Diesel emissions from biofuels derived from Spanish potential vegetable oils

Methyl esters obtained from the most interesting Spanish oleaginous crops for energy use-sunflower and Cynara cardunculus-were both used as diesel fuels, pure and in 25% blends with a commercial fuel which was also used pure. A stationary engine test bed, together with the instrumentation for chemical and morphological analysis, allowed to study the effect of these fuels on the engine emissions, soluble organic fraction of the particulate matter, origin of adsorbed hydrocarbons, sulphate content, particle number per unit filter surface, and mean particle diameter. Both the consideration of the thermochemical properties of the tested fuels and the computations of a chemical equilibrium model were helpful for the results analysis. These results proved that the use of these vegetable esters provides a significant reduction on particulate emissions, mainly due to reduced soot and sulphate formation. On the contrary, no increases in NOx emissions nor reductions on mean particle size were found.