Engine emissions with biodiesel fuels and biodiesel blends

CHED 464

Bryan W. May, maybw@cctech.edu, Department of Science, Central Carolina Technical College, 506 North Guignard Drive, Sumter, SC 29150
Biodiesel is renewable fuel source composed of mono-alkyl esters derived from long chain fatty acids of vegetable oils or animal fats. Biodiesel fueled engines produce lower emissions of particulate matter (PM), carbon monoxide (CO), volatile organic compounds (VOCs), sulfur oxides (SOx), and total unburned hydrocarbons (HC) including polycyclic aromatic hydrocarbons (PAHs) than conventional petroleum based diesel fuels. However, biodiesel fueled engines produce higher emissions of nitrogen oxides (NOx). Engine emissions are directly related to the structural features of the mixture of mono-alkyl esters that comprise a biodiesel fuel. These structural features include length, degree of saturation, and branching of the mono-alkyl ester chain. By controlling the structure of the mono-alkyl esters the composition of emissions can be optimized.