This project is super cool. I would recommend the author starts tracking the amount of CO2 he emits in a year, which could easily be approximated with the flight/transportation and food data he has. Carbon emissions per Capita per year in the US: 18 metric tonnes. In Italy: 8 metric tonnes [1]. Author is probably close to 60-80 with all the transatlantic flights.
[1] https://www.theguardian.com/environment/datablog/2009/sep/02...