Trucker,
Skepticism is healthy, and an essential part of weeding out truth from advertisement.
There are not than many 'givens' as you think there are in this paper.
Everything is pretty darn irrefutable analysis.
Unlike Dimitrov, I do not have a Phd in microbiology, but let me try to comment and clarify some of the issues that you call 'given'
below.
Rob
"The Trucker"
verizon.net> wrote in message news:pan.2008.06.28.20.39.03.808648@verizon.net...> I was recently presented with a supposed "scientific paper" that was
> meant to prove that algae based biofuels were unscientific hokum and
> snake oil. I was, to say the least, rather upset when I read this paper.
> I am not a scientist and all the stuff about PAR's and joules and the
> like was really confusing. But I think I managed to deal with all of
> that and still find the false framing.
>
>
http://www.nanostring.net/Algae/CaseStudy.pdf
>
> In the "study" we find the following pronouncement:
>
> E is the Energy in the biomass
> PAR is the energy from the sun
> Q is the efficiencey of the conversion of sun energy to biomass energy
>
> W = PAR * Q
>
> All of this is well and good and reasonable. And then we have:
>
> Photosynthetic organisms use 8 photons to capture one molecule of CO2
> carbohydrate (CH2O). Given that one mole of CH2O has a heating value of
> 486kJ (486 kilo jules) and that the mean energy of a mole of PAR photons
> is 217.4kJ then the maximum theoretical conversion efficiency of PAR
> energy into CH2O is:
>
> 468kJ/(8 * 217.4kJ) = 27%%
>
> Well!!! GIVEN that the moon is made of green cheese and Pinocchio Bush
> tells the truth then the economy is sound and stabilizing. This dude is
> hoisting himself over a fence by grabbing his own underwear. I could not
> find any credible source for these "givens"
Nice, but you simply do not understand what he is saying.
Here it goes, in slightly different wording :
Start with PAR : 100 Watt/m^2 of (average over 365 days/24 hours) power of photons that engage in photosynthesis.
Do you agree with this number ? If not, let me know.
Now this 100 Watt are PAR photons. What's the average energy of these photons ?
Dimitrov uses 217.4 kJ/mole. Is that given ? Yep, kind of, for photobiologists.
But here is how we can verify the number :
We know that PAR photons are mostly red and blue, since the green is already reflected (and not part of PAR).
The average energy of a PAR photon is thus somewhere between red and blue (closer to red, since there are more red than blue
photons).
Let's see if that is correct : 217.4 kJ/mole is 3.62 E -19 J per photon (217.4E3/6E23 (number of particles in a mole)).
What's the wavelength of such a photon ? lamba=hc/E, a photon of 3.62E-19 thus has wavelenth of 546 nm.
That's in the yellow-green boundary, nicely between red and blue, a little closer to red, as we expected.
So we have 100 Watt/m^2 of PAR photons (FYI : about 2.7E20 photons per m^2 per second).
You need 8 photons to convert CO2+H2O to a carbohydrates (CH2O)n) molecule. Is this given ? Yep, kind of, for microbiologists it is.
I have read this in different papers. It's overly simplified, because the process itself is much more complex than this (via ATP and
stuff).
But in the end, this is what it does. Can you accept that ?
So 8 photons generate one carbohydrate molecule. The 2.7E20 photons per m^2 per second generate 3.375E19 carbohydrate molecules per
m^2 per second (if ALL of them get absorbed!!!). Then he shows that the energy gain (carbohydrate heating value) from these 3.375E19
molecules is 27%% of the energy that we put in with PAR photons.
So again : The 27%% of PAR is only obtained if ALL (PAR) photons get absorbed (engages in the process).
The other 73%% of energy in PAR gets lost in heat (heats up the plant). There is NO MORE energy available. Once a photon is absorbed,
that's it. C'est ca. End of story.
In reality, there are many, many other losses, and he makes a pretty compelling argument (explains all the other steps to get to
biodiesel) that realistic upper bound, for highly optimized systems, is 10%% of PAR.
>
> But I will leave that aside for sake of argument and just "give" him his
> "givens".
>
> I am going to guess at this because that is what I do. I am not a
> scientist. I am a poker player.
Pretty bold move to try to call his bluff.
Problem is : he was not bluffing. He has a royal flush (that's the best hand right?).
Sorry. You loose.
>
> What is missing from this frame job is that great and wonderful
> realization in economics of the "unseen". Yes, we can "see" that these
> photons were absorbed by the algae as the algae made these CH2O things.
> But what happened to the rest of the energy? Did George Bush spend it on
> imperialism? Did those thieving Democrats use it to bribe the welfare
> bums?
People only see what they understand. You should know that as a poker player.
There is nothing "unseen" if you understand the basic physics.
>
> The envelope please:
>
> It says here that the rest of the energy bounced off or passed through
> this particular algae or this square micrometer of algae or this bag full
> of algae and it is still available. It did not run away and join the
> circus. It is still available to be used by a different algae.
> That's right! 73%% of the energy is still hopping around in the immediate
> vicinity and available to be used by another fuel producing algae. And
> if we can just manage to get this algae into the vicinity of this
> available energy then it too will suck up 27%% of what is left on the way
> to being 10%% efficient in making some fuel.
>
> Later in the document he uses the 27%% to produce the 10%% because we all
> know that the algae are going to use some of the energy (some of the 27%%)
> for reproduction and respiration. But the problem will inevitably trace
> back to the 27%% false framing and the assumption that the rest of the
> energy just disappeared.
>
> Still later in the document he speaks of the patent awarded GreenFuels
> for a system that seems to do the conversion at more than 40%% (of the
> 10%% or the 27%% or whatever) and accuses the patent office of malfeasance.
> The truth is that bio-reactors _USE_ that reflected/passed through energy
> that was not used by the first plane of algae. Even in a pond the second
> plane of algae will use the energy that passed through the first plane.
> Most of the energy is actually reflected and that is how we are able to
> _see_ the pond scum.
>
> It seems a good probability that this guy's last job was as a consulting
> scientist to a tobacco company. He has now been hired by the league of
> oil and nuclear fascists to fight the competitive free market algae
> farming economy.
Sorry dude. He has a royal flush. Bad move to call his bluff.
You loose, regardless of your disrespectful words.
What were you thinking man ? The guy has a Phd in microbiology !
>
> --
> "I know no safe depository of the ultimate powers
> of society but the people themselves; and
> if we think them not enlightened enough to
> exercise their control with a wholesome
> discretion, the remedy is not to take it from
> them, but to inform their discretion by
> education." - Thomas Jefferson
>
http://GreaterVoice.org/extend
>
