In the early '70s I did a project like this for my biology senior thesis at
UCSC. It was a time when it looked like we would need a replacement for oil
within 20 years. I saw it as a two part system in which algae would be grown in
ponds, and then pumped into tanks that contained digestive bacteria that would
"eat" them. I built an apparatus that used two big jugs with turbidity feedback
pumps (photocells across the vinyl tubing) between them. So, as the algae grew
under the lights, the pump diverted enough of it to keep the population somewhat
constant, and the digestive bacteria (in a jug covered by foil) stayed at a
population limited by the rate of food source.
The photosynthetic side of this system produced oxygen, which bubbled out on that
side, and the dark side produced a combination of methane and hydrogen. What is
being done today at Berkeley is better than what I did because they use just one
organism, that is not broken down on the dark side. Thus, they do not have to
waste energy rebuilding on the light side.
However, I suspect they will run into some of the problems I did (not counting
making all the pumps work, which was a nightmare before embedded processors).
One of which was getting the oxygen out of the soup that goes into the dark. If
you do not get rid of it, the dark side will use it, and you will get less
product (they also have to get rid of the sulfur too). The flip side is that the
ph drops on the dark side, and you do not want to pump a lot of acid over to the
photosynthetic side, where it slows down growth.
I found that it was possible to take care of both of these "problems" by passing
the solutions to and from the dark side through half cells with platinum
electrodes. The result was that the low ph on one side (think of it as protons
in solution) would combine with the oxygen on the other to produce electricity
and water. So, I got electricity and methane from the system, until I ran into
the typical electrode fouling problems. I could have kept going (sonicated
electrodes, etc.), but I did enough to satisfy my advisor, and I wanted out, so
that was it, my contribution to biomass techniques.
All biomass techniques have one basic problem, cheap oil and natural gas. In the
project above, I argued that the fact that bio conversion of solar power is low
efficiency is not important if you can get the system to build itself, so the
overall cost per kwatt-hr is low. This is still true, but the cost of
photovoltaic energy is dropping fast, and nanotechnology is going to give us
photovoltaic systems that have high efficiency, and low cost because they *will*
Bottom line: Been there, done that, works fine, won't be cost effective.
> In a message dated 02/22/2000 1:57:20 PM Eastern Standard Time,
> EvMick@aol.com writes:
> > BERKELEY-- A metabolic switch that triggers algae to turn sunlight into
> > large quantities of hydrogen gas, a valuable fuel, is the subject of a new
> > discovery reported for the first time by University of California,
> > scientists and their Colorado colleagues. The news appears in this month's
> > issue of the journal "Plant Physiology."
> EvMick-yes I read and enjoyed the article myself yesterday. One of the
> frowners, though, was the expectation, that "perhaps in 20 years this will be
> the fuel that powers civilization.." Look, you're a fellow of enough age to
> have read a few Weekly Readers, and Popular Mechanics in your time. So you
> know that when energy scientists speak of an energy technology being "20
> years away" that they are blowing smoke and begging for more research grants!
> Please remember:" Z-pinch Fusion is 20 years away! Solar power is 20 Years
> away! Muon Catalyzed Fusion is only 20 years away! Commercial
> Hydrogen-Powered Vehicles are only 20 years away! Laser Fusion is only 20
> years away! Solar Power Satalites are only 20 years away! I don't regret the
> money spent on research-only I don't like being lied to, by these scientists.
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