District Energy St. Paul, the nonprofit downtown power plant known for its sustainable practices, plans to stop burning coal entirely by the end of the 2020-21 heating season, officials said Wednesday.

The move is being made not because of any mandate but to reduce greenhouse gases and because there are more alternative resources to fill the void left by coal, said Ken Smith, District Energy's CEO and president.

Eliminating coal would reduce District Energy's carbon dioxide emissions by 27 percent, which is the same as taking 4,400 cars off the road annually.

"This has been a conversation we've had at our board of directors over time," Smith said. "We set a goal to end it and we're planning toward that, and we've established a schedule to meet that goal."

He added that District Energy will complete a transition away from coal that reaches back more than 30 years, when the plant began as a 100 percent coal-burning facility.

Today the plant is fired mostly by waste wood, a renewable energy source, with assists from natural gas, fuel oil and coal in the winter months. The wood comes from such sources as trees, pallets and carpentry scraps.

Smith said that waste wood generates 35 to 60 percent of the plant's energy over a year's time, with coal accounting for 20 to 30 percent, depending on how cold winter gets.

To replace coal, plant officials will consider increasing natural gas usage and capturing waste heat from local sewage systems.

Smith said that he didn't anticipate that dropping coal would result in a big rate hike. Most increases have been below the rate of inflation, he said, and District Energy is coming up on its fifth straight year without a rate increase.

"We'll look at the most economical solutions, and we'll continue to have a mix of energy sources," he said.

District Energy provides heated and chilled water to most of downtown St. Paul, including the state government complex, large employers such as Ecolab, and the convention area surrounding Xcel Energy Center. Using a variety of energy sources has helped maintain reliability while keeping customer costs stable.

The plant comprises the largest hot water energy system of its kind in North America, and has been visited by officials from other cities and countries looking to do the same.

Kevin Duchschere • 651-925-5035