Gas stoves can release methane even when not in use, a new study shows (Environ. Sci. Technol. 2022, DOI: 10.1021/acs.est.1c04707). Three-quarters of methane emissions from cooktops evaluated in the study occurred when the gas ranges were unlit. The emissions were from either leaks or incomplete burning of the greenhouse gas. Eric Lebel and colleagues at Stanford University estimate that methane escaping from 40 million–plus US homes with gas cooktops has the same annual climate impact as the carbon dioxide emissions of 500,000 cars.
When turned on, stoves also emit harmful nitrogen oxides (NOx), the researchers found. In small kitchens with poor ventilation and exhaust fans off, NOx concentration could quickly pass 100 ppb, the hourly outdoor exposure limit for nitrogen dioxide set by the US Environmental Protection Agency.
The researchers measured emissions from stoves of various brands and ages in 53 California homes. They sealed the space around the stove and took measurements when the stoves were not lit, being turned on and off, and burning continuously. They scaled their findings using a national survey’s data on gas use to estimate that total US methane emissions are 28 billion g/year.
“In terms of NOx emissions, make sure you turn the hood on every time the burner is on,” Lebel says. Switching to electric stoves could curb methane emissions. Methane’s global warming potential can be 86 times as high as that of CO2. Yet while leaks from oil and gas pipelineshave captured attention, emissions from buildings are largely ignored, he says. “Limiting methane emissions even at these small levels is important to address climate change.”