Michael Graham Richard, November 26 – Dr. Hartmut Michel won the Nobel Prize in Chemistry in 1988 for his work on photosynthesis, and he's currently the director of the Molecular Membrane Biology department at the Max Planck Institute for Biophysics. It's fair to say that he's not only one of the smartest people in the world, but also one of the top experts on how plants turn sunlight into energy. To say that he's qualified to comment on biofuels – which is basically all about turning sunlight into chemical energy via plants – is an understatement. His views on this topic should carry a lot of weight.
The Math Doesn't Add Up
Being a top scientist, Dr. Michel reasons from first principle. What are the physical limits to each step of the process, and when you then put it all back together, what have you really got? Here are choice excerpts from a recent editorial that highlight his reasoning:
1. How efficient is photosynthesis?
The photosynthetic pigments of plants can only absorb and use 47% (related to energy) of the light of the sun. Green light, UV, and IR irradiation are not used. […] Photosynthesis is most efficient at low light intensities. It is already saturated at 20% of full sunlight and 80% of the light is not used […] As a result of the limitations described above, 4.5% is considered as the upper limit of the photosynthetic efficiency of C3 plants. However, in reality, values of only around 1% are observed, even for rapidly growing trees like poplars.
So right from the start, plants are only converting about 1% of the sun's energy into chemical energy. Leaving 99% of the energy on the table isn't a very good start… And this compares very badly with commercially available solar panels which can convert around 20% of sunlight into electricity, two orders of magnitude more (and better efficiencies are possible).