HOW DOES CARBON FOOTPRINT OFFSETTING WORK?
To offset it you need to start by estimating your journey's CO2 consumption. The majority of sites offering to offset your carbon footprint include a CO2 calculator. The way these calculators work and the result quantified in Euros that they provide vary depending on the platforms.
Greentripper.org, a Belgian website that only works with projects certified by the Ethibel Forum: "an independent organisation, internationally recognised, designated and checked by the Gold Standard and by the UN", also offers to offset radiative forcing. This factor is added to the CO2 calculation which now essentially concerns the plane's consumption of kerosene. As travelling by plane has complex consequences which are not limited to burning fuel.
The CO2 consumption calculation for a flight is still complicated to carry out today and there is, of course, a variation depending on the type of plane, how full it is and its age.