Solazyme’s process of growing the algae in the dark has a couple of advantages over approaches that use ponds or bioreactors. First, keeping the algae in the dark causes them to produce more oil than they do in the light. That’s because while their photosynthetic processes are inactive, other metabolic processes that convert sugar into oil become active.
Just as important, feeding algae sugar makes it possible to grow them in concentrations that are orders of magnitude higher than when they’re grown in ponds using energy from the sun, says Eric Jarvis, a biofuels researcher at the National Renewable Energy Laboratory, in Golden, CO. (Jarvis is not connected to Solazyme.) That’s in part because the sugar provides a concentrated source of energy. These higher concentrations reduce the amount of infrastructure needed to grow the algae, and also make it much easier to collect the algae and extract the oil, Jarvis says, significantly reducing costs. High capital costs have so far stymied other attempts to make fuel from algae.
In spite of these advantages over other approaches, Solazyme’s method for creating fuel is not yet cheap enough to compete with fuels made from petroleum, Dillon says. Indeed, Jarvis warns that one of the most expensive parts of making fuels from cellulosic sources is processing them to create simple sugars, a part of the process that Solazyme isn’t focused on improving. But in the past 18 months, improvements in the amount of oil that the algae produce have convinced the company that competitive costs are within reach. Solazyme hopes to begin selling its fuel in two to three years, Dillon says.