The St. Paul Saints are billing brand-new CHS Field as the "Greenest Ballpark in America." And while they may get an argument or two from any number of stadiums — including the big-league ballyard at the other end of the Green Line — they make a good case.

When the Saints begin their season Thursday night in downtown St. Paul, they will play in a ballpark that collects rainwater from atop a nearby building to help irrigate the field and flush toilets in the outfield restrooms.

Tree trenches and rain gardens will filter runoff before it reaches the storm sewers. An array of 300 solar panels above left field will provide 12 percent of the ballpark's electricity, enough to power the scoreboard and eight light towers.

The balance will be supplied by District Energy, the nonprofit utility that heats and cools most downtown buildings and generates electricity by burning waste wood.

And there will be "recycling umpires" at the team's first homestand, directing fans to deposit their cups and half-eaten hot dogs in specially marked bins for recyclables and organics. The goal is to recycle or compost 90 percent of ballpark waste, enough to qualify CHS Field as a "zero waste facility."

"It may be the most visible sustainable initiative that the fans experience," said Jill Curran, who directs environmental programs for the Minnesota Chamber of Commerce.

The chamber is working with the Saints, a chamber member, and the Ramsey/Washington County Resource Recovery Project to reduce waste in the ballpark.

The solar and water systems added a little more than $1 million to the cost of the $65 million ballpark project, while saving about $24,000 in annual operating costs. Most of the installations were covered by corporate and publicly funded grants.

"This is something that a lot of ballparks do, but we wanted to take it to the umpteenth degree — the rainwater cisterns, the trenches, the solar power. We wanted to do everything," Saints' spokesman Sean Aronson said. "If you can help the planet, you try to do that."

The Twins regularly boast about the sustainable elements at Target Field. The major league stadium was the second ballpark in the United States to get LEED certification, the gold standard for green development.

St. Paul didn't seek national LEED certification for CHS Field because it can cost tens of thousands of dollars. But the ballpark's construction followed Minnesota's B3 standards, which are similar to LEED's.

CHS Field was built on a former factory site heavily polluted by years of industrial use, more so than originally thought.

The St. Paul City Council was forced to approve a last-minute $6 million loan for the project to cover the increased cost of stabilizing and cleaning the soil.

But contractors were able to use some of the retaining walls and floors of the former Diamond Products/Gillette factory for the ballpark, and more than 95 percent of the structure was recycled, mostly as crushed material.

The Minnesota Chamber of Commerce and the Minnesota Composting Council will host four events at the ballpark this summer when fans can take home free compost for their gardens. The first such event will follow a Saints game on June 9.

"We're going into a neighborhood where [sustainable practices] were important to the neighbors, and we want to be a good neighbor," Aronson said. "They've paved the way already."