Energy that grows back: Burning wood
considered carbon neutral
Apr 15, 2007 McClatchy-Tribune Business
News, John Myers Duluth News-Tribune, Minn.
With greenhouses gases and global warming
capturing everyone's attention these days, people
who promote burning biomass to generate electricity
note that wood is a carbon-neutral fuel, at least
in the long run.
Wood combustion spews carbon into the
air, contributing to the buildup of gases most scientists
say is spurring global warming. But the new trees
that grow where the cut tree had been eventually will
absorb that carbon, offsetting the increase.
With some biomass, such as grass, harvesting
and burning the fuel may lead to a net decline of
carbon in the atmosphere. That's because the root
system of the grass continues to grow, and new grass
absorbs carbon even between cuttings. Some researchers
say there may be some tree varieties that do the same.
Aspen forests, for example, continue to grow underground
after cutting and quickly re-sprout with more stems
than were cut.
It remains to be seen whether such forests
truly are long-term carbon sinks or if other interactions
in the ecosystem may mitigate any gain. Also, the
energy used to harvest and process biomass and get
it to the powerplant releases carbon, making the end
product somewhat less carbon-neutral.
Under orders from the state to start
churning out more electricity from renewable fuels,
Minnesota Power officials are looking out their office
windows for the next big thing.
They're intercepting pallets, paper
mill waste and demolition materials that had been
headed to landfills. They're grinding them to pieces
and churning out steam and electricity in Duluth and
Grand Rapids. And they're looking at leftover treetops
and limbs at logging sites across the Northland's
Minnesota Power supplies about 1 million
megawatt hours of electricity from renewable sources.
But they must more than double that, adding an estimated
1.5 million megawatt hours, by 2020, company spokesman
Eric Olson said.
"Biomass will need to be a significant
piece of our renewable portfolio in order to meet
the state mandate,'' Olson said. "We already know
how to use biomass. It's available. It's local. It's
renewable. It's going to be a big part of the mix
While the company plans on expanding
biomass electrical generation, no details have been
released on where or how big a new biomass plant might
How much wood is available to burn is
unclear. Wood prices are historically high. Private
land available for logging is shrinking as more forest
is developed or moved out of timber management. There's
already pressing demand on public forests from sawmills,
board plants and paper mills.
While biomass burners generally use
leftovers from traditional logging practices, the
overall demand for wood fiber could eclipse supply.
The economics of removing large amounts of low-value
wood from the forest isn't certain.
"What we don't want is to get into competition
with our biggest [electrical] customers for the wood
that they need for their mills,'' said Mike Polzin,
renewable fuels coordinator for Minnesota Power. "We're
going to remain a secondary customer, using the byproduct.''
It's also not clear how much more wood the forest
can provide without ecological consequences. Leaving
some leftovers from logging on the forest floor is
critical for bird and wildlife habitat and to help
re-charge the soil for the next growth of trees.
Despite the unknowns, the allure of
a locally produced, renewable fuel is too much to
In addition to any new Minnesota Power
project and the company's two wood-burning boilers,
the Minntac taconite plant in Mountain Iron uses waste
wood for some of its fuel needs. The new Laurentian
Energy Authority boilers in Hibbing and Virginia are
burning tons of wood every hour. Meanwhile, the Bois
Forte Band of Ojibwe is eyeing a possible wood-to-ethanol
plant that would use local waste wood, and a similar
facility is being built in Little Falls.
Don Arnosti, forestry coordinator for
the Minnesota-based Institute for Agriculture and
Trade Policy, said Minnesota Power and others eyeing
biomass for new energy production should move carefully.
"There's a real danger if we start demanding
our forest give up a certain amount of energy, if
we build new plants and assign a quota to our forest
to come up with the fuel ... rather than first determining
how much energy is sustainably available and going
from there,'' Arnosti said.
Minnesota imports a larger percent of
its electricity than any other state, and much of
that is produced from coal. Burning coal is cheap,
but it contributes to the load of mercury in fish
and to carbon dioxide pollution and a warming climate.
In an effort to lessen those problems
and keep energy dollars in the state, Minnesota lawmakers
and Gov. Tim Pawlenty last month approved landmark
legislation requiring that Minnesota's big electric
utilities make 25 percent of their electricity from
renewable sources by 2020.
To satisfy that law, Minnesota Power
is looking at adding even more wind generators to
replace electricity currently generated by burning
coal. And the utility has hydroelectric dams that
But windmills are expensive, don't turn
when it's calm and aren't welcome in all communities.
And it's not likely federal regulators will approve
any new dams on Northland rivers.
"So we're looking at the third W: wood,"
Polzin said. "We think there's opportunity there.
But there are also some challenges."
Minnesota Power is generating electricity
from wood at its Hibbard plant in West Duluth and
at its plant adjacent to the Blandin paper mill in
Grand Rapids. Each plant burns about 70 percent wood
and 30 percent coal to provide steam sold to paper
mills and generate electricity to sell.
"There's no reason any wood should ever
go into a landfill again,'' said Norm Opack, owner
of Demolicious, the Duluth company that supplies Minnesota
Power with its shredded waste wood in Duluth. "We
can take a lot more than we're getting. But we have
to change the way people think about [wood waste.]
It's too valuable to be buried.''
Burning on the Range
Terry Leoni, Virginia Public Utilities
manager who helps oversee the new Laurentian Energy
wood burning project in Virginia and Hibbing, said
there are ample logging leftovers in the forest to
supply the boilers. The plant has months of supply
already on hand.
The two plants are burning 36 tons of
wood every hour, every day to produce steam to heat
their communities and electricity to sell to Xcel
Energy and Minnesota Power. Laurentian hopes to reach
100 percent capacity -- burning 50 tons of wood per
hour -- in coming months.
But Leoni agrees that northern Minnesota
can't support infinite biomass burners.
"The capacity for more [biomass energy
projects] is there. Am I concerned that it could get
out of hand? Yes,'' Leoni said. "I think our lawmakers
realize that we can't oversaturate our area with [biomass]
Arnosti said accumulating wood to burn
for energy may be a good way for loggers to make extra
money from a logging site primarily intended for mills.
It may also be a way to help pay for logging that's
intended to create wildlife habitat, fire prevention
or forest thinning for productivity.
"We've been doing it since 1973. It
works for us,'' said Tom McCabe, owner of Duluth-based
McCabe Forest Products. His company sells so called
"non-merchantable'' timber -- tree tops, stems and
branches -- to Minnesota Power and other industries
"It's about 25 percent of our business,''
McCabe said of biomass. "I'm not sure what's going
to happen with the markets. But there's [supply] out
there if the demand comes.''
Arnosti said harvesting for biomass
may never pay for itself without subsidies. His group
has been studying the cost of harvesting biomass from
forest plots, and researching the environmental impacts,
in conjunction with the U.S. Forest Service and Laurentian.
The final report is due in August, but some aspects
already are clear, he said.
"Biomass isn't the entire solution.
Minnesota Power can't get to 25 percent renewable
[only] by burning tree tops,'' Arnosti said. "It would
be a recipe for collapse of our forests and a recipe
for perpetual conflict between the users of our forests,
from recreation to the paper mills ... We'd be killing
the golden goose for everyone."