Life Cycle Analysis – Environmental Effects

Recently, I met a representative of World Auto Steel, actually the Director, Cees ten Broek, at a Lightweight Transportation conference in Stuttgart.  He told me about a paper study that had been funded by World Auto Steel, (a consortium of Steel companies), and written by a professor at UC Santa Barbara. Their findings were that if the entire Life Cycle Analysis is taken into consideration, that carbon fiber is worse for the environment than steel because the manufacturing of carbon fiber generates more greenhouse gasses than steel (per Kg) and carbon fiber is not recyclable.  I had heard about this study about a year ago, when it was first released, but could not find out more at the time.

A link to study is provided in the following link:  http://www.worldautosteel.org/life-cycle-thinking/greenhouse-gas-materials-comparison-model/

The Downloads are called “Version 3 Model”, and “User’s Guide”, check them out.

Here are the problems I found with this study:

For one thing, it looks like the amount of heat energy it takes to make a Kg of material was compared 1 to 1 between carbon fiber and steel, but since carbon fiber would produce a vehicle structure that weighs only half that of the steel it replaces, that should have been accounted for, but I don’t see that calculation.  Then, a composite structure is usually made of about half its weight in fibers, (45%-65%), and the rest is a thermoset resin, like epoxy or polyester.  However, I don’t see any calculations for the carbon footprint of making these polymer matrix materials.

The second issue I saw was that the life cycle of the vehicle was assumed to be exactly the same as a steel vehicle, even though a composite vehicle structure would never rust, corrode, or fatigue.  Why was the life cycle assumed to be the same?  The marine industry tried to do a life cycle analysis of fiberglass boats, several years ago, but they found that they just never reached the end of their useful life – they just rebuilt their engines, repainted them, and kept going.  (The study included boats up to 30 years in age).  After working on that study for years, they just gave up.  I would have thought that the environmental impact of a vehicle that never rusts, or fatigues would be very positive, yet the University of California study makes it look like the useful life of composites is the same as steel.  Even if you assumed the composite structured vehicles would only last twice as long as a steel one, (a conservative assumption) that would have had a significant effect on its Life Cycle Analysis.

Third, I noticed that recycling information was completely absent, (all zeros in their list of data) even though carbon fiber is quite recyclable and a great deal of work has gone into the development of recycling of carbon fiber.  Boeing, and BMW are already recycling their off-fall from the production of the 787 and the i3, (as are Plasan, Trek Bicycles) but none of that information made its way into the study.  Currently MIT-RCF is working on developing markets for the recycled CF.  See their website:  http://mitrcf.com/

Finally, the author of the study took great pains to point out that different grades of steel and aluminum have a different carbon footprint and different mechanical properties, but they simply lumped all glass fiber and all carbon fiber into one simplistic category.  This is striking because of how truly diverse the composite materials are.  There are many different grades of carbon fiber, and glass fiber, as well as other fibers like nylon, Aramids, polypropylene, and cellulosic fibers.  When it comes to resins, (the other ~50% of a composite), there are polyesters, vinyl esters, DCPD, epoxies and polyurethanes, not to mention a variety of thermoplastics. In addition to these little facts that were conveniently left out of the equation, the optimized composite structure is most likely not going to be pure carbon fiber or pure glass fiber.  (And don’t forget the cores).

It may have been a simple mistake that the author of the study, Roland Geyer (geyer@bren.ucsb.edu), didn’t know that all composites are not the same, or didn’t know that CF is being widely recycled in large volume, and didn’t know that thermoset resins make up about half the content of almost any composite, and just did not realize the longer life cycle of composites would change its average useful life.  Or it could have been that he knew his study was funded by the consortium of steel manufacturers, World Auto Steel, and he didn’t want them to be upset about the findings.

Hopefully, he responds to either of the two emails I have sent him in the last week, or responds to the composites community as a whole by commenting on this blog.  Because without his own response, we just don’t know if it was a simple case of making a series of mistakes, or deliberately slanting the data to please his sponsors.

Andy Rich, Chairman Composites Division SPE

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2 thoughts on “Life Cycle Analysis – Environmental Effects

  1. GOOD NEWS: I managed to speak to the author, and he was very helpful in explaining a few things. For one thing, the Version 3 Model is interactive, so you can change inputs, (up to a point) and see the changes in predicted outcomes. The model started out very simple, but has grown to be much more complicated, and Version 4 looks like it will be even more complex. He is still working on Version 4, and is open to our ideas and suggestions.
    The subject of Average Life Cycle was a good example of the limitations of the Version 3 Model. The only input variable that can be changed will automatically do so for all models simultaneously, so if the life cycle of one type of vehicle is 120,000 miles, the model automatically changes the output numbers for all the material models. In addition, the option to refurbish and re-use has not been included in the model in Version 3, but he said it might be possible to do so in Version 4.
    He also stated that he is not a car designer, but a physicist by training, so when I asked him about the effects of welding and other manufacturing techniques, he just said he couldn’t speak to that. What also came out of this very productive conversation is that he had to rely on “published data” which may or not be accurate. For instance, he used Aluminum industry data, Steel industry data, and Magnesium industry data without having good resources for cross-checking that data.
    That has led to another problem, which he is still trying to solve, the lack of data from the Composites industry. There was little or no published data for how much greenhouse gas emissions are generated by the production of glass fiber or carbon fiber which comes from the industry itself, so he had to extrapolate this from other information, and make an educated guess for most of that data. I have offered to help him find better data for composites, and hopefully within the SPE, we can also create a good network for an improved resource for such data.

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