In this study,the efforts to reduce NO_x and particulate matter(PM)emissions from a diesel engine using both ethanol-selective catalytic reduction(SCR)of NO_x over an Ag/Al_2O_3 catalyst and a biodiesel-ethanol-diesel fuel blend(BE-diesel)on an engine bench test are discussed.Compared with diesel fuel,use of BE-diesel increased PM emissions by 14% due to the increase in the soluble organic fraction(SOF)of PM,but it greatly reduced the Bosch smoke number by 60%-80% according to the results from 13-mode test of European Stationary Cycle(ESC)test.The SCR catalyst was effective in NO_x reduction by ethanol,and the NO_x conversion was approximately 73%.Total hydrocarbons(THC)and CO emissions increased significantly during the SCR of NO_x process.Two diesel oxidation catalyst(DOC)assemblies were used after Ag/Al_2O_3 converter to remove CO and HC.Different oxidation catalyst showed opposite effect on PM emission.The PM composition analysis revealed that the net effect of oxidation catalyst on total PM was an integrative effect on SOF reduction and sulfate formation of PM.The engine bench test results indicated that the combination of BE-diesel and a SCR catalyst assembly could provide benefits for NO_x and PM emissions control even without using diesel particle filters(DPFs). In this study, the efforts to reduce NO x and particulate matter (PM) emissions from a diesel engine using both ethanol-selective catalytic reduction (SCR) of NO x over an Ag / Al 2 O 3 catalyst and a biodiesel-ethanol-diesel fuel blend (BE- diesel) on an engine bench test are.Compared with diesel fuel, use of BE-diesel increased PM emissions by 14% due to the increase in the soluble organic fraction (SOF) of PM, but it greatly reduced the Bosch smoke number by 60% -80% according to the results from 13-mode test of European Stationary Cycle (ESC) test. The SCR catalyst was effective in NO x reduction by ethanol, and the NO x conversion was approximately 73%. Total hydrocarbons (THC) and CO emissions increased significantly during the SCR of NO_x process. Two diesel oxidation catalyst (DOC) assemblies were used after Ag / Al_2O_3 converter to remove CO and HC.Different oxidation catalyst showed opposite effect on PM emission. PM composition analysis revealed that the net effect of oxidation catalyst o n total PM was an integrative effect on SOF reduction and sulfate formation of PM. The engine bench test results indicated that the combination of BE-diesel and a SCR catalyst assembly could provide benefits for NO x and PM emissions control even without using diesel particle filters ( DPFs).