>
> "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".
>>
>> 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.
>>
>> 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?
>>
>> 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.
>>
>> --
>> "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

>
> That's not the way I read it. The PAR is the energy (power) of the sunlight
> available for photosynthesis. According to this paper, that's about 100
> watts per square meter, peak I guess?

> The typical mid latitude insolation is
> a 1000Watts per square meter. peak power total of all wavelength. The PAR is
> only the wavelengths photo active in plants, mostly red. Therefore the PAR
> in percentage must be 100 out of 1000 or about 10%% of the total.

> Now, according to this paper, the photosynthesis efficiency is about 27%%
> based on the photon-carbon dioxide analysis that you mentioned. But, that's
> 27%% of the PAR not 27%% of the total light. Therefore the overall efficiency
> must be about 2.7%%

> Now I appreciate that the paper is not peer reviewed and we haven't seen any
> scientific discussion of this, we are taking the authors word for it.
> Furthermore, there is confusion in the paper between energy and power, a
> fault NO serious scientist should make, but I think the basic premise is
> correct.

> Typical insolation in the mid latitudes is about 5 kWHr per sq meter per
> day. That equals about 7.3 million kWHr per acre per year. Now, if the oil
> has an energy content of 40kWHr per gallon, the absolute maximum gallonage
> at 100%% efficiency equals 183,000 gallons of oil. If the photosynthesis is
> 2.7%% efficient, the gallons produced is 4927 Gallons of oil. That's where
> the 5,000 number comes from.

> I have no reason to doubt this, it sounds reasonable to me. The question is,
> can this number be improved on? I think it can and have written on that.
> There are two approaches, one broadens the active PAR to include more
> wavelengths and the other shifts unused wave lengths into the PAR region.