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Farm-Scale Straw-Burning Furnace
Danish policy for providing heating for homes and
businesses begins with district heating systems. Entire towns are heated
with hot water or steam emitted from power plants which also produce
electricity. The huge fossil fuel electric plant we visited in Kalundborg
supplies heat for the buildings in the town as well as a number of local
industrial plants. The Sakskobing electric power plant, in addition to its
district heating benefits, also uses renewable straw for its fuel.
District heating requires fairly dense housing arrangements. Where homes
are more spread out, Danish energy policy requires natural gas furnaces in
homes. When it comes to farms and small rural business far from gas lines,
furnaces that do not use oil are encouraged. We visited two straw-burning
furnaces a bike ride from Hobro, a town between Aarhus and Aalborg.
Farms here have an abundance of straw and other waste material that can be
burned in efficient furnaces to heat the farm house, work areas and animal
feeding operations. One farm we visited utilized a very slow conveyor to
transport large round bales of straw to the furnace. The farmer loaded the
conveyor every few days. Machinery slowly moved the straw to an auger
which supplied the right amount of straw for the heating needs. Waste ash
from the furnace was automatically discharged to a wagon, which allowed
the ash to be returned to the fields as a soil amendment.
Straw and wood chips are used in tens of thousands of furnaces in Denmark.
Some are used in large electric units that also use a fossil fuel; some
use straw or other biomass as the only fuel to produce electricity and
heat, and some heat homes and small businesses in remote locations. As
with wind power, biomass allows the Danes to gain a degree of energy
independence as they efficiently use renewable resources.
-- David Osterberg
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