<DrumBeat: August 17, 2006 The Oil Drum DrumBeat: August 18, 2006>

142 comments on A little more on algae

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joule on August 17, 2006 - 5:56pm Permalink | Subthread | Parent | Comments top
drwater -

My only familiarity with the concept of fuel from algae is what I have read on the internet so far.  However, I do have quite a bit of background in wastewater treatment and sludge processing.  The three big problems with algae that you mention are exactly the same problems I think will be encountered.

I think it should be plainly evident that it's one thing to grow high-yield special-strain algae in a totally enclosed sterile lab reactor, but something else again to try it in a large open pond, which will eventually acquire its own ecology, an ecology that may not be favorable to the type of algae you want growing.

And covering even a small pond with a transparent roof is exceedingly expensive.

Still, I'd like to see more results by researchers in this field.

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joule on August 17, 2006 - 6:48pm Permalink | Subthread | Parent | Comments top
Addendum re algae:

Another consideration is the harvesting of the algae. Even though an algae-choked pond may look quite dense, I very much doubt if the algae concentration, in terms of percent solids dry weight, is much more than one percent. It is not easy to maintain sufficient dissolved oxygen by natural means if the algae concentration gets too high. Mechanical aeration can boost this, but that of course consumes energy.

So, I would image that the harvesting operation must include some sort of liquid/solid separating step(s) - possibly chemical flocculation and settling and/or belt filtration. Even with a good dewatering step, the best you are probably going to achieve is to get the solid concentration up to maybe 40%. If that is good enough for the oil extraction step, fine; but if it has to be drier then that, then we are talking about energy-intensive heat drying.

Does anybody here know exactly what operation is used to extract the oily material from the harvested algae?  Is it just physical pressing, or does the algae have to be cooked in some fashion? Any chemical reagents used?

Then there is the question: what to do with the organic residue that remains after the oil extaction step?

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Brother Kornhoer on August 17, 2006 - 7:53pm Permalink | Subthread | Parent | Comments top
I don't think you would necessarily have to remove the algae plants & dry them.  You could just run the pond water through a high-shear mixer or or through an ultrasonic resonance chamber to break open most of the algal cells, then use an inclined plate phase separator to collect the oil spilling out of the cells.  Recycle the water back to the ponds, allowing the waste algal solids to settle.  Periodically drain ponds and use a bulldozer to scrape up the solids for fertilizer.  Design your algal facility to have a fairly wide latitude regarding pumping rate between stages, and use direct-drive wind-powered pumps to pump water from ponds to storage tank towers for processing.
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joule on August 17, 2006 - 8:55pm Permalink | Subthread | Parent | Comments top
Brother Kornhoer -

I would think that if you ran the  straight algae-containing water through a high-shear mixer or ultrasonic device, you are are liable to emuslify the oily fraction.  If so, then you are not going to remove it with a gravity plate separator unless you first put it through demulsification step, most likely involving some form of chemical treatment.

Furthermore, high-shear mixing is very energy intensive, due to the fact that the required mixing energy very rapidly increases with mixer volume. So, if you have a large flow rate going through the mixing step, it could get expensive real fast.

I haven't read anywhere about what is the prefered method of extracting the oily material from the algae.

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Engineer-Poet on August 17, 2006 - 10:22pm Permalink | Subthread | Parent | Comments top
If you can get the solids fraction high enough to use a process like thermochemical conversion on the cake, you could produce hydrocarbons directly.
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Brother Kornhoer on August 18, 2006 - 12:27am Permalink | Subthread | Parent | Comments top
Good points about emulsions and the energy involved in high-shear mixing.  It does look like commercially available de-emulsification equipment is around, however, that uses oileophilic mesh filters to separate emulsions down to the 1 micron oil droplet size - no continuous chemical inputs needed.  I bet you could use oileophilic membranes as well, so this may not be as energy-intensive as it seems at first glance.

Also, I found this neat retrospective on DOE's algal-biodiesel research.  Two interesting points made - first, start with native species of algae that colonize your pond, and experiment with nutrient deprivation and/or breeding/genetic engineering on them to increase oil production, rather than try to adapt your lab culture to the outdoors.  Second, some of the research was on green algae.  This includes the kinds of algae that form colonies - the clumps you find in stagnant ponds.  If you can use a species that forms macro-sized clumps, harvesting would be vastly simpler & less energy intensive than sewage-sludge separation, where you're dealing with a sludge of micro-sized groups of cells.  As far as I can see, you could simply filter it out, drain it, and press the oil out.

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JoulesBurn on August 17, 2006 - 8:23pm Permalink | Subthread | Parent | Comments top
Why would you want to bubble oxygen? Algae produce oxygen.
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joule on August 17, 2006 - 8:46pm Permalink | Subthread | Parent | Comments top
JoulesBurn -

I know algae produce oxygen (at least during photosynthesis), but what about the respiration period during hours of darkness?  I'm not saying you would or should use mechanical aeration, but if the algae concentration gets too high, I suspect there might be mass transfer problems that might require some physical mixing.  Not sure - just speculating.

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realist on August 17, 2006 - 8:53pm Permalink | Subthread | Parent | Comments top
This issue was worked out ten years ago. They even calculated the speed of the pumping to maximize lipid production and minimize power use.
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joule on August 17, 2006 - 9:09pm Permalink | Subthread | Parent | Comments top
realist -

Well, that's good.

