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UA Researches Algae Growth Optimization

UA Researches Algae Growth Optimization

April 27, 2011, by Shelley Littin, NASA Space Grant intern
AlgaeIndustryMagazine.com
Wastewater has nitrates and phosphates that need to be removed anyway, so why not just feed it to the algae?

In a collaborative research effort between several departments, scientists and engineers at the University of Arizona are studying ways to optimize the environmental factors to control the rate at which algae grow and produce lipids, both in order to maximize production while also reducing the cost of resources needed to grow algae.

“Right now the cost of production still exceeds the value of the final product,” said Joel Cuello, professor in the department of agricultural and biosystems engineering. “So the challenge research-wise is trying to lower the production cost while increasing algae productivity.”

One way to lower production cost is to use treated secondary wastewater to grow the algae. The algae purify the water by absorbing nutrients such as nitrogen and phosphorus, and at the same time eliminate the need to use costly fertilizers to supply the algae with nutrients. “Wastewater has nitrates and phosphates that need to be removed anyway, so why not just feed it to the algae?” said Cuello.

Graduate student Joe Ley extracts an algae sample from the Accordion, which he is using to grow Botryococcus braunii, an oil-rich alga that could be used to produce jet fuel.

Graduate student Joe Ley extracts an algae sample from the Accordion, which he is using to grow Botryococcus braunii, an oil-rich alga that could be used to produce jet fuel.

The researchers grow colonies of algae in flasks to test the effects of different environmental conditions on growth and lipid production.

Kimberly Ogden of the department of chemical and environmental engineering has a lab full of algae-filled flasks. “We grow the algae and then separate the lipid material that can be turned into fuel from the rest of the algae, which is mostly protein. The goal,” said Ogden, “is to learn enough about the chemical structure of the oils to be able to process them into biodiesel with the same facilities currently used to process petroleum.”

“We use alternative water supplies and look at water recycling and reuse,” says Ogden. “We don’t want to use tap water—for one thing all the chlorine is probably not a good idea, and we don’t want to be using the freshwater supplies.”

One of the challenges is selecting a species that produces the right lipids at the right rate, said Mark Riley, professor and head of the department of agricultural and biosystems engineering. “We can look at algae that grow very quickly, but they generally make very little oil. Or there are algae that grow really slowly, but they make a lot of oil. So the challenge is how to mix the two of those characteristics to maximize the amount of oil.”
Depriving the algae of sulfur stops photosynthesis so  that oxygen can’t  be produced and the algae instead will make hydrogen gas.

“One of the ways to try to stimulate the algae to produce a lot of lipids is to deprive them of one resource,” said Riley. “The idea is to give them some sugar or a lot of sunlight, and then not give them nitrogen because they need nitrogen to make protein and they can’t replicate unless they can make protein. What happens is the algae keep running photosynthesis and instead of being able to replicate they store all of those compounds inside their cells.”

“We also look at life cycle assessment,” said Ogden. “We look at the impact of the entire process on the environment, everything from the nutrients that the algae need, such as phosphate, nitrogen and carbon dioxide, through the actual processing. We’re trying to understand how to optimize production from what we learn in the lab and apply that knowledge to methods for mass production of algae.”

The researchers are experimenting with open ponds at an outdoor facility in Tucson, Ariz. However, controlling environmental factors becomes much more difficult with the larger-scale, outdoor operation. “The water, the sunlight and the ambient temperature are all factors you want to keep in a fairly narrow range,” said Riley. “One of the problems in these large ponds is just the temperature change from day to night. If the liquid gets too hot, then you kill the algae. If it gets too cold, then you decrease their rate of growth and their rate of metabolism.”

“One interesting technology in this area was developed at the University of California, Berkeley, and that’s essentially depriving the algae of sulfur,” said Cuello. Sulfur is a component of certain amino acids and proteins the algae need for photosynthesis. Depriving the algae of sulfur stops photosynthesis so that oxygen can’t be produced and the algae instead will make hydrogen gas.

“That’s a great idea and it works,” said Cuello. “But it’s cumbersome because you have to transfer the algae from a sulfur-containing medium to a non-sulfur-containing medium to produce hydrogen gas, and then back again to allow the algae to photosynthesize and recover.”

In order to optimize this process, Cuello and his team came up with a way to make the algae switch between photosynthesizing and producing hydrogen gas using light. The researchers are able to turn parts of the photosynthesizing machinery on and off by exposing them to different wavelengths of light.

“I collaborated with professor Stanley Pau in the College of Optical Sciences, who is an expert on lasers,” said Cuello. “We both thought it would be interesting if we could demonstrate production of algae using a laser as the light source.” Cuello and Pau were able to grow algae successfully using lasers, which can be set to very specific wavelengths to control photosynthesis.

The UA studies are funded by the U.S. Department of Energy’s National Alliance for Advanced Biofuels and Bio-Products and by local and national companies.

Photos courtesy of Joel Cuello

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Thu April 28 2011 12:33:59 PM by Tomcatino 1931 views
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