Exhaust Emission Effects of Fuel Sulfur and Oxygen on Gasoline Nonroad Engines (EPA-420-P-02-012)

NOTICE This technical report does not necessarily represent final EPA decisions or positions. It is intended to present technical analysis of issues using data that are currently available. The purpose in the release of such reports is to facilitate the exchange of technical information and to inform the public of technical developments which may form the basis for a final EPA decision, position, or regulatory action. Purpose The purpose of this memo is to document the effects of changing gasoline specifications on exhaust emissions from nonroad gasoline-fueled engines that are incorporated in EPA's draft NONROAD2002 emissions inventory model. There have been a number of gasoline specifications that have changed or have been considered for change in the past few years. The most prominent of these changes has been summer volatility restrictions, wintertime oxygenated fuel requirements, and reformulated gasoline requirements which incorporate year-round oxygenate requirements and summertime emission requirements. For reasons described below, the effect of these fuel changes on nonroad gasoline engines' exhaust emissions of carbon monoxide (CO), nitrogen oxides (NOx), and volatile organic compounds (VOC) is ascribed mainly to the oxygen content. Any expected changes to the fuel sulfur is expected to reduce SOx emissions only.