Ethanol in diesel also forms carbon PM emissions, scientists find

Diesel Fuel News, May 27, 2002

While ethanol-diesel blends are touted for reducing particulate matter (PM) emissions, ethanol also forms certain types of PM, according to a U.S. Department of Energy study at Lawrence Livermore Lab and University of California-Berkeley. "The relatively large amounts of ethanol-derived carbon in the PM points to potential problems of using oxygenates which form unsaturated [C.sub.2] fragments during combustion," the researchers reported this month (see SAE 2002-01-1704).

"Ethanol produces some acetylene and other soot precursors during combustion," but its contribution to soot is "less than diesel fuel," they found. Emulsions of ethanol in diesel tend to yield larger volatile organic fraction (VOF), although exhaust catalysts can oxidize these. Cosolvent blends by contrast tend to reduce PM mass, the study found.