Wednesday, August 8, 2012
SAN DIEGO San Diego Gas and Electric's Palomar Energy Center in Escondido is a state of the art facility. The 550 megawatt natural gas-fired power plant generates enough electricity to power 360,000 homes.
San Diego researchers are exploring the idea of using algae to keep major gas-burning power plants from clogging the atmosphere with carbon dioxide. The solution could also generate fuel as the algae scrubs power plant emissions.
Pollutants are scrubbed out of the plant's exhaust, but carbon dioxide still gets into the air because natural gas is burned to create electricity. That has energy companies thinking about ways they can shrink their carbon footprint.
"Starting in 2015, gas companies will also have a carbon limit imposed, carbon caps," said Jeff Reed, director of Emerging Technologies for SoCalGas. That company sells natural gas to the power plant. "So, gas companies also need to start looking for sources of renewable natural gas and I think we're ahead of the curve."
Getting ahead of the legislatively-created curve means looking at two things: cleaning carbon out of power plant smoke stacks and using a clean, low carbon fuel. Algae has the potential to do both at gas fired power plants like Palomar Energy Center.
"The tops of those stacks, instead of just going out into the atmosphere, after the scrubbing that already happens, they would just be turned over," said Reed. "And they would effectively bubble through a very large algae pond."
The carbon dioxide would feed the algae, which could be harvested, fermented and turned into methane. Methane is linked to global warming, but it releases less carbon dioxide than natural gas when burned.
The technology is just a concept right now, but researchers at the Scripps Institution of Oceanography are trying to figure out if it will work in real life.
"So this bottle of carbon dioxide gas is fed into this apparatus. Which is then fed into the tubes and then we can set the pH at different levels that might be found in nature," said Dominick Mendola of the Scripps Institution of Oceanography.
Mendola is working on a two-year project with fellow researcher Greg Mitchell. The researchers want to see if the algae carbon trap will work out in the real world.
"Algae are plants. They happen to be submerged plants," said Mendola. "But we can put CO2 into water by bubbling CO2 into an algae culture raceway for example. Or a photo bio-reactor. You put bubbles of CO2 in and then you tune it to the right rate of emission to the growth of the algae in that system and in that environment."
Mendola is working with different algae strains and different levels of CO2. He hopes to be able to pinpoint the most efficient blend and find out if the idea is practical.
"If man has had some contribution to putting extra CO2 into the atmosphere, then man has a moral responsibility to help do something about it. So in this laboratory, we're studying how algae can absorb CO2 from the atmosphere," said Mendola.
The concept carries a price tag. A power plant like the one in Escondido would need a major retrofit. And land nearby to build enough algae ponds to filter the plant's emissions. Land costs money, especially in Southern California.
"You can't do this for free. It has to pay for itself," said Mendola. "Or at least come close to paying for itself. And the way you do that is by letting the algae convert the CO2 into useful biomass."
That biomass can be diesel, methane and even high protein animal feed. All can be sold to help pay for the retrofit. Scientists hope to know a lot more about the idea's potential when the two-year project is complete.