District Energy of St. Paul, which heats and cools about 500 commercial-and-residential buildings in and around downtown, has turned off the coal spigot.
The move was made for economic as well as environmental reasons.
District Energy gradually moved from 100 percent coal in 1983 to heat and cool customers to a recent mix of 50 percent waste wood, 30 percent natural gas and 20 percent coal. It quit coal last Friday.
As a result of the transition, including more efficient boilers, carbon emissions have declined over the years. And the move to half-and-half waste wood plus natural gas, as well as some new burners and controls, will further reduce pollution.
CEO Ken Smith said nonprofit District Energy will invest about $5 million in new, efficient burners and other equipment, financed by 20-year, low-interest bonds that will be paid back from the expense savings over time.
"Coal was our highest-priced fuel in terms of price per million British thermal units," he said. "About a third higher than our wood-natural gas mix. The payback will be less than 20 years."
Natural gas only emits 50-to-60 percent of the carbon dioxide that does coal.
Between 2000 and 2017, District Energy reduced carbon emissions for the heating system by 57 percent, mostly through the integration of the biomass-fired combined heat and power plant and systematic reduction in coal usage. Eliminating the use of this fuel reduces the heating system's CO2 emissions an additional 16 percent or 10,000 tons per year.
This is the same as removing 2,100 cars from the road each year, Smith said.
"District Energy is in the process of setting new, ambitious sustainability goals that will continue to advance the system and further reduce our CO2 emissions," Smith said Monday.
Nonprofit District Energy, with $33 million in 2018 revenue, employs 45 people.
