Quantifying Methane Emissions from Natural Gas Appliances in Single-Family Homes

Considerable research has examined methane emissions from natural gas production and distribution infrastructure, while very little research has focused on emissions of uncombusted or leaked gas after it has reached the consumer. This project aims to detect and quantify methane emissions from single-family residential homes in the Bay Area of California. We directly measure methane and carbon dioxide emissions from each major gas appliance during steady state, while both on and off, and while the appliance is turning on and off. Our methodology uses a combination of high flow sampling using a Minneapolis Duct Blaster and flux chambers coupled with a Picarro Cavity Ring-Down Spectrometer to directly measure the total volume of emissions. We scale our measured emissions based on recorded observations of typical appliance usage, which we directly measured using motor and temperature loggers. Here, we focus on the major residential gas appliances, including water heaters, furnaces, and stoves, which together account for over 90% of residential natural gas use. We found that 98% of the emissions from storage water heaters are attributed to leakage while the appliance is off (mainly from incomplete pilot light combustion) and 57% of emissions from tankless water heaters are attributed puffs of uncombusted methane that is released while the appliance turns on and off.