Gas Leaks Are Designed To Attract Turkey Vultures

Carry on, carrion birds

Turkey Vulture

Turkey Vulture

U.S. Fish and Wildlife Service Headquarters

There are things beyond human perception. Beyond that, we have to rely on tools to understand the world around us. It’s why we use infrared cameras to look for heat far away, or employ bomb-sniffing dogs to check for hidden drugs. And it’s why, when it comes to natural gas leaks, we might just turn to turkey vultures circling overhead, their avian senses finely attuned to an otherwise imperceptible danger.

Let me back this up. In October, a leak in an underground pipe north of Los Angeles started spewing methane into the air above the city. Methane is an extremely potent greenhouse gas, and it's troubling even when released naturally from seafloors. It's less studied than carbon dioxide, though that's changing, and scientists are working on new storage solutions. The California leak is from a storage facility, which means the normally odorless gas has had an odorant added to alert humans of its presence.

The smell is described as ""rotten-egg," "garlicky," or "skunk-like"" by the Los Angeles County Public Health Department, which further clarified in a fact sheet that the gas:

can be irritating to the eyes, skin, and respiratory system at low levels. In this incident, the levels are so low they can escape detection by most monitoring equipment, however individuals are capable of detecting these odors. These low level exposures may cause eye, nose and throat irritation, coughing and nasal congestion, shortness of breath, nausea, stomach discomfort, dizziness, and headaches.

That’s not pleasant for anyone involved, and there has to be a better way than nausea for humans to find out there’s a leak going on. The putrid smell, it seems, has a secondary role. What’s gross to humans is enticing to turkey vultures.

As Geoff Manaugh writes at BLDGBLOG, this was deliberate.

It was thus interesting to read last night that the noxious smell artificially introduced to otherwise odorless natural gas was originally added, at least partially, because it would attract turkey vultures. In a 1964 paper by Kenneth E. Stager called “The Role of Olfaction in Food Location by the Turkey Vulture” (PDF) we read that the “decision to conduct field tests with ethyl mercaptan (CH3CH2SH) as an olfactory attractant [the odorant added to methane] for turkey vultures came as a result of conversations with field engineers of the Union Oil Company of California.” Its purpose would be “to aid in locating leaks in natural gas lines.”

Thus, Manaugh concludes, we have the strange weirdness of a natural gas artificially given the scent of death. Perhaps, if one sees turkey vultures circling overhead and cannot see any animal corpses nearby, the rotten flesh they’re looking for instead is that of our overheating world itself.

If, instead, we want to rely on cameras and not vultures to see the gas, that methane leak looks like a damned chimney in infrared: