Biomass and alternative energy in St. Paul

Rick Person
Public Works Program Administrator
Solid Waste and Recycling
City of St. Paul, Minnesota
Member, APWA Solid Waste Management Committee

Biomass energy comes from any renewable organic matter (trees, food crops, grassy and woody plants, and residues from agriculture or forestry) that can be used as solid fuel, or converted into liquid or gaseous forms for the production of electric power, heat, or fuels. Burning biomass releases about the same amount of carbon dioxide as burning fossil fuels, but the carbon dioxide releases are balanced by the carbon dioxide captured during biomass growth.

Wood continues to be the largest biomass resource. Feedstocks for biomass fuels are primarily corn for ethanol and soybeans for biodiesel. Although not considered renewable biomass resources, municipal solid waste and methane from landfills along with wastewater treatment solids are also widely used as energy sources.

District Energy hot water district heating system
Several biomass and alternative energy projects are underway in St. Paul, Minnesota. District Energy St. Paul owns and operates the largest hot water district heating system in North America, along with a large chilled water cooling system. District Energy brings green energy to downtown St. Paul buildings from its new combined heat and power plant fueled by clean urban wood waste.

District Energy uses 300,000 tons of wood chips per year, along with natural gas, oil or clean-burning coal to fuel its district heating and cooling systems. With the startup of the new facility located on the Mississippi River, District Energy has reduced its reliance on coal and oil 80 percent and its particulate emissions by 50 percent.

President Bush visits the District Energy wood-fired combined heat and power facility.

Efficiency gains over the previous steam heating system allow District Energy to heat twice the building space with the same amount of fuel, and the closed-loop distribution system has eliminated the use of groundwater for heating and cooling. In summer, the district cooling system uses two tanks which store chilled water at night, using off-peak electricity for daytime distribution to customers.

District Energy systems offer many environmental benefits. They increase energy efficiency; reduce greenhouse gas emissions and other pollutants; decrease emissions of ozone-depleting refrigerants; enhance fuel flexibility; facilitate the use of renewable energy; help manage the demand for electricity; and in St. Paul help the community solve a wood waste disposal problem.

Buildings connected to District Energy do not need hundreds of boilers and auxiliary equipment used in the past, freeing up valuable space. Each building needs only a heat exchanger and control valve, which transfer thermal energy from the district system to the building's heating and cooling systems. The water is then returned to District Energy's plant to be reheated or rechilled and circulated once again to buildings connected to the system.

District Energy's system provides heating and/or cooling service to more than 170 buildings and 300 single-family homes, representing over 29 million square feet of building space, or 80 percent of St. Paul's central business district and adjacent areas.

District Energy is continuing to expand its service area beyond downtown every year. For example, District Energy is currently partnering with Rock Tenn paper recycling plant in St. Paul's Midway district, Ramsey County, the City and Port Authority, the Green Institute and Eureka Recycling to study the feasibility of building a second biomass-fired combined heat and power plant in St. Paul near Rock Tenn.

B20 biodiesel fuel is used in all of Eureka Recycling's collection vehicles.

City and Eureka Recycling flexible fuels programs
Beginning in April 2006 the Department of Public Works fleet of 55 flexible-fuel Ford Tauruses, driven by several of the City's departments, is phasing into fueling up with E85 (85 percent ethanol blend fuel) at the University of Minnesota St. Paul Campus, paying a competitive price for the fuel. The City is installing its own tank for E85 in 2007, and phasing into higher mileage Ford Focus sedans and light trucks over time.

Besides the E85 vehicles, Public Works' diesel trucks started running on B10 last summer—fuel containing 10 percent biodiesel. The diesel fleet will phase into using B20 during 2007-2008. The fleet burns B5 during the winter months.

When Eureka Recycling, nonprofit recycling contractor for the Cities of St. Paul, Roseville, Maplewood, and Lauderdale, launched its fleet of 20 recycling trucks in 2004, the decision to fuel with B20 biodiesel was a natural. The biodiesel in Eureka's fleet replaces 12,000 gallons of petroleum-based fuel with 216 acres of soybeans annually. Eureka received a grant from the Minnesota Lung Association Clean Cities Coalition to launch the program.

The Ford Dam provides 18 megawatts of clean power to the Ford Assembly Plant.

Ford Plant Hydroelectric Dam
The promise of cheap hydropower was the chief reason Henry Ford agreed to build an assembly plant in St. Paul. Ford Motor Company's Twin Cities Assembly Plant is located on the Mississippi River in the Highland Park neighborhood. It is the oldest Ford plant still in operation, built in 1924. The company-owned hydroelectric dam was built in 1917, making it one of the oldest on the Mississippi. For many years, the soft sandstone underneath the dam was mined to make window glass.

The plant runs on 18 megawatts of clean power from the dam, resulting in significant savings in cost and fuel usage. Excess power generation connects to the Xcel Energy electric power grid. The dam is currently up for sale due to the impending closure of the Ford Plant, and will likely be retrofitted to generate more power in the future. The entire Ford Plant site will be redeveloped into an "eco-community."

Metropolitan Wastewater Treatment Plant
The Twin Cities are reaping the benefits of a new $160 million project at the Metro Wastewater Treatment Plant located on the Mississippi River near downtown St. Paul that reduces pollutant emissions, cuts fuel consumption and lowers operating costs. The project was planned and developed by Metropolitan Council Environmental Services (MCES), a division of the Metropolitan Council. Each day the Metro Plant treats 215 million gallons of wastewater from throughout the seven-county metro area.

The new solids management building includes three fluidized-bed incinerators that replace an outdated system. The combined heat and power facility uses 82 percent less natural gas than the old incinerators, saving $3 million a year. The electric generator produces an average of three megawatts, enough to meet 20 percent of the plant's power demand and save $600,000 annually in avoided electricity costs. MCES also received a one-time energy rebate from Xcel Energy of $1.06 million.

Enhanced air pollution control equipment removes greater amounts of particulates, heavy metals, carbon monoxide, nitrogen and sulfur oxides, achieving upwards of 90 percent reduction from previous emission levels. Odors are also better contained and neutralized.

Rick Person can be reached at (651) 266-6122 or rick.person@ci.stpaul.mn.us.