people standing in a lab. wearing masks

Lahiru Jayakody, foreground, assistant professor of microbiology at Southern Illinois University Carbondale, holds a petri dish in his laboratory recently. Jayakody is working with SIU researchers Ken Anderson and Matt McCarroll, back, left to right, on perfecting a process incorporating spent tea leaves and coffee grounds that would make single-use plastics biodegradable and more readily recyclable. The work also will involve student researchers, left to right, Lakshika Dissanayake and Sandipty Kayashta, graduate assistants, and Ryaan Ligon, a senior in chemistry. (Photo by Russell Bailey)

October 21, 2021

SIU researchers aim to turn trash from coffee, tea into biodegradable plastic treasure

by Tim Crosby

CARBONDALE, Ill. — They’re a big problem, single-use plastics. They’re popular, cheap, one of the most common trash and landfill items, and they don’t recycle very well. Researchers at Southern Illinois University Carbondale, however, are working on promising technologies that could bring a molecular-level, sustainable solution to the table while still making it easy to enjoy your favorite beverages. All we have to do is keep drinking coffee and tea.

Lahiru Jayakody, assistant professor of microbiology, is leading the project. He is working with veteran SIU researchers and senior investigators Ken Anderson and Matt McCarroll on perfecting a process that would make everyday, single-use plastics biodegradable and more readily recyclable. The process builds on another one, pioneered by Anderson. It also relies on spent tea leaves and coffee grounds to produce high-value chemicals that in turn can make biodegradable, efficiently recycled plastics. 

Jayakody received a $290,000 grant from Green Core Ltd, Japan, and Ito En USA for the research project, which also will involve SIU undergraduate and graduate students.

Big problem

Plastics, with their versatility and low cost, play an outsized role in the global economy, packaging everything from food and drinks to technological products. It’s hard to imagine a world without them.

Plastics account for more than $400 billion in annual revenue to the U.S. economy alone. Consequently, they play a large role in the waste stream, accounting for more than 15% of solid waste in U.S. landfills. The material also might have a detrimental effect on human health, with so-called “microplastics” polluting our air and shedding from plastic packaging.

“Plastics are a major environmental burden on land and especially in the ocean,” Jayakody said. “There are some projections that by 2050 there will be more plastics in the ocean than fish on a mass basis.”

Polyesters are a subgroup of plastics, and those made from polyethylene terephthalate (PET) are the most commonly produced around the globe. More than 26 million tons of PET annually goes into making carpet, clothing and single-use beverage bottles, among other products.

Although the means exist to recycle PET chemically back into a useable form, the costs of doing so make it economically disadvantageous. Other recycling technologies that rely on mechanical means result in a lower quality, and therefore lower value, product. All this means that only about 30% of PET product is recycled each year.

Cross-pollinating technologies

The process under review by the researchers would happily marry microbial processing with another process that uses heat, pressure and oxygen to combine two different waste streams into a recycled high-value material. Fortunately pioneers of both processes can be found at SIU.

As post-doctoral researcher, Jayakody found ways to use microbes to selectively deconstruct PET into its original chemical building blocks. He further used metabolically engineered microbes to convert those building blocks into high-value “platform chemicals,” or chemicals that serve as valuable precursors to other types of plastics or substances.

After arriving at SIU, Jayakody met Anderson, who in 2010 created a patented process called oxidative hydrothermal dissolution (OHD) technology, which he then used to start Thermaquatica, a company based in SIU’s Dunn-Richmond Economic Development Center. The process uses a “reactor” that initially combined coal, water, heat, pressure and oxygen, resulting in liquid chemical precursors for polymers and plastics. OHD, however, also can be used to turn other organic materials, such as plastic or plant biomass, into water-soluble, low-molecular-weight compounds.

“I realized that we could leverage microbial technology to add further value to the OHD-derived compounds,” said Jayakody, who has since developed microbial strains that demonstrated the proof of concept of a hybrid OHD-microbes system.

Waste not…

Single-use plastic bottles are one problem. But as a worldwide staple, tea and coffee wastes are also plentiful and ubiquitous, even if they are more readily biodegradable. Thirsty humans create some 400,000 metric tons of waste grounds each year, much of it ending up in landfills or being used as low-value fertilizer, or recycled into paper or compost. Ito En, a Japanese multinational beverage company and the largest green tea distributor in Japan, creates some 51,000 metric tons of waste tea leaves each year, alone.

But the SIU researchers think this plant-based waste may hold the key to solving the plastics waste stream, too. Their process would combine waste coffee and tea biomass with deconstructed PET molecules derived from the OHD-microbes hybrid process, resulting in a new, advanced PET alternative that not only works well as a packaging material but is also biodegradable and recycles better.

Biodegradable plastic is already available, but it is generally of poor quality and therefore not used on a large scale. The microbial-based selective degradation system the researchers are investigating, however, would ensure nearly 100% recirculation of bioplastic monomers. This means that material made from recycling would have the same properties as the original material — unlike the current mechanical-based PET recycling technologies now available, which result in a lower quality material.

For these reasons, the research project made for a good fit with a company such as Ito En, Jayakody said.

“Our goal is to establish a green production platform with Ito En that will help protect our planet from single-use synthetic plastic by packaging its high-quality bottled green tea in novel eco-friendly biodegradable, recyclable plastic bottles,” Jayakody said. “Our technology adds value to the waste carbon in tea and coffee while creating high-value chemicals that provide a new revenue stream to the tea industry, while also helping the environment.”

Students heavily involved

The three-year project is expected to result in a pilot plant and process. But it also will result in intensive, hands-on opportunities for SIU graduate and undergraduate students. SIU places a premium on involving students – even undergraduate students – directly in cutting-edge research.

The grant directly supports two graduate and one undergraduate student, Jayakody said. Several additional students from different disciplines also will be indirectly involved in developing the technology.

“The students will be involved in real-world applied research,” Jayakody said. “This is a multidisciplinary project, and the students will have experience of being involved in a high-risk, high-reward industrial project.”