We Can't Believe Everything We Read — Hybrids and Hummers


This week the sparks have flown over the constantly revisited debate of whether hybrids are as efficient as they claim in comparison to a regular gasoline powered vehicle. Again, this is a controversial topic, and I will start by saying that I am in no way trying to bash hybrids. Both the Economist and Grist have had their say regarding a controversial report , so now it's one Treehugger's turn. It started with the Economist's article that "Diesels are the Smart Green Choice", which says,

The dirty little secret about hybrids is that their batteries and extensive use of aluminium parts make them costly to build in energy terms as well as financial terms. One life-cycle assessment claims that, from factory floor to scrap heap, a Prius consumes more energy even than a Hummer H3. Diesels are unlikely to consume anything like as much over their lifetime. That could change, of course, if some bright spark decides to replace a hybrid's petrol engine with a diesel—to launch a family car capable of 100mpg. Now there's a thought.

They could read this to help answer that question (among a variety of other studies).

Then the smart green folks at Grist also put the article to the test along with the study that supposedly claims that a Prius consumes more energy per mile over its life cycle than a Hummer H3.


The folks at Grist did the same thing that I did — they went straight to this "life cycle assessment" prepared by CNW Marketing in Oregon (a firm that supposedly carried this study out objectively, but seems to work only with reports about the automotive industry - odd). Well, the bottom line is that Biodiversivist wrote a great rebuttal to this Economist article and critiques the study. You should read it here. Apart from their comments I have a few things to add / reiterate regarding this LCA. Firstly, nowhere in the study do the authors refer to ISO14040 standards for life cycle assessment, the internationally accepted norm to which all LCAs are compared. There is no critical review by peers or professionals working in the LCA field (of which there are many!). The information is presented in very very long tables listing each car by type or class segment. This is so uninviting to the reader that you almost rush through the information. Some charts of graphs would be useful when trying to digest all of this information that has supposedly been made "easy to read" for the general public. The results are presented in energy per mile, but nowhere do they discuss global impacts, damage to human health, resources, contribution to global warming, eutrophication or other accepted impact categories recognized within the LCA field. Note that ISO standards note that results of studies that are intended for the public should not be reduced to single scores. Perhaps these flaws are due to the fact that the authors of the study are a marketing firm (?). Certainly this type of study could have been carried out on an equally un-biased basis by life cycle professionals.

Among many other assumptions the study claims that the currently high cost of maintenance and repair for hybrids makes their expected life time shorter. They assume that hybrids will be held on to about the same amount of time as a regular budget car — approximately 5.6 years. As Biodiversivist points out, that seems odd. I would think that any greenie buying a Prius would drive it until it can't go an emission-free mile further. But that is something that will always vary by owner. The CNW article is based on averages and assumptions and they do note that it seems that regardless of original purchase price, owners tend to keep vehicles for the same amount of time on average (5.0-5.9 years). The next issue I have with this study is its lack of data sharing or methodological transparency. Nowhere do you see how these calculations were carried out. In fact, they say (as Grist also points out):

The database used for the Excel spreadsheets is proprietary to CNW and will not be released.

Additional data, other than what is presented on CNW Marketing Research, Inc.'s various web sites will remain unavailable to protect the proprietary nature of the data and the research methodology.

All rights to this information are held by CNW Marketing Research, Inc. Use of this information without prior approval except as noted above is strictly prohibited and will be treated as theft of intellectual property valued at US $25 million.

Anyone wanting data (even subscribers) cannot receive raw data bases. We control how data is released and maintain final approval on how information is presented because too often selective data points are used to "prove a point" rather than being complete, objective or neutral.

I think those statements are enough to make one feel like something is being hidden. Not only that, LCA professionals are quite open when it comes to explaining results and showing the transparency of their data and methodology to the public. In fact transparency is one of the principles of LCA: life cycle perspective, environmental focus, relative approach and functional unit, iterative approach, transparency, comprehensiveness, and priority of scientific approach.

Additionally, I have never seen customer surveys about reasons behind their purchases included in an LCA report. Nor have I ever seen surveys about the premium a buyer is willing to pay for a hybrid over a non-hybrid included in an LCA study. I suppose what I am getting at here is that I wouldn't consider this CNW report a true LCA according to ISO standards, even though they claim to use data from the entire life cycle of each car type. Using the term life cycle in a report does not an LCA make.

We could go on for days, weeks or an entire life cycle debating this study, its robustness, its accuracy and its opaqueness but for now we'll leave it at that. I invite you to take a look at it yourself, to read Grist's great review and to post your comments here about the findings. Read more by TH and CNW here .

We Can't Believe Everything We Read — Hybrids and Hummers
This week the sparks have flown over the constantly revisited debate of whether hybrids are as efficient as they claim in comparison to a regular gasoline powered vehicle. Again, this is a controversial topic, and I will start by saying that I am in