
Ethylene Production via Sunlight Opens Door to Future - ph0rque
http://www.nrel.gov/news/features/feature_detail.cfm/feature_id=19532
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PaulAJ
Sounds good, but how much CO2 production do those precursors imply? I've seen
too many over-enthusiastic write-ups for bio-solar technologies that don't
include the carbon cost of the inputs.

Of course if the answer is "not much" then this could be big.

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trhway
>Sounds good, but how much CO2 production do those precursors imply? I've seen
too many over-enthusiastic write-ups for bio-solar technologies that don't
include the carbon cost of the inputs.

from the article:

"Normally, algae convert carbon dioxide during photosynthesis into biomass or
sugars."

The issue with these technologies isn't CO2 balance (that balance is great -
CO2 is input, hydrocarbons is output), the issue is productization, i.e.
reaching the technological stage which would be able to attract massive
investment. With cheap oil [i.e. with major costs of oil externalized in
today's society and economy] these technologies face uphill battle. (compare -
if Big Oil wants pipeline or drill somewhere, the government uses all its
ultimate power, like eminent domain domestically or aircraft carriers
internationally, to make it happen and push it through public interests here
or there, if you want a pond for algae ...)

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regularfry
Productisation inherently has to overcome the fundamental energy density
problem: with photosynthesis, you've got an upper limit of about 300W/m2 that
you can ever capture. To get energetically useful amounts of fuel out, that
means you need acres of the stuff. Not impossible, but a right pain to keep
your chosen strain dominant in the sort of volumes that area implies.

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trhway
>that means you need acres of the stuff.

in a hot desert unused for anything else.

From
[https://en.wikipedia.org/wiki/Algae_fuel](https://en.wikipedia.org/wiki/Algae_fuel)

"The United States Department of Energy estimates that if algae fuel replaced
all the petroleum fuel in the United States, it would require 15,000 square
miles (39,000 km2), which is only 0.42% of the U.S. map,[10] or about half of
the land area of Maine. This is less than 1/7 the area of corn harvested in
the United States in 2000.[11]"

A federal scale project with political, social and economical effects
comparable with atomic bomb development. 15000 sq. miles sucking in CO2 and
producing fuel. Saudi princes and Putin may go enjoy themselves. Well, with a
lot of rich and politically connected Texas oilmen as well ... and this is the
main issue, not the energy density :) And with another oily Texan about to be
elected, we can forget about any serious advancements for the next 8 years
(he'll get us into another war and thus will stay for the full show)

~~~
entee
The hardest thing about algal fuels is keeping your bioreactor working at peak
efficiency. This is quite difficult, consider the following:

Problem: Outside organisms keep contaminating your pools of algae.

Solution: cover them up.

Problem: your reactor surface keeps fouling

Solution: open it up and wash it

Problem: Now you gotta clean the whole thing to make sure you don't have
contamination

Problem: some parts of the pool are far denser in algae than others leading to
inefficiency

Solution: pump/stir it!

Problem: now you have to move huge volumes of water. Plus your equipment could
foul/breakdown

Partial solution: solar powered pumps. Fouling still an issue though

Problem: Organisms raised in water take a lot of water with them for the ride
even when you spin/filter them out for harvesting

Partial solution: Dry it out with energy, maybe more sun? Now you need more
space.

After all this you have to wonder whether the cost and additional energy
invested leaves you with enough left over to make sense. It's not impossible,
and I believe it's the only real way to a sustainable future, but it's really,
really, really hard to scale these things up.

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bcg1
> The key benefit to making bio-ethylene would be in reducing the amount of
> carbon dioxide released into the atmosphere by the traditional ethylene
> manufacturing process

This ignores the political, economic, and military implications of moving away
from petrochemicals. There are potentially many benefits aside from the cost
of raw materials and the amount of carbon dioxide released into the
atmosphere.

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thomasrossi
These are the news that makes me believe there can be a better world:)

