UIC engineers develop plant-based plastic alternative for use in shopping bags

Shopping at a pharmacy, grocery or other store in the city of Chicago? You’ll now pay $0.15 for every disposable plastic bag you pack your purchases in. The bag tax, which went up  from $0.10 on Jan. 1 this year, was implemented in part to discourage reliance on single-use plastics.

Most shopping bags today are made of low-density polyethylene, which can take hundreds of years to decompose in the environment. But one research group at the University of Illinois Chicago has created a sustainable alternative: a plant-based bioplastic, designed for use in everyday objects like shopping bags. It’s biodegradable, meaning it can be decomposed by natural microorganisms in the environment. And it’s designed to match the strength and performance of conventional plastic bags while reducing environmental impact, the team reports in a recent study published in Chemical Engineering Journal.

“Most plastics are derived from crude oil, which is a finite resource and is fast depleting,” said Taiwo Zacchaeus Adesanya, first author of the new study and a PhD student in Ezinne Achinivu-Ibagere’s lab in the UIC College of Engineering.

Humanity has produced at least 9 billion tons of plastic, according to estimates, and a large chunk of that volume has been discarded into landfills or the environment.

“There are recycling facilities for some, but the percentage recycled is still very low compared to the stock volume of plastics produced,” Adesanya said.

Pollution, greenhouse gas emissions and wildlife harm result, said Achinivu-Ibagere, an assistant professor in the department of chemical engineering.

“Developing alternatives that are renewable, biodegradable and lower in environmental impact is becoming essential for advancing a more sustainable, circular materials economy,” she said.

To tackle these challenges, Achinivu-Ibagere’s research team focuses on using materials from plants, like cellulose and lignin, to create biodegradable plastic substitutes.

Most plants have cellulose and lignin in their cell walls. Cellulose gives a plant stalk or stem its strength, while lignin acts as a glue that binds cellulose and other structural molecules together.

“Our research is focused on harnessing the strength of cellulose and the barrier properties of lignin to make a bioplastic,” Adesanya said.

In their new study, the researchers used a combination of commercially available cellulose and lignin from Miscanthus, also known as silvergrass. They also tested lignin from a variety of plant sources, including hybrid poplar (a hardwood), pine (a softwood), corn and sugarcane, as well as lignin derived from paper-processing byproducts.

“Over the years, cellulose has been used to make paper and a lot of other materials,” Adesanya said. “But in the process of extracting cellulose from crops and from trees, there is a brownish, gooey material that is taken out and discarded or used as fuel; that is lignin.”

On a molecular level, lignin is extraordinarily complicated, composed of random, varied linkages of organic molecules.

“This creates a complex structure that differs from one crop to another, from one season to another, from the roots to the stem,” Adesanya said. This structural intricacy can make working with lignin difficult. It doesn’t easily dissolve into other substances, an issue also encountered with cellulose.

Cellulose and lignin also don’t easily mix, and attempts to combine them often lead to separation, weak bonding and uneven quality of the resulting material. To circumvent this, the scientists dissolved the two together into a special type of salt that remains liquid at temperatures below 100 degrees Celsius. They then adjusted the viscosity of the solution and formed thin films through controlled cooling and drying.

The team evaluated the films’ strength, stretchiness, permeability to water and ability to block UV rays. The bioplastic held up in tests against conventional low-density polyethylene plastic, also called LDPE, and against a compostable waste disposal bag available on the market called Biobag.

“While LDPE still performs strongly in certain areas, our material offers a significantly improved environmental profile while maintaining competitive functional properties,” Achinivu-Ibagere said.

With soil samples gathered in UIC’s greenhouse, they also tested the bioplastic’s ability to break down in the environment.

“If you toss it into your backyard, it will degrade,” Adesanya said. How long would that take? About one month at room temperature, the researchers found.

Next, the lab plans to continue studying the complex chemical interaction between cellulose and lignin in the bioplastic. They’re also drilling down into how the material decomposes, and how to optimize its flexibility.

“We are looking at the microbial communities that are responsible for the biodegradation,” Adesanya said. “We also have another study looking at how to enhance the elongation of these materials; we’re looking at how to make them more stretchy.”

Meanwhile, the researchers are working on developing ways to manufacture large sheets of the bioplastic and testing how it performs in everyday applications.

“We’re interested in integrating additional natural polymers or additives to further enhance performance and biodegradation rates,” Achinivu-Ibagere said. “Our goal is to move toward pilot-scale production to evaluate commercial potential.”

In addition to Adesanya and Achinivu-Ibagere, co-authors of the study include Jessica Fajardo, Matthew Gaughan, Ogechikanma Ihenacho and Hussein Rezk from the UIC College of Engineering.