Carbon Pseudo Science

As self-appointed eco watch dog for scientific accuracy, I can't help commenting on Adam Stein's "Science corner: why carbon sequestration and clean energy are equivalent" on the TerraPass site.

I agree that sequestering a ton of CO2 and avoiding emitting a ton of CO2 can be viewed as scientifically equivalent, assuming that both activities happen within the same period of time. However, Adam ignores this time stipulation, and unfortunately the common practice in forest-based sequestration is to ignore it as well.

Here's the issue. Many tree-based carbon sequestration programs use the money to plant a tree, which will then sequester the targeted CO2 over a period of years. However, that period may be a long time, such as the 70 year period targeted by Dell's Plant a Tree program. That means that 35 years from now, only half of the CO2 will be sequestered.

If someone argues that we can wait a few decades to do something about CO2 emissions, alot of us, including, presumably Adam, would have a fit. However, the forest-based sequestration crowd follow Adam's argument and are somehow comfortable with sequestration which has 2/3 of its effect over 20 years from now.

What we really need is a net present value (NPV) of CO2, just like we have with money. A dollar in the future isn't worth as much as a dollar in hand today, so a discount rate is applied to the future dollar to give you a current value. Similarly, a ton of CO2 30 or 40 years from now isn't as value as a ton of CO2 today. In fact, I could argue that its worth a lot less, if in fact we are faced with a 10 to 20 year horizon to really make a real dent in our atmospheric CO2.

Unfortunately, since we have no NPV for carbon, and the idea of it isn't widely understood, people are putting programs into place that pretend that the value of a future ton is worth a ton today. And when defenders of sequestration-based offsets apply flawed reasoning, and worse yet call it 'scientific', it only lessens my already weak faith in the offset system as an element of a functional and effective carbon market.

Note: I've ignored another potential issues with Adam's argument. He is assuming that investments and circumstances cooperate in order to keep sequestered CO2 sequestered. Our ability to do this at massive scale still seems a little dicey to me.


Hey Dave:

Thanks for the comments -- we totally agree with you on trees and the fact that front loading is less than ideal in a world where we have 10 years to get on top of this issue. We need all the help we can get now. Put differently, the discount rate should be 50+%, not the 1-2% that some folks are using.

Just as a clarification, you can read a pretty extensive discussion of why TerraPass focuses on renewables on our blog. Adams post was just in response to many consumer questions about why we \*dont\* do trees.

Posted by Tom Arnold on September 07, 2007 at 04:14 AM EDT #


based on things you've posted I was surprised at Andy's statements. He's added some explanation, but he is still stuck on this "trees and renewables are equivalent" thing, and its not till the very last line where he says, "well, we still don't think you should use trees".

In my position I'm barraged with offset proposals. All of them seem well intentioned, but many of them are very suspect. Terrapass appears to be doing a good job on this front (I have personally recommended them to other), but posts like Andy's only add to the confusion that already exists.


Posted by David Douglas on September 07, 2007 at 04:29 AM EDT #

Hi David,

It's me Adam (not Andy). I think the reason you might be misinterpreting the intent of my post is that you don't talk to as many offset purchasers as we do. There's a ton of confusion around the issue of sequestration vs. avoided emissions, and it needed to be addressed.

We review a lot of offset proposals as well, and we're well aware of the issues with tree projects, which I've covered elsewhere on the blog. But we also talk to lots of consumers, who are often under the mistaken impression that tree projects are somehow different than or even better than renewable energy projects because trees absorb carbon that's already in the air. (Sadly, some offset providers who sell trees like to encourage this confusion.) So my post was debunking the notion that this is a meaningful metric along which to evaluate offset projects. My post was, in this respect, an argument against tree-planting projects, because I was debunking a perceived advantage of such projects.

I've covered the other aspects of this issue, including timing and permanence, extensively (and taken a lot of heat for it: Unfortunately, it's simply not possible to cover every angle in every blog post. But rest assured, we're on the same page.



Posted by Adam Stein on September 07, 2007 at 05:01 AM EDT #


Thats unfortunate, because the post was part of a series exploring the many issues with tree-based offsets (which we won't do).

I'd link to all of them, but you're not letting HTML in. Titles are:

\* Rules of the road for carbon offsets: the trouble with trees
\* Does the new Duke study prove that tree-based offsets are no good?
\* Science corner: why carbon sequestration and clean energy are equivalent

Posted by Tom Arnold on September 07, 2007 at 05:06 AM EDT #

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