The Potential VOC Offset by Carbon Monoxide Reduction by

This paper updates a previous analysis (Whitten, 2005) of the carbon monoxide (CO)-related VOC offset built into the California RFG regulations. This new offset amounts to 72 tons per day of on-road VOC equivalents from using E10 compared to non-oxy fuel or E0; consideration of non-road impacts could add another 19 tons per day to this bringing the total to about 90 tons per day VOC equivalents. In terms of grams per on-road gasoline vehicle the CO reduction calculated here is 105 grams per day for E10 and 60 grams per day for E5.7, which compares to a recent ARB estimate of only 7.8 grams per day of CO for E5.7. The net balance between these offsets and ethanol-related permeation emissions continues to be an issue (along with a NOx issue discussed below) in the current plans to modify these RFG regulations. As the present regulations for Phase 3 of the California RFG program were finalized, a concern over increased permeation emissions of volatile organic compounds (VOC) due to the use of ethanol lead to the creation of an offset between CO and any anticipated permeation increases from its use in CaRFG3. The form of this “offset ” was to not debit non-oxygenated CaRFG3 for increases of CO over the base “flatline ” CaRFG3, which contains 2 weight-percent oxygen. The ARB (2000) stated; “Moreover, a gasoline with zero oxygen will have lower rates of permeation emissions than fuels with ethanol or MTBE. The lower permeation emissions from gasoline with no oxygen appear to more than offset the increase in ozone-forming potential from the higher CO emissions. Thus, it is not necessary to include a CO debit mechanism in the final regulations.” Along with banning MTBE, CaRF3 was designed to give increased flexibility for the use of 100 % petroleum non-oxygenated fuel