Biodiesel from saturated and monounsaturated fatty acid methyl esters and their influence over noise and air pollution

A combined analysis of exhaust and noise emissions of an three-cylinder direct injection diesel engine running on palm oil methyl esters (PME) and olive pomace oil methyl esters (OPME), both blended with diesel fuel in different proportions, is proposed to evaluate their suitability as partial substitute to fossil fuels. Moreover, engine sound quality (derived from the use of these fuels) based on loudness and roughness metrics has been analyzed. A strong correlation between sound pressure maximum level and loudness was found. Although it was observed that both parameters improved with the use of both set of blends, PME blends depicted the best behavior. In terms of roughness, OPME blends achieved the maximum attenuation. In addition, roughness attenuation was found to be more meaningful than loudness when the blends were used. Considering the exhaust emissions tests, it was observed that the use of both sets of fatty acid methyl ester blends allows a significant reduction of CO emissions. Moreover, lower NO exhaust emissions were produced when PME blends were used instead of OPME blends or diesel fuel. NOx emissions were lower when PME blends were used instead of OPME blends, though diesel fuel depicts the lowest values. In general terms, it may be concluded that saturated fatty acid methyl esters produce biodiesel with a positive influence over air and noise emissions.