You know algae. It’s the gunk that collects on the sides of a fish tank when you forget to clean it. It’s the slime that makes you slip on rocks while crossing a stream. You probably think of algae as a nuisance, if you even bother to think of it at all.

Milt Sommerfeld and Qiang Hu think of algae as one of the most useful things in existence. And they think about it every day. In fact, they have an entire laboratory dedicated to the study of algae. The Laboratory for Algae Research & Biotechnology (LARB) is located at Arizona State University’s Polytechnic Campus.

“We have algae everywhere,” says Sommerfeld with a smile, gesturing around the lab at flasks and beakers filled with bright green liquid. There are algae spinning in centrifuges and algae shaking on platforms. There are algae growing in bubbling reactors. There are algae in refrigerators and algae under microscopes. No murky pond scum here—these algae are the shade of a shamrock on St. Patrick’s Day.

Where other people see slime, the ASU biologists see solutions. They see environmentally friendly fuel. They see pollution control. They see food. They see fertilizer. In short, they see algae as an answer to many problems that currently stare humanity in the face.

Clean and green
One of those problems is agricultural wastewater. Runoff from crops and livestock contains fertilizer, pesticides, and microbes that can pollute water supplies. People living in rural areas often pump drinking water from private wells that are not monitored for these chemicals.

Nitrates found in fertilizers can be dangerous to human health, especially to babies less than six months old. When nitrate-laden water is used to mix infant formula, it can interfere with oxygen absorption, causing “blue baby syndrome.” The syndrome can cause brain damage and death.

Agricultural runoff also makes its way into the oceans, disturbing the balance of marine life. Too much fertilizer in ocean water can produce excessive growth of algae called algal blooms. These blooms deplete oxygen, “choking” other plants and animals. Some species of algae produce toxic blooms known as red or brown tides, which can poison fish and mollusks.

Sommerfeld and Hu want to fight algae with algae. By running wastewater through bioreactors that contain algae, they produce their own algal blooms that don’t harm anything around them. The algae gobble up nitrogen and phosphorus—two common fertilizer ingredients—leaving the water cleaner and safer than before.

The wastewater feeds the algae with the nutrients from the fertilizer. The ASU scientists can then harvest the algae for many possible uses.

“We’re working on algae that have a purpose,” Sommerfeld explains. “The goal is to collect the algal biomass and use it as fertilizer or animal feed, and return the water free of nutrients.”

Fish tank to gas tank
Another possible use for all this algae is biofuel.

Imagine if you could scoop algae out of your fish tank and put it in your gas tank. It’s not quite that easy, but it is possible to extract usable fuel from algae. Sommerfeld and Hu are working on a way to produce algae-based biodiesel for cars and trucks.

Scientists around the world are working to make alternative fuels from a variety of plant materials. Ethanol made from corn is already widely used. Unlike corn, however, algae aren’t food crops. And algae don’t have to be grown on good soil that could be used for growing food instead.

The problem with using food crops for fuel made headlines around the world in 2007 with the Mexican “tortilla crisis.” As world corn prices skyrocketed, the cost of corn tortillas rose nearly 14 percent from 2006 to 2007. Low-income Mexican families became unable to afford this staple of their traditional diet. Economists say the increased demand for corn-based ethanol was the main reason for the price increases.

Unlike corn plants, algae can be grown in reactors on land that isn’t suitable for farming. The algae need only water and sunlight. Arizona has plenty of sunlight and many farms producing nutrient-rich wastewater.

“One dairy cow produces 800 pounds of nitrogen per year,” says Hu. “The average dairy farm has 1,000 to 2,000 cows. We can convert 100 percent of the nitrogen they produce into fuel. In Arizona we have plenty of waste nutrients. Any kind of farm that produces manure—cattle, hogs, chickens—would work.”

Algae are also extremely productive. Like all plants, algae turn sunlight into fuel using photosynthesis. But algae do it more efficiently. Other plants have roots and stems. Only the leaves can do photosynthesis. With algae, however, every cell is like a leaf cell. Every cell is photosynthetic.

The researchers have nearly 40,000 known species of algae to choose from. They look for types that are highly productive in Arizona’s climate. So far they are working only with naturally occurring species. However, they might consider genetic modification down the line, if necessary.

If anyone knows algae, it’s Sommerfeld. He has been studying the stuff at ASU for more than 30 years. He is always on the lookout for species that reproduce rapidly. “Our goal was to have organisms that could do at least one doubling per day,” he says. His group is now working with cells that can reproduce two to three times in a 24-hour period.

The researchers are also looking for species that produce the largest quantities of lipids—or fats—under local conditions. Biodiesel is made from the lipids. Growing algae in a reactor, it turns out, helps increase lipid production.

“Algae increase production of oils when they are stressed. They grow fast in a bioreactor,” Sommerfeld says. “When they’ve used all the nutrients they can, and can’t grow any more due to nutrient limitations, they store chemical energy in fat. That is in contrast to humans. When we eat too much, our bodies accumulate fat. Algae accumulate fat when they are starved.”

Reacting with efficiency
ASU’s Polytechnic Campus is located in Mesa on the eastern end of the Phoenix metropolitan area. The area is just beginning to hit its growth spurt. Set against a backdrop of the Superstition Mountains, the campus still has a desert wilderness feel. Roadrunners and Gambel’s quail can be seen trotting alongside students rushing off to class. It was all this open space that lured Sommerfeld and Hu from ASU’s main campus in Tempe. They needed space for a new lab, and also space to build bioreactors.

Hu is the go-to guy for bioreactor design. A biologist by training, he has always been strongly interested in engineering. Efficient bioreactor design is crucial for producing fuel that is cheap enough to be useful to consumers. The researchers must not use more energy to make algae than the algae provides in biodiesel fuel. So they are working to create the most efficient, cost-effective reactors possible.

Behind the building that houses the LARB stands a 30-foot-long bioreactor. It can hold 1,000 liters. The tank is only a fraction of the size that a fullscale production model would be. But it allows the researchers to test and tweak its efficiency. The reactor can produce about 20 pounds of algae feedstock per batch. That in turn yields about 2 gallons of biodiesel—enough to fuel a small car for 40-60 miles.

The reactors don’t require much energy, but they do need some. For example, pumps are needed to circulate the water. In hotter weather, the reactor also runs an evaporative cooling system.

Sommerfeld and Hu are always looking for ways to make their production more efficient.

“We know we can make diesel from algae,” explains Hu. “The next question is—is it economical?” The pair is betting that it is. They believe that algal-based biofuel could be ready for the market in three to five years. If that happens, people may start thinking a lot more highly of that slimy green gunk.