The National Park Service recommends that hikers and campers carry bear spray when venturing into grizzly country, and with millions of park visitors each year — more than 3 million annually to Yellowstone alone — all those bear spray canisters add up.

Bear spray isn’t allowed on commercial flights, so numerous cans are typically discarded in and around parks — often improperly.

Capsaicin, the active ingredient in bear spray, is a strong irritant to the eyes, nose, mouth, throat and lungs, so the spray should be disposed of as hazardous waste. However, while many parks have collection bins, plenty of canisters end up in regular trashcans, which can cause serious problems.

In addition to the environmental issue of waste and chemicals piling up in landfills, if a forklift or other heavy machinery runs over a bear spray canister at Yellowstone’s composting facility, the building must be evacuated for several hours.

bear spray

Bear spray is a non-lethal bear deterrent that's designed to stop aggressive behavior in bears. (Photo: Ben Gregory/flickr)

To combat these problems, in 2011, Yellowstone implemented the first bear-spray recycling program with the help of Montana State University.

A group of engineering students built a device that allows the canisters — even full, unused ones — to be emptied and crushed. It removes the chemical that burns bears’ eyes and mucus membranes, as well as the refrigerant that enables the spray to shoot from the canister, and the machine crushes the cans so they can recycled.

The entire process takes 30 seconds.

In its first year, the recycling program collected 2,022 canisters, resulting in 210 pounds of aluminum, .4 cubic yards of plastic and 48 gallons of pepper oil, which Yellowstone is able to reprocess and reuse.

These days, collection is a bit slower, with Yellowstone amassing 300-500 canisters a year at collection sites located throughout the park, surrounding national forests and local retail outlets.

“Collection seems to have slowed probably because when we started the program people could get rid of all of the old bear spray they had been storing,” said Molly Nelson, a civil engineer at Yellowstone.

Currently, the park is working with MSU to improve its student-designed machine and make the process of recycling bear spray more efficient.

And so you have it, here's a complete list of bear spray canister-collection sites in Yellowstone.

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