Re: Can Microorganisms Be A Solution To The World's Energy Problems?
- From: Mark Thorson <nospam@xxxxxxxxx>
- Date: Wed, 16 Jul 2008 16:06:15 -0700
Dave wrote:
On Jul 16, 12:29 pm, Mark Thorson <nos...@xxxxxxxxx> wrote:
rpautrey2 wrote:
Unlike the E. coli situation, using just one species may not work well
for bioenergy, since, in nature, bacteria do not grow in isolation. In
other words, no bacterium is an island. The very biodiversity that
fills the Earth with bacteria and offers great bioenergy potential
also presents a challenge for engineers. Even if one picks the ideal
"bug," growing, maintaining, and optimizing conditions for its use in
bioenergy applications remains a daunting challenge in terms of
scalability and reliability.
That is the main problem. You can't keep a large culture
completely free of invading organisms, viruses, etc.
Scientists have been beating on this problem for over
half a century. One approach is to grow the organisms
in a closed photobioreactor, but you'll never be able
to prevent contamination with competing organisms or
organisms that eat the desired organisms. Also, the
low density of these systems makes them very expensive
for the amount of energy they collect.
The other approach is to grow the organisms in open
cultures such as shallow pits. In this case,
contaminating organisms can be controlled by adjusting
pH or salinity. That's how _Spirulina_ for human
consumption is usually grown -- _Spirulina_ can grow
in brackish water that would kill most other algae.
Then, you have the problem of processing the product
into fuel. Unless the organisms are directly producing
methane (as discussed in the article), this is likely
to be difficult and consume energy (lowering the
efficiency of the system even more).
Much better would be a drought-resistant plant
that can be grown in scrub lands unsuitable for
food production, with a sap that is easily convertible
into liquid fuel. The late William Calvin identified
certain species of Euphorbia that meet these requirements.
Euphorbes occupy the same ecological niche in the
Old World that cacti occupy in the New World. Some
euphorbes look just like a cactus, but they are not
closely related. They have a milky sap, which consists
largely of water and alkanes. Remove the water, and
you end up with something very similar to diesel fuel.
No photobioreactors or pits. Just scrub lands for
growing the plants, and minimal processing gets you
liquid fuel for transportation.
Mark,
You're suggesting that we take the desert southwest and start
populating it with scrub cacti that would each produce a thimble full
of gasoline at the end of the day, after sacrificing the plant? I
don't think that sounds very smart from such an astute poster as
yourself. Our energy demands are much greater than what could be
delivered using cacti.
It's far more viable than algae. But you're right to be
skeptical about any biofuel scheme returning more than
it's energy cost. The beauty of euphorbes is that
they require no man-made energy input during the growth
phase, and minimal energy input for processing into fuel.
And the plant is not fully sacrificed. As you obviously
don't know, after the top of the plant is cut down,
it regrows from the stump.
Instead, the desert southwest is the ideal growing climate for large
algae ponds which can be used to produce ethanol. The technology is
being developed right now, both by government (in CO, at the National
Energy Research Laboratories) and in private industry -- and like in
many fields, private industry is winning.
The problem with ponds is they lose lots of water to
the atmosphere (even if you cover them with plastic
film, the air you pass through them will carry out
a lot of water). All large pond operations currently
are uncovered. The largest covered ponds are the
Aquasearch Growth Modules operated by Mera Pharmaceuticals
in Hawaii, which are arguably a closed system bioreactor.
They are far too small to be used for production of
fuel. The water losses from an uncovered pond in the
southwest would be tremendous. Game over.
In addition to water losses, a large continuous
energy input is required to run the motors for
aerating the culture and keeping it moving.
A typical large pond operation consists of a
wide, shallow channel in a racetrack configuration,
with a set of paddlewheels that crosses the track
at one point. That's how Earthrise grows _Spirulina_
near Irvine, CA. The cost of the energy input
can be justified there, because they are producing
a high-value product -- it's sold for human
consumption.
I just heard a talk delivered by a leading scientist from Sapphire
Energy (http://www.sapphireenergy.com) at a conference called by the
National Science Foundation to discuss the future of biotechnology and
science education. This fellow told a remarkable story of how the
wasted energy and agricultural resources we have going into today's
corn ethanol can be turned around in the very near future if we as a
country can get behind the production of what he called "Green crude"
via algae.
I've got books from the 1940's and 1950's making similar
predictions. This field has a long, sorry history of
broken promises with which you are completely unfamiliar.
It's mostly a field of eternal optimists and a few
charlatans, seeking government funding or venture
capital.
I'd prefer to see growing ponds and processing plants for these
systems in the southwest, as opposed to fields of low-producing
plants like Euphorbes.
That's because you are ignorant of the science.
If you knew more about algal culture systems,
you'd recognize the staggering problems they face
as a (not) practical source of fuel.
Euphorbes are not low-producing plants, though
there's no way you would know something like that.
Calvin estimated that _Euphorbia_tirucalli_
could produce 10 to 50 barrels of oil per acre.
That is not "low-producing".
http://www.hort.purdue.edu/newcrop/duke_energy/Euphorbia_tirucalli.html
There are no staggering technical problems here.
The plants grow themselves. The processing technology
is simple. Existing technology used for processing
sugar cane and petroleum can be adapted for making
liquid fuels from euphorbes.
.
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