Life Cycle Analysis of Biodiesel: An Application to Portugal

The main objective of this research was to update the GREET model (developed by the Argonne National Laboratory, USA), to accomplish the Portuguese reality. Following this step, a LCA for biodiesel in Portugal was carried out. A case study was selected, considering the use of biodiesel in the urban buses fleet of the city of Braga, in the north of Portugal. Through the study it was possible to verify that throughout the biodiesel’s life cycle (well to wheels), the total energy consumption is about 17.820 kJ/km, while for diesel is 16.292 kJ/km. This increase of 9.5% in energy consumption is due not only to the increase of fuel use (due to biodiesel’s lower PCI) but also to higher energy consumption during the production stages of biodiesel (about 6% higher). With the use of biodiesel, significant reductions can be obtained for most of the pollutants considered. For emissions of CO2 there is a 15% reduction compared with diesel, for CO and NOx the reductions are about 17%, for VOC the reduction is 16%, for emissions of particulate matter and CH4 the reductions are about 22% while in the case of the SOx the reduction is 52%. The only exception to the trend occurs in the emissions of N2O where there was a total increase of 0.5% compared with the emissions obtained for diesel.