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The Energy Independence and Security Act of 2007 established a new Renewable Fuel Standard (RFS2) requiring increased biofuel use (through 2022) and greater fuel economy (through 2030) for the US light-duty vehicle (LDV) fleet. Ethanol from corn and cellulose is expected to supply most of the biofuel and be used in blends with gasoline. A model was developed to assess the potential impact of these mandates on the US LDV fleet. Sensitivity to assumptions regarding future diesel prevalence, fuel economy, ethanol supply, ethanol blending options, availability of flexible-fuel vehicles (FFVs), and extent of E85 use was assessed. With no E85 use, we estimate that the national-average ethanol blend level would need to rise from E5 in 2007 to approximately E10 in 2012 and E24 in 2022. Nearly all (97%) US gasoline LDVs were not designed to operate with blends greater than E10. FFVs are designed to use ethanol blends up to E85 but comprise only 3% of the fleet.

Urea SCR is an established method to reduce NOx in dilute exhaust gas. The method is being used currently with stationary powerplants, and successful trials on motor vehicles have been conducted. The reason most often cited for rejecting urea SCR is lack of urea supply infrastructure, yet urea and other high nitrogen products are traded as commodities on the world market as a fertilizer grade, and an industrial grade is emerging. For a subset of commercial vehicles, urea can be provided by service personnel at designated terminals. But this approach does not support long distance carriers and personal use vehicles. The preferred delivery method is to add urea during vehicle refueling through a common fuel nozzle and fill pipe interface: urea / diesel co-fueling. Aqueous urea is well suited to delivery in this fashion.

The selection of fuels for use in transportation has been based upon cost, function, available energy resources and convenience. Petroleum-derived fuels, gasoline and diesel, have consistently been the fuels of choice. Concern for the effects of selected species in the products of combustion of hydrocarbons on the environment continues to increase, and will influence choice of fuels in the future. Fuel properties vary widely among the alternatives worthy of consideration for the future. Utilization of alternative fuels will require innovative approaches in sensors and controls in order to develop vehicles with features and function to rival current vehicles. The fuel composition sensor, on-board computer and related controls used on Flexible Fuel Vehicles have resolved the transition issue to methanol fuel. Sensors and control systems remain to be developed for other fuel alternatives.