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- Harvesting is much more difficult and energy intensive than most people realize. I have had to deal with this issue in regards to wastewater pond effluent.
- Random natural algae tend to start taking over from artificially seeded algae fairly rapidly unless the pond is covered, and covering ponds is a fortune.
- Ponds often have to be lined to meet groundwater regulatory requirements, which adds quite a bit to costs.
However, I concede that with a great deal of research, algae ponds may eventually have a role in biofuels in select locations.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.
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?
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.
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.
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.
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?
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.
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?
We are in a race against the peak oil clock and we need to focus our research dollars where they are most needed.
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!
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.
I suggest you read some papers on the subject. You are just adding confusion to the discussion with incorrect statement.
Can you point me to any such papers that discuss the actual method(s) used for extracting the oily material from the algae?
I think you might be picturing algae physically similar to seaweed. It's not. It is typically a dispersed growth of very small clumps of oganisms that don't even settle very well, much less be amenable to skimming.
It appears to me that there are some serious (but not necessarily insurmountable) material handling considerations that need to be sorted out before algae can go full scale commercial.
Algae encompasses quite a bit of different taxonomical areas - including 'seaweed.' It's not even confined to one kingdom - simple marine plants and some protists qualify for the title.
Obviously that wouldn't work in a bioreactor. Still, it's basically just a filtration problem: run the water through a screen, and scrape the screen periodically. That's not rocket science. What am I missing here?
A) floating sun-loving microalgae in the absence of predators will tend to form a film on the top 10cm of the pond
B) the top of that layer tends to be dead from overexposure to the sun
Skimmers should be viable. So should filters:
http://www.spirulinasource.com/microjourdan.html
I also believe it is the only possible alternative for petroleum for liquid fuels. (Of course, that doesn't mean we should stop all conservation, etc)It would be tough to calculate a EROEI without having a known system, but I'd bet it would be pleanty high if the right system were employed.
An unused piece of land [bigger than] the size of New Jersey is avaiable in the USA. It also has lots of sunshine and access to lots of needed saltwater. It's called the Sonoran desert in Arizona etc, with 120000 mostly empty square miles.
If we can solve a couple of engineering problems it would probably get us over the hump. Keeping the desired strain of algae growing doesn't require covered ponds, just an artificial river with a beginning and an end. Spike it with known good algae at the beginning, and harvest gobs at the end, recycling the water. Even the stuff left after the oil is removed could be fermented into Butanol. I think the secret will be to have a series of tanks full of different microorganisms each taking the previous stuff and attacking the previous organisms, then fermenting the result. Tada... out comes biodiesel and butanol and fertilizer.
By the way, does anybody know if biodiesel can be catalytically cracked into something like gasoline?
It can, but it would be far better if we took measures to increase penetration of diesel vehicles in this country. You will take a substantial energy penalty by cracking to gasoline.
These tenacious little beasts serve as the lingua-franca for transportation in the African bush, the Australian outback, they work as troop carriers for terrorists in the mountains of Afghanistan, they do the work of larger counterparts in most of Eastern Europe and they are celebrated as the four wheel drive of choice in South America.
One would think that duty as grocery getter in American suburbia would be a foregone conclusion and a comparitively cushy job for the little monsters.
Curiously they are wholly absent from the American vehicle formulary.
So is any American equivalent and also any small and efficient diesel option in compact American sedans.
I find it hard to believe that the American vehicle buying public cannot be marketed in a manner which would help them identify the attractiveness of a small and efficient diesel option on a wide variety of vehicles and find myself wondering if "other market forces" might not be at work to keep them sealed off from the American consumer consciousness instead...or am I merely a paranoid?
I think that building a pond that large is kind of a waste of time. It's better to think of something decentralized. That way any part of any country are less vulnerable of a centralized glitch.
Also I think that algae grow only in the first 4 inches of water depth. Thats why some pilot projects use bioreactor (i.e. clear plastic or glass tubes) growing the algae.
When in tubing the problem become an engineering problem.
But it would be fun to go with all the buldozers to build a canal for bringing seawater in the sonoran desert.
That's the one I had heard about. It is not surprising. I had suspected that your first bullet point was also a problem, but had seen nothing to verify that.
I am bullish on biodiesel, but I suspect that there are some pretty challenging problems that aren't getting much attention. I liked the analysis by the UNH Biodiesel Group that showed what it would take to run our society on biodiesel, but if it was as easy as that we would probably be scaling up as fast as we could.
