Exhaust gases discharged from automobiles are noticed as one of the reasons for resent increase in atmospheric methane (CH4) and nitrous oxide (N2O) concentration, which have been considered as greenhouse effect gas.
In order to make an accurate estimation of methane and nitrous oxide discharged from automobiles, measurement methods of them were experimentally developed and their emissions were measured for different kinds of automobiles under various driving conditions.
Then, we have tried to estimate the annual global emissions from automobiles using these measurement results and statistical data such as the number of automobiles, the total annual mileage, and the total annual fuel consumption etc.
As results, their emissions from passenger vehicles which have been estimated from global number of automobiles were 477.263 t/year for methane and 313.472 t/year for nitrous oxide. These numbers are higher than what had been estimated.