Effects of Ethanol or ETBE Blending in Gasoline on Evaporative Emissions for Japanese In-Use Passenger Vehicles 2007-01-4005

Biomass derived ethanol is thought to be a promising gasoline blend stock to reduce carbon dioxide (CO₂) emissions from vehicles, and its practical use is under discussion. In Japan, the maximum permissible limit of ethanol content in gasoline is 3 vol%, which almost corresponds to 1.3 mass% of oxygen content, which is defined by gasoline quality standards at present. In addition to ethanol, the use of Ethyl tert-Butyl Ether (ETBE), which is synthesized from biomass ethanol and isobutene, is under discussion as a kind of biomass fuels in Japan.

This study examines and discusses the effects of ethanol- and ETBE-blended gasolines on evaporative emissions, especially on refueling loss and diurnal breathing loss (DBL) emissions, from in-use passenger cars in Japan. This study shows that refueling loss emissions don't increase with ethanol- or ETBE-blended gasoline as long as Reid Vapor Pressure (RVP) is adjusted. However, DBL emissions significantly increased with 3vol% ethanol-blended gasoline (E3 gasoline), compared to base gasoline (non-oxygenated gasoline) or ETBE blended gasoline, even though RVP of each fuel was adjusted to within similar levels. The effects of ethanol-blended gasoline on evaporative emissions were studied from the view point of vapor composition. As a result, the increased DBL emissions with ethanol-blended gasoline were presumed to be caused by permeation through vehicle fuel systems.