New Methane Research

ICRT Research

In January 2022, a journal article, Methane and NOx Emissions from Natural Gas Stoves, Cooktops, and Ovens in Residential Homes[1], was published by researchers at Stanford University. The researchers claim that ~30,000 tons of methane are emitted annually by natural gas stoves in the US, which equates to a greenhouse gas (GHG) impact of ~500,000 cars, and more than 75% of those emissions occurred while the stove was off and not conducting any useful cooking work. This paper cited previous research[2] conducted by the Illinois Applied Research Institute’s Indoor Climate Research and Training (ICRT) group. ICRT found comparable emissions of unburned methane while cooking appliances were in use, but did not investigate standby leakage.

The Lebel et al. research calculated that gas cooking appliances in the U.S. emit ~31,000 tons of methane annually, including emissions from incomplete combustion and from quiescent leakage. The ICRT research calculated that methane emissions from all gas appliances was ~33,000 tons, only considering in-use operation (excluding any pilot lights or quiescent emissions). Each of these emissions estimates correspond to ~0.01% of US GHG emissions when using the US EPA’s 25x CO₂-equivalence and their 2019 emission inventory[3].

The new research suggests that a large portion of methane emissions from gas cooking is not from the appliances themselves, but rather from leaks in the distribution system within homes, and noted that a small percentage of leaks might be responsible for a disproportionately large quantity of emissions (~10% of the stove accounted for ~50% of the total leakage). If homes with these leaks could be identified and the leaks were easily located and accessed, fixing them could be a cost effective way to both reduce emissions and improve household safety.

For people who currently have or prefer to use gas stoves, there are steps they can take to make sure their stoves are burning as cleanly as possible. Stoves with steady blue flames are burning well and producing minimal harmful emissions (aside from unavoidable CO2 and water vapor). If the flames show a lot of orange or sound like they are gusting, it means that the air fuel mixture is not optimal and lots of incomplete combustion is occurring which increases the generation of harmful pollutants like carbon monoxide (CO), nitrogen oxide (NOx), and unburned methane. People can help their stove perform better by keeping the surface and the burners clean, making sure the burner caps are centered and well seated, and fixing any issues with the ignitors if the stove is not lighting quickly or completely. If you can smell a gas leak in your house you should contact your gas company and/or the fire department, and any identified leaks should be repaired by a qualified plumbing or HVAC professional.

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