Greenhouse Gas Emissions Payback and Economic Assessment for Lightweighted Vehicles using Aluminum and High Strength Steel
In this paper we consider life cycle emissions paybacks and costs associated with lightweighting (LW) automobiles. Both aluminum and high strength steel (HSS) are considered with LW ranging from 6% to 23% based on literature references and input from industry experts. First we compare the increase in greenhouse gas (GHG) emissions associated with producing lightweight vehicles with the saved emissions during vehicle use. This yields a calculation of how many years of vehicle use are required to offset the added GHG emissions from the production stage. GHG savings for aluminum LW varies strongly with location the aluminum is produced and whether secondary (recycled) aluminum can be utilized. HSS is less sensitive to these parameters. However achieving intense LW with HSS requires achievement of secondary LW by downsizing other vehicle components. In principle payback times for vehicles lightweighted with aluminum can be shortened by closed-loop recycling of wrought aluminum. However over a 15-year time horizon it is unlikely that this could significantly reduce emissions due to the need for wrought aluminum recycling infrastructure and end-of-life vehicle returns.
Second life cycle GHG emission costs are evaluated associated with vehicle LW options. The results show greater GHG savings derived from greater LW and added manufacturing costs as expected. However the associated production costs are disproportionately higher than the fuel cost savings associated with higher LW options. A sensitivity analysis of different vehicle classes shows that LW is more cost effective for larger sized vehicles. Also the cost of GHG emissions reductions via lightweighting is compared with alternative GHG emissions reduction technologies such as diesel hybrid and plug-in hybrid electric vehicles. The results find intensive LW to be a favorable approach relative to the technological alternatives but more costly than GHG mitigation strategies available to other industries.