Biomass Feasibility Project Final Report - Xcel Energy

esidues leave energy on the table by using inefficient technologies, their power output could
grow significantly by using newer systems.
The second point is that industries processing crops instead of wood generate very little biomass
power from their wastes. In 2002, agricultural residues accounted for only 373 MWs of capacity.
That quantity may soon increase, however. The rapid growth of ethanol and biodiesel has set
the stage for more co-generation with agricultural biomass in bio-fuels plants. Fortuitously, just as
ethanol and bio-diesel are coming of age, advanced energy technologies also being
perfected.
Biomass Co-Generation in Minnesota
Unlike California, Minnesota never developed a fleet of stand-alone biomass plants. Most of
Minnesota’s biomass power is generated, as it always has been, in manufacturing plants. The
largest of these are five pulp and paper mills. They are old, well established contributors to
northern Minnesota’s economy, but not to the electric grid.
Minnesota’s ethanol plants, on the other hand, are relative newcomers to the state. The oldest
one dates from the 1990s. Ethanol has brought new income – but not new electricity – to
farmers and rural communities in southern and central Minnesota.
A third Minnesota industry, municipal power, resembles the model of a stand-alone power plant
in that it buys fuel rather than tapping an internal waste stream. But municipal plants usually cogenerate
power as as an adjunct of their established facilities. District Energy St. Paul, for
example, built America’s largest municipal biomass CHP plant by adding a large wood-fired
boiler to its existing district heating system. Recently, a joint powers authority of the Iron Range
cities of Virginia and Hibbing added wood-fired boilers to their existing municipal CHP plants. In
addition to providing power to their own cities, all three municipal plants sell electricity to Xcel
Energy.
Those three industries, paper, ethanol and municipal CHP, may provide a larger share of
Minnesota’s electrical energy in the future. But so far, ethanol is the only one making a start in
advanced, high efficiency technologies. We’ll review those three industries in their global,
national and Minnesota contexts and then focus on specific Minnesota plants that already have
developed biomass power or that show the potential to do so.
THE U.S. PULP AND PAPER INDUSTRY
Because the paper industry is global in scope, we can understand Minnesota’s industry best in its
larger setting. The paper industry is one of the largest industrial consumers of electricity in the
U.S., satisfying some of its huge needs internally by burning biomass in the form of bark, wood
and pulping wastes, and supplementing that with power purchased from the grid. At present,
generators in pulp and paper mills only displace power from the grid; they very rarely export it to
the grid.
Although they collectively represent a huge block of biomass power capacity in the United
States, present-day pulp and paper mills offer few, if any, examples of advanced energy
technologies. They rely on simple, reliable, robust direct-combustion boilers to burn rough,
unprepared and undifferentiated wood wastes in a wide range of particle sizes, moistures, and
BTU contents. In an industry whose huge capital investments -- often more than $1 billion per mill
– dictate 24/7 operation, reliability trumps efficiency. Pulp and paper mill managers don’t want
Identifying Effective Biomass Strategies: Page 73
Quantifying Minnesota’s Resources and Evaluating Future Opportunities