This work focuses on analysis of fine particles and carbonyl compounds and the efficiency of a four-way catalytic converter towards these pollutants using two different biodiesel fuels in 20% v/v with a reference petroleum diesel. The biodiesel tested are fatty acid methyl ester (FAME) of soybean oil and fatty acid ethyl ester (FAEE) produced from Waste Cooking Oil. The combustion of the reference petroleum diesel (B0) and biodiesel blends was carried out in the engine of a diesel power generator.Number size distributions of fine particles (≺10 μm diameter, named PM10) emitted were obtained using an Electrical Low Pressure Impactor (ELPI). It is shown that whatever the blend tested, particles are mainly composed of ultrafine particles with a diameter less than 0.4 μm. The 4-way catalytic converter allows to reduce fine particle emission by at least 96.7%. Although the emission factor is dependent of the composition of the biodiesel blend, it was observed that introduction of FAME does not influence the number size distribution. The fraction PM0.1 represents then about 42% of the total number of particles. On the contrary, using FAEE blend leads to a shift of the number size distribution towards larger particles with a contribution of 70% of the fraction PM0.1-1.The use of FAEE blend leads to an increase of carbonyl compounds emission especially for acetaldehyde, acrolein, propanal and acetone production. However, it appears that the 4-way catalyst is not efficient towards carbonyl compounds conversion.