Cornell engineers propose new recycling method for medical PPE waste

Engineers at Cornell University, Ithaca, New York, have proposed a new solution to sustainably recycle discarded medical waste, such as used surgical masks, plastic face shields and medical gloves and gowns.

The method, called pyrolysis, is a medium-temperature reaction that can reduce the plasticized medical protection garb back into an original form—including chemicals and petroleum—and then recycle it, perhaps into fuels, according to a new study. The method involved no incineration or landfill use.

“The scale of disposing used medical personal protective equipment (PPE) is enormous,” says Xiang Zhao, a doctoral student and an author on the paper. “Fast pyrolysis is proven to effectively convert waste PPE into value-added products. The pyrolysis method can replace PPE incineration or sending it to landfills, which is what happens now.”

Zhao, working with his advisor Fengqi You, the Roxanne E. and Michael J. Zak Professor in Energy Systems Engineering, in the Smith School of Chemical and Biomolecular Engineering, published the proposed technology framework, “Energy and Environmental Sustainability of Waste Personal Protective Equipment (PPE) Treatment Under COVID-19,” in January in the journal Renewable and Sustainable Energy Reviews.

Their framework, which first focuses on New York state, proposes collecting waste PPE from hospitals and medical centers and then sending it to preprocessing and decontamination facilities in New York or Suffolk counties. There, it would be shredded, sterilized and dehydrated to become small particles and then brought to an integrated pyrolysis plant, like one contemplated for Rockland County, north of New York City.

In the case of You and Zhao’s model, the medium-temperature (about 1,200 F) pyrolysis can deconstruct the plasticized gowns and gloves into chemicals such as ethylene, butane, gasoline, bauxite, propene, propane, diesel, light naphtha and sulfur.

“For an analogy, pyrolysis is similar to baking in an oven,” says You, a senior faculty fellow at the Cornell Atkinson Center for Sustainability. “If you set the oven temperature very high, your meat becomes a chunk of charcoal. But if you use a lower oven temperature, the meat is going to be juicy. In pyrolysis, the temperature is the trick.”

Health care facilities around the world are creating about 7.5 pounds per person of PPE waste daily through COVID-19-associated services, according to the United Nations Environment Programme.

In the paper’s energy analysis and environmental lifecycle assessment, the proposed optimal PPE processing system avoids 41.52 percent of total landfilling and 47.64 percent of the incineration processes. This method shows an environmental advantage by reducing total greenhouse gas emissions by 35.42 percent emissions from conventional incineration and energy saving by 43.5 percent from landfilling, the researchers told the Cornell Chronicle.

“This is a viable strategy for disposing and processing waste PPE,” You says. “It is a treatment method with low greenhouse gas emissions, it alleviates fossil fuel emission depletion and it saves a lot of polluting material from landfills.”