How to clean up a lake? Floating islands might be the answer.

Bruce Kania built his large home atop a bluff with an expansive view of the Yellowstone River, which flows past on its 670-mile journey from Yellowstone National Park to its confluence with the Missouri River.

Mr. Kania moved here a decade ago to enjoy the natural setting. But he soon began to worry about the surface water draining into the Yellowstone. Kania’s black dog went for a swim one day in a pond on his property, and the dog came out of the water covered in slime.

“You could smell him from 50 feet away,” Kania said.

The experienced inventor got to thinking about water quality. Irrigation ditches divert clean water from the Yellowstone. The ditches feed pastures and fields, and what is left drains back into the river. Beef cattle roam the land. In the nearby town of Shepherd, a giant feedlot produced tons of manure every day.

Where some saw pollution, Kania saw nutrients.

“It became apparent that this represented a terrific opportunity for somebody,” he said. “What can be done with those nutrients?”

The answer is floating bio-islands.

In his college days, Kania had been a fishing guide in northern Wisconsin. There, he saw giant natural floating islands that had grown over generations, big enough to support trees. These areas had huge muskellunge, prized sport fish, and Kania thought the islands were one reason. They scrubbed the water clean and provided the forage that grew big fish.

In Montana, Kania decided to produce man-made floating islands that could do the same. They’re constructed of layers of mesh and insulating foam. The mesh feels like the rough side of a sponge: The bigger islands are buoyant enough to hold people.

Most are at least 25 square feet, and the least expensive costs around $600. They’re topped with soil and seeds and then launched in lakes and ponds. The islands act like magnets for microbes, and the seeds sprout into vegetation that pulls nitrogen, phosphorus, and other nutrients that cause slime from the surrounding water, cleaning it and allowing aquatic life to flourish.

Kania shows off pictures of giant perch that his employees have caught in test ponds on his property. The perch’s bellies were full of snails, which Kania thinks consume the vegetation growing from the islands, which he calls “floating supermarkets.”

Kania, a tall, bearded man who moved to Montana in 1976, has turned his invention into a business called Floating Islands International. He has about a half-dozen employees and is now licensing the islands to companies that will make them full time.

That leaves time for Kania to get back to inventing. “Our license holders do the hard work of manufacturing,” he says. “We do the fun work of invention.”

The mesh for the islands is made from recycled plastic bottles and comes in wide black rolls. Each island consists of several layers, which are stacked before a worker shoots expanding foam between the layers. When the foam dries, the layers are locked together.

1 | 2

Next