ENERGY FROM TREES
(Training Powerpoint Available)
Students will determine the amount of energy that could be produced from a group of trees.
OBJECTIVES
The student will be able to
 Determine how many cords of wood/board feet could be derived from trees of varying sizes.
 Explain how wood is a renewable energy source.
 Compare the cost of wood as a fuel to the cost of fossil fuels used for heating
VOCABULARY
 Cord: 128 cubic feet of wood, usually in a block 4 feet by 4 feet by 8 feet
 Fossil fuel: A fuel, such as coal, oil, or natural gas, that formed in the earth
from plant or animal remains over million of years
 Non-Renewable Energy: Energy resources which are consumed much faster
than nature can create them. (i.e. fossil fuels)
 Renewable Energy: Energy resources that are naturally regenerated over a
short time scale and derived directly from the sun (such as solar), indirectly
from the sun (such as wind, hydropower, and biomass), or from other natural movements and
mechanisms of the environment (such as geothermal and tidal energy).
MATERIALS/EQUIPMENT
 Tape measures
 Biltmore sticks (optional)
 Small white board and marker
 Energy Cards (Appendix B)
 Conversion Tables (Appendix C)
 Fuel posters – oil, wood, natural gas, coal (Appendix D)
 Equivalency posters – 4 copies (Appendix E)
 Cost Calculation cards (Appendix F)
TIME NEEDED: 30-40 minutes
DEGREE OF PHYSICAL ACTIVITY: moderate to high
SET-UP
Biltmore Sticks: If you would like to make this a more authentic activity and relate it to work done by
foresters, use Biltmore Sticks rather than the tape measures to find out how much wood is available from
a given tree. A Biltmore Stick looks like a yardstick but is a tool for determining the number of board feet
in a tree. (A board foot is a piece of wood with a volume of 144 cubic inches.) The “Tree Scale” side of
the stick is used to find the diameter of the tree. The “Hypsometer” side is used to determine how many
16’ logs could be cut from the tree. A chart on the “Tree Scale” side shows the number of board feet
available based on the diameter and number of 16’ logs. When determining the number of logs, foresters
only measure the trunk from the base of the tree to the base of the crown. Foresters don’t include the
wood where the tree thins toward the top or where there are many branches coming out of the trunk.
More specific directions for using a Biltmore Stick are given within the activity. If your site does not have
Biltmore Sticks, you can make simplified versions. Directions are included in Appendix A of this activity.
Before the class, find out how many cords of wood or pounds of pellets are used during the year by this
facility. You’ll also want to find out how much it costs for the wood or wood pellets used during the
heating season, or the average amount paid in this area.
RUNNING THE ACTIVITY
Discuss with the students how they think their schools and homes are heated. Ask the students what the
terms “fossil fuels,” “renewable energies,” and “non-renewable energies” mean. Give them a brief
explanation of each term. Then divide the class into groups. Pass out Energy cards (Appendix B) - one
card to each group. (Several groups can have the same card.) Give the students time to read the
information and discuss the question. Then have everyone share their question and answer.
Next, you’ll be focusing on understanding how wood is a fuel source. Point to one of the trees or hold up
the piece of wood. Explain to the group how wood is measured in a unit called a “cord” which measures
4 feet X 4 feet X 8 feet. Have the students use their bodies to measure the space. (Your arm span is
equal to your height.) Point to one of the trees and explain, “If this tree was felled and used for heating,
how much of a cord would it fill? After several guesses have been made, explain that there is a way to
predict the amount of wood we can get by measuring the tree.
Depending on the equipment you have available, students can determine the amount of wood available
either using a tape measure and the Conversion chart or by using a Biltmore Stick.
Using a tape measure:
Measure up about 4½ feet from the ground. Using the tape measure, measure the circumference of the
tree at this height. Look at the Conversion Table (Appendix C) and select the row in the Circumference
column that is the closest to the measurement you got from your tree. Go across the same row to the
right-hand column to read the number of cords of wood this tree could provide.
.
Using a Biltmore Stick:
First, find the diameter of the tree:
1. Make sure you are using the “Tree Scale” side of the stick and
NOT the “Log Scale” side.
2. The stick needs to be held 25” from your eye against
tree you are measuring. This is approximately an arm’s length.
3. Close one eye, line up the left end of the stick (zero mark) with
the left side of the tree about 4-1/2 feet from the ground.
4. Without moving your head, look over to the right and read the
diameter on the stick where the imaginary line between your
eye and the edge of the right side of the tree intersects the stick (see diagram).
5. For elliptical trees, measure the small side and large side.
Take the average.
