https://www.sciencedaily.com/releases/2021/06/210624135546.htm

"Ethane is a gas that is related only to certain sources of methane," said Zachary R. Barkley, researcher in meteorology and atmospheric science, Penn State. "Methane, however, is produced by oil, gas and coal fields, but also by cow's digestive systems, wetlands, landfills and manure management. It is difficult to separate out fossil fuel produced and natural methane."

The Atmospheric Carbon and Transport (ACT) America data made it possible to quantify methane emissions from oil, gas and coal sources, because the project measured not only methane, but also ethane. The researchers note that methane identified with ethane can be reliably connected to fossil fuel sources, however, the ratio of ethane to methane does vary with individual sources.