The Massachusetts-based, nonprofit organization OpenBiome is willing to pay healthy individuals for feces donations.

The organization has been processing and shipping loads of feces samples around the United States since 2013. It turns out that healthy human feces can be used to treat Clostridium difficile, which is a bacteria that causes inflammation of the colon. The bacteria can cause extreme gastrointestinal distress to the point that some patients cannot leave their homes. The typical treatment administered to these patients is a round of antibiotics, but the treatment isn’t always effective for long.

However, there is another, less traditional treatment option. Introducing healthy fecal matter into the stomach of a patient, by way of endoscopy or capsules, can kill Clostridium difficile permanently. Finding a donor is a difficult process and desperate patients often treat themselves with the feces of friends or family. That’s where OpenBiome comes in. The nonprofit has opened the first nationwide bank for feces donations.

So far, they’ve shipped about 2,000 treatments to 185 hospitals around the country, according to the Washington Post.

The nonprofit will pay for healthy poop: $40 for each sample plus a $50 bonus for donors who come five times a week. That totals up to $13,000 a year.

This entices plenty of volunteers, but there’s a rigorous screening process before one can become a donor. Only 4 percent of the last 1,000 applicants were accepted after the health screenings and stool tests. The screening process can cost up to $5,000, so OpenBiome wants to keep their donors for as long as possible.

Fortunately, most of the donors seem to be in it for more than the money.

“Everyone thinks it’s great that they’re making money doing such an easy thing,” said co-founder Carolyn Edelstein to the Washington Post. “But they also love to hear us say ‘Look, your poop just helped this lady who’s been sick for nine years go to her daughter’s graduation.'”

For now, the fecal matter is only useful for treating Clostridium difficile. However, OpenBiome is currently providing samples to several trials exploring further uses.

“There’s a lot of promise in other conditions,” said co-founder Mark Smith to the Washington Post. “But also a lot of hype. Treating C. difficile is a bit less sexy, but that’s the one area where we know this works.”