Gas stoves emit significant amounts of methane when they’re lit and even when they’re off, according to a recent study that adds to a growing discussion about the effects gas-fired appliances have on human health and climate change.
Based on measurements of stoves, ovens and grills used in 53 California homes, the small study estimated that stoves emit, in the form of unburned methane, a potent greenhouse gas, between 0.8% and 1.3% of natural gas they consume. Over the course of a typical year, three-quarters of these emissions occur when appliances are turned off, the study showed, suggesting the possibility of leaks in home connections or street gas connections.
The study estimated that over a 20-year period, emissions from stoves in the United States could have the same planet-warming effect as half a million gasoline-powered cars.
“People are very attached to the stove,” said Eric D. Lebel, a scientist at the PSE Health Energy research institute and lead author of the study, published Thursday in the journal Environmental Science & Technology. “Preparing food on a gas stove or over an open flame is very human.”
But, he said, more and more evidence indicates that stoves “are harming health and the climate at the same time.”
A growing number of American cities, particularly in Democratic-majority states like California and Massachusetts, are moving away from using gas in kitchens and home heating.
Last month, the New York City government banned the use of gas in all new buildings. But at least 20 Republican-dominated states have banned municipalities from limiting gas use. In many cases, states have received support from natural gas companies and utilities who see electrification as a threat to their profit margins.
In 2015, the last year for which there are detailed data from government polls, there were more than 40 million gas stoves in American homes. Homes and buildings are responsible for an estimated 13% of the country’s greenhouse gas emissions.
Methane is the main component of natural gas and, if not burned when it is released, it can heat the Earth 80 times more than the same volume of carbon dioxide over a 20-year period. Methane also contributes to tropospheric ozone pollution, which can cause breathing difficulties and other health problems.
In recent years, methane leaks from oil and gas facilities have attracted increasing attention, and efforts are being made to shut down thousands of inactive oil and gas wells across the country that emit methane. But emissions from inside homes haven’t been similarly researched, said Rob Jackson, a Stanford University geoscientist who was involved in the new study.
Lebel, Jackson and two co-authors used plastic sheeting to seal off kitchens in private homes, Airbnb rental properties, and properties offered for sale or rent. They found that lighting a gas stove burner on average emits the same amount of methane as leaving the burner on for ten minutes. Gas ovens emit more methane than stove tops, they found, because the ovens turn their main burners on and off periodically to maintain the desired temperature.
The researchers also measured emissions over periods of five to ten minutes while the stoves were off. But they did not try to identify the sources of the gas leaks.
“Methane leakage is an inevitable by-product of the natural gas supply chain,” Jackson said. “Every connection, every pipe, has the potential to leak, especially over time as stoves stay in homes for years.”
Lebel said none of the gas leaks measured by the researchers reached a concentration that could trigger explosions.
The researchers found that, in terms of methane emissions, the performance of older stoves did not differ from that of newer appliances. And more expensive models performed no better than cheaper ones.
But they admitted that they would have liked to have tested more in the homes of people who can’t afford to maintain or replace old appliances. That would help them get a better idea of ​​the disproportionate effects of gas emissions on low-income households, they said.
Atmospheric levels of methane have been rising sharply in recent years, and scientists don’t really understand why, said Kathryn McKain, a researcher at the National Oceanic and Atmospheric Administration’s Geosystem Research Laboratory.
More methane appears to find its way into the air than can be attributed to gas consumption on land. For McKain, home appliances are “just one piece of the puzzle.”
Translation by Clara Allain
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Source: Folha
