What is in this article?:
- Algae holds tremendous promise for biofuels future
- Right rate
- Accordion photobioreactor
It's green, it's slimy and it smells. It also abundantly produces lipids, sugars and sometimes hydrogen gas, all of which are sought-after sources for renewable energy. You may think of it as mere pond scum, but algae could be a highly productive biofuel crop in the near future.
Cuello's lab developed a device called the accordion photobioreactor – which very loosely resembles the musical instrument – to provide a controlled environment for growing algae.
"A bioreactor is just a container or a vessel where you can control various environmental factors inside such as light, temperature and pH," said Cuello.
"So there's this long chain of events," said Riley. "We've got to grow the algae and then switch the metabolism to produce the lipids, and not just any lipids but the right lipids, then purify them and process them to make the biodiesel."
And algae don't just make lipids. Some species also are capable of producing hydrogen gas, another alternative fuel. Cuello is experimenting with one such species, Chlamydomonas reinhardtii.
Algae only produce hydrogen gas when they're not photosynthesizing. Photosynthesis yields oxygen, which inhibits the enzyme that catalyzes the hydrogen-producing reaction.
"In order to produce hydrogen gas the oxygen needs to be depleted or markedly reduced," said Cuello. "One interesting technology in this area was developed at the University of California, Berkeley, and that's essentially depriving the algae of sulfur."
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."
On a quest for a more efficacious method, 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 because no one had done that before."
Cuello and Pau were able to grow algae successfully using lasers, which can be set to very specific wavelengths to control photosynthesis. "Bottom line, the method works," said Cuello.
With continuing innovations, both open ponds and bioreactors could be used to mass-produce algae in the near future. "I would think that probably it will take another five years for biofuel production from algae to become feasible economically," said Cuello.
The 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.