Transient environmental effects of light alloy substitutions in transport vehicles

Materials indices and exchange constants are combined with Field et al.’s fleet analysis [Field F, Kirchain R, Clark J. Life-cycle assessment and temporal distributions of emissions: developing a fleet-based analysis. J Indust Ecol 2000;4:71–91, doi:10.1162/108819800569816] to examine the time-dependent CO2 emissions attached to the production of the Al and Mg alloys used to reduce the mass of transport vehicles. The model is used to breakdown the temporal pattern of upfront emissions of passenger cars according to the mass and CO2-footprint efficiency of typical automotive structural substitutions (castings, stiff panels and stiff beams), accounting for the effect of recycling. The fleet’s upfront emissions of Al and Mg castings with high content of secondary metal are offset by the increased fuel efficiency after 4 years of driving. Al beams and panels and electrolytic Mg panels require between 8 and 15 years, whereas for panels and beams of Pidgeon Mg no environmental benefits ever materialise.