greater than previously thought
Study estimates that methane leaking from stoves inside US homes has the
same climate impact as about 500,000 gasoline-powered cars and the stoves can expose people to respiratory disease-triggering pollutants

Date:
January 27, 2022
Source:
Stanford University
Summary:
Natural gas stoves release methane -- a potent greenhouse
gas -- and other pollutants through leaks and incomplete
combustion. Researchers estimate that methane leaking from
stoves inside U.S. homes has the same climate impact as about
500,000 gasoline-powered cars and the stoves can expose people to
respiratory disease-triggering pollutants.



FULL STORY ========================================================================== Humans have cooked with fire for millennia, but it may be time for
a change.

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. A new Stanford-led study reveals that the methane leaking
from natural gas- burning stoves inside U.S. 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 findings, published Jan. 27 in Environmental Science & Technology,
come as legislators in numerous U.S. municipalities and at least one state
-- New York -- weigh banning natural gas hookups 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, who conducted the research as a graduate student in 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."
An overlooked contributor to a growing problem 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 U.S. 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.

Findings and implications To better understand cooking appliances'
potential climate and health impacts, the researchers measured methane
and nitrogen oxides released in 53 homes in California, not only during combustion, ignition and extinguishment, but also while the appliance
was off, something most previous studies had not done.

Their study included 18 brands of gas cooktops and stoves ranging in
age from 3 to 30 years.

The highest emitters were cooktops that ignited using a pilot light
instead of a built-in electronic sparker. Methane emissions from the puffs
of gas emitted while igniting and extinguishing a burner were on average equivalent to the amount of unburned methane emitted during about 10
minutes of cooking with the burner. Interestingly, the researchers found
no evidence of a relationship between the age or cost of a stove and its emissions. Most surprising of all, more than three-quarters of methane emissions occurred while stoves were off, suggesting that gas fittings
and connections to the stove and in-home gas lines are responsible for
most emissions, regardless of how much the stove is used.

Overall, the researchers estimated that natural gas stoves emit up
to 1.3 percent of the gas they use as unburned methane. While the
U.S. 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.

Larger stoves tended to emit higher rates of nitric oxides, for
example. Using their estimate of emissions of nitrogen oxides,
the researchers found that people who don't use their range hoods or
who have poor ventilation can surpass the EPA's guidelines for 1-hour
exposure to nitrogen dioxide outdoors (there are no indoor standards)
within a few minutes of stove usage, particularly in smaller kitchens.

"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." Jackson is
also a senior fellow at the Stanford Woods Institute for the Environment
and the Precourt Institute for Energy. Lebel is currently a senior
scientist at PSE Healthy Energy. Study co-authors also include Colin
Finnegan, an environmental science research professional in Earth system science, and Zutao Ouyang, a postdoctoral scholar in Earth system science.

special promotion Get a free digital "Metabolism Myths"
issue of New Scientist and discover the 7 things we
always get wrong about diet and exercise. Claim_yours_now_>>> ========================================================================== Story Source: Materials provided by Stanford_University. Original written
by Rob Jordan.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Eric D. Lebel, Colin J. Finnegan, Zutao Ouyang, Robert B. Jackson.

Methane and NOx Emissions from Natural Gas Stoves, Cooktops, and
Ovens in Residential Homes. Environmental Science & Technology,
2022; DOI: 10.1021/acs.est.1c04707 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220127104316.htm

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