LIFE CYCLE ANALYSIS OF EURO IV URBAN BUSES

Abstract

ABSTRACT The Euro 4 standard sets a pollutant emissions limit respect to NOx and particulate matter emissions that have forced to automobile manufacturers and, specifically, to engine manufacturers, at make studies about the engine performance and exhaust aftertreatment technology that have resulted in systems radically different. Specifically systems presented have been two, on one side, engines that reduce the temperature inside combustion chamber, by exhaust gas recirculation (EGR) for NOx reduction and incorporate a particulate filter in the exhaust and, on the other side, engines operating at high temperatures to reduce particulate matter, and incorporate a selective catalytic system (SCR) for NOx reduction using urea. This paper presents a comparative study about using both systems in an urban bus, to determinate the best behavior against the energy requirement and greenhouse gas emissions (GEI) by means a Life Cycle Analysis (ACV). Furthermore, the study includes a comparative analysis of different fuels: diesel, biodiesel (B100) and a blended biodiesel at 20% (B20) (Well to Tank analysis) and the environmental impact due to the use of these fuels in the bus (Tank to Wheel analysis). For this purpose, data on fuel consumption and pollutant emissions were acquired by tests in real driving cycle, using a measurement equipment on board the bus. Also has been evaluated the environmental impact of the manufacturing and recycling process of the urban bus tested, as well as, of the exhaust after treatment systems (where the production and recycling of precious metals that are used as a catalysts, has been considered). The data on energy requirement and GEI emissions of different process that are involved in the ACV stages of an urban bus , have been obtained from industry, scientific publication and data bases as GaBi 4 and GEMIS. Among the most relevant results of this comparative analysis has found that the ACV of the SCR+Urea technology has an energy consumption and GEI emissions higher than the ACV of the EGR+DPF technology, mainly due to AdBlue production and supply (formed from deionized water and urea), that this technology requires for its continuing treatment of the exhaust gases. However, the bus that includes this technology generates, in use, lower environmental impact.