[extropy-chat] Nuke 'em

Robert J. Bradbury bradbury at aeiveos.com
Sun Oct 23 18:25:40 UTC 2005

On Sun, 23 Oct 2005, Damien Sullivan wrote:

> With vigorous handwaving!
Thought so... :-)

> Or maybe being able to liquefy air would make CO2
> extraction more efficient?

I don't think CO2 extraction is the problem.

> "Clearly plants are really inefficient and we can do better!"  But I suspect
> the limiting factor is the low concentration of CO2; dealing with a 300 ppm
> input can't be pretty.

I think that may only be a small part of the problem.  For land plants
like corn and vegetables, the problem is lack of complete coverage
(sunlight on soil doesn't help much).  Sugarcane and wheat are better
in this respect.  Part of the problem is incomplete absorption of the solar
energy.  Plants should *not* be green.  They should be black.  Obviously
they are losing the energy in the green photons (which is significant).
Ultimately the problem is that the standard photosynthetic harvesting
apparatus is not using the full energy of each photon.  Its delivering
red photon energy and blue photon energy to the photosynthetic reaction
center in the same quantities (the rest presumably is radiated as heat).
One needs solar energy harvesting apparatus structured like multi-layer
solar cells or the water column in the ocean -- where the energy harvesting
material (photosynthetic antenna, etc.) are designed to pick up photons
with very precise energy and utilize it fully.  So uppermost layers would
harvest red photons, then lower down one harvests green photons, then at
the bottom one harvests the blue photons.  You can do this type of a structure
in solar ponds.  It is very difficult to do it in the thin leaves of plants.

If you study the light absorption frequencies of various photoplankton
you will discover they are very precisely tuned for the light energy
which reaches the water depth they inhabit.  Land plants are not so clever.

> But unavoidable, if we're using carbon as an energy
> store and burning it.  No wonder hydrogen looks attractive.  Realistically I'd
> guess we'd be hard put to even approach plants at what they're doing.

Phytoplankton are *not* that complicated.  One doesn't need everything
a land plant needs because one can always drain and "reseed" the pond.

> What's the efficiency for solar ponds with bacterial methanogenesis?  Are
> there ways of turning the methane into liquid fuel, and at what rates?

It isn't clear at this time because some tricks are involved getting the
enzymes that perform methanogenesis to operate in phytoplankton.  I think
I know how to do it but I'll not discuss it in public.  As pointed out
above -- the real problem is tuning the photosynthetic reaction centers
to make the most efficient use of the photon energy.  Enzymatic chemical
conversions are generally quite efficient and there are companies now
that make a business out of making the enzymes more efficient at the
processes.  Of course, if you are concerned with the CO2 concentrations
one can always feed the solar ponds the output of the coal based power

With regard to liquid fuels.  Converting methane to propane or octane
is fairly straight forward.  Its the inverse process that is currently
done at petrochemical plants where one is generally converting heavier
hydrocarbons into lighter hydrocarbons.  So in theory with some slight
infrastructure retooling one should have the capabilities one needs.


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