University researchers have said the world should seriously consider an end to cooking with natural gas as at least one US state moves towards a ban on gas systems in new buildings.
The team from Stanford University said while humans have cooked with fire for millennia, now may be the time for a change. They said natural gas appliances warm the planet in two ways: generating carbon dioxide by burning natural gas as a fuel and leaking unburned methane into the air.
The study found the methane leaking from natural gas-burning stoves inside US homes has a climate impact comparable to the carbon dioxide emissions from about 500,000 gasoline-powered cars.
This extra warming from home methane leaks contributes about a third as much warming as the carbon dioxide generated by combustion of the stove’s natural gas, and sometimes exposes users to respiratory disease-triggering pollutants. The study comes as legislators in numerous US municipalities and the state of New York weigh banning natural gas hook-ups from new construction.
“Surprisingly, 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,” said study lead author Eric Lebel, from Stanford’s School of Earth, Energy and Environmental Sciences (Stanford Earth). “It’s probably the part of natural gas emissions we understand the least about, and it can have a big impact on both climate and indoor air quality.”
The study said although carbon dioxide is more abundant in the atmosphere, methane’s global warming potential is about 86 times as great over a 20-year period and at least 25 times as great a century after its release. Methane also threatens air quality by increasing the concentration of tropospheric ozone, exposure to which causes an estimated 1 million premature deaths annually worldwide due to respiratory illnesses. Methane’s relative concentration has grown more than twice as fast as that of carbon dioxide since the beginning of the Industrial Revolution because of human-driven emissions.
While pipeline leaks of natural gas, which is more than 90 percent methane, have been studied extensively, natural gas-burning cooking appliances have received comparatively little attention.
Over one-third of US households, more than 40 million homes, cook with gas. Unlike other gas appliances, such as space and water heaters that are usually placed away from living quarters, cooking appliances directly expose people to their emissions, which can include formaldehyde, carbon monoxide and nitric oxides that can trigger asthma, coughing, wheezing and difficulty breathing, occasionally resulting in hospitalization. Hood use and ventilation help reduce concentrations of nitrogen oxides and other co-produced pollutants in kitchen air, yet surveys show that home cooks on average use hoods for kitchen ventilation only 25–40 percent of the time.
Overall, the researchers estimated that natural gas stoves emit up to 1.3 percent of the gas they use as unburned methane. While the US Environmental Protection Agency (EPA) does not report emissions from specific residential natural gas appliances, it does report methane emissions for residential appliances collectively. From stoves alone, the researchers estimated total methane emissions to be substantially more than the emissions currently reported by the EPA for all residential sources.
“I don’t want to breathe any extra nitrogen oxides, carbon monoxide or formaldehyde,” said study senior author Rob Jackson, the Michelle and Kevin Douglas provostial professor and professor of Earth system science. “Why not reduce the risk entirely? Switching to electric stoves will cut greenhouse gas emissions and indoor air pollution.”