A Review on Available Evidence for Effects of Ethanol Fuels on Air Pollutant Emissions from Motor Vehicles

This paper is based on the available evidence for the air quality impacts of using ethanol fuels in transport and also focuses on regulated and unregulated air pollutant emissions from vehicles running on ethanol fuels. Fuel options for reducing emissions include reformulating conventional fuels to reduce or increase particular components, or use of alternative fuels such as ethanol. Ethanol is a liquid alcohol that is manufactured by the fermentation of a wide variety of biological materials. These materials include grains such as wheat, barley, corn, wood, and sugar cane. Agricultural crops particularly grains are likely to be used in some countries because they have both high productivity and high levels of carbohydrates needed for ethanol manufacture. The review begins with a general overview of the air quality impacts of burning fuels in vehicle engines, listing the types of pollutants normally produced and their impacts on human health and the environment. The specific impacts of using ethanol in both petrol and diesel engines are compared. Control of fuel composition and characteristics provides an important option for limiting pollutant emissions from motor vehicles. By reducing fuel components known to contribute to particular pollutant emissions, it is possible to produce reductions in those pollutants. However, changes to fuel specifications may require design changes to different vehicle subsystems such as engine, fuel system and emission controls.