Data sources and assumptions

Sources and assumptions

When it comes to estimating CO2 emissions, at Zerofy we aim to have the most relevant and scientifically sound sources and assumptions. In the following, we list our sources and assumptions for calculations.


CO2 emissions are calculated based on fuel consumption and “well-to-wheel” emissions for a liter of fuel (gasoline or diesel). Vehicle fuel consumption is based on US EPA and EU data, which are based on actual usage and not manufacturer data. The values for CO2 per liter are based on calculations by Auke Hoekstra, TU Eindhoven, and are as follows

- Gasoline: 3.1400 kg CO2 / liter 				
- Diesel: 3.3100 kg CO2 / liter 		
Passenger planes

0.200 kg CO2 / passenger-km. Source: UK Gov Conversion factors


0.041 kg/passenger-km. Source: UK Gov Conversion factors


0.104 kg/passenger-km. Source: UK Gov Conversion factors


Emissions per meal are based on assuming 180g of the main ingredient of meat based meal (chicken, beef, pork) and neglecting the rest. For fish/seafood 200g/ meal is assumed, and for vegan/vegetarian 300g. The CO2 per kg is based on Poore, Nemecek: Science, 2018: Vol. 360, Issue 6392, pp. 987-992.


Daily emissions are estimated from the yearly averages of electricity consumption per household size. Household size is determined by the number of household members. Yearly average household electricity consumption is obtained for each country from the statistical offices of the respective countries.

The emissions factor of kg CO2 per kWh is either based on the yearly averages for each country EU or on real time data feeds from sources such as ENTSO-E.

Goods and Services

Emissions are calculated from the amount of spending and the vendor and/or category. There are emissions factors based on lifecycle analysis per category and dollar spent. Some vendors such as Apple publish detailed per-product analysis. We combine these various sources and models. (We’ll publish more detail on our sources here soon.)