Methodology

Updated: March 4, 2015

Earth Deeds offers innovative online tools for understanding and then transforming carbon footprints through supporting sustainability projects.  We help groups and individuals

(1) make sense of their CO2 emissions related to specified events, and

(2) build resiliency and sustainability within communities that matter to them.

This document outlines the assumptions and methodology that underlie Earth Deeds’ Carbon Footprint Calculator. All carbon calculators include a margin of error, but we strive to use the best available data and assumptions to provide the best estimate of emissions possible.  We rely heavily on the methodology outlined in the UK Government’s Department for Environment, Food, & Rural Affairs (DEFRA) in their July 2013 Methodology Paper for Emissions Factors[1].  DEFRA’s guidelines on GHG emissions calculations are considered to be a standard of good practice within the voluntary carbon market.  Earth Deeds annually updates its methodology based on DEFRA’s guidelines and other industry data and seeks  feedback by experts in the field. Please send any feedback and suggestions to support@EarthDeeds.com

Most web-based carbon calculators measure individual’s annual emissions. Earth Deeds calculator focuses on the travel emissions for individual or group events (e.g. study abroad programs, weddings, conferences).  Over time, we intend to incorporate additional carbon footprint categories (e.g. food, electricity, heating) and environmental impacts (e.g, toxic waste, water usage) so users can better understand and acknowledge the emissions and impacts from their everyday activities.

Flight Emissions

The full calculation to measure flight emissions is as follows:

CO2e = GCD x EF x CF x #P x #L x UF* x RFI*

where

GCD = Great Circle Distance

EF = Emissions Factor

CF = Class Factor

#P = Number of Persons

#L = Number of Legs

UF* = Uplift Factor (*optional)

RFI* = Radiative Forcing Index (*optional)

Let’s walk through these factors one by one.

Great Circle Distance

“Great Circle” refers to the shortest distance between two points on a sphere, measured along the surface of the sphere (as opposed to a straight line through the sphere's interior).[2]

 

Emissions Factor

DEFRA develops emissions factors based on typical aircraft fuel burn over trip distances listed in the EMEP/CORINAIR Emissions Inventory Guidebook.[3]  These factors account for methane (CH4) and nitrous oxide (N2O) in addition to Carbon Dioxide (CO2) and express them in units of metric tonnes of CO2 equivalent (CO2e).  So in most cases results are slightly higher than if only calculating CO2.

 

The 2012 Guidelines to DEFRA/DECC’s GHG Conversion Factors for Company Reporting[4] categorizes UK flights into three distance brackets: “Domestic”, “Short-Haul”, and “Long-Haul”[5].  “Domestic” is obviously not a useful category outside of the UK due to the varying sizes of countries, so we have recategorized these distance brackets as “Short-Haul”, “Medium-Haul”, and “Long-Haul.”

Table 1: Emissions Factors within three distance brackets

 

DERFA Categories

Earth Deeds Categories

Distance Brackets (kilometers)

Emissions Factors (gCO2/pkm[6])

Domestic

Short-Haul

0 - 483

158.3

Short-Haul

Medium-Haul

484 - 1,126

93.4

Long-Haul

Long-Haul

1,127+

109.8

 

 

Administrators of Teams within colleges or universities that are using the Clean Air - Cool Planet Campus Carbon Calculator have the option to use CA/CP’s single air travel emissions factor of 0.524804879 kg CO2e/passenger mile, which includes a 2.7 Radiative Forcing Index.[7]

Class Factor

Economy, Business, and First Class seating take up varying amounts of space on airlines, which affects the total number of potential passengers they can carry and the percentage of GHG emissions they are responsible for.  DEFRA’s 2008 update reviewed seating configurations on 24 aircraft variants and suggested the following average conversion factors for different seat classes:

 

 

DERFA Categories

Earth Deeds Categories

Seating

Emissions Factors (gCO2/pkm)

Domestic

Short-Haul

Average (all)

158.3

Short-Haul

Medium-Haul

Average (all)

93.3

 

 

Economy Class

88.9

 

 

Business/First Class

133.4

Long-Haul

Long-Haul

Average (all)

109.8

 

 

Economy Class

80.2

 

 

Economy+ Class

128.3

 

 

Business Class

232.5

 

 

First Class

320.7

 

 

Number of Persons

This simply allows users to calculate emissions for multiple persons traveling on the same flights.

