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Growing Algae from Wastewater Runoff in the Ocean

Algae Magazine Interview: NASA’s Dr. Jonathan Trent aimad160x90_-EP

By David Schwartz

NASA scientist, Jonathan Trent, Ph.D., the inventor, heart, and soul of the OMEGA system (Offshore Membrane Enclosures for Growing Algae) has been developing an idea for a way to grow algae using wastewater, but not on land! His OMEGA system is a floating algae growth environment composed of a system of connected pods that convert the nutrients in wastewater to algae in the ocean.  Here are excerpts from an interview with Dr. Trent.

Give us your elevator pitch on the OMEGA System.
Well, given that some species of microalgae are the fastest growing biomass on the planet and the best oil producers, we can probably agree that algae are the organism of choice for biofuels. If we further agree that biofuels production cannot compete with agriculture for freshwater or fertilizer, which means to me we have to use domestic wastewater to grow them, then let’s consider our options.

I think the fact that in all our coastal cities we already have the infrastructure for “disposing” of our wastewater offshore, we need to consider the possibility of using this wasted water and the existing infrastructure for growing microalgae offshore.

In addition to using wastewater from existing offshore outfalls for developing algae systems, there are other good reasons for OMEGA, or float photobioreactors (PBRs) in seawater. For example, there’s the heat-capacity of the seawater that can be used to control the temperature of the PBRs – temperature control of PBRs on land is a huge and expensive problem. The sea provides other energy savings also. Wave action can be used for mixing and the salt gradient can be used for forward osmosis, which not only cleans the wastewater released into the sea, it also concentrates the algae for harvesting.

If the freshwater algae cultivated in wastewater escape into the surrounding seawater they die (freshwater algae can’t survive in salt water), which means they will not become invasive species in our coastal waters. The OMEGA structure itself can be used as an enormous substrate for developing aquaculture to grow edible seaweeds, mussels, oysters, or some other marine “crop” appropriate for the local conditions.  

If you see where this is going, OMEGA is a system of systems – or an “ecology of technologies” – in which the concept of waste disappears: a waste product from one part of the system becomes a resource for another part. As far as possible the whole system, which includes the environment, is in balance. 

Describe a little more about the physical properties of the system.
The OMEGA system we are now testing on a small scale consists of manifolds connected to floating clear flexible plastic tubes, pH/dissolved oxygen/temperature sensors control systems for pH, gas exchange columns, and harvesting systems. Wastewater is the source of nutrients and photosynthesis occurs primarily in the plastic tubes. Dissolved oxygen is removed as the culture falls through an airspace in the gas exchange column, while the pH is controlled and CO2 is added by bubbling flue gas through the water in the column.

When the algae reaches a density that limits photosynthesis, it is shunted to an experimental forward osmosis chamber to pre-concentrate, and then to a harvesting chamber. Wastewater is added back to the system to maintain a supply of nutrients and a concentration of algae optimum for photosynthesis. In other words, we want to make sure that the algae never gets so dense that we’re just harvesting photons in the upper few millimeters of our bioreactor, but we are harvesting enough algae biomass to cover the energetic costs of harvesting.

At commercial scale each module would be between 50 and 100 feet long. Obviously, pumping water through the system is going to have the biggest energy requirement.  We’re looking at wind, wave, and solar energy to supply most of this energy.

What do you think needs to happen, not just for the OMEGA project but for the future of this industry in general?
If you mean the algae industry as a way to make biofuels, my personal opinion is that the US should be investing the kind of money and brainpower that we invested in the Manhattan Project and Apollo. The Manhattan project was an investment of something like $22 billion (in 2008 dollars) over a five year period. And the whole Apollo program was about $98 billion over 14 years. They were amazing government-funded programs that mobilized the best and the brightest, actually from all over the world to reach socially and scientifically important goals.

Given the importance of liquid fuels, not only to the transportation industry, but to so many aspects of our society, and considering both the limited availability (peak oil and the location of reserves) and desirability (environmental impacts and national security) of fossil fuels, it’s highest time we make the transition away from fossil fuel dependence. The fossil fuel industry is nearly 150 years old and it represents some $5 trillion a year in revenue.

I think if we want to maintain a semblance of our lifestyle in the future, we need to seriously ask ourselves what it will take to replace the bulk of the fossil fuels we are currently using with sustainable, carbon neutral biofuels and can we do this in the next five to ten years? Then, we as a nation, should take on that enormous challenge with the determination of the Manhattan Project and the enthusiasm of the Apollo mission. With our current focus on the “economic crisis” I don’t know if the U.S. is up to this challenge. On the other hand, if we can invest over $1.2 trillion in the last ten years for wars in the middle east, perhaps we can find the resources to secure our own energy sources, energize a green economy, and make those wars obsolete. 

– Dr. Jonathan Trent received his PhD in biological oceanography at Scripps Institution of Oceanography. He went on to post graduate work in Europe studying the biochemistry and molecular biology of microorganisms living in geothermal hot springs, the so-called “extremophiles.”

He got involved with NASA shortly after they started a program in astrobiology in the late 90s. “It was a perfect job for me,” he says. “NASA was looking for people studying the most extreme organisms on this planet to understand if there could be life on other planets.”

To read more on Dr. Trent:

See the video:

David Schwartz is Editor/Publisher of




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