Notes on Use of Taming Bigfoot Carbon Calculator
To the greatest extent possible, the conversion factors indicated herein are CO2e (effective
carbon dioxide) which attempts to account for the additional effective of other greenhouse
enhancing gases in terms of their equivalent greenhouse effect in terms of CO2. Wherever
possible, references for Jefferson County have been used so conversion factors most accurately
reflect Jefferson County greenhouse gas emissions.
ENERGY
Electricity
Units: kWh (kilowatt-hours); likely reported on energy bill
Calculation: the most recent data (for 2015) for the region including power supplied to
Jefferson County by the Bonneville Power Administration is 0.0442 lbs. CO2e/kWh.
(http://arb.ca.gov/cc/reporting/ghg-rep/ghg-rep-power/acs-power.htm).
Propane
Units: gallons; requires repeated tank readings, in %, and knowledge of storage tank size in
gallons.
Calculation: used conversion factor of 12.59 lbs. CO2/gal. from
http://www.carbonfootprint.com/calculator.aspx
Wood
Units: cubic feet; cord is a more common unit of measure for sale but estimating use by
fractional cord is difficult so cu. ft. is selected. 1 cord is 128 cu. ft. and commonly referred to as
a pile of stacked logs 8 ft long x 4 ft wide x 4 ft high.
Calculation: used data from Jefferson County Emissions Inventory, p. 10 footnote: (1.035 lbs
CO2 per lb wood) x (2,737 lbs wood per cord of Douglas fir) = 2833 lbs. CO2 per cord of wood.
This equals 22.13 lbs CO2/cu ft. Cord stacking causes cord density to be less than the pure
wood density. Cedar is less dense and maple more dense than Douglas fir so it is a good
average for this region.
Moisture content matters as burning wet wood is inefficient because more of the heat must be
used to evaporate the excess water in the wood. Air dried lumber generally can’t be dried
beyond 18%. Densities of various woods at 20% moisture content can be found at
http://www.engineeringtoolbox.com/weigt-wood-d_821.html.
Some carbon calculators set wood burning for energy as carbon neutral noting that wood from
quick-growing trees recapture the carbon emitted by burning. By harvesting subsequent wood
fuel from those trees, the cycle is repeated. However, a number of factors lead us to include
the direct carbon emissions of wood burning in our calculator. Foremost among these factors is
the time scale of this cycle: even one of the fastest-growing, quickest carbon-sequestering trees
that sprouts up today would require 50 years or more to absorb the carbon emitted by burning
a single cord of wood (about the amount in a foot-thick 40-foot-long log). Also, the production
of slash from the harvesting process leads to reintroduction of much of the sequestered carbon
back into the environment when it is burned. Finally, trees sequester carbon from all sources,
not only from wood burning, making it more legitimate to include a carbon sink “credit” for
tree-growth efforts, rather than limit the carbon offset effect to wood-burning alone..
Wood pellets
Units: pounds: requires weighing before consumption, or consistent use of a container whose
capacity is weighed once and monitoring number of uses.
Calculation: used conversion factor of 0.054 lbs. CO2/lb. from
http://www.carbonfootprint.com/calculator.aspx
Heating oil
Units: gallons; requires repeated tank readings, in %, and knowledge of storage tank size in
gallons.
Calculation: used conversion factor of 24.28 lbs. CO2/lb. from
http://www.carbonfootprint.com/calculator.aspx
WATER
Units: gallons for supplied water requires repeated meter readings; Yes/No for connection to
municipal septic
Calculation: the calculation is limited to those on municipal water networks. Others with
private wells pay for water supply through electricity expended by well pumps. Private septic
systems are similarly accounted for through electricity usage. For municipal water supply, the
conversion factor is 0.0000521 CO2e/gallon of water used. This is a population-adjusted ratio of
the City of Port Townsend water supply number (Jefferson County Emissions Inventory,
adjusted for the gallons of water supplied in 2005, and adjusted to reflect the BPA electricity
carbon footprint above), and the Jefferson County PUD water supply number (based on
correspondence from the PUD). A slightly smaller amount of wastewater is produced as a
byproduct of consuming this water. From the same document, the actual ratio of wastewater
to supplied water is 81.68% and the conversion factor of wastewater treatment (adjusted to
reflect the BPA electricity carbon footprint above) is 0.0001525 CO2e/gallon. The higher value
for wastewater reflects the additional energy required to treat wastewater.
