Currently, medical waste streams are complicated to recycle because these single-use products — such as facemasks, syringes, nitrile gloves and non-woven gowns — consist of multiple materials and must be considered contaminated with potentially infectious particles. Now, researchers at Chalmers University of Technology (Göteburg, Sweden; www.chalmers.se) have made progress toward a viable method for recycling mixed medical waste using thermochemical recycling.
Mixed medical waste can be effectively recycled with a new technology
In a study published recently in Resources, Conservation and Recycling, the Chalmers team showed that a steam-cracking process could be effective for breaking apart mixed streams of medical waste into its chemical building blocks. Depending on the types of waste and proportions, recycled medical products can yield mixtures of light olefins, ethane, BTX (benzene, toluene, xylenes) and other molecules that could then become feed material for the petrochemical industry to make new plastics.
The team designed a bubbling fluidized-bed reactor that could handle solid material, and heated the material to 700–800°C to initiate a reaction similar to the steam cracking of naphtha. In the reactor, the waste materials are broken into small molecules and microorganisms are destroyed. Through a series of tests, the researchers processed mixtures that approximate hospital waste, containing 10 different plastic types, as well as cellulose.
The hospital waste was tested at different temperatures (700, 750 and 800°C) in a laboratory-scale reactor. “A significant portion of the carbon in the feedstock could be effectively recovered as valuable chemical building blocks… enabling their direct application in the chemical industry and reducing reliance on fossil resources,” the researchers write. “At 700°C, carbon recovery percentages were approximately 79% for face masks, 82% for plastic syringes, 38% for nitrile gloves, and 76% for non-woven gowns, they found.
The Chalmers scientists are currently developing the recycling technology based on an in-house industrial-scale fluidized-bed steam cracker with a capacity of 100 kg/h for various plastic-rich feedstocks together with industrial partners.