All across the U.S., there are aging oil and natural gas wells no longer in use.A lot of them don't have anyone on the hook to seal them up. Some estimate over a million such "orphan wells" still exist.Because they haven't been plugged, they're still leaking greenhouse gases and other chemicals into the atmosphere and into the land around them.What would it take to plug them — or even just one of them?For sponsor-free episodes of Consider This, sign up for Consider This+ via Apple Podcasts or at plus.npr.org.Email us at [email protected] more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy