BIODIESEL Renewable Energy From Oils and Fats Clint Johnson Energy Technology and Policy University of Texas Fall 2006

French Fried Fuel

Biodiesel = FAME Fatty Acid Methyl Esters (FAME) Fatty acids taken from oils or fats Reacted with MeOH Washed, dried to remove impurities Must comply with fuel standards (U.S., European, etc.) Variety of blends, from B5 to B100 FAME

Chemistry of Oils and Fats Fatty acids are long- chain carboxylic acids A glycerol bonded to 3 fatty acids is called a triglyceride Oils/fats contain triglycerides and unbonded, or free, fatty acids (FFA’s) A Fatty Acid A Triglyceride

Transesterification First observed in 1850’s One main reaction for biodiesel production Exchanges an ester’s functional group Must be catalyzed, either base or acid R’ (below) is methyl, and it replaces glycerol group Viscosity is reduced significantly Transesterification

Feedstock Selection MaterialFFA ContentCost Refined oils (soybean, etc.) 0 - 1%High Waste oils (fry grease) 2 – 7 %Low Animal fat (lard) 5 – 30 %Low Yellow grease 7 – 30 %Moderate Brown grease > 30 %Very Low Source: Kemp, William H. “Biodiesel Basics and Beyond.” p. 108

Catalyst Selection Acid or base catalyst Base is faster, more economic With high FFA, base catalyst will produce soap Base catalyst also produces glycerol as coproduct Acid catalysis can fix the soap problem Most commercial processes use base catalysis

Production

Emissions Biodiesel reduces most problematic emissions NOx (greenhouse) emissions are increased Led to regulatory problems with TCEQ Can be addressed with NOx reducing additives Source: U.S. EPA

Future Biodiesel Research Processing and marketing of waste glycerin Improved FAME yields, residence times New techniques for using cheap, high FFA oils: Fischer esterification, pyrolysis, micro emulsion Engine performance testing

Questions?