Water bills usually don’t include a separate metering of wastewater so for those sending
wastewater into the municipal system, the assumed volume is equal to 81.68% of the water
drawn.
PERSONAL TRANSPORTATION
Cars, trucks and motorcycles powered by either gasoline or diesel are the primary means of
transportation using privately owned conveyances. However, smaller recreational vehicles
(ATV and boat) are also included here.
Accumulated miles traveled is a common way to monitor transportation, but mileage
performance can vary significantly between even seemingly identical vehicles (make, model,
year) because of factors such as tire inflation, engine condition and driving style. The burden to
monitor gallons directly is deemed minimal and worth the effort to extract more precise
calculation of carbon emissions.
Gasoline
Units: gallons; requires monitoring each vehicle.
Calculation: 19.64 lbs. CO2/gal. are produced by burning a gallon of gasoline that does not
contain ethanol. Fuel with 10% ethanol reduces the CO2 emission to 18.95 lbs. CO2/gal. [Source:
U.S. Energy Information Administration http://eia.gov]. The latter fuel is most common in
Jefferson County so that conversion factor is used.
Diesel
Units: gallons; requires monitoring each vehicle.
Calculation: 22.38 lbs. CO2/gal. are produced by burning a gallon of diesel. [Source: U.S.
Energy Information Administration http://eia.gov].
PUBLIC/SHARED TRANSPORTATION
This category refers to ride sharing when the vehicle is not owned by the individual whose
footprint is being determined. Thus, monitoring gallons of fuel used directly is not feasible and
mileage becomes the next best method.
Carpooling
Units: miles derived by dividing total miles traveled by total number of people sharing the trip.
If the number of sharing people changes, the participant’s share should be calculated for each
trip and then summed.
Calculation: Because fuel efficiency varies so widely among vehicles, an average mileage
efficiency of 25 miles per gallon is assigned for simplicity. Miles traveled are then converted to
gallons using this fuel efficiency value. Most carpooling is accomplished using 10E-gasoline
powered vehicles, so the emission factor of 18.95 lbs. CO2/gal. (see Gasoline, above) is used.
Users may wish to account more precisely for vehicles with better (or worse fuel efficiency).
The best means to do this is to adjust the miles travelled using the formula:
M = m x 25 / MPG, where m is the actual miles travelled, MPG is the actual fuel efficiency and
M is the adjusted miles travelled that would then be entered on the report. Attempting to
adjust for different fuel types is likely less significant.
Business vans/shuttle
Units: miles derived by dividing total miles traveled by total number of people sharing the trip.
If the number of sharing people changes, the participant’s share should be calculated for each
trip and then summed.
Calculation: diesel fuel is assumed along with an average fuel efficiency of 10 mpg for these
vehicles which are typically larger and carry more passengers.
Bus
Units: miles; number of other passengers is not used as it varies widely, changes constantly and
can be onerous to collect.
Calculation: emission conversion factor for bus travel varies depending on type of fuel used,
service area (urban or rural) and number of passengers. http://www.carbonfund.org
references EPA Climate Leaders (table 3, page 5) with an average emission factor for bus travel
of 0.107kgs CO2/passenger mile (or 0.236 lbs. CO2/passenger mile) but this works out to an
average busload of 19 passengers. On the other hand,
http://www.fta.dot.gov/documents/PublicTransportationsRoleInRespondingToClimateChange.
pdf gives (page 2) a national average of 0.653 lbs. CO2/passenger mile and a specific value for
King County, WA of 0.492 lbs. CO2/passenger mile (page 10). We chose the middle value of
0.492, which is close to the average of all three values.
Train
Units: miles; number of other passengers is not used as it varies widely, changes constantly and
can be onerous to collect.
Calculation: from http://www.carbonfund.org, the CO2 emissions for rail travel vary by distance
of the trip. On average, commuter rail emits 0.175 kgs CO2 per passenger mile and subway
trains emit 0.159 kgs CO2 per passenger mile, and long distance trains (i.e., intercity rail) emit
0.145 kgs CO2 per passenger mile (Source: EPA Climate Leaders, table 2, page 5). These factors
may overestimate emissions in Washington State but are used in lieu of more regionally specific
data. An average value of 0.16 kgs CO2/passenger mile (0.353 lbs. CO2/passenger mile) is used.
Ferry
Units: miles; number of other passengers is not used as it varies widely and is onerous to
collect. As shown below, an average trip Washington State Ferry is 11 miles; this number can
be used to assist in reporting miles traveled if the WSF system was used..
