In a June 20, 2008 e-mail to P2TECH, my pal MIchelle Gaither wrote, in part: "[I'm] looking for perspectives/verification that using CO2 as a foam blowing agent does not directly contribute to global warming."
To which I'm responding:
Since practically EVERY economic activity contributes in some way to global climate change, isn't the real issue is whether CO2 as a blowing agent contributes more or less than the alternatives?
There was an interesting paper by Seager and Theis, " A taxonomy of metrics for testing the industrial ecology hypotheses and application to design of freezer insulation" in the Journal of Cleaner Production (vol 12, no 8-10, October-December 2004), which looked at how the selection of metrics can determine the outcome of environmental decision making. As an example of how the analytical results depended in part on the metrics, the authors used the selection of a blowing agent for foam insulation which would be used in a refrigerator.
One of the metrics the authors considered was Total Equivalent Warming Impact (TEWI), which examines the full lifecycle of the insulation from manufacture through use and recycling (turns out as much as 50% of the blowing agent either leaks out during use or during the recycling phase of the refrigerator).
While CO2 as a blowing agent scored well on ozone depletion potential and toxicity scales, its relatively high themal diffusivity means that the foam made with CO2 is a relatively poor insulator, compared to that made the other blowing compounds. Over the lifetime of the appliance, then, a refrigerator insulated with CO2-blown foam actually will use more electricity than one insulated with HCFC's. Thus, the net carbon impact of using CO2 as a blowing agent may be higher than the conventional materials, even though the product claim is factually correct when only the manufacturing and recycling phases are considered.
Now, one might still choose to use CO2 as a blowing agent, depending on how one weighed in the relative importance of toxicity, workplace exposure, ozone depletion potential, etc......but this example illustrates that the decision is far from clear-cut.
It is results like this which underscore the importance of using lifecycle analysis, not as a means of certifying products/materials as "green" but as a means of gaining insight into products and services at the design stage.
hope this helps.
Pacific Northwest National
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of michelle gaither
Sent: Friday, June 20, 2008 11:15 AM
Subject: CO2 as foam blowing agent
Looking for perspectives/verification that using CO2 as a foam blowing agent (other than the energy required to blow foam and the energy to get the CO2 to the point of manufacure, etc.), does not directly contribute to global warming.
here is a product claim -
"The use of 100 percent CO2 offers optimal environmental performance because CO2 does not deplete the ozone layer, does not contribute to ground level smog, and will not contribute to global warming since CO2 will be used from existing by-product commercial and natural sources. The use of CO2 by-product from existing commercial and natural sources such as ammonia plants and natural gas wells, will ensure that no net increase in global CO2 results from the use of this technology. Carbon dioxide is also non-flammable providing increased worker safety and is cost effective ..."