Measuring the carbon footprint of a health service is substantially more complicated than adding together energy bills and fleet mileage. NHS emissions extend across buildings, medicines, procurement, staff travel, patient and visitor journeys, freight and a large international supply chain.
Methods
Our contribution included supporting the review of the carbon-estimation approach, alongside our more detailed work on transport decarbonisation.
The national methodology combined two complementary forms of carbon accounting. A top-down approach used expenditure data and environmentally extended input-output carbon intensities to estimate emissions from complex areas such as the NHS supply chain. A bottom-up approach used physical activity data—including energy use, waste and travel mileage—combined with government carbon factors.
Travel presented a particularly important analytical problem. The methodology used National Travel Survey evidence to estimate patient journeys, accompanying and visiting travel, and staff commuting where consistent NHS-wide surveys were unavailable. Carbon factors were then mapped to different modes of travel. Business travel, freight and related transport were incorporated through the broader top-down methodology.
Findings
The analysis demonstrated both the scale of NHS emissions and the importance of looking beyond emissions generated directly by NHS buildings and vehicles. The published assessment estimated the wider NHS Carbon Footprint Plus at 24.9 MtCO₂e in 2020, approximately 26% below its estimated 1990 level.
Travel was a significant component of that footprint. NHS England estimated that journeys by patients, visitors, staff and suppliers accounted for approximately 9.5 billion road miles annually and around 14% of the NHS’s total emissions. This made the treatment of travel behaviour, mode choice and future vehicle emissions an important part of credible net-zero planning rather than a peripheral transport issue.
The resulting evidence contributed to the analytical foundation for the NHS’s national net-zero pathways: net zero by 2040 for emissions under direct NHS control and by 2045 for the wider emissions it can influence.