Next, find how many 16’ logs this tree could produce:
1. Use the side of the stick labeled “Hypsometer.”
2. Measure 66’ from the tree in question – about 12 paces.
3. Hold the stick 25” from your eye, line up the bottom of the
stick with the base of the tree and read the number of 16’ logs/
sections on the stick.
Finally, determine the number of board feet of wood:
1. Using the chart on the “Tree Scale” side, find the diameter of
the tree.
2. Look at the log numbers on the left-hand side of the chart.
3. Read down the diameter column and across the log row until they intersect.
4. This value is the number of board feet of wood that could be taken from this tree.
Using a Biltmore Stick allows you to figure out the amount of board feet of wood a tree produces. In this
activity, we are talking about cords of wood because that is how firewood is measured and sold. A cord
of wood fills a space 4’ X 4’ X 8’. But there is a great deal of variability in how tightly the wood may be
packed into that space. For that reason, there is no direct conversion from board feet to cords. In
researching what the conversion might be, most sources listed a little over 2 cords of wood per 1000
board feet of lumber, with the understanding that this is just a rough estimate.
Depending on the size of your group, either have each student select a tree or have students pair up.
Pass out measurement tools to each student or pair of students.
As everyone completes their calculations, tally the amounts by writing them on the white board and then
add them to find the total number of cords the trees would provide.
Ask the students to guess how many cords of wood are used each year by this facility. Share the actual
number. Have the students figure out how many more the trees would need to be harvested to have
enough wood for heating for the year.
Then have the students compare the relative costs of using a cord of wood for heating to equivalent
amounts of fossil fuels. Pass out the four Fuel posters (Appendix D). Then pass out the “produces the
same amount of energy” posters (Appendix E). Have students with those signs stand between the
students holding the Fuel posters. Point out that, to produce equal amounts of energy, different amounts
of fuel are needed. Each fuel is sold in different units (e.g. gallons, kilowatt hours, cubic feet) and costs a
different amount per unit. (The values shown were found on the U.S. Energy Information Administration
website.)
Depending on your group, either pass the calculator around for students to use or use estimation to
determine the equivalent costs. Record the costs on the white board or use the Cost Calculation cards
(Appendix F).
Fuel Oil
How much is
equivalent to one
cord of wood
150 gallons
Natural Gas
21,000 cubic feet
Kind of Fuel
Electricity produced
from coal
6158 kilowatt hours
Cost per unit
$3.60/gallon
$0.01084/ cubic feet
$0.1044/kWh
Total
cost
Estimation
$227.64
150 X $4 = $600
21000 X $0.01 =
$210 (move the
$642
6158 X $.10 =
$615.80 (move the
$540
decimal point two place to
the left)
decimal point one place
to the left)
The cost of one cord of wood will vary. (In February 2011, in an online search, costs in Minnesota ran
between $150 - $225, but costs increased if the wood had to travel farther.) Share with the group how
much this facility pays for a cord of wood or a load of pellets. Talk about where the wood comes from and
how using local sources lowers the cost because transportation costs are less.
Then have students think about what other kinds of costs there are, besides financial ones, for using
different kinds of fuel. Refer the students back to the Energy Cards – what needs to be done to get the
fuel to our homes? Point out that paying for fuel has additional costs because of the equipment you need
to get the fuel out of the ground, to process the fuel into a usable form, and to transport and store it. Talk
about impacts to the Earth and dangers to humans (e.g. oil spills like Deep Horizon - the one in the Gulf
of Mexico, mine collapses like the one in Chile, pollution from burning coal to produce electricity, adding
greenhouse gases to the atmosphere which affects global temperatures.)
Ask the students what impacts there are when we cut trees for fuel (e.g. loss of habitat, exposing soil to
greater risk of erosion). But then point out, that by being a renewable fuel, we are able to reverse
negative effects – we can replant the area and provide habitat to animals, reduce soil erosion, produce
oxygen as part of the growth cycle of plants, and remove carbon dioxide (a greenhouse gas) from the
atmosphere.
WRAP – UP
Visit the area where your site’s wood burning or pellet stoves are located. Discuss how they work and
where the wood comes from that is used. If yours is a wood-burning stove site, give students an
opportunity to look at the cut wood; talk about how and why the wood is seasoned.
Then discuss why wood is the best choice for heating at this location, but wouldn’t necessarily work for
the students. Have the students brainstorm ways they can lessen their dependence on fossil fuels
without needing to switch to wood burning heating systems. (e.g. put on layers rather than turning up the
heat, walk or bike instead of always using cars, wash clothes in cold water)
WAYS TO USE/INTEGRATE THIS ACTIVITY
Incorporate into Forestry classes.
Combine with Improving Fire Through Technology.
STEM CONNECTIONS
Science: Students will need to investigate and classify.
