From PPE to water, vinegar: a circular solution to healthcare waste

A new process developed by engineering researchers from New Zealand and Canada converts personal protective equipment (PPE) waste into harmless by-products — water and vinegar.

Shredded masks, gowns, gloves and plastic safety glasses are put into a machine, then hot, pressurised water and compressed air are applied; and the end products are water and acetic acid.

The PPE-to-liquid process is carried out at a temperature of 300°C and takes about an hour in a small prototype machine in a laboratory in the faculty. Gaseous by-products from the process are oxygen and low concentrations of carbon dioxide, which can be safely discharged. “This is a clean, chemical-free solution which will be a game changer internationally,” said Dr Saied Baroutian, an associate professor in the faculty’s Department of Chemical and Materials Engineering at the University of Auckland.

“The technology used is a hydrothermal deconstruction or valorisation process and it destroys the waste completely. The liquid produced in the process is safe, inert and can be reused — the vinegar or acetic acid can be used for disinfecting and the water can be reused for the processing cycle therefore minimising water consumption and helping with sustainability,” Baroutian said.

The process was developed in partnership with the Faculty of Medical and Health Sciences and the Universities of Otago and Waterloo (Canada). The research teams are now taking steps to develop the solutions into a larger scale pilot system and, learning from that, will develop a full-scale proof of concept. “That is the point where we can showcase the technology, ensure the designs will work with the flow of PPE waste and find funding or potential partnerships with commercial organisations so these technologies can be implemented in New Zealand and overseas,” Baroutian said.

In terms of cost, the researchers have already completed an economic analysis which shows a large-scale hydrothermal deconstruction system could process PPE waste at a cost comparable to the current practice of autoclaving and landfilling. “And in terms of the environment, the savings on offer are huge,” Baroutian said.

Funding for the project has been provided through a $1.3m grant from the NZ Ministry of Business, Innovation and Employment (MBIE) through the COVID-19 Innovation Acceleration Fund and a $46,000 grant from the Medical Assurance Society Foundation.

Image credit: The University of Auckland