Quote:
Originally Posted by DGthe3
the CO2 would most likely come directly from factories. It was either these guys or someone doing practically the same thing that were going to set up shop next to a brewery and use them as the CO2 source.
The basic concept is put algea into a plastic bag filled with water-> inject CO2-> expose to sunlight-> harvest oils-> make fuel. Not a whole lot of energy is needed, I think the oils are extracted by using a giant press (don't quote me on that though).
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Much better economics coming from a combustion process.
BUT still a daunting challenge.
Consider a furnace consuming 200 million BTU/hr natural gas. (I happen to have 10 of these where I work.) The flue gas from one furnace produces 13,500 tons CO2 per year. (theoretical potential 28,000 b.o.e./yr.) What happens when the sun goes down? This is a 24 hr operation.
I suppose we either store it or 'waste it'. Storing 4500 CFM is not very feasible, so we will only go for daylight hours. Or about 60% recovery. 17,000 boe per year.
Now the best we can get our stack gas down to economically is about 300 F after that we get condensation, I bet the algae doesn't survive at that temp so lets get it down to 90 F. It would require a very large expensive (materials of construction) exchanger to condense 3600 #/hr water and cool the gas.
We need to fill the bags with algae, water (take it from the condensate), and CO2. Whats the residence time to convert the CO2 to oil? Let's say it's real fast - 1 hour. (I bet it's much longer.) All this has to be exposed to sunlight, how thick does it work, maybe 6 inches? We have to process 4500 CFM flue gas and hold for one hour with the algae and the water. Volume is 99% gas. At six inches thick we need 24 football fields of land to lay out these bags, and then need to replace them every hour. A daunting task.
How many BTU's of the 200 Million BTU/hr can I get out of the 17,000 boe/yr produced? About 9 MM BTU/hr or 4.5% of what was put in.
Since all of this was generated by the sun, it is a good thing. The capital required would be enormous. That's a lot of land and unless it's automated it would be very manpower intensive. (automation costs capital too.)
Make the digestion period a week and you need over 3 square miles of land for the algae.