Chemistry.......
Hydrocarbon = mainly carbon
Jet A-1 is approximated by C12H26
Atomic weights: H = 1, C = 12, O = 16 (ignoring isotopes)
Molecular weight C12H26 = 12x12 + 26 = 170
Burnt hydrocarbon = CO2 + H2O
Total molecular weight of resulting CO2 = 12x(12 + 16x2) = 528
Ratio of resulting CO2 weight to originating hydrocarbon = 528/170 = 3.1
Burning 40t = 40,000kg of jet A-1 produces
40,000 x 3.1 = 124,000kg CO2.