Refining Economics of U.S. Gasoline: Octane Ratings and Ethanol Content

Increasing the octane rating of the U.S. gasoline pool (currently similar to 93 Research Octane Number (RON)) would enable higher engine efficiency for light-duty vehicles (e.g., through higher compression ratio), facilitating compliance with federal fuel economy and greenhouse gas (GHG) emissions standards. The federal Renewable Fuels Standard calls for increased renewable fuel use in U.S. gasoline, primarily ethanol, a high-octane gasoline component. Linear programming modeling of the U.S. refining sector was used to assess the effects on refining economics, CO2 emissions, and crude oil use of increasing average octane rating by increasing (i) the octane rating of refinery-produced hydrocarbon blendstocks for oxygenate blending (BOBs) and (ii) the volume fraction (Exx) of ethanol in finished gasoline. The analysis indicated the refining sector could produce BOBs yielding finished E20 and E30 gasolines with higher octane ratings at modest additional refining cost, for example, similar to 1 not subset of/gal for 95-RON E20 or 97-RON E30, and 35 not subset of/gal for 95-RON E10, 98-RON E20, or 100-RON E30. Reduced BOB volume (from displacement by ethanol) and lower BOB octane could (i) lower refinery CO2 emissions (e.g., similar to 3% for 98-RON E20, similar to 10% for 100-RON E30) and (ii) reduce crude oil use (e.g., similar to 3% for 98-RON E20, similar to 8% for 100-RON E30).