By Edwin L. Aguirre
A team of faculty researchers led by Chemical Engineering
Assoc. Prof. Hsi-Wu Wong
was recently awarded a three-year grant totaling more than $1.6 million by the U.S. Department of Energy (DOE) to help combat waste plastic films through upcycling, which is converting discarded materials into products of higher value than the original.
“Our goal is to develop an integrated process to upcycle single-use, multilayer waste plastic packaging films from cling wraps and prepackaged food bags into high-value chemicals and carbon materials,” says Wong.
According to Wong, the integrated upcycling process combines chemolytic delamination (separating the plastic layers using environmentally safe chemical solvents) and plasma carbonization (turning the plastic waste into pure carbon using jets of electrically charged gas with high energy, ideally powered by renewable electricity).
The resulting products include monomers for plastic production, hydrogen gas as an energy source, and carbon black, which is a fine carbon powder used mainly as reinforcing filler in tires and other rubber products as well as a color pigment for plastic products, paints, coatings and inks.
Reducing Plastics’ Detrimental Impact
Single-use, multilayer plastic films are not only energy-intensive to produce, but they are also difficult to recycle, reuse and discard.
“One prime example is the potato chip bag, which is typically composed of three to five layers of different materials, including polyethylene [PE], polyethylene terephthalate [PET] and aluminum foil,” Chen says. “Grocery bags and bubble wraps typically are made of single material and are most likely a single layer.”
She adds, “Multilayer plastic films not only clog up machineries and are hard to shred or break up, but the layers are also challenging to separate. Their components typically do not blend well if you are using conventional mechanical recycling methods.”
The research team hopes its upcycling project will lead to significant economic and environmental benefits.
“The modular nature of our processing technology will enable it to be distributed and implemented in local communities to assist with their economic growth and resiliency. We also expect to reduce the amount of waste plastic films that end up in landfills and the environmental exposure to hazardous materials associated with them,” says Wong, who received a $500,000 CAREER award from the National Science Foundation
in 2019 for his research on converting biomass waste into biofuels and additives.
The researchers say that although each element of their process has been explored to some extent, the entire integrated process has not been tested and used to tackle plastic waste.
“Our technology offers advantages over current recycling methods, including its capability to process films with a wide array of compositions and the production of high-value chemicals rather than repurposed or downcycled plastics,” Wong says.
Chen envisions broader uses for the upcycling process. “Our delamination process can be used to treat other waste polymer composites from electronics and wind turbine blades, in which multilayer structures are commonly used,” she says.
Trelles adds, “Our plasma carbonization technology can be used to treat other hydrocarbon-containing substrates, such as waste biomass and potentially municipal waste, for generating renewable hydrogen gas and carbon-based materials.”
UMass Lowell’s grant is one of seven that the DOE awarded to universities and industrial companies as part of the agency’s $13.4 million initiative
to help advance technologies that reduce greenhouse gas emissions from plastic production and enhance plastics’ recycling and biodegradation capabilities.
The other recipients include Iowa State University of Science and Technology, Michigan State University, North Carolina Agricultural & Technical State University and West Virginia University Research Corp., as well as Braskem in Pittsburgh, Pennsylvania, and TDA Research Inc. in Wheat Ridge, Colorado.