Environmental implications on the oxygenation of gasoline with ethanol in the metropolitan area of Mexico City

Motor vehicle emission tests were performed on 12 in-use light duty vehicle s, made up of the most representative emission control technologies in Mexi co City: no catalyst, oxidative catalyst, and three way catalyst. Exhaust r egulated (CO, NO, and hydrocarbons) and toxic (benzene, formaldehyde, aceta ldehyde, and 1,3-butadiene) emissions were evaluated for MTBE (5 vol %)- an d ethanol (3, 6, and 10 vol %)-gasoline blends. The most significant overal l emissions variations derived from the use of 6 vol % ethanol (relative to a 5% MTBE base gasoline) were 16% decrease in CO, 28% reduction in formald ehyde, and 80% increase in acetaldehyde emissions. A 26% reduction in CO em issions from the oldest fleet (< MY 1991, without catalytic converter), whi ch represents about 44% of the in-use light duty vehicles in Mexico city, c an be attained when using 6 vol % ethanol-gasoline, without significant var iation in hydrocarbons and NO,emissions, when compared with a 5% vol MTBE-g asoline. On the basis of the emissions results, an estimation of the change in the motor vehicle emissions of the metropolitan area of Mexico city was calculated for the year 2010 if ethanol were to be used instead of MTBE, a nd the outcome was a considerable decrease in all regulated and toxic emiss ions, despite the growing motor vehicle population.