To measure the environmental impact of a product, it is essential to look at the entire Life Cycle of a product and its various inputs.
These are typically called the manufacturing phase, the use phase and the end-of-life (recycling) phase.
EPA is presently considering vehicle regulations for the period from 2017 - 2015. If EPA considers only the emissions during the driving phase ("use phase") of a vehicle’s life, it could very likely result in the design and production of very high emitting vehicles. This is because the emissions during the manufacturing of materials are not only significant (as shown in Figure 1) but the difference between steel and other auto materials emissions is large. The analysis using a study done by Lotus Engineering (commissioned by EPA) shows the difference in materials manufacturing emissions overwhelms the difference in driving phase emissions making steel-intensive vehicles in the lowest emitting design.
This example considers the potential CO2 reduction from an approach that incorporates life cycle emissions involving several factors including the difference in materials manufacturing emissions, which are summarized below:
Figures 1 and 2 describe four variants of the Lotus Study: the baseline Venza [Venza], the Low-Development Case [Lotus-LD], the High-Development Case [Lotus-HD], and the High-Development Case with the AHSS body substituted into the vehicle [Lotus LD BIW in HD].
In Figure 1, one can see the GHG emissions in materials production can be substantial, e.g., 29% of the total vehicle emissions. This is important as it counters a common misperception that materials manufacturing emissions are insignificant and can be ignored in vehicle regulations.
Figure 1 also shows the lowest emitting vehicle is the steel intensive body structure [“Lotus LD BIW in HD”] which is estimated to emit 3.42 tonnes of GHG less over its life than the Lotus HD case. Considering an estimated 15 million vehicle build in 2017, this totals over 51 million tonnes of additional CO2e annual emissions, or nearly half of the steel industry’s entire annual emissions for its highest production year this decade [see below]. Further, the comparison between these two cases only considers the body structure so the use of GHG-intensive materials in, for example, closure panels will only further increase materials manufacturing emissions of the Lotus HD case and total vehicle emissions advantage of the Lotus LD BIW in HD.
This comparison understates the actual difference in emissions because of considerations like the closure panels example above and the differences in the recyclability and recycling infrastructure for GHG-intensive materials. At the very least it is clear production of such vehicles from recycled material will not occur until the first fleets of vehicles are returned after their useful life, some twelve years or more in the future. Therefore, a more accurate comparison of the emissions difference for the first twelve years of production of such vehicles would be not to credit GHG-intensive materials for recycling until end-of-life vehicles can provide it. This calculation yields 49.56 t-CO2e for the Lotus HD vehicle [12,719 plus 36,840 kg] vs. 42.1 t-CO2e for the steel case [3078 plus 39,014 kg] or a difference of 7.4 t-CO2e per vehicle.
Finally, studies done by Kendall, et al [Accounting for the Time Dependent Effects in Biofuels GHG Calculations, Environmental Science and Technology, 43, 7142-47] to evaluate bio-fuel impacts on land use change found that “up-front” emissions cause greater damage to the environment due to Cumulative Radiative Forcing [CRF] and proposes these be accounted for using a Time Correction Factor [TCF] to deal with such temporal effects. Figure 2 applies these principles to the Lotus Study. This chart [which includes the recycling credit] shows the Lotus HD case [the lower body weight structure using GHG-intensive materials] can result in 25% more emissions, or approximately 10.9 t-CO2e per vehicle.