CLIMATE CHANGE AND GREENHOUSE GAS EMISSIONS IN AUTOMOTIVE APPLICATIONS Globally, existing or proposed regulations regarding vehicle greenhouse gas (GHG) emissions address only the use phase (driving) of a vehicle’s total life cycle. From this perspective it is easily understood that, assuming all other things are equal, a lighter weight vehicle results in reduced fuel consumption and consequently reduced use phase GHG emissions. Material choices that result in the lowest mass vehicle may be preferred if one considers only a vehicle’s use phase (Figure 1). Figure 1 : Vehicle Use Phase Emissions Only   However, to fully assess a vehicle’s environmental footprint, all vehicle life phases must be considered. This includes the GHG emissions resulting from materials production, the manufacturing of the vehicles themselves, the use phase and the end-of-life phase. This approach which considers all aspects of vehicle life (Figure 2) is called Life Cycle Assessment (LCA) and is recommended for evaluating a product’s impact on climate change. Figure 2: Total Life Cycle Assessment (LCA) Greenhouse gas (GHG) global warming potential is usually measured in kilograms of carbon dioxide equivalents (CO2eq) accounting for the greenhouse gasses shown in the following table (Figure 3). Figure 3: Global Warming Potential of Key Substances SUBSTANCE GLOBAL WARMING POTENTIAL (GWP1000 IN kg CO2EQ) ATMOSPHERIC LIFETIME (YEARS) Carbon Dioxide (CO2) 1 50-200 Methane (CH4) 21 9-15 Nitrous Oxide (N20) 310 120 CFC-12 (CCL2F2) 6,200-7,100 102 HCFC-22 (CHCIF2) 1,300-1400 12 PERFLUOROMETHANE (CF4) 6,500 50,000 PERFLUOROETHANE(C2F6) 9,200 10,000 SULPHUR HEXAFLUORIDE (SF6) 23,900 3,200 Material selection is a critical aspect to the GHG emissions during the material production phase. As shown in the following table, alternatives to steel in automotive structural applications produce 5 to 10 times as much GHG emissions during their production. Energy sources used in material production (e.g. coal, hydro, petroleum, etc) significantly affect the amount of GHG emissions in LCA studies. Analysis of material selection decisions that require new material production capacity must incorporate the impact of new marginal production energy sources. For example, hydro power may be used for some current production, but new production likely requires some other energy source such as coal. GHG emissions from steel production consist of only carbon dioxide whereas GHG emissions from aluminum consist largely of carbon dioxide and up to 20% perfluorocarbons (CF4 and C2F6) , and magnesium has up to 20% Sulphur Hexafluoride (SF6). Consequently, applications of alternative materials front-load the environment with more GHG emissions resulting from the production of the material than the steel application they replace. In the case where the alternative material results in reduced mass and reduced fuel consumption, the GHG emission improvement achieved during the driving phase is unlikely to offset the upfront loading of the material production phase when being compared to optimized design with Advanced High Strength Steel. Typical vehicles built with alternative materials will often net more GHG emissions during their lives than AHSS-intensive vehicles. An LCA approach is the correct approach for assessing a vehicle’s climate change footprint and requires vehicle manufactures to balance the possible driving phase improvements against the manufacturing phase disadvantages when considering GHG intensive materials, such as aluminum, magnesium and plastics. To investigate the aspects of material selection on automotive Life Cycle Assessment (LCA) GHG emissions, a study titled The Impact of Material Choice in Vehicle Design on Life Cycle Greenhouse Gas (GHG) emissions - The Case of HSS and AHSS versus Aluminum for BIW applications (see www.worldautosteel.org ) was conducted at the University of California, Santa Barbara (UCSB), Bren School of Environmental Science and peer reviewed model for material comparisons was developed. Consider two case study examples, using the UCSB model, based on a C-Class vehicle with a gasoline internal combustion engine (ICE). The case studies focus on the body-in-white and assume of 25% mass reduction from a conventional steel baseline for Advanced High Strength Steel (AHSS) and 40% mass reduction for aluminum along with additional secondary weight savings in both cases. Fuel savings and driving cycles are based on the fka study. The UCSB model calculated GHG reduction that is achieved by optimizing the design with AHSS instead of conventional mild steel (Figure 4a). This is the situation of ‘steel re-inventing itself’ and replacing former steel material and design with new steel material and design. The effect of 25% mass reduction in the body-in-white is to reduce CO2 emissions in both the material stages and vehicle use phase so that the total life cycle emissions of the vehicle are reduced by 3%. And, this is accomplished no additional cost. Figure 4a: Life cycle GHG comparisons – Conventional Steel and AHSS The UCSB model also compared an optimized aluminum design with the AHSS design (Figure 4b). Although, this scenario assumes some additional mass savings can be achieved with aluminum, the increase of CO2 equivalent emissions from the material production phase more than offsets the reductions generated in the use phase. The vehicle’s total life cycle emissions are increased by 2%. To add insult to injury, this environmental burden also comes with a significant cost increase. Figure 4b: Life cycle GHG comparisons – AHSS and aluminum A key finding is that although the AHSS is shown in these case studies to provide an advantage over the aluminum solution, it is only a small percentage of the total. In fact, the preferred material depends on the assumptions and inputs for the specific application and manufacturing processes. So although the preponderance of reasonable inputs demonstrates AHSS to be the preferred material over aluminum, there are sets of assumptions where the conclusion could be reversed. Regardless of all reasonable inputs, the impact of material production and recycling on LCA GHG emissions are relatively small compared to total emissions, and significant improvements in reducing automotive GHG emissions will not be made by material substitution alone. The LCA approach is able to make comparisons between other advanced automotive capabilities such as powertrain, fuel choices and driving scenarios that are emerging into mainstream automotive technologies. Figure 5 compares an AHSS body to an aluminum body and the cumulative impact of these technologies on the total LCA of GHG emissions. The comparison finds that use of these upcoming technologies can have a dramatic influence on the total LCA GHG emission of a vehicle. The use of advanced powertrains (such as hybrids), advanced fuels (such as grain and cellulose ethanols), and improved driving cycles (such as the implementation of timed lights and roundabouts), can result in a dramatic reduction in the use phase GHG emissions.   Figure 5: Life cycle GHG comparisons – powertrains & fuels A key point that needs to be made and as demonstrated by this graph, that although the material production phase GHG emissions remain the same, they become a much more significant percentage of the total LCA GHG emissions as use phase efficiencies are achieved. It is concluded that as other green technologies that improve vehicle GHG emissions are implemented in mainstream vehicle designs, the emissions from material production will become more important, placing greater emphasis on selecting a low GHG-intensive material such as steel. For more information on this case history and similar information, visit www.autosteel.org or www.worldautosteel.org.