Closing the gasoline system – control of gasoline emissions from the distribution system and vehicles

Report no. 3/90: This report shows that a series of measures effectively closing up the gasoline system of distribution and use in motor vehicles is the preferred strategy to control gasoline emissions. These emissions contribute about 40% to the volatile organic compound (VOC) element of photochemical ozone, and control is being given priority in the EC. The European Commission is proposing to control gasoline evaporative emissions from cars in the draft directive which sets stringent exhaust emission limits, requiring 3-way exhaust catalysts for all cars. A further draft directive is expected during 1990 to control emissions from distribution of gasoline from refineries and terminals to service stations.The effectiveness of each of the main options to control gasoline emissions is examined.

Carbon canisters are capable of 90% control of evaporative emissions from parked cars, but full effectiveness depends upon choice of test conditions which realistically represent road fuels and the more testing ambient conditions found.This leads to the conclusion that the strategy being followed by the Commission should be followed through by taking the opportunity presented by the enlarged on-board carbon canister to control vehicle emissions, giving control of refuelling and evaporative emissions in one step, including running losses.

This strategy is more effective and energy efficient than the alternative of restricting the quality and composition of gasoline.The enlarged carbon canister is the most effective way of achieving the "closed gasoline system". To underline this conclusion, the effectiveness of the closed system approach is assessed for the control of benzene emissions derived from gasoline. Limiting the benzene content of gasoline would be a much less effective approach.