Elk River Powerplant turns dirty garbage into
clean energy
 |
| A fuel handler unloads a truck of refuse-derived
fuel to burn at Great River Energy’s Elk River Station.
The waste-to-energy powerplant recently tested a heat-processed
feedstock that could significantly reduce its maintenance
costs. (Photo courtesy of Great River Energy) |
Taking out the trash was cause for celebration
last December when Great
River Energy’s Elk River power station converted its
4 millionth ton of solid municipal waste to electricity.
At a party held earlier in the fall to
mark the milestone, the public, community leaders and other
supporters toured the waste-to-energy facility and enjoyed exhibits,
refreshments and a special program. “We wanted the people
who were instrumental in the station’s success to share
in the achievement,” said Wayne
Hanson, Great River Energy’s Minnesota generation
manager.
Great River Energy supplies power to 28
cooperatives in Minnesota and Wisconsin, including several Western
customers. Hanson operates and maintains existing, state-based
generation sources for the Minnesota generation and transmission
cooperative, 32 MW of which Elk River Station generates. That’s
not a huge power source, Hanson admits, but it is one that now
qualifies as a renewable resource.
“We worked with several county groups to get the state
legislature to recognize waste-derived fuel as a renewable resource
like solar, wind and biomass,” he explained. “The
statute passed last year,” he added proudly.
Landfill restrictions create
new fuel source for old powerplant
The municipal waste stream may conjure a less aesthetically
pleasing image than solar or wind energy, for example. However,
it is hard to argue with the wisdom of turning something we
will always have (trash) into something we will always need
(electricity). This is especially true of the Elk River Station,
which diverts 300,000 tons of trash annually from landfills
in Anoka, Benton, Hennepin, Stearns and Sherburne counties.
Only 20 percent of the fuelstock returns to a state-approved
disposal site in the form of ash.
Trash disposal is not enough for a waste-to-energy
facility to qualify as a renewable power source; it must meet
strict state regulations. Elk River Station does this with a
state-of-the art combustion process, pollution control equipment
to filter and scrub emissions of harmful gases and an emission
monitoring system that allows the plant to make adjustments
in the burning process.
Such an environmental record is especially impressive
considering that Elk River Station began operation as a coal-
and oil-burning plant in the 1950s. Great River Energy converted
it to nuclear energy in the 1960s, switched back to coal and
oil in the1970s and finally decommissioned the plant in the
1980s. “The Coal Creek Station went online with 1,100
MW in 1981, so we had surplus capacity.”
Elk River Station sat dormant through the 1980s
until another environmental issue gave the facility new life.
Concerned about the amount of waste going into landfills, the
state Office of Environmental Assistance began to pressure counties
to come up with other solutions for trash disposal. Since the
state classified burning as recycling, the mothballed powerplant
offered an alternative to dumping. Several counties in Great
River Energy’s service territory took out bonds, and the
co-op converted Elk River Station to a waste-to-energy generator
in 1989.
NRG Energy,
a power wholesaler that formed the same year, entered into a
partnership to provide Great River Energy with processed waste
material. The company brought waste management and processing
experience to the table, and the Elk River Station gave NRG
the opportunity to diversify its energy portfolio.
The participating counties truck their garbage,
most of which is residential, to the processing plant. Metal
and other non-combustible items are separated from the waste
stream and the cellulose-containing refuse is ground and delivered
to Elk River Station for burning.
New waste treatment process could lower
maintenance costs
Elk River power station has been producing electricity from
this replenishable fuel source ever since. There is always room
for more innovation at Great River Energy, however.
Last fall, the station test burned 60 tons
of clean fuel that had been heat-treated instead of shredded.
In a process Hanson described as “the opposite of papermaking,”
raw garbage is heated to 260 to 270 degrees Fahrenheit, breaking
the cellulose content down to fiber without burning it.
The treated fuel component looks a lot like
peat moss, making it easier to screen out the shriveled plastic
and the glass, metal and aluminum, all unchanged by the heat.
“Plastic contains chlorine, which is very corrosive, and
glass fouls the boilers,” explained Hanson. “Eliminating
those two elements could dramatically cut down our maintenance
costs.”
The waste material for the demonstration
project came from a Reno, Nev.-based fuel supplier that developed
the process to make feedstock for the paper industry. The feedstock’s
origin affected its performance as a fuel, it turned out. “Papermaking
adds a lot of moisture, so the waste was too wet to burn efficiently,”
Hanson noted.
Although the first test burn did not produce
enough energy to be considered a success, the generation manager
believes that reducing the moisture content in the feedstock
will solve the problem. The fuel supplier is going ahead with
the construction of a small pilot plant near Minneapolis, and
Great River plans to do another test burn with drier fuel later
this year. “It costs several million to replace boiler
tubes, so we’re willing to go through the learning process,”
he said.
As Hanson sees it, it’s all part
of an electric co-op’s mission. “It’s Great
River Energy’s job to provide our members with low-cost,
reliable energy, but we also work hard to be a good neighbor,”
he insisted.
Then again, any good neighbor keeps his
own yard clean. One who provides the neighbors with an environmentally
friendly way to dispose of the their own trash, and works for
rules to help keep other neighborhoods clean qualifies as a
great neighbor. That makes Great River Energy one great neighbor.
