Monday, June 02, 2008

Journey through the Secret Life of Plants

From an interesting book review by Freeman Dyson:
.. it turns out that about 8 percent of the carbon dioxide in the atmosphere is absorbed by vegetation and returned to the atmosphere every year. This means that the average lifetime of a molecule of carbon dioxide in the atmosphere, before it is captured by vegetation and afterward released, is about twelve years.
I'm amazed by this fact. I used to be a chemical engineer, so I could get out my calculator and start messing about with a mass balance, though a trivial daily blog post is not the place to do it.

But it really is intriguing, as it implies that the net contribution of CO2 to the atmosphere from human agency is mathematically trivial compared to the carbon volume of the respiration of plant life. The question I would like answered is how much net carbon does photosynthesis remove from the atmosphere each year.

Stray thoughts:
  • Bio fuels must - by definition - be carbon neutral.
  • All the carbon in fossil fuels was fixed from the atmosphere at some time or other so given a long, long perspective everything is carbon neutral.
I really need to read and think more about this.


Simon Brunning said...

"Bio fuels must - by definition - be carbon neutral."

Only if no fossil fuels are consumed during the manufacture or distribution of the bio-fuels, and there are no secondary effects that cause consumption of fossil fuels; e.g. food having to travel further. It's a lot more complicated than it looks.

Nick Browne said...

It's a good point. I hadn't thought of that.