Pond Scum Prized Again
as Potential Biofuel

By Carl Zimmer

The four flasks look like they’re filled with bubbling lime juice. “If you look closely,” says Hamid Rismani-Yazdi, a Yale postdoctoral researcher, “you can see the algae.” It’s true: put your nose to the Pyrex, and you can make out tiny flecks of Dunaliella tertiolecta, an ocean-dwelling species, riding the turbulence.

Rismani-Yazdi’s flasks may look like nothing more than improvised aquariums. But Rismani-Yazdi and his colleagues have great hopes for the algae they’re rearing. It’s possible that these organisms may help start an industrial revolution.

Like a growing number of other scientists, they think algae may someday be able to churn out huge amounts of environmentally friendly fuel. It’s an idea on which investors are also betting, and in a big way. Some $800 million in venture capital has flowed into companies working on algae fuels, most of it arriving over just the past few months. From green flasks like these may come a postpetroleum economy.

At least that’s the idea. Despite all the cash and all the headlines, the quest for algae biofuel has a long way to go. There are many open questions about whether it can really work on an industrial scale. Last year three professors at Yale—Jordan Peccia, Julie Zimmerman and Paul Anastas—decided to combine the brainpower in their labs to solve many of the mysteries about algae fuel. They are deciphering the complex network of genes inside of algae to learn how to manipulate them to be better fuel factories. And they are also deciphering the complex economic network that will emerge to support the industrial-scale production of fuel from algae. After all is said and done, they want to know if we would actually be better off environmentally if algae, like the ones in Rismani-Yazdi’s flasks, fueled our cars and airplanes.

Today the algae have decided to be particularly mysterious. Rismani-Yazdi, who works in Peccia’s lab, has been adjusting his recipe of artificial seawater to coax his Dunaliella tertiolecta into growing quickly. The algae have become dense enough to give his flasks a lime-green hue. But Rismani-Yazdi would like them to grow a thousand times denser. To show what he’s shooting for, he picks up another flask, which looks as if it’s full of spinach soup. It’s crammed with a freshwater species called Scenedesmus dimorphus.

“Something is limiting their growth,” he says, looking back to the lime-green flasks of Dunaliella teriolecta. Maybe his fluorescent lamps are too bright. Maybe he’s giving them too much carbon dioxide. Or maybe it’s something he hasn’t thought of yet.

Peccia listens to Rismani-Yazdi describe his frustration. He shrugs his shoulders with a faint smile. It’s a puzzle that he’s very familiar with. “One alga looks just like another, but they respond so differently,” says Peccia, associate professor of chemical engineering. “Sometimes they don’t want so much light; sometimes they don’t like the nitrogen. After a while, we talk about them like people.”

The current excitement over algae may be new, but the basic concept underlying it is old. Today we produce fossil fuels, like gasoline and diesel, from crude oil buried deep in the ground. That crude oil got its start as carbon compounds in organisms that lived millions of years ago. Scientists have long wondered whether it would be possible to skip those millions of years of waiting—not to mention the drilling and the other demands of petroleum production—and gather energy-rich compounds from living things.

Some of the most promising compounds are oily molecules called lipids. All living things make them. Our bodies make lipids to build the membranes of our cells and to store extra energy for lean times. In the past, people have extracted lipids from animals for fuel. Lipid-rich whale oil fueled lamps and lighthouses across the United States  during the 19th century, for example.

You can’t fuel a modern economy on whale oil, though. Whales are just too scarce and reproduce themselves too slowly. As a result, whalers nearly drove many species of whales extinct by the early 20th century. But there are other organisms that make lipids in far greater quantities and at a far-faster rate. They are algae.