ENVS 200 – Case Studies in Environmental Science
Spring, 2012
CALCULATING YOUR CARBON FOOTPRINT
In this exercise, we will use an online tool to estimate the number of tons of
carbon dioxide each of us emits into the atmosphere on an annual basis. We will
examine which components of our lives contribute the most to that “footprint”,
and use the information to draw conclusions about changes we could make to
reduce that impact.
OBJECTIVES:
At the end of this lab, you should be able to:
1. Identify the major areas of your lifestyle and activities that contribute to your carbon
footprint, and compare them quantitatively.
2. Display the components of your carbon footprint graphically.
3. Calculate the impact on your carbon footprint from the use of compact fluorescent lamps in
place of incandescent lamps in your home, and compare that to your overall carbon
footprint.
4. Identify two or more changes you could make in your lifestyle or activities that would have a
significant impact on your personal carbon footprint.
WHAT YOU WILL TURN IN:
Each student will turn in an analysis of his or her individual carbon footprint. The analysis will
include:
- a graphical representation of your total footprint and the components contributing to it;
- a graphical representation of the impact that changing to compact fluorescent lamps
would have on your footprint;
- a graphical representation of the impacts that two other lifestyle changes would have on
your footprint
- a written interpretation of the graphs that identifies the major contributions to the
footprint, analyzes the effect of switching to CFLs, and compares it to two other lifestyle
changes that could lead to reductions in your carbon footprint.
Specific instructions are given on the last page of this handout. The analysis is due by 5 pm
on Friday, February 10. Late assignments will lose half a grade for each day late, including
weekends.
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ENVS 200 – Case Studies in Environmental Science
Spring, 2012
Personal Footprint Calculator
To begin, you will each estimate your personal carbon “footprint”—that is, the amount of carbon
dioxide you contribute to the atmosphere each year, both as a direct result of your activities, and
indirectly through products you purchase. Later, you will examine how specific changes in those
activities might reduce your footprint.
To calculate your carbon footprint, go to http://www.carbonfootprint.com and click on the “Free
calculators” link. Select the individual/Household calculator, and create an account. This allows
you to save your results and come back to them, so you can make changes and compare the
outcomes.
Once you are ready to start the calculator, start on the Welcome tab and enter a name for this
first data set and set the date range for the calculations. Use January 1, 2011 – December 31,
2011 as the range.
Then, step through the remaining tabs, entering the information requested. When you complete
the calculator, update the file. Write the components of your footprint in the first column of the
following table. Write the name of the data set above the column.
Component
Amount (metric
tons)
Amount (metric
tons)
Amount (metric
tons)
Amount (metric
tons)
House
Flights
Car
Motorbike
Bus & Rail
Other Fuel
Secondary
Total
Compare your results with your colleagues. Which categories are the largest? Which are the
smallest?
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ENVS 200 – Case Studies in Environmental Science
Spring, 2012
Impacts of Lighting Changes:
Now that we have some baseline data, we can see what the effects would be of making some
simple changes. Specifically, we will look at the impacts of converting from incandescent lamps
to compact fluorescent lamps (CFLs).
Calculate your current energy use due to lighting:
Use your Household Lighting Inventory data to do the following:
For each lamp listed, multiply the average hours of use per day by the wattage of the bulb. This
will give you the daily energy use in Watt-hours (1000 Watt-hours = 1 kilowatt hour, kWh). Total
the energy use across all of the bulbs, multiply by 365, then divide by 1000. This will give you
the total energy use due to lighting for one year in kWh. Write that number down.
Calculate your potential (or actual) energy savings:
If a majority of the lamps in your home are incandescent, calculate the savings you could
achieve by converting all of your lamps to CFLs. If a majority of your lamps are already CFLs,
then you can calculate the energy you are already saving (see below).
If most of your lamps are incandescent, do the following:

For each incandescent lamp that could be converted, replace the current wattage with the
wattage for an equivalent CFL. Use the comparison table included with the Household
Lighting Inventory.

