Wood-Chip Heating Systems - Biomass Energy Resource Center

maintenance time has been reduced to less than 30
minutes in most cases. All parties have listened to and
acted on what operators have been saying: that larger
bins make life much easier for the user, compared to
bins that only hold only one truckload of chips.
Fuel supply is an area that continues to require
ongoing vigilance, on the parts of both users and state
offi cials. Users rarely have the luxury of long-term,
stable relationships with a single chip supplier without
the need for yearly reassessment. When users regularly
stay on top of chip prices and the competitive fuel
market, prices tend to stay low. Having said that, users
fi nd that keeping a stable relationship with a single,
reliable fuel supplier is an invaluable asset.
Users have learned that mill residue chips provide
the most trouble-free operation. They tend to prefer
mill chips over fuel chipped in the woods. However,
in some regions mill chips may be hard to fi nd at
a reasonable price. Bole-wood chips from logging
operations have been used successfully in many cases.
The critical factor is that the supplier of forest chips
be very interested in serving the institutional market
and be committed to producing a uniform quality
chip similar to a mill chip. If a forest chipper slips into
delivering school customers loads with too many oversized
chips, they will quickly lose the confi dence of
their customers and their business.
State forestry and education offi cials can play
a critically important role in helping to create and
maintain a stable fuel market for school users.
Vermont’s energy offi ce, in partnership with the
state forestry agency and the school superintendents’
association, created a support program that has
benefi tted schools with wood energy systems. Each
year a meeting is held for system operators to discuss
issues of concern and share information about fuel
supply and other matters of common interest. The state
collects and shares data on wood fuel prices, energy
consumption and fuel supply, so that all users (and
others) can see who is supplying who at what price and
can compare their fuel consumption with other schools
on a square-foot basis. The state initiative also helps to
link individual schools with fuel suppliers and to solve
short-term fuel supply problems.
New Uses on the Horizon
In the future we may see more use of biomass in
heating plants, both for smaller commercial facilities
and for applications larger than those discussed in this
guide. On the large side, using biomass to fuel “district
heating” plants is becoming a recognized option,
economically viable in some settings.
District heating is the use of a central boiler facility
with buried piping that serves the heating needs of a
number of nearby buildings. District heat systems have
been common in settings such as college and university
campuses for many years. Since one of the drawbacks
of biomass heating plants is their relatively high capital
cost, it makes sense to have one plant provide heat to a
number of buildings.
Large district heat systems that burn biomass are
fairly common today. A number of colleges in the
Northeast and elsewhere currently have biomass-fi red
district heating systems. St. Paul, Minnesota, has a very
large urban-district heating and cooling system that
burns biomass, as do the complexes of government
buildings in Montpelier and Waterbury, Vermont. The
St. Paul system uses hot water to distribute heat, while
the Vermont state district systems (and most older
campus systems) use steam as the medium.
In Scandinavia, district heating is widely used and
the technology is highly developed. The capital of
Prince Edward Island, Charlottetown, has a 20-yearold
modern Scandinavian-style downtown hot-water
district heating system that burns whole-tree chips and
other forms of waste biomass.
Small district heating systems are also common in
settings where one plant may heat two or more adjacent
buildings. Examples include schools with two or three
buildings on the same property, and hospitals with
plants that also heat nearby medical offi ce buildings or
nursing homes.
A fi rst-of-its-kind district system was installed
in 1991 to provide low-cost wood-chip heat to nine
buildings of a 50-apartment, low-income family
housing project in Barre, Vermont. This system now
has over a decade of reliable operation, with a monthly
fuel cost of $26 per apartment for all heat and hot
water, averaged over ten years. In 2003, the fi rst school
wood energy system in the Rocky Mountains was
installed to serve a three-school campus in western
Montana.
On the small side, expect to see an expanded use of
semi-automated systems to serve smaller schools and
commercial buildings. Fully automated systems have
proven to be economically viable in large schools, but
the high capital cost sometimes puts them out of reach
of smaller schools, facilities with less access to capital,
and those that expect a quicker return on investment.
Gasifi cation: Promise for the Future
Gasifi cation of biomass is an exciting technical
development that promises to open up new and more
effi cient uses of wood chips and other forest fuels. 1 A
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