrades without an environmental impact because salt ions can reverse polyelectrolyte complexation at high enough concentration.
Cai’s innovative solution to this challenge recently earned her an Arnold O. Beckman Postdoctoral Fellowship, providing $224,000 over two years for salary, fringe benefits and research expenditures as Cai builds the team to make a new plastic for packaging dry goods.
Tirrell called Cai's research "the type of innovative science PME was built to foster."
"PME was founded to be a place where creative minds tackle global issues," he said. "By building a replacement for the non-biodegradable, non-recyclable plastic causing environmental damage across the planet, Pam has risen to this challenge."