Re-do the calculations above to get the annual energy use you would have after replacing
the lamps.
If the majority of your lamps are already CFLs, calculate the savings you are achieving by doing
the following:

For each CFL lamp in your inventory, replace the current wattage with the wattage for an
equivalent incandescent lamp.

Re-do the calculations above to get the annual energy use if you were using all
incandescent lamps.
Calculate the impact on your carbon footprint:
To see how changing your lighting affects your carbon footprint, go back to the calculator and
change the value for your annual electrical usage to reflect either the “all incandescent” or the
“all CFL” scenario. Rename the file and update it to reflect the changes. Enter the new values in
the second “Amounts” column in the table on page 2.
Compare with your colleagues. How much of a difference in your carbon footprint would
changing your lighting make? Calculate the percentage reduction in your “House” contribution to
your footprint, and the percentage reduction in your total footprint. Write those numbers below
the table on page 2.
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ENVS 200 – Case Studies in Environmental Science
Spring, 2012
Calculate the savings in your energy bill:
Saving energy can also save you money. Currently, Avista Utilities charges $78.83 per 1000
kWh of electrical power (= $0.07883/kWh). Use that value to estimate the annual cost savings
you would get (or are currently getting) from switching to CFLs. Write the amounts in the table
below:
Current
“All CFL” or “All
incandescent”
$0.07883/kWh
$0.07883/kWh
Annual electricity use (kWh)
Rate
Total annual cost
What Else Could You Do?
Changing the lighting in your home is one way to reduce your carbon footprint, but there may be
others. The benefit of a footprint calculator is that it allows you to explore the potential impacts
of specific actions. Take a look at the categories that contribute to your footprint; which are the
largest? Where do you think you could have the biggest impact?
Choose a specific change that you could make in your lifestyle or habits that you think would
reduce your carbon footprint. Make it a reasonable change—one you think you could actually
do. For example, don’t say you’ll become a vegan if that is highly unlikely. In the space on the
next page, write down the change you want to examine, and explain why you want to examine
that particular change. Be specific and quantitative in describing your change, as in, “I want to
reduce the number of miles I drive in my car each year by 25%.”
What change do you want to examine, and why?
Now, go back to the online calculator, rename the data set to reflect the change you are making,
and update the numbers according to your change. Record the resulting amounts in the third
“Amounts” column in the table on page 2. Calculate the percentage change in your footprint,
both for any categories that changed, and for the total.
Compare with your colleagues—what did you change? How much of an impact did it have?
Was it greater or less than the impact from changing your light bulbs?
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ENVS 200 – Case Studies in Environmental Science
Spring, 2012
Now do it again. Think of one more change you could make, and examine the impact it would
have on your carbon footprint. In the space below, write down the change you want to examine,
and explain why you want to examine that particular change.
Record the results in the table on page 2. Compare with your colleagues, and with the previous
changes you made. What is the percentage change in your footprint that resulted?
Assignment:
To complete this lab, each of you will turn in a brief written analysis of the data you have
collected. This will be a narrative description of what you did, what you found, and what it
means. The paper should include:
-
An brief introductory paragraph explaining the purpose of the analysis.
-
A paragraph or more explaining which calculator was used, where the data came from, and
any assumptions you had to make. For example, if you only had four months of energy use
data and you used that to estimate usage for a full year, explain how you did that. Similarly,
you should explain if you used actual or estimated mileages for transportation, and how
those numbers were determined.
-
A graph showing your carbon footprint and the components contributing to it, as well as the
results of any changes you modeled.
-
Several paragraphs of analysis that identifies and compares the major contributions to your
footprint, the effect of switching to CFLs, and the effects of the other lifestyle changes that
you modeled.
You paper must be typed, double-spaced, and in a 12-point font. Papers are due by 5:00 pm
on Friday, February 10. Late assignments will lose half a grade for each day late, including
weekends.
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