As NOx emissions generated by traffic have fallen over recent years, those created by other sources are coming more clearly into focus. New research has found that the primary source of NOx in central London is now the burning of natural gas for heating.
Using data from monitors situated on the BT Tower, the team from the University of York found that between 2021 and 2023, the combustion of natural gas in boilers accounted for 72% of NOx emissions in the surrounding area.
They point out that this source of emission has come to the fore as transport emissions in central London have fallen. They are thought to be 73% lower now than they were in 2016.
It was possible to identify the source of the pollutants by examining the ratio of NOx to CO2, which differs between traffic and boilers.
The study was led by Professor James Lee, professor of atmospheric chemistry at the University of York who led the study said: ‘Our research highlights how much NOx emissions from transport have improved, but also the task still ahead in getting combustion out of cities.
‘Whilst talk of switching from gas to heat pumps is mainly framed around the decarbonisation benefits, it would be a major gain for air quality too.’
Dr Sam Cliff, who carried out the research while carrying out a PhD at York added: ‘Without action on gas boilers it could be hard for central London to meet the WHO (2021) guideline values for NO2, no matter how clean the vehicle fleet.’
Following the publication of the report, Martin Lewerth, CEO of heat pump specialists Aira Group said: ‘Despite being one of the most congested cities in the world, the single biggest source of air pollution in central London is no longer traffic — it’s gas boilers. This research makes it clear: we need to move away from gas boilers in favour of clean heat solutions, such as heat pumps, to improve air quality.
‘While schemes like the Boiler Upgrade Scheme are a step in the right direction, we need the Government to act decisively and rebalance the cost of electricity relative to gas, provide implementation dates for heat pump planning permission changes and revisit the gas boiler ban to accelerate the clean energy transition.
‘These changes need to be handled with care, but failure to progress only causes more harm to people’s health, environment and finances. Now is the time for change.’