In 2005, Harrison Dillon and Jonathan Wolfson, the founders of Solazyme, a San Francisco-based algae biofuels company, came to a shocking realization: the biofuel they were producing from algae was going to cost approximately $1,000 a gallon. While photosynthesis is free, the cost of maintaining algae is not.
HETEROTROPHS Organisms, such as humans and other animals, that obtain energy by eating organic molecules that were produced by other organisms.
Photosynthetic algae can be expensive to maintain because they are either grown in large transparent tanks called photobioreactors, which are costly to operate, or they are grown in open ponds, which require lots of freshwater and constant monitoring for contamination. Wolfson and Harrison looked for a solution. They knew that, of the more than 100,000 species of algae, there are rare strains that do not rely on sunlight. Instead, they survive by “eating” sugar. If they used these algae to make biofuel, could they save money? Algae that could be grown in closed, nonphotosynthetic vats and fed cane sugar could conceivably be much cheaper.
With support from their investors, Wolfson and Harrison changed their business model and gave the new idea a whirl. It was a good decision: they now believe that they can make oil using these nonphotosynthetic algae that cost only $60 to $80 a barrel (roughly the cost of a barrel of regular oil), in part because they can save money on overhead costs. The sugar is also relatively cheap to obtain since it comes from plant scraps, switchgrass, and other plentiful sources that aren’t of direct use to humans as food. Many other algae companies still use photosynthetic algae, and they have developed cost-effective ways to make them work, but for Solazyme, the rare sugar-eating algae are a better choice.
Organisms like ones that Solazyme uses— organisms that can’t photosynthesize and must eat molecules produced by other organisms to obtain energy—are called heterotrophs (“other-feeders”). It’s a group that includes not only sugar-feeding algae but also all animals, fungi, and most bacteria. When humans and other heterotrophs eat plants—or eat animals that have eaten plants—specialized processes release chemical energy stored in the molecules making up the plant or animal (see the discussion of aerobic respiration in Chapter 6). Heterotrophs can then either use this energy to grow, in which case the energy will become stored in the chemical bonds in their bodies, or to move and power other chemical reactions in cells. The result: energy is converted from one form into another, flows from the sun to autotrophs to heterotrophs, and finally is released back into the environment as heat.
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