 

Number of Legs

This allows users to specify whether a flight is One-Way or Round-Trip.  Obviously, Round-Trip flights will be double the emissions of a One-Way flight.

 

Uplift Factor

Flights never quite follow Great Circle paths between airports.  An 8% “Uplift Factor” is added to account for circling and non-direct routes.[8]

Radiative Forcing Index (Optional)

Atmospheric greenhouse effects are caused by more than direct CO2 emissions from fuels, especially at high altitudes (e.g. contrails, water vapor, NOx emissions).  While there is active research on this Radiative Forcing Index, there is not a consensus on a figure, so Team Administrators have the option to choose amongst several commonly used multipliers:

 

DEFRA[9] 1.9
Kollmuss[10] 2.0
Cool Air/Clean Planet[11] 2.7
IPCC[12] 3.0

Ground Transportation Emissions

Car

The basic calculation is

 

kg CO2 = (kg CO2 / gallon) x <# miles> / (miles / gallon)

 

where  kg CO2 / gallon = 8.887[13]

miles / gallon = <user input> or 23.1[14] default (CA-CP uses 24.17)

 

so        kg CO2 = 8.887 / <user input> or 23.1[15] default (CA-CP uses 24.17)

Train

The basic calculation is

 

kg CO2 / passenger mile = MMBtu / pass. mile x kg CO2 / gallon x gallon /MMBtu

 

where  MMBtu / passenger mile = 0.001628[16]

kg CO2 / gallon = 8.887[17]

gallon /MMBtu = 8.772[18]

 

so        kg CO2 / passenger mile = 0.1269

Bus

The basic calculation is

 

mT CO2 / passenger mile = MMBtu / pass. mile x mT CO2 / gallon x gallon /MMBtu

 

where  MMBtu / passenger mile = 0.003343[19]

kg CO2 / gallon = 8.887[20]

gallon /MMBtu = 8.772[21]

 

so        mT CO2 / passenger mile = 0.2606

 

Vehicle Type

kg CO2e/mile

kg CO2e/mi - CA/CP

Car

0.3847

0.366766239

Train

0.1269

0.148333015

Coach Bus

0.2606

0.321217508

 

In each case, the emissions generated = emissions factor X distance

Fuel

Fuel Type

kg CO2e/gal

Propane

5.8

Heating Oil

10.2

Gasoline

8.9

Fuel Type

kg CO2e/1,000ft3

Natural Gas

54.4



[1]https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/224437/pb13988-emission-factor-methodology-130719.pdf

[2] For more information on Great Circle Distance, see http://en.wikipedia.org/wiki/Great-circle_distance

[3] http://www.eea.europa.eu//publications/emep-eea-emission-inventory-guidebook-2009

[4]https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69554/pb13773-ghg-conversion-factors-2012.pdf

[5] “The long haul estimate is based on a flight length from the EMEP/EEA Guidebook of 6482 km, short haul 1108km and domestic 463km.  Domestic flights are between UK airports, short haul international flights are typically to Europe (up to 3700km distance), and long haul international flights are typically to non-European destinations (or all other international flights over 3700km distance).”

[5]

[6] pkm = passenger-kilometre

[7] http://cleanair-coolplanet.org/campus-carbon-calculator (Column BN, Sheet: EF_Transportation)

[8] According to DEFRA, “The revised average emission factors for aviation … include the uplift of 10% to correct underestimation of emissions by the CORINAIR methodology (discussed above) and DO NOT include the 8% uplift for Great Circle distance, which needs to be applied separately.”

[9]https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/224437/pb13988-emission-factor-methodology-130719.pdf (point 190)

[10] http://sei-us.org/publications/id/13

[11] http://sustainability.duke.edu/documents/Air%20Emissions%20Calculator%20Comparison.pdf

[12] http://www.ipcc.ch/ipccreports/sres/aviation/index.php?idp=86

[13] http://www.epa.gov/cleanenergy/energy-resources/refs.html

[14] http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_04_11.html

[15] Ibid

[16] http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_04_20.html

[17] http://www.epa.gov/cleanenergy/energy-resources/refs.html

[18] http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent

[19] http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_04_20.html

[20] http://www.epa.gov/cleanenergy/energy-resources/refs.html

[21] http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent

[22] http://www.eia.gov/environment/emissions/co2_vol_mass.cfm

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