Can pond scum save the planet from its greenhouse gas-induced fever? Green algae consume carbon dioxide and convert it to triglycerides, which can be chemically converted to fuel for our cars, trucks, trains, and planes.
We talked with AAAS member Richard Sayre, the director of the biofuels project at the New Mexico Consortium, working in conjunction with Los Alamos National Laboratory, about the progress being made on algal biofuel. Sayre is also Chief Tecnology Officer of a start-up company called Phycal. He is taking part in a session titled Employing Cutting-Edge Plant Science To Address Global Issues that Threaten Mankind, at the 2013 Annual Meeting in Boston on Saturday, February 16 at the Hynes Convention Center from 1:30-4:30 p.m.
AAAS Member Central: How did you become interested in the use of algae to create fuel?
Richard Sayre, the Director of the Biofuels project at the New Mexico Consortium: I had worked since the 1980's on a green alga called Chlamydomonas, a favorite model system to study photosynthesis. My lab was also interested in using algae for bioremediation and potentially as an antigen delivery system for vaccines. In 2006, I was approached by some entrepreneurs who were developing a type of fuel cell that generated a lot of carbon dioxide. They wanted to explore whether algae could be used to reduce their carbon footprint. We eventually formed a company called Phycal to focus on the use of microalgae to produce fuel. In 2010, we were awarded a $50 million dollar contract from the Department of Energy. We also have grants from the Air Force and we are a member of the National Alliance for Advanced Biofuels and Bioproducts (NAABB), a government funded consortium.
MCAAAS: What is the state of knowledge of algal genetics?
Sayre: It was pretty bad when we first started, but of course, it has improved quite a bit. There are number of algae strains for which there are complete genomic sequences. On the other hand, there are 14 different phyla that use chloroplasts for photosynthesis, one of which is higher plants. The rest we know relatively little about.
MCAAAS: Solazyme feeds sugar to its algae to produce lipid; are you able to produce lipid photosynthetically?
Sayre: I am in contact with Solazyme's technical people and we go back and forth on this. The advantage of using sugar as a carbon source is that you can transform sugar into lipid very quickly, in about 24 hours. The disadvantage is that only about one third of the carbon is captured as lipid, the rest is released as carbon dioxide. I think the best method will be a hybrid system whereby algae are grown in ponds, using photosynthesis to create biomass, and then transferred to fermentation tanks to convert carbohydrate into lipid. The carbon dioxide can then be captured and pumped back into the ponds. Of course, the carbohydrates are produced through photosynthesis, so it is still a sustainable method.
MCAAAS: How much lipid can you get from algae? I've heard estimates of up to 80% of dry weight.
Sayre: It turns out that there is a trade-off between lipid content and the speed of growth. The strains that are used typically have about 30-50% dry weight of lipid. The NAABB has been sampling algae in the wild, and we now have a strain that is much more efficient at conversion than previous laboratory strains.
MCAAAS: Are the NAABB strains publicly available?
Sayre: Once they are fully characterized and annotated, they will be available through the University of Texas Culture Collection. It may take some time before they are released.
MCAAAS: You use eukaryotic green algae; is there anybody exploring the use of prokaryotic blue-green algae?
Sayre: Yes, there is a company called Algenol in Florida that is using a heat-tolerant cyanobacteria to produce ethanol for fuel. They grow their cultures in big plastic bags in the sun. As the cultures grow, ethanol condenses on the plastic above the culture, and they are able to collect it in a trough, so they have a non-destructive harvesting method.