A TALE OF
TWO BIOMASS BOILERS
What could be better than using
energy grown locally to heat your facility?
Two school districts in Pennsylvania are using biomass
boilers to provide thermal energy:
The Benton Area School District biomass boiler was
constructed in 2009 and is using locally grown
switchgrass for fuel.
The East Lycoming School District biomass boiler
construction will finish in 2010 and they are planting
hybrid willow on their property for fuel.
Richard Skinner, Energy Engineer
McClure Company
[email protected]
717.232.9743
33rd World Energy Engineers Conference, Washington, D.C. Dec. 8-10,2010
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Biomass Boilers
• Uses a clean burning, solid fuel combustor and
traditional boiler technology to produce
thermal energy
• Has a large fuel storage
area and impressive
fuel handling system of
belts and augers
• Can burn a variety of fuel:
wood chips, switchgrass,
corn, manure, etc.
Reasons for Considering a Biomass Boiler:
 Uses renewable fuels
 Locally produced fuels reduce dependence on
foreign energy sources
1 in 10 students
in Vermont
 Significant cost savings to oil and gas
attends a biomass
 Considered carbon neutral
heated school.
 Is a well established technology
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Biomass Can Save Up To
75% On Cost Of Fuel
$25.00
$/MMBTU
$20.00
$15.00
$10.00
$5.00
$0.00
Fuel
Cost
Btu Content
$/MMBTU
Wood Chips
$34/ton
5,000 Btu/lb
$4.25
Switchgrass
$60/ton
7,500 Btu/lb
$5.00
Coal
$120/ton
25 MMBtu/ton
$6.00
Oil
$2.50/gal
140 MBtu/gal
$22.32
$1.25/therm
100 MBtu/therm
$15.63
Natural Gas
1st year wood chip cost from East Lycoming;
Switchgrass cost from Benton;
Boiler efficiency 80% for all fuels.
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Benton School District
• Biomass Boiler heats High School and
Elementary School
• Fueled by switchgrass grown locally
• Received $700k in grants; cost $2.1 M
• About 13 year payback with $3.25 oil
The 7.5 MMBtu/hr
input boiler at
Benton operated for
an abbreviated
heating season in
2010 and saved
17,177 gallons of oil
and consumed 210
tons of switchgrass.
An addition was constructed on the Maintenance Building located between the
High School and Elementary School to house the biomass boiler and fuel storage.
About 2,100 feet of underground pipe was installed to connect the three buildings.
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Switchgrass
• A native, warm season grass
• Requires minimal fertilizer
and water
• Can grow on marginally
productive land
• Harvest with traditional
agricultural equipment
• Switchgrass will yield 3-4
tons per acre
• Low density, benefits to
densifying
• Immature market
Photos courtesy of Ernst Seed
Specialized machinery creates densified switchgrass “pucks” that are four
times as dense as ground switchgrass. Switchgrass pucks provide more fuel
in the storage bin, are less costly to transport, and easier to handle. The
Benton fuel pit will hold about 40 tons of switch grass pucks and at a
typical burn rate of 3 tons per day, can last for 13 days.
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East Lycoming School District
• Biomass boiler will provide
heat & domestic hot water to
High School
• Biomass boiler will handle
about ¾ of thermal load and
displace all oil usage
• Biomass boiler portion of
project: $2.1 M
• Received $800k in grants
• Project has 15 year payback
• Planting hybrid willow
The biomass boiler, rated at 130 boiler hp, is
housed in an addition to the rear of the High
School and adjacent to the existing boiler room.
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Hybrid Willow
•
•
•
•
•
Fast growing with high planting densities
Can grow on marginally productive soils
Harvest every three years
Plants have a 21 year life; 3 years to mature
Cut, chip and burn, no additional processing
Photos courtesy of Double A Willow
1 year growth on mature root system.
East Lycoming intends on planting about 60 acres of hybrid
willow that will yield about 600 tons of 50% moisture content
wood chips. This will supply nearly all of the projected 600-800
tons per year of wood chips needed for the biomass boiler.
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Biomass Boiler Challenges
Fuel storage
and handling
Biomass fuel energy contents
that range between 5000-7500
btu/lb require relatively large
storage volumes. Solid fuel
handling is more challenging
(belts and augers) than liquid or
gaseous fuels.
Ash handling
and removal
Biomass fuels create ash that
must removed, typically on a
weekly basis.
Air permitting
Cost of system
Shoulder
season heating
The complex air permitting
requirements in Pennsylvania
necessitated the use of an
environmental consultant;
future national standards are
expected to increase.
The cost of a biomass boiler can
be significant ; cost evaluations
should include building additions
and fuel storage.
A biomass boiler will rely on
traditional heating systems
during the shoulder heating
season due to limited turndown
ratios.
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Conclusions
• Biomass boilers are a proven,
successful technology
• Uses Renewable Energy
• Reduces dependence of
foreign energy
• Up to 75% savings on cost of fuel
• Significant installation cost
It will take several years to determine the cost effectiveness of using
switchgrass and hybrid willow at these locations. While these two
schools are pleased with their biomass boiler decisions, only time
will tell whether it makes more sense to produce your own, or buy
commercially available fuel such as wood chips.
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