It's a beautiful Sunday in a Colorado park. The birds are chirping, a creek flows softly through the woods, and just off the trail sit piles of dog poop.

Nine years ago, Bill Airy ran into a scene like that at a Denver park, and it struck a nerve.

"I was sick and tired of people leaving their dog poop behind in the park," he said.

He called the city about it, and didn't like what he heard.

"The Park said the city couldn't afford to pay for it through tax payers money, so I thought why not find advertisers to pay for it,” Airy said.

So he did.

That was the genesis for Poo Free Parks, Airy's business installing and maintaining dog poop bag stations. He came up with the idea when he noticed other stations would sit bag-less for weeks at a time.

Airy decided he'd install and refill the stations, and while some cities did subsidize maintenance, the bulk of the profits came from selling space to advertisers.

“Right now we've got over 1,000 of these throughout Colorado another couple thousand throughout the United States," he said.

A proprietary app made for the company spits out numbers that say Poo Free Parks dog bags are responsible for removing about 5 million pounds of dog waste since Airy founded the business.

If people picked up their own dog's poop, Bill would have never had this business.

Now all that is someone else's job. Airy sold the company for an undisclosed price in early May.

"It was time to turn it over to a group of individuals who are specialized and can grow it larger," he said.

He says that group plans on expanding the business.