Annex 41 Complementary information to source category 5a 4-Stroke Engines
Overview of recent revisions
New information on emission factors for air releases was assessed and a revised emission factor is included for gasoline-powered vehicles with catalyst. Studies by several authors (Hagenmaier et al. 1990, Oehme et al. 1991, Abrantes et al. 2011) have shown that the emission factor for gasoline cars equipped with catalyst is not null, as suggested previously. Although the emission factor for this class is very small, a high number of these vehicles is in use worldwide.
Further, a new class ‘ethanol fuel (with catalyst)’ was introduced. Abrantes et al. (2011) showed that ethanol powered vehicles have lower emissions than gasoline powered vehicles. Thus an emission factor for ethanol vehicles equipped with catalyst is also considered.
Derivation of emission factors
Release to Air
The annual average mileage, type and level of maintenance of vehicles are different worldwide. The use of leaded fuels decreased dramatically in Europe, Japan, and North America as a result of legislation; however, leaded fuel is still used in some other countries. Phase-out of leaded gasoline and adoption of catalytic converters as required in the EU Guideline 94/12/EG or similar legislation means that 4-stroke gasoline engines will become an almost negligible source of PCDD/PCDF emissions to air.
The emission factors listed in the Toolkit are based on studies in Germany and Belgium. Other countries, like North America and Asia, have very limited data on vehicle emissions.
Recent work on gasohol (gasoline with 22% ethanol) and ethanol powered vehicles, with a three-way catalyst in good working conditions, showed PCDD/PCDF releases of 0.39 10-3 and 0.25 103 µg TEQ/t of fuel burned, respectively for gasohol and ethanol vehicles (Abrantes et al. 2011). The average results obtained by Abrantes et al. (2011), Hagenmaier (1990) and Oehme et al. (1991) are of 0.00075 µg TEQ/t of fuel burned. Thus, an emission factor to air of 0.001 µg TEQ/t of fuel burned is specified for class 3. Based on these results, an emission factor for ethanol- powered vehicles of 0.0007 µg TEQ/t of fuel burned is equally included for class 4.