Algae Bioreactors are the Future for Growing Algae

Growing algae to produce biofuel is becoming a popular option to meet the US future energy needs.  Currently, the two main ways to grow algae are open pond systems and algae bioreactors.  Open pond systems are large outdoor ponds, which usually consist of a closed loop channel that continually circulates the water/algae mix.  The algae bioreactor grows algae in a controlled closed-loop system that uses water, sun, carbon dioxide, and nutrients.  The algae are pumped through vertical clear plastic bags and/or transparent pipes to allow for continuous addition of carbon dioxide and nutrients.  From the research I’ve done, growing algae in an open pond system is possible, but the bioreactor is a much better alternative to implement large scale production.

Algae bioreactors and open pond systems have the same core idea of producing algae to create biofuel, but the bioreactor can do so much more effectively.  Compared to open pond systems, bioreactors are much better at controlling the growing conditions, which allow the bioreactors to grow enhanced strains of algae that result in higher productivities.  One study estimated that bioreactors can produce nearly 30 times the biomass concentration than general open pond systems, which results in a larger amount of oil per acre produced compared to open ponds.

The algae bioreactor is also able to use the greenhouse emissions from industrial plants to help the algae grow more efficiently, while also breaking down harmful greenhouse gases.  By having a power plant pump its carbon dioxide into the bioreactor, the carbon dioxide will actually be fueling the creation of an energy source, rather than directly polluting the atmosphere.  An independent testing firm measured the gas composition going into and out of the algae bioreactor at MIT.  Their results showed that there was an 85.9% reduction in NOx emissions, an 82.3% reduction in CO2 emissions on sunny days, and a 50.1% reduction on rainy overcast days.

Lastly, bioreactors are able to produce biofuel cheaper than open pond systems.  According to one source, when both systems are producing 100,000 kilograms of biomass, “the estimated cost of producing a kilogram of microalgal biomass is $2.95 and $3.80 for photobioreactors and [open pond] raceways, respectively.”

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2 Comments

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2 responses to “Algae Bioreactors are the Future for Growing Algae

  1. utpqd

    Sounds interesting and I’d like to know some more details concerning the process of using both “open-pond” and “bio-reactor” systems. Although you stated that the cost of producing a kilogram of microalgae biomass is cheaper when using photobioreactors, my first intuition leads me to think that an open pond is both cheaper to build and maintain. I would, however, agree that a photobioreactor would allow for stronger additions of carbon dioxide and nutrients for algae growth, which could lead to better efficiencies in the long run.

  2. brobertson1509

    Bioreactors look to be a good alternative to open pond systems, especially with the current limitations in harvesting technologies for open pond systems. However, in order to replace all petroleum based transportation fuels with biodiesel from algae, I think it will take a combination of open pond systems, bioreactors, and other methods such as the OMEGA project underway by NASA that uses wastewater and the ocean to create algae and freshwater. Open pond systems alone will become more cost effective, especially once they become large scale, but the amount of land needed for open ponds on a stand-alone basis is huge. I wonder if bioreactors would have the same scalability issues if they were the only means of algae production. I agree that algae is our best biomass alternative to replace petroleum, but I think more than one algae production methods will be necessary to produce the large amount needed to meet our current transportation fuel demand.

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