Minnesotans are looking for a biomass revival—a combination of the growing movement toward decarbonization, expectations of continued high natural gas prices, and the need to better manage the state’s forest resources.
The St. Paul utility’s use of woody biomass is based more upon providing an outlet for urban waste wood than meeting the state’s renewable power standard, so it survived the policy shifts. The facility, launched in the mid-1980s, began cofiring wood chips with coal in 1997 to provide heating and cooling to St. Paul’s downtown area through District Energy St. Paul. Cogeneration was added in 2003. The system generates 33 MW of electricity and provides heating and cooling for 33 million square feet of building space, which includes the state capitol grounds, downtown offices and businesses, hotels and residential properties.
Today, woody biomass comprises about 50% of the boiler fuel, followed closely by natural gas. Fuel oil serves as a backup and a large solar thermal array supplies about 1% of the annual energy load. Coal is no longer used. The goal is to decarbonize entirely by 2050, says Ken Smith, CEO of Ever-Green Energy, the District Energy St. Paul subsidiary that manages St. Paul’s system along with nine others in five states.