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6ER-007 Reducing our medicines’ carbon footprint by tackling nitrous oxide waste
  1. L Stevenson
  1. King’s College Hospital NHS Foundation Trust, Pharmacy, London, UK


Background and Importance There is a focus on the NHS becoming greener underpinned by the NHS Green Plan and closing the gap to net zero. One of the biggest contributors to the NHS carbon footprint is medicines, accounting for 25%. Nitrous oxide confers the largest carbon footprint of the anaesthetic gases within the acute sector accounting for at least 75% of the total footprint.

It is crucial we work to reduce our carbon footprint – the climate crisis is a health crisis, and it is our duty as health care professionals to act to protect our patients and planet.

Aim and Objectives Our project aimed to tackle the largest cause of anaesthetic emissions, nitrous oxide. Nitrous oxide is a bigger problem than most gases due to frequency of use and reliance in dental and paediatric procedures. Our goal was to reduce our carbon footprint of these gases by tackling waste.

Material and Methods We carried out a clinical audit across all clinical areas that are served by piped nitrous oxide, 1605 litres were used weekly on average (83,460 litres per year). We were able to compare our clinical audit data with the total gas bought into the trust (915,000 litres per year). Figure 2 shows clinical use of 5%, and therefore 95% waste.

Results In establishing a solution to the problem we knew the main source of waste of nitrous oxide was from the piped supply. Therefore, our plan was to completely decommission areas that had zero clinical usage and convert anaesthetic gas machines to take portable cylinders in all other areas. Converting to smaller, portable cylinders we could provide a leaner supply with no change in patient care or experience.

Conclusion and Relevance From switching to a leaner supply of medical gases, we have saved over 250 tonnes of CO2e since beginning our project, as well as over £20,000. The project continues with aims to reduce to less than 100 tonnes of CO2 emissions per year from our nitrous oxide footprint.

References and/or Acknowledgements 1. Greener NHS » Areas of focus (

2. Nitrous oxide could be harming people as much as the planet – The Pharmaceutical Journal (

3. NHS England » Putting anaesthetic emissions to bed: commitment on desflurane.

Conflict of Interest No conflict of interest.

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