Calculation: In 2009 Washington State Ferries transported 22.4 million passengers over 9
routes totaling 85.5 nm in 167,355 sailings while using 17 million gallons of biodiesel [Source:
http://www.wsdot.wa.gov/ferries/]. Using these data to derive network-wide averages, the
average route is 9.5 nm. (11mi.) and the total distance travelled is 1,829,190 miles with a fuel
efficiency of 0.108 miles per gallon. Biodiesel produces 22lbs. CO2e/gal, so the emission rate is
204 lbs. CO2e/mile. This is distributed among all passengers: 134 per sailing. The net result is a
carbon emission factor of 1.525 lbs. CO2e/mile.
Airplane
Units: miles; number of other passengers is not used as it varies widely, changes constantly and
can be onerous to collect.
Calculation: from http://www.carbonfund.org, an average carbon emission factor for air travel
is 0.277 kgs CO2/ passenger mile (0.61 lbs CO2/passenger mile). Much like vehicle emissions,
this number can vary by the size of the airplane and the distance travelled as well as the
number of stops (i.e., more fuel-hungry take-offs and landings). A good site to find this detail is
http://blueskymodel.org/air-mile.
NON-RECYCLED GARBAGE
Units: pounds; weighed garbage is preferred and more accurate for the calculator. Stepping on
a bathroom scale with and without the garbage bag is an easy method.
Less precise is counting the number of large trash bags filled. A very rough rule of thumb is
bagged curbside garbage weighs 95 lbs./cu. yd. Bagged garbage weighs closer to 150 lbs./cu.
yd.. Large outdoor trash cans are typically35 gallons in volume. One full trash bag will typically
weigh about 18 lbs; more if heavily packed.
[Refs: http://www.aqua-calc.com/page/density-table/substance/garbage-coma-and-blankhousehold-blank-rubbish
http://recycle-bowl.org/wp-content/uploads/Recycle-Bowl-Estimating-Data-Fact-Sheet.pdf].
Calculation: from Jeff Co Emissions Inventory (pg. 12-13), 20,800 tons of solid waste generated
3457 tons of CO2e (including transportation of the waste). That results in a ratio of 0.166, so 10
lbs of waste produce 1.66 lbs of CO2e.
FOOD
Meat
Store-bought red meat has a higher carbon footprint than any other broad food category.
Units: # of meals that include red meat as a main entrée. For most people these would only
include dinners.
Calculation: from http://shrinkthatfootprint.com/shrink-your-food-footprint, USDA reports
meat has a 0.77 ton CO2e per year per capita footprint. Assuming a serving per day, a
conversion factor of 4.22 lbs CO2e/serving is used.
Local Source
Units: % of total food purchased originating from local sources.
Calculation: from three options for proportion of food purchased locally (all, most, none) on the
carbon calculator website http://www.carbonfootprint.com/calculator.aspx, a linearly scaled
coefficient was derived. The values used were 0% local is 0.09 metric tons CO2e (198 lbs.) to
100% is 0.02 metric tons CO2e (44.2 lbs.), so the linear coefficient is -1.539 lbs CO2e /%.
Organic fruits & vegetables
Units: % of fruits and vegetables that are grown organically
Calculation: from three options for proportion of fruits grown organically (all, some, none) on
the carbon calculator website http://www.carbonfootprint.com/calculator.aspx, a linearly scaled
coefficient was derived. Using the two extremes, “all organic” is 0 metric tons CO2e and “no
organic” is 0.03 metric tons CO2e (66.15 lbs CO2e), the linear scaling factor is 0.6615 lbs CO2e/%.
SHOPPING
It is very difficult to quantify carbon footprint contributions from shopping behavior because
there is so much variation in the manufacture of similar products themselves and the energy
that must be expended to get them to stores. Online shopping is becoming more popular, but
for the savings in transportation that are realized, there are greater costs in packaging
materials. Examining a number of on-line carbon calculators, there are two categories that
were selected to incorporate into this calculator.
Clothing
Units: dollars spent on new clothing.
Calculation: from http://coolclimate.berkeley.edu/calculator, a linear scaling coefficient of 1.2
lbs. CO2e/dollar spent was extracted and used in the calculator.
Paper reading material
Units: dollars spent on paper reading material such as newspapers and books.
Calculation: from http://coolclimate.berkeley.edu/calculator, a linear scaling coefficient of 0.65
lbs. CO2e/dollar spent was extracted and used in the calculator.