A clean solution to the greenhouse gases we aren’t yet talking about

The good news is that the same researchers have developed a way to capture those gases and dispose of them in an environmentally benign way.

Millions of operations take place around the world each year and many of them wouldn’t be possible without anaesthetic gases. Yet those necessary and sometimes life-saving surgeries come at a cost to the planet – anaesthetic gases are also greenhouse gases, some of them hundreds to thousands of times more potent than carbon dioxide.

Dr Saeid Baroutian, who leads the Waste & Biomass Processing Group at the Faculty of Engineering, was prompted to investigate the problem after being approached by concerned anesthetists at Middlemore Hospital.

“They said, ‘we have a problem; anaesthesia, and surgery is a polluting industry’. They were aware of the problem, wanted the health community to be made more aware of it, and they wanted to find ways to address it.”

The main anaesthetic gases used in New Zealand hospitals are sevoflurane and desflurane, halogenated ethers that are usually administered in a carrier gas comprised of oxygen and nitrous oxide, or a mixture of both.

Yet more than 95 percent of anaesthetic gases given to patients are expelled by them, and then into the atmosphere where they contribute to the heating of our planet.

“We know the aviation industry is one of the most polluting industries, but the healthcare sector is as bad as aviation,” says Dr Baroutian. 

Liquid anesthetics are sometimes used as a way to reduce carbon emissions, but it’s estimated that up to 50 percent of liquid anaesthesia drugs are sent to landfill, leading to environmental pollution, and a high risk of water contamination.

This is also the case with many other pharmaceuticals entering the waste stream untreated, such as antibiotics, steroid-based drugs and opioids, says Dr Baroutian.

High temperature incineration is currently the only way to dispose of pharmaceutical waste, but the incineration of such products isn’t permitted in New Zealand due to the toxic gases and particulates emitted in the process.

Instead, our pharmaceutical waste is shipped to Europe for high temperature incineration. Just as China has declined to dispose of our plastic products, says Dr Baroutian, it’s a matter of time before Europe declines to take our pharmaceutical waste products. 

He and his team have developed a new adsorptive capture and hydrothermal deconstruction technology for the removal and decomposition of toxic anaesthetic waste.

It’s a two-step physiochemical process. Firstly, it involves capturing the anaesthetic gases from hospital operating rooms before they are released into the atmosphere.

Hot, pressurised water is then used to break down the anaesthetic compounds into safe, inert compounds, mainly water and organic acids such as acetic acid.

He describes the process as ‘busting waste with water’. It can be used for both gas and liquid anaesthetics and could also be used for other medical, pharmaceutical and veterinary waste products.

“This high temperature hydrothermal processing technology is scalable (‘right-sized’), clean (the process involves only water) and energy efficient, therefore reducing operational costs,” says Dr Baroutian.

Dr Baroutian and his team have been working with medical practitioners from Counties Manukau Health (CMH) and their industry partner, Interwaste, New Zealand’s largest medical and clinical waste disposal company, to establish the technology for hospitals, pharmacies and veterinary clinics.

“It could transform New Zealand’s pharmaceutical waste disposal system, including anaesthetic waste disposal.”

“Our integrated capture and hydrothermal deconstruction systems will reduce emissions in New Zealand by 20,000 tonnes of CO₂ equivalent per annum, as well as eliminate 5,000 litres of liquid anaesthetic waste entering the environment each year.”