Automotive Emissions Control

Motor vehicles account for 38.9% of the total mass of man-made air pollutants in the U.S., according to a recently published HEW inventory. However, when relative harmfulness of individual pollutants is considered, the motor vehicle contribution is reduced to about 12%. Current model motor vehicles emit approximately 83% less hydrocarbons and 70% less carbon monoxide than precontrolled vehicles. By 1976, vehicles are expected to reduce HC emissions by 98%, CO by 97%, and oxides of nitrogen by 90%. The California Air Resources Board has shown that motor vehicle emissions of HC and CO in the South Coast Basin have been reduced by 18% and 13%, respectively, from peak values which occurred during the mid-1960's. NOx emissions continued to increase until 1971, but are now declining. Total nationwide emissions from motor vehicles are also declining, in spite of an increasing car population. Automotive power plants for the balance of this decade will be highly refined derivatives of today's internal combustion engines. Exhaust gas recirculation, thermal reactors, and catalytic converter systems are being developed to meet future requirements, although both customer acceptance factors and emission control are not fully acceptable at this time. Lead-free fuel will be required to insure satisfactory component life, to minimize harmful effects of combustion chamber deposits, and to significantly reduce the emission of particulate matter. Major variations of the reciprocating internal combustion engine, gas turbines, Rankine cycle engines, and electric propulsion systems are also being actively developed to meet future needs for virtually emission-free vehicles.