This is an engineering problem and deciding how to do it cheaply depends on many factors but it is not a show stopper.
I agree that covering ponds is not practical but coming up with a species that will outcompete other forms could be solved in a number of different ways.
These problems are simpler than the problems facing the ethanol crowd.
Harvesting is an engineering problem, but it is a more difficult one than you might think. Joule had some good comments on this. Sedimentation is difficult because algae floats well. If the pond (or other vessel) is kept gently agitated throughout, green algae will tend to be selected over blue-green algae and you can get some separation using sedimentation (see work by Oswald at UC Berkeley). Dissolved air flotation and filtration together with polymer flocculants are also used to separate algae from water, but it takes a lot more effort, energy, and chemicals than one might expect. Microfiltration keeps getting better and may become practical for the process.
If growing algae for biodiesel does become practical, you will see it first in conjunction with wastewater treatment where the nutrients are free and there is a lot of value to the treatment aspects of the process.
I would love to see a follow-up story, with some more details on the technical aspects of this... any TODers in NZ who can go out to the plant in Marlborough?
I couldn't have put it any better myself!
I think there is a tendency on the part of the theoretical, researchy types to be rather cavalier about what these various separation and processing steps will look like in large-scale commercial practice: "Oh, that's just an engineering problem."
As you and I understand well, when you start getting up into very large flowrates, you can't get overly fancy with the processing equipment (unless you have something like NASA's budget).
I'm just starting to familiarlize myself with the state-of-the-art of making algae biodiesel, so perhaps these problems have already been worked out, but I tend to be somewhat skeptical, as most of the work looks like academic type research.
Physically, most algae appears to be quite slimy and sticky, the perfect characteristics for rapidly clogging filters.
And as pointed out earlier, gas bubbles associated with the exchange of gases between the algae and water will create settling problems (and from my own experience in water treatment, it doesn't take much in the way of bubbles to wreck the performance of a clarifier). As such, perhaps it would be better to go with the bubbles rather than fight them and use some form of dissolved air floation. (?) Still, what you get off of a DAF unit will still be quite wet.
I also have a hard time visualizing extracting the oily fraction from this mass of wet gloop simply by pressing (lab equipment doesn't scale up very well). These aren't sunflower seeds, you know, and regardless of how good the dewatering is, there is still going to be a considerable amount of water remaining, so some sort of phase separation step might be needed.
Well, I'm still trying to find out how this is supposed to be done on a large scale, but no one around here seems to be able to supply that info. Must do some more digging.
clear, cheap "waterbeds" of growing algae, connected with swimming pool technology.
Roll them out in the desert, pump in sea water and algae.
You now have a closed system and can keep out undesirable species.
Shouldn't be that expensive, right? A barrel of oil can make a fair number of plastic bags and it would be a good use thereof.
But the ERoEI of the process remains the same as the lipo doc burns it in his Gulfstream 5 business jet. (similar to the "Gitmo Express" jet) Politically, it can be a problem only if he "drives" it in the wrong areas. Apart from lipodiesel (and misuse of jets fuelled with it) there should be no political problems with algae-diesel except for lobbyists. The sugar lobbyists already have us getting fattened, seemingly for a slaughter.
For the conspiracy fans, has the Gitmo Express plane been "souped up" as a hot-rod Gulfstream 5? Doubling engine power should just push that gem supersonic. That would make it fun for a pilot to "drive" it!
- You say harvesting is difficult and expensive. My understanding is that algae elements are 1-2mm in size. Surely a relatively coarse mesh filter on a moving conveyer is sufficient to extract the particles and present them for further processing? After all, the question is not to remove all, just enough for a constant volume to be maintained. Where is the difficulty and cost? Drying is no more complex than squeezing or laying out for the sun to dry?
- You say covering costs a fortune. However provided you employ glowplates we are talking about volume, not surface area. A single, thin sheet of polyurethane is enough to separate inside from outside, and that certainly does not cost a fortune. Why should the economics of a covered, deep, pond be any worse than any other internal cultivation? Cultivation that continues perfectly OK on today's cost base.
- You say lining of a pond against groundwater is expensive, but we are talking about less expense than lining a pond in a garden. Why should this be expensive?
I'm interested to understand why you think this type of engineering is any worse than transporting tanker fulls of crude around the globe, then passing it through complex distillation engineering?If we are talking about turning out barrels of a very valuable and sort after resource, what exact elements of the process are going to make it unacceptable? To me it sounds very plausible.