The Xcel Energy Center and RiverCentre are certified in three major international sustainability standards, making the downtown St. Paul complex the first in the world to attain such comprehensive validation.

The three independent environmental organizations -- Green Globes, LEED and APEX/ASTM -- evaluate the sustainability of building design and events all over the world. Each certification requires a comprehensive audit of specific practices and building operation, according to a release from complex management.

"It's certainly not the finish line," Jim Ibister, the general manager of the St. Paul RiverCentre said in a release. "We want to continue making progress and share what we've learned to help others."

In 2009, the complex's annual recycling rate was 15 percent. Now, the rate is more than 60 percent of the two million pounds of waste generated on average each year.

Beyond specific management practices that increase sustainability, fixtures and equipment in the RiverCentre and Xcel Center have been upgraded over the years, and RiverCentre's rooftop solar thermal array was the first in U.S. to integrate solar thermal into a district heating system.

Xcel Energy Center opened in 2000; the RiverCentre in 1998 and the accompanying Legendary Roy Wilkins Auditorium was built in 1932.