Math: Students will need to measure, estimate, calculate, and analyze.
SOURCE(S)
Adapted from The Renewable World lesson from Growing Schools Science Outdoors at
http://www.ase.org.uk/htm/teacher_zone/outdoor_science/outdoor_science.php
and the Estimating Firewood from Standing Trees article from the University of New Hampshire
Cooperative Extension at http://extension.unh.edu/resources/files/Resource001044_Rep1200.pdf
APPENDIX A: Make Your Own Biltmore Stick
(www.agriculture.purdue.edu/fnr/stoutwoods/activities/Building%20a%20Biltmore%20Stick.pdf)
APPENDIX B: Energy Cards
Coal
Oil / Petroleum
I was formed millions of years ago when
plant material in swamps died. Over time,
the plant remains built up to form peat. As
pressure from the peat increased, coal was
formed.
I was formed millions of years ago when
small animals, algae, and other animals
living in the oceans died.
Before I can be used, I have to be dug out
of the ground. Then I am burned in power
plants to produce electricity.
Am I a renewable or a non-renewable
energy? Why?
Natural Gas
I was formed millions of years ago when
small animals, algae, and other animals
living in the oceans died.
I am pulled up to the surface through wells
and into large pipelines.
Before I can be used, I have to be pumped
out of the ground and processed. Then I am
turned into gasoline, diesel, or other
products like ink, crayons, deodorant, and
CDs and DVDs.
Am I a renewable or a non-renewable
energy? Why?
Trees/Biomass
I started growing 25-30 years ago. I am
used for fuel, furniture, buildings, toys,
paper, and much more. When I am burned,
I release chemical energy as heat.
The gases that are produced include
methane, butane, and propane.
Once I’ve been cut, others of my species
can be replanted where I grew and in
another 20-30 years, another tree can be
harvested for fuel.
Am I a renewable or a non-renewable
energy? Why?
Am I a renewable or a non-renewable
energy? Why?
APPENDIX C: Conversion Table to be used with tape measure
Conversion Table
 Measure the circumference of your tree.
 Find a circumference value on the chart below that is closest to your measurement.
 Read across the chart to find out how many cords of wood this tree will provide.
Circumference
(Distance around the tree
4 ½ feet from the ground)
16 in
19 in
22 in
25 in
28 in
31 in
35 in
38 in
44 in
50 in
57 in
69 in
How many
cords of wood
will this tree
provide?
0.02
0.05
0.08
0.12
0.17
0.21
0.25
0.30
0.40
0.50
0.65
1.00
Number of
trees this
size to make
one cord of
wood
50
20
12
8
6
5
4
3.5
2.5
2
1.5
1
Conversion Table
 Measure the circumference of your tree.
 Find a circumference value on the chart below that is closest to your measurement.
 Read across the chart to find out how many cords of wood this tree will provide.
Circumference
(Distance around the tree
4 ½ feet from the ground)
16 in
19 in
22 in
25 in
28 in
31 in
35 in
38 in
44 in
50 in
57 in
69 in
How many
cords of wood
will this tree
provide?
0.02
0.05
0.08
0.12
0.17
0.21
0.25
0.30
0.40
0.50
0.65
1.00
Number of
trees this
size to make
one cord of
wood
50
20
12
8
6
5
4
3.5
2.5
2
1.5
1
Appendix D: Fuel Posters
Coal
(used to produce electricity)
–
6158 kilowatt hours
Wood –
one cord (4’ x 4’ x 8’)
Fuel Oil –
150 gallons
Natural Gas –
21,000 cubic feet
Appendix E: Equivalence signs
produces
the
same
amount
of energy
as
APPENDIX F: Cost Calculation Cards
Fuel Oil
Cost per gallon = $3.60
150 X $4 = $ _____________
Natural Gas
Cost per cubic foot = $0.01
21000 X $0.01 = $_________
Coal
( to produce electricity)
Cost per kilowatt hour = $0.10
6158 X $0.10 = $ __________
Wood
Cost per cord = $ __________
APPENDIX G – Fuel Equivalencies
From the National Ag Safety Database
(http://nasdonline.org/document/1441/d001235/home-heating-with-wood.html)
HOW MUCH WOOD
The following is called the Smithers method for estimating the number of cords of wood to heat a house.
A standard cord is a well stacked pile of wood 128 cubic feet in volume, a pile 4 feet by 4 feet by 8 feet.
Most people have some way to arrive at the amount of conventional fuel it takes to heat the house for an
average year.
The Smithers method assumes the following equivalents to one cord of average dry hardwood* (W):
150 gallon No. 2 fuel oil
230 gallon LP gas
21,000 cubic feet natural gas
6,158 kWh electricity
*Dry hardwood is not as commonly sold as green hardwood, which requires about 20 percent more
volume to yield equivalent energy to the air dry hardwood.
