On Mon, 30 Jun 2008 16:58:35 -0700, Rob Dekker wrote:
> 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.
I see no way to argue it. He gave a map of PAR numbers which mean
something about the energy in the PAR range. I am going to assume that
this is 100 Watt/m2 (but I have full spectrum claimed to be 1Kwatt/m2
from someone in a different post). All I can do is go along for the ride
for now. If this number is wrong then the correction is easy enough.
> 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.
For me this represents the available usable energy. I have no objection.
> 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).
We know that the PAR spectrum contains red and blue by definition (I
think). I really see no reason to get all wrapped around the axle here.
> 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.
OK
> 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 ?
OK
> So 8 photons generate one carbohydrate molecule.
Well I see that it will take a certain amount of energy to create a
molecule of carbohydrate and that therefore we have the stuff using up the
light energy to make the carbohydrates and I will accept this part of the
deal.
> 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!!!).
If it takes that amount of light watts to make a carbohydrate unit than
that is fine. I have no reason to doubt this.
> 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.
I think he shows that the algae MUST HAVE used up 27%% of the _AVAILABLE_
energy to make a carbohydrate molecule based on all the stuff before. I
suppose that is OK.
> So again : The 27%% of PAR is only obtained if ALL (PAR) photons get
> absorbed (engages in the process).
Well.... He claims that 27%% is REQUIRED to create the carbohydrate. I am
giving this based on all the stuff he and you have presented. I do not
claim to understand it. But I will accept it.
> The other 73%% of energy in PAR gets
> lost in heat (heats up the plant).
BZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZTTTTTTTTTTTTTTTT!!!!!!!!!!!!!!!!!!!!!!
This is the part that is in dispute.
> There is NO MORE energy available.
> Once a photon is absorbed, that's it. C'est ca. End of story.
That is fine. But you have not shown that the rest of the energy got
turned into heat. He says that since the plant produces carbohydrates
and we know how much energy is in a carbohydrate then the plant must have
sucked up that much the energy (and more) to make a carbohydrate. I can
go along with that even if the absolute numbers are off somewhat.
> 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.
What he claims and what I have no real argument with is that the plant
must use a good bit of the energy it sucks up to respirate and procreate.
The energy isn't all devoted to making carbohydrates. The reality seems
to be that the plant sucks up more than 27%% of the available energy in
order to sustain itself while making carbohydrate units. He chooses to
show this as an efficiency loss after the fact for some reason, but it is
not really part of my argument against this paper.
>> 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.
He has a busted straight.
>> 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.
You are obviously _NOT_ a poker player. Most is not seen.
You are telling me that the grand wizard of physics will not allow the
energy to pass through the plant and also that the grand wizard of physics
will not allow the light to be reflected unless it is indigestible light.
That is the part I don't accept.
>> 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 don't care if he is the queen of England. Unless there really is a law
of reality that says the light energy can't be refracted or just pass
through and that it _MUST_ be turned to heat, then he is simply wrong in
his conclusion.
--
"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
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