Do you know what is the proposed method in some of these schemes for extracting the oily material from the algae?

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realist on August 17, 2006 - 10:18pm Permalink | Subthread | Parent | Comments top
Here is a start:

Shelef, G. (1984b) "Marine microalgae separation and harvesting." Proceedings of the April
1984 Principal Investigators' Meeting, Aquatic Species Program, Solar Energy Research
Institute, Golden, Colorado, SERI/CP-231-2341, pp. 206-224.

Shelef, G.A.; Sukenik, A.; Green, M. (1984a) "Microalgae harvesting and processing: A
literature review." Report to the Solar Energy Research Institute, Golden, Colorado, SERI/STR-
231-2396.

Shelef, G.; Sukenik, A.; Sandbank, E. (1985) "Separation and harvesting of microalgae from
saline media." Proceedings of the March 1985 Principal Investigators' Meeting, Aquatic Species
Program, Solar Energy Research Institute, Golden, Colorado, SERI/CP-231-2700, pp. 244-270.

Benemann, J.R.; Goebel, R.P.; Weissman, J.C.; Augenstein, D.C. (1982a) "Microalgae as a
source of liquid fuels." Proceedings of the June 1982 SERI Biomass Program Principal
Investigators' Review Meeting, Aquatic Species Program Reports, Solar Energy Research
Institute, Golden, Colorado, SERI/CP-231-1808, pp. 1-16.

Benemann, J.R.; Goebel, R.P.; Weissman, J.C.; Augenstein, D.C. (1983) "Production of liquid
fuels and chemicals by microalgae." Proceedings of the March 1983 Principal Investigators
Meeting, Aquatic Species Program, Solar Energy Research Institute, Golden, Colorado,
SERI/CP-231-1946, pp. 19-32.

Weissman, J.C. (1984) "Cultivation of microalgae for liquid fuels." Proceedings of the April
1984 Principal Investigators' Meeting, Aquatic Species Program, Solar Energy Research
Institute, Golden, Colorado, SERI/CP-231-2341, pp.132-149.

Weissman, J.C.; Goebel, R.P. (1985) "Design, fabrication, and operation of innovative
microalgae culture experiments using open ponds." Final Report, Subcontract XK-3-03135, Solar
Energy Research Institute, Golden, Colorado.

Weissman, J.C.; Goebel, R.P. (1985) "Production of liquid fuels and chemicals by microalgae."
Proceedings of the March 1985 Principal Investigators' Meeting, Aquatic Species Program,
Solar Energy Research Institute, Golden Colorado, SERI/CP-231-2700, pp.141-161.

Weissman, J.C.; Goebel, R.P. (1987) "Design and analysis of pond systems for the purpose of
producing fuels." Report to the Solar Energy Research Institute, Golden, Colorado
SERI/STR-231-2840.

Weissman, J.C.; Goebel, R.P. (1987) "Factors affecting the photosynthetic yield of microalgae."
FY 1986 Aquatic Species Program Annual Report, Solar Energy Research Institute, Golden,
Colorado, SERI/SP-231-3071, pp. 139-168.

Weissman, J.C.; Goebel, R.P.; Benemann, J.R. (1988) "Photobioreactor design: comparison of
open ponds and tubular reactors." Bioeng. Biotech. 31:336-344.

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joule on August 17, 2006 - 11:02pm Permalink | Subthread | Parent | Comments top
realist -

Thanks for the references.

I will try to check some of these out the next time I'm at the local university library.

You obviously have quite a bit of familiarity with the subject.  Have you ever did any work in this area?

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realist on August 18, 2006 - 4:39am Permalink | Subthread | Parent | Comments top
I currently work in human biology but I'm seriously considering moving to microbiology. Research in this area is going to become very important in the next 5-10 years and studying algae is quite a bit easier than the humans. It is impossible to do genetics on humans in the US, so you need to establish collaborations with the Europeans. It is all very complicated.

We are in a race against the peak oil clock and we need to focus our research dollars where they are most needed.

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Wolfric on August 17, 2006 - 11:12pm Permalink | Subthread | Parent | Comments top
I will take a look to them as well.

Being more informed on this is the first step that I will have to go trough.

Is the UNH group doing a good job?  Is it also a good place to start reading?

You seem to have read a lot, can you tell what are the main issue?

Thanks a lot for the info!

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Robert Rapier on August 18, 2006 - 12:07am Permalink | Subthread | Parent | Comments top
Is the UNH group doing a good job?  Is it also a good place to start reading?

I think it's a great place to start reading. I spoke with Michael Briggs there about a year ago, and he gave me some useful information. I am not sure exactly what they are doing, though, at this point. It would be nice to know if they are testing various strains of algae and turning it into diesel, but that isn't apparent from the material I have read on their site.

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realist on August 17, 2006 - 8:38pm Permalink | Subthread | Parent | Comments top
Joule,
I suggest you read some papers on the subject. You are just adding confusion to the discussion with incorrect statement.
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joule on August 17, 2006 - 9:12pm Permalink | Subthread | Parent | Comments top
realist -

Can you point me to any such papers that discuss the actual method(s) used for extracting the oily material from the algae?

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realist on August 17, 2006 - 10:19pm Permalink | Subthread | Parent | Comments top
see my earlier post
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142 comments on A little more on algae

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