This review discusses vehicle emissions and air quality impacts for bioethanol, biodiesel and biomethane vehicle fuels. The discussion of bioethanol and biodiesel will be based on previous publications  and , and will be supplemented by more recent information. The effects of biomethane use will be assessed by reviewing the effects of compressed natural gas (CNG) and liquid natural gas (LNG) on vehicle emissions.
The resulting concentrations of both formaldehyde and acetaldehyde observed in Brazil AZD8055 generally higher than observed in other countries ; acetaldehyde, formaldehyde and nitrogen oxides are all important initiators of photochemical air pollution problems such as ozone. Severe ozone air quality problems have been observed in a number of cities in Brazil. The concentrations of ozone precursors and ozone have decreased in recent years from more stringent vehicle emissions standards, but ozone issues persist in Brazil.
Results of the analysis of I/M240 emissions data for 1995 and 1996 .19951996Number of vehicles tested721,942651,223HC emissions−1.3%a−0.2%CO emissions−7.0%−4.9%NOx emissions+13.5%+13.1%aThe table shows the % difference between the winter (E10) months and the summer (non-oxygenated fuel) months.Full-size tableTable optionsView in workspaceDownload as CSV