How does FAIRTIQ calculate, how much carbon emissions I saved using FAIRTIQ?
FAIRTIQ calculates your carbon emissions based on a national baseline of the country you travelled in. We then deduct the car emissions from the public transport emissions to come up with the amount of CO2 that you saved. To calculate the time period required to absorb the difference between these two CO2 emissions, we divide the saved CO2 by the absorption rate of a tree.
Here's an example to illustrate our approach:
So far this year, Lisa has used the FAIRTIQ app to travel in Switzerland between Bern and Zurich (95 km one way) by train. She did this trip twice, meaning she travelled 380 km.
To calculate the CO2 emissions for the train, we multiply 380 km * 8.43 (rail CO2 emissions rate in Switzerland, see reference section below). The result is approximately 3.2 kg of CO2 emitted.
To calculate the CO2 emissions saving, we then approximate the CO2 emissions made using a car (the car CO2 emissions rate in Switzerland is 197.23) over the same distance. The result is approximately 75 kg of CO2. Hence, the CO2 emissions saving is (75 kg - 3.2 kg =) 71.8 kg of CO2.
To calculate the time required for a tree to absorb the surplus of CO2 that would have been emitted if the trips were done by car instead of public transport (71.8 kg of CO2), we divide the difference between the car emissions and the public transport emissions (71.8 kg) by the absorption rate of an average tree (approx. 22 kg per year). The time required to absorb the amount is around 3 years and 3 months.
Thus, it would take a single tree approximately 3 years and 3 months to absorb the CO2 that Lisa would have emitted, if she had chosen to take the car instead of the train for her two return trips from Bern to Zurich!
References:
- Vehicle CO2 Emissions: The values FAIRTIQ uses are derived from mobitool-Faktoren v2.0.2, https://www.mobitool.ch/de/tools/mobitool-faktoren-25.html?tag=18.
- Tree absorption rate: FAIRTIQ approximates the tree absorption rate as 22 kg per year, according to https://en.wikipedia.org/wiki/Deforestation_and_climate_change#Reforestation.