APPENDIX H: Standards
Subject
English
Language Arts
K-12 (2010)
Code
6.13.3.3
9.13.3.3
11.13.3.3
Social Studies
(2004)
Geography
V.D.2.
Grades
4-8
Mathematics
K-12 (2008)
4.1.1.5
5.1.1.4
6.1.2.1
6.1.3.4
Science K-12
(2010)
4.1.2.1.1
4.2.1.1.1
5.1.3.4.1
5.3.4.1.1
5.3.4.1.2
5.3.4.1.3
5.4.4.1.1
6.2.3.2.2
9.2.4.1.1
Standards
Common Core Standards for
Literacy in Science and Technical
Subjects 6-12
Common Core Standards for
Literacy in Science and Technical
Subjects 6-12
Common Core Standards for
Literacy in Science and Technical
Subjects 6-12
The student will describe how
humans influence the environment
and in turn are influenced by it.
Demonstrate mastery of
multiplication and division basic
facts; multiply multi-digit numbers;
solve real-world and mathematical
problems using arithmetic
Divide multi-digit numbers; solve
real-world and mathematical
problems using arithmetic.
Understand the concept of ratio
and its relationship to fractions and
to the multiplication and division of
whole numbers. Use ratios to solve
real-world and mathematical
problems.
Multiply and divide decimals,
fractions, and mixed numbers;
solve real-world and mathematical
problems using arithmetic with
positive rational numbers.
Engineers design, create and
develop structures, processes and
systems that are intended to
improve society and may make
humans more productive.
Objects have observable
properties that can be measured.
Tools and mathematics help
scientists and engineers see more,
measure more accurately, and do
things that they could not otherwise
accomplish.
In order to maintain and improve
their existence, humans interact
with and influence Earth systems.
In order to maintain and improve
their existence, humans interact
with and influence Earth systems.
In order to maintain and improve
their existence, humans interact
with and influence Earth systems.
Humans change environments in
ways that can be either beneficial
or harmful to themselves and other
organisms.
Energy can be transformed within
a system or transferred to other
systems or the environment.
There are benefits, costs and risks
to different means of generating
and using energy.
Benchmark
Follow precisely a multi-step procedure when carrying out
experiments, designing solutions, taking measurements, or
performing technical tasks.
Follow precisely a complex multi-step procedure when carrying
out experiments, designing solutions, taking measurements, or
performing technical tasks, attending to special cases
(constraints) or exceptions defined in the text.
Follow precisely a complex multi-step procedure when carrying
out experiments, designing solutions, taking measurements, or
performing technical tasks; analyze the specific results based on
explanations in the texts.
Students will analyze the advantages and drawbacks of several
common proposals to change the human use of environmental
resources.
Solve multi-step real-world and mathematical problems requiring
the use of addition, subtraction and multiplication of multi-digit
whole numbers. Use various strategies, including the relationship
between operations, the use of technology, and the context of
the problem to assess the reasonableness of results.
Solve real-world and mathematical problems requiring addition,
subtraction, multiplication and division of multi-digit whole
numbers. Use various strategies, including the inverse
relationships between operations, the use of technology, and the
context of the problems to assess the reasonableness of results
Identify and use ratios to compare quantities; understand that
comparing quantities using ratios is not the same as comparing
quantities using subtraction.
Solve real-world and mathematical problems requiring arithmetic
with decimals, fractions and mixed numbers.
Describe the positive and negative impacts that the designed
world has on the natural world as more and more engineered
products and services are created and used.
Measure temperature, volume, weight and length using
appropriate tools and units.
Use appropriate tools and techniques in gathering, analyzing and
interpreting data.
Identify renewable and non-renewable energy and material
resources that are found in Minnesota and describe how they are
used.
Give examples of how mineral and energy resources are
obtained and processed and how that processing modifies their
properties to make them more useful.
Compare the impact of individual decisions on natural systems.
Give examples of beneficial and harmful human interaction with
natural systems.
Trace the changes of energy forms, including thermal, electrical,
chemical, mechanical or others as energy is used in devices.
Compare local and global environmental and economic
advantages and disadvantages of generating electricity using
various sources or energy.
Science K-12
(2010)
9.2.3.1.2
9.3.4.1.2
There are benefits, costs and risks
to different means of generating
and using energy.
People consider potential benefits,
costs, and risks to make decisions
on how they interact with the
natural systems.
Describe the trade-offs involved when technological
developments impact the way we use energy, natural resources
or synthetic materials.
Explain how human activity and natural processes are altering
the hydrosphere biosphere, lithosphere and atmosphere,
including pollution, topography and climate.