We just completed our first major update of the technical parameters behind AutoEcoRating. We’ll soon resume writing about how some of the latest and greatest vehicles fare on the updated eRating scale. But for now, a few words about the new version and what to expect (and not).
The fundamentals of the AutoEcoRating methodology haven’t changed; rather, what we’ve done is put in more up-to-date values for the “upstream” portion of emissions for all fuels. These upstream factors characterize the pollution that occurs when drilling and refining oil, when mining coal or extracting gas and when generating electricity or hydrogen. They are among the more uncertain aspects of any environmental impact analysis because data about what’s going on, especially in fossil fuel extraction and processing, are quite sparse. That’s in contrast to the data on fuel economy and the pollutants directly emitted by cars and trucks, which are required to have their emissions tested and certified by EPA in order to be “street legal.”
The biggest change in upstream parameters is related to the information recently coming out about excess emissions and other impacts from oil and natural gas extraction. “Fracking” has been in the news, and concerns about it have spurred EPA and state environmental agencies to look more closely at what’s going on in oil and gas fields. We included estimates of these impacts (as well as impacts of oil spills as well as other land and water contamination related to all fossil fuels) when we first developed AutoEcoRating two years ago. But now — surprise, surprise — researchers have found greater pollution than previously assumed, and so we’ve revised AutoEcoRating’s impact factors accordingly.
A lot of research was published over just the past few months and we were fairly far along in our revisions when Argonne National Laboratory (ANL) released a new version of the GREET model in mid-October. Among other things, GREET saw major revisions to its upstream emissions factors, which we use as inputs to AutoEcoRating. That explains why we’re calling this edition Version 2.1; Version 2.0 (which never went live) had the updates made in summer 2011 prior to the new version of GREET.
What’s the upshot? The greatest impact is on the eRatings for natural gas vehicles, which have dropped relative to other vehicles. Cars that run on compressed natural gas (CNG), like the Honda Civic GX, are still super clean at the tailpipe. But drilling for that gas isn’t as clean as everyone thought, and that’s where the AutoEcoRatings for CNG cars “take the hit,” so to speak. Because natural gas is used to generate electricity and hydrogen, ratings for EVs and hydrogen fuel cell cars also drop a bit.
All in all, however, most ratings haven’t changed much simply because most vehicles run on gasoline. We also take the higher upstream impacts into account for gasoline and diesel fuel, but most of their environmental impact occurs at the tailpipe. For example, about 70% of greenhouse gas (GHG) emissions are at the tailpipe for the average new gasoline-powered car, compared to 20% upstream during fuel production and 10% when manufacturing the vehicle and the materials that go into it. In contrast, upstream pollution accounts for a greater share of the overall impact for CNG vehicles and it accounts for most of the environmental impact for electric and hydrogen cars.
Stay tuned for articles stories about how specific makes and models fare under the updated AutoEcoRating system.