Sun or sugar?

It's the big debate in the algae world. Most startups claim they will grow algae for food with sunlight and captured carbon dioxide.

A small number of firms like Solazyme and Martek Biosciences, however, assert that the only way to grow massive amounts of algae economically is to put select species in fermentation kettles and force feed them algae.

BP gave a nod to the fermentation camp today when it announced a $10 million dollar deal with Martek to study techniques for growing algae through fermentation for fuel production. Martek is one of the older and larger algae companies on the market. To date, however, it has grown algae for nutraceuticals and baby foods.

What makes fermentation tick? Water. There is none. Photosynthesis companies grow their algae in water. Circulating carbon dioxide in water requires energy – algae maker Solix in fact attributes most of the operating costs of growing algae to carbon dioxide bubbling. Algae also have to be circulated so the latest blooms don't block sunlight to older members of the colony. Then, when the algae is ready to harvest, the water has to be eliminated. There might be only one to three grams of usable algae in a liter of water. Sucking that out isn't easy.

Some startups are trying to come up with ways around those problems. Synthetic Genomics, for instance, is trying to genetically modify algae so that they will expurgate their oil while the algae float in water. Oil and water don't mix so the algae could float to the surface. (Synthetic is working with Exxon on algae fuels and with BP on ways to use microorganisms to increase oil production in conventional oil fields.) OriginOil touts a way to shake the oil out of the microorganisms.

But, as fermentation specialists like to point out, those techniques are deeper in the experimentation stage than fermentation. Solazyme claims it will be able to show that it will be possible to make algae fuel via fermentation in two to three years.