Household gas use much worse for health and climate than first thought

The amount of air pollution and greenhouse gas emissions produced by residential gas appliances are substantially larger than previously thought, with new research finding that most gas stoves continue to leak gas even when turned off.

A new academic paper published by researchers from Stanford University found that due to the higher than expected levels of pollution, the health and environmental impacts of the use of gas stoves were also much worse than previous studies had suggested.

The results of the latest study have been published in the journal Environmental Science and Technology, and examined the emissions produced by 18 brands of gas cooktops and stoves across a wide range of appliance ages.

The researchers found that an estimated 1.3 per cent of fossil gas used in household stoves is released into the environment as unburnt methane.

Methane, which is the main constituent of fossil gas, is a potent greenhouse gas with a global warming potential that is 28 times greater than carbon dioxide over a 100-year period.

The researchers also monitored the amount of gas released by gas appliances when they are turned off, leading to the “surprising” discovery that around three-quarters of the methane released by stoves resulted from gas escaping through fittings and connections.

“There are very few measurements of how much natural gas escapes into the air from inside homes and buildings through leaks and incomplete combustion from appliances,” study lead author Eric Lebel from Stanford’s School of Earth, Energy and Environmental Sciences, said.

“It’s probably the part of natural gas emissions we understand the least about, and can have a big impact on both climate and indoor air quality.”

Previous studies had generally overlooked gas that escaped from appliances when they were not being used, which the researchers suggest has led to a significant underestimate of the emissions released by household gas appliances.

“We quantified steady-state-off emissions from stoves because they were not included in most previous cooktop emissions studies and because, previously, we found steady-state-off emissions to be a substantial, sometimes dominant, component of total methane emissions from storage water heaters,” the study says.

The paper suggests that because the amount of methane release while stoves are not being used has not previously been measured in detail, the amount of residential greenhouse gas emissions may have long been underestimated.

Using the United States as an example, the study estimated that the greenhouse gas emissions footprint of residential gas stoves from use and through the leakage of gas was the equivalent of 500,000 petrol-fuelled cars.

The study also found that gas stoves were responsible for the release of significant levels of other air pollutants into homes, including nitrous oxides, noting that the appliances were somewhat unique for releasing exhaust gases directly into living spaces.

“Among all gas appliances, the stove is unique in that the by-products of combustion are emitted directly into home air with no requirement for venting the exhaust outdoors,” the study says.

“In fact, some kitchens have “ductless” hoods that recirculate fumes through activated charcoal filters, which are generally less effective at cleaning the air.”

The US-based study found that households that use gas stoves without a rangehood or with poor ventilation could surpass Environmental Protection Agency guidelines for exposure to nitrogen dioxide.

Senior author of the study, Rob Jackson of Stanford University’s Earth System Science department, said there needed to be some consideration of how these risks can be eliminated.

“I don’t want to breathe any extra nitrogen oxides, carbon monoxide or formaldehyde,” Jackson said.

“Why not reduce the risk entirely? Switching to electric stoves will cut greenhouse gas emissions and indoor air pollution.”

Gas companies have gone to great lengths to convince people that they should prefer using gas stoves for cooking, even commissioning Instagram influencers to promote using gas to their followers.

Electric stoves, including induction hotplates, provide a gas-free alternative that can avoid the release of methane and other pollutants into people’s homes and be entirely emissions-free when powered by renewable electricity.

Last year, a report published by the Climate Council detailed how residential gas use was estimated to be responsible for around 12 per cent of the childhood asthmas burden, finding the health risk for children was comparable to living in a household with cigarette smoke.