Biomass derived fuel is regarded as a carbon neutral fuel. Therefore, biomass ethanol is thought to be a promising gasoline blend stock to reduce CO2 emissions from vehicles, and its practical use is under discussion. However, there are many considerations for blending ethanol into conventional gasoline. One of the important considerations is a vapor pressure rise of the gasoline that might cause an increase in evaporative emissions from ethanol-blended gasoline. This study examines and discusses the effects of ethanol-blended gasoline on evaporative emissions, especially on refueling and running loss (RL) emissions. Furthermore, in addition to ethanol, the use of ETBE (Ethyl tert-Butyl Ether), which is synthesized from biomass ethanol and isobutene, is also under discussion in Japan. Therefore, the effects of ETBE on evaporative emissions were also examined and compared to ethanol effects.
As a result of the study, it is clear that RL emissions are influenced by vehicle characteristics, such as fuel temperature and canister purge flow rate during running, and RL emissions of ethanol-blended gasoline would increase compared with base gasoline, in the case of vehicles with high final fuel temperature this is true even if the RVP of both fuels was adjusted to within similar levels. On the other hand, it was verified that RL emissions would not increase with ETBE blended gasoline, regardless of vehicle type. Furthermore, refueling loss emissions did not seem to be influenced by the type of Japanese passenger car or to increase with ethanol or ETBE blended gasoline, as long as RVP was adjusted.