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Photoautotrophic Cultivation- Open ponds Vs Photobioreactors 14

Useful article and I dont know who the author is.
The article leads one on to oilgae.com site.

Algae-cultivation on a whole faces several challenges. There are two methods of growing algae -  one is the photoautotrophic cultivation  and the other is the  heterotrophic cultivation.

 Photoautotrophic cultivation as the name suggests is cultivating algae in the presence of light ? the light can be either freely available sunlight or artificially provided light.

  Heterotrophic cultivation essentially means  the algae is cultivated in the dark by providing it with some carbon sources such as sugar for its growth.

Photoautotrophic cultivation can be carried out in open-ponds as well as PBR?s . There are many advantages of cultivating photoautotrophic algae in open-ponds- the first being the cost, it is about 7 ? 10 times cheaper than growing algae in a PBR.

Not only that the evaporative cooling maintains the temperature as well. However, its extremely difficult to maintain monocultures by using  open-ponds. Moreover, the control over temperature and sunlight is also not possible.

Photoautotrophic cultivation in a PBR might sound very exciting as  there is much less water loss when compared to open ponds, ability to maintain the cultures for a longer period.

However, if costs are considered, its too much . Cleaning the PBR will also a major issue, the interiors of the PBR must be frequently cleaned due to biofilm formation.   All the more, there are several scaling up challenges as well.

As a result, it remains to be seen which system will be preferred at scale over long periods of operation. Sometimes it will be neither  open-ponds or PBR?s  through the photoautotrophic way, the heterotrophic route might prove successful.
Mon October 11 2010 09:36:23 AM by Arden algae cultivation  |  photoautotrophic cultivation  |  photobiorectors 2322 views

Comments - 10

  • Mon October 11 2010 11:35:38 AM

    Arden, good to talk to another Purdue grad. My grandson graduated this year, A&S engineering.

    How about a few comments on the above article and in general trying to clearify were we should be heading in this great algae opportunity.

    If our goal is to capture as much CO2 as possible from the big emitters ( 25,000 cfm) and make a profit then the cost of the reactor should not be an issue. If a system 'works', (takes all the CO2 and converts it into a saleable product) and yields a profit after paying all costs including depreciation then the cost is not as important as everybody is focused on. Instead of wasting time talking about cheap facilities that are impossible to operate at scale for a profit with commodity prices and NO govt. help, let's talk about the perfect PBR. Granted, this 'perfect' PBR will only come into full operational status in the future when a few advances in algae culturing are relised.

    It is not practical to have 14,000 acres of ditches to mitigate the CO2 problem from a plant that puts out 25,000cfm.... 24/7/365.

    Algae are plants. Growing plants, fertilizing them, tending to thier every need, harvesting
    the plants,etc. that is called "FARMING".

    A farmer does what he does as efficiently as
    possible. If he farms 2500 acres of corn he doesen't use a team of horses because they are 'cheap'. With a team of horses he may be able to farm 50 acres of corn, and work his butt off doing that. So he leaves 2450 acres idle because he is using 'cheap' horses. What are his opportunity costs for using cheap tools????

    You couldn't give me an open pond (system ?), it's way too expensive.

    A modern farmer may have a million or more dollars invested in machinery and it all sets in a building most of the year. But, when the time is right he can go out and do all the things a farmer does to plant, harvest,etc. and get the job done in a timely manner and make a profit.

    One can't drag a stick through the ground, line it with plastic, and call oneself an algae-farmer.

    Alan Schaefer

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  • Larsyn wrote:
    Mon October 11 2010 02:24:27 PM

    I draw another pararell to a PBR. It's like growing in as field as opposed to growing in a greenhouse. In most cases the same plants can be grown either way. But a greenhouse grows a higher quality plant due to its ability to control all elements in the plants life. Often times multiple crops as opposed to 1 seasonal crop.Plants in the field are at the mercy of mother nature.

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  • Veronica wrote:
    Mon October 11 2010 02:45:19 PM

    @ Alan and @ Larsyn

    Here the farmer is forced to work for an industrialist who is bellowing 25000 cfm of CO2 night and day. He actually doesnt have a choice to use his horses:-)

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  • Tue October 12 2010 12:31:11 AM

    Huh?? I guess I missed the humor. Veronica, I assure you that the thought of horses never entered into the 'farmers' mind. Perhaps he might be thinking of a 100 year contract with the emitter. Pay us only (x) amount per ton of their CO2 emissions and we will build a system that will come very close to utilizing 100% of their
    CO2 and nox emissions.

    Nobody is going to force anybody to do anything. It's not a healthy way to do business!

    Alan Schaefer

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  • Veronica wrote:
    Tue October 12 2010 04:12:46 AM


    I meant that the farmer cant afford to think small, when he has to absorb 25000 cfm.

    While it is clear that open ponds are a no no and pbr is the only way to go, inspite of the initial cost, it is important to know
    as to what solutions have been found to the well known challenges / hurdles in pbrs.

    a. Lighting .
    How efficient is the current methods of lighting.
    How are we to know that we are providing the optimum lighting?

    How effective is the Helix of Origin oil's lighting system ?

    First let us try and finish the lighting system and then we will move to other points regarding a PBR.

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  • Arden wrote:
    Tue October 12 2010 04:19:35 AM

    I agree with all three of u.
    There is this capital cost of a PBR which is high and dont forget the operating cost of the PBR, which is also pretty high.

    But, given the fact that we need to attend to large quantities of CO2 emission, we can worry about cost later.

    If someone can think of laying down large pipes covering long distances and liquefying the CO2 and storing it under the sea, am sure pbrs will cost far less to begin with. (CCS).

    May be we cld look at lighting and Control of O2 ina pbr to start with and as Veronica says, we can look at other things later.

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  • Tue October 12 2010 04:28:43 AM

    Andres posted a long note on light management just recently, here

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  • Tue October 12 2010 04:35:06 AM

    Sorry Veronica, its been a long day. Will pick up again in the morning. Lots to comment on.


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  • Krupali wrote:
    Wed October 13 2010 12:06:26 AM

    Bionavitas is supposed to be making low cost PBRs, isnt it ? Anyone who has tried their pbr ?

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  • Anna wrote:
    Wed October 13 2010 04:12:14 AM

    Not everyone in the algae industry look at this as an opportunity to save the world by absorbing CO2.
    The fact is in the process u make biofuel too.

    Very soon the cost of CO2 sequestering will take off exponentially and therefore the cost of a pbr
    be it Operating cost
    Capital cost
    it wouldnt matter.

    What will matter is if one will sequester CO2
    and make some fuel that is renewable.

    Those who look at it as a synergistic way to sequester CO2 while making renewable fuel, see it as a great opportunity to save the world and dont bother about the cost.

    Others who are more concerned about the cost are looking at keeping the capital cost down, managaing with contamination, evaporation etc and
    looking at making bye products like plastics, feed, food etc to make profits. They are at present cost conscious - both Capital cost of the PBR and the Operating cost of the PBR.

    In most high value products where they need more control, they will bewilling to go for an expensive PBR as viability is there financialy.

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