ALTERNATIVES TO CONVENTIONAL DIESEL FUEL-SOME POTENTIAL IMPLICATIONS OF CALIFORNIA'S TAC DECISION ON DIESEL PARTICULATE

Limitations on the use of petroleum-based diesel fuel in California could occur pursuant to the 1998 declaration by California's Air Resources Board (CARB) that the particulate matter component of diesel exhaust is a carcinogen, therefore a toxic air contaminant (TAC) subject to provisions of the state's Proposition 65. It is the declared intention of CARB not to ban or restrict diesel fuel, per se, at this time. Assuming no total ban, Argonne National Laboratory (ANL) explored two feasible ''mid-course'' strategies. (1) Increased penetration of natural gas and greater gasoline use in the transportation fuels market, to the extent that some compression-ignition (CI) applications revert to spark-ignition (SI) engines. (2) New specifications requiring diesel fuel reformulation based on exhaust products of individual diesel fuel constituents. Each of these alternatives results in some degree of (conventional) diesel displacement. In the first case, diesel fuel is assumed admissible for ignition assistance as a pilot fuel in natural gas (NG)-powered heavy-duty vehicles, and gasoline demand in California increases by 32.2 million liters per day overall, about 21 percent above projected 2010 baseline demand. Natural gas demand increases by 13.6 million diesel liter equivalents per day, about 7 percent above projected (total) consumption level. In the second case, compression-ignition engines utilize substitutes for petroleum-based diesel having similar ignition and performance properties. For each case we estimated localized air emission plus generalized greenhouse gas and energy changes. Economic implications of vehicle and engine replacement were not evaluated.