Clearly, this is beyond the growth rates experienced by the biofuels industry in the past several decades and it would require very concerted effort industry and government to achieve by 2030. Beyond this timeframe, algal biofuels may make even greater contributions to liquid fuel supply. Certainly the analysis reported here suggests that large scale algal biofuel productions may eventually become economic viable.
Graeme wrote:So five years after this report was written, the DOE decide that the algae biofuel industry is worth supporting. That doesn't sound like a dead horse.
pstarr wrote:What would sync up?
Carnot wrote:Isgota has provided an example form Algenol. Algenol have made many claims and have been plying their process for years. I doubt if it can be made to work commercially. But let us examine their claim, provided by the Isgota post, of an ethanol yield of 8000 gallons per acre. As ever the devil is in the detail and misleading units are always used to mask the truth. For simplicity I will use the following conversions:
1 acre as 4000 square metres.
Average PAR lower US 100 watts/square metre (8760 hrs/year) = (8760 x 100 x 3600) = 3.153 GJ per square metre
(For simplicity- I have not calculated photon density or number of photons which is more correct)
PAR source: http://www.atmos.umd.edu/~srb/par/Figure01.htm
8000 UG galls ethanol per acre = 2 US galls per square metre
2 US galls ethanol = 6 kg ethanol
1 kg ethanol = 30 MJ HHV
Energy of Ethanol produced = 180 MJ (6 x 30)
Efficiency on ethanol yield = 180/3153 x 100 = 5.7%
Now for a C3 plant, which algae is, to produce a 5.7 % yield of ethanol (+ other products which are required by the algae cell) this would be exceptional
(some might say impossible, which is where I sit).
Algenol aims to produce about 56 000 L of ethanol
per hectare per year using about 430 polyethylene photobioreactors
per hectare, each with about 4500 L of culture
medium containing about 0.5 g/L of cyanobacterial
biomass (10). This production target is within achieved
photosynthetic yields (2-4) and corresponds to 1.8% solar
energy conversion efficiency for average incident sunlight
energy levels in the United States (3).
Carnot wrote:Talk is cheap. Now do the economics and the EROEI and net energy gain. Oh, and by the way the circulation has to be maintained in a raceway ponds to avoid settling. A PBR could be drained down to a circulating tank I guess.
Carnot wrote:What PAR figure did you use? I took the data from the PAR project which for the US gives about 100 w/m2 annual mean average which calculates to the 3.15 GJ per square metre. I am open to persuasion but if we take the annual maximum from the same source it is 140 w/m2 making the insolation 44.15 GJ/m2. That brings the conversion down to 4.07% . Remarkable for a C3 plant. The PAR project source link is in the post. I have not found a better source for PAR insolation and I did look again. I think this source is as good as any.
Carnot wrote:But remember the 2.4 is the maximum achieved. That does not make it achievable 365 days per year.
SeaGypsy wrote:I just did a hack job on the numbers provided & broke them down to each kilo of biomass creating a kilo of oil a week, year round. Obviously an impossibility.
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