A widespread switch to burning hydrogen to heat UK homes has been suggested to meet the country鈥檚 new climate targets 鈥� but a leaked report has warned the government that such a move risks inadvertently releasing harmful nitrogen oxide (NOx) pollution in densely populated towns and cities.
An unpublished report by air quality experts for the Department for Environment, Food and Rural Affairs (Defra) lays out the pros and cons for air pollution stemming from the UK鈥檚 new legal target of cutting carbon emissions to net zero by 2050.
The document obtained by 快猫短视频 lists the unintended ways new carbon-cutting policies could make the air dirtier. Hydrogen, which is backed by industry and government advisers as a key fuel to decarbonise heating, could lead to NOx emissions if burned in boilers in homes and businesses, it says.
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鈥淭he use of hydrogen as a significant energy source for domestic and commercial space heating would potentially lead to NOx emissions being concentrated in higher density population areas,鈥� the report says.
The construction of large, clean energy projects wouldn鈥檛 harm air quality nationally but could temporarily increase air pollution at a local level. The report cites nuclear plants as a concern due to long build times. For example, the number of trucks near Hinkley Point C, a nuclear power station being built in Somerset that isn鈥檛 expected to be online until 2025, .
The report says the continued shift to electric cars will bring 鈥渦nambiguous benefits鈥� by eliminating the release of toxic nitrogen dioxide (NO2) which is mostly pumped out by diesel cars.
But it cautions that particulate matter, which can lead to serious illness or death, will remain unless there is a switch away from cars to more walking and cycling. This is because a lot of particulates come not from exhausts on modern cars but from dust released by tyres, brakes and road surfaces. 鈥淭hese could plausibly increase if overall vehicle-miles driven were to increase,鈥� the air quality experts say.
As buildings become much more energy efficient to meet carbon targets, they must also be designed to avoid the accumulation of indoor air pollutants聽due to inadequate ventilation, the report says. However, well-designed building upgrades can avoid the risk. 鈥淧oor indoor air quality is by no means an inevitable consequence of energy efficiency,鈥� the report says.
Other measures for cutting carbon emissions from homes, such as district heating schemes, could also have a temporary negative effect on air quality because they may use polluting fuels such as biomass before later transitioning to cleaner sources such as fuel cells.
Growing more crops for bioenergy also poses a potential downside for air quality, as some fast-growing plants have the potential to increase volatile organic compounds (VOCs) and therefore ozone too,which is another pollutant.
While highlighting the danger of unintended consequences, the researchers say that overall, moving to net zero carbon emissions will create 鈥渕ajor opportunities鈥� for better air quality. Moves to clean up farming are largely seen as a universal good, with low-carbon measures such as better manure management also cutting air pollutants, including ammonia and NO2.
Using hydrogen instead of natural gas in the gas network would, despite the concerns over NOx, 鈥渃ompletely eliminate鈥� VOCs such as ethane, propane and butane which leak from pipes, according to the analysis. Another technology to clean up heating 鈥� heat pumps 鈥� is seen as 鈥渉ighly beneficial鈥� for cutting both VOCs and NOx. And more energy efficient homes should curb the use of wood-burning stoves, which have become an increasing source of air pollution in cities. Moves to far more renewable electricity generation will bring a range of air quality benefits, it adds.
The report, written by the Air Quality Expert Group for Defra, is based on one scenario of how to get to net zero, provided by the UK government鈥檚 statutory climate advisers, the Committee on Climate Change.
Robert Gross at the UK Energy Research Centre, who wasn鈥檛 involved in the work, says it is important to guard against unintended consequences, for example past policies promoted diesel cars to cut carbon emissions but inadvertently made air pollution worse. While the issue of hydrogen boilers鈥� impact on air quality is worth looking at, he says it is unlikely we should be 鈥渄esperately worried鈥� about the issue.
鈥淔or the most part, the solutions we need to be moving to net zero involve moving away from combustion-based energy conversion altogether and therefore are quite likely to have beneficial local air quality implications,鈥� he says.
In response to the report, boiler manufacturer Worcester Bosch said lab tests of its working hydrogen boiler had found NOx emissions were half those from a natural gas boiler.
A government spokesperson says: 鈥淲e are working to clean up the air we all breathe at the same time as reducing emissions to meet our landmark net zero target.鈥�
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