Algae come in all sizes and shapes: from single-celled microbes in pond scum to 100-foot-long seaweeds in kelp forests. They can live in salty, fresh and even waste water.

The speed at which algae grow can overwhelm marine habitats and fish tanks, but that same productivity could make these organisms the best choice for supplying biofuels. Attracted by this potential, researchers and entrepreneurs are trying to reduce the costs of current harvesting methods.

The relation between algae and fuel actually goes back millions of years. The remains of ancient algae are generally thought to have mulched into the petroleum we now pump up from underground.

"We're sort of going 'back to the future' in making biofuels with living algae," said Thomas Byrne, a Minnesota-based renewable energy consultant and secretary of the Algal Biomass Organization.

Despite there being no big algae farms to lobby for it, algae-based biofuels have been getting a fair amount of support. The airline industry, in particular, is considering algae biofuels as a way to reduce its carbon footprint. This past January, Continental Airlines flew the first commercial test flight with algae-derived jet fuel.

Total private investment in the bourgeoning algae industry has been more than $500 million — and may be closer to $2 billion, according to Byrne. With that money, several companies are developing new routes to deliver algae oil at a price competitive with other plant-based oils.

A better "plant" than plants

Algae are some of the fastest growing organisms on the planet. Although technically not considered plants, they convert sunlight into chemical energy with much greater efficiency than land-based crops.

"A lot of algae species — if placed in perfect growing conditions — will double every six hours," Byrne told LiveScience.

The sugars in algae can be fermented to make ethanol, but the emphasis so far has been on making biodiesel from oils produced by algae.

"Algae oil is a very pure oil," Byrne said. "It doesn't carry fats that other [plant-based] oils do." These fats freeze at low temperatures and cause clogging.

Some forms of algae are 50 percent oil by mass. Compared to current biodiesel feedstock, algae can churn out 30 times more oil per acre than palm trees, and 400 times more than soybeans. It also doesn't require using productive farmland, so it shouldn't affect food supply.

Algae can be grown in the desert in man-made ponds or at waste treatment facilities. Small algae farms are even being planned for coal-fired power plants, where the algae can feed off the carbon dioxide spewing out of the smokestacks.

With all its environmental advantages, algae biodiesel is too expensive right now, costing three times that of other biodiesels, Byrne said. Research is underway to bring the price down.

Rising to the challenge

The first step in making biofuel is selecting the right type of algae (typically microalgae) for the given climate and the desired end-product. This can be daunting, since there are more than 100,000 species of algae to choose from.

The Carbon Trust — a U.K. government-funded company that aims to stimulate carbon reductions — has recently initiated the Algae Biofuels Challenge to tackle several problems, including the isolation of algal strains that can be optimized for oil production.

By rewarding innovative companies, the Trust plans to help finance a commercial plant in a sunny location (obviously outside England).

"Initial forecasts suggest that algae-based biofuels could replace over 70 billion liters [18 billion gallons] of fossil derived fuels used worldwide annually in road transport and aviation by 2030 (equivalent to 12 percent of annual global jet fuel consumption or 6 percent of road transport diesel)," according to the Trust Web site.

Wringing out

Currently, there are two main strategies for growing algae: open ponds or closed bioreactors. Ponds are cheaper, but there's a danger of unwanted species blowing in.

In either case, one of the difficult steps is separating the tiny organisms from the water. Ohio-based AlgaeVenture Systems announced a new way to "dewater" algae using capillary action rather than centrifuges.

"We have demonstrated a truly disruptive technology that reduces [the dewatering] cost by more than 99 percent - from $875 per ton to $1.92 per ton," said Ross Youngs, CEO of Univenture, parent corporation of AlgaeVenture Systems, in a press release.

Once the algae is dry, the oil can be extracted using mechanical or chemical crushing, Byrne explained. It could then be burned as is, but some chemical processing is usually done to make it into biodiesel or jet fuel.

For this last step, United Environment and Energy (UEE) in Horseheads, N.Y., has developed a solid catalyst that can drive the chemical reactions without generating as much waste as do current methods that rely on liquid catalysts.

"No water is used in our process so that no waste water is produced," said Ben Wen of UEE, who presented the new method at last week's American Chemical Society meeting.

And because the solid catalyst can be used over and over, the production of biodiesel can be more continuous.

Auguring the algal future

Even with all this progress, Byrne thinks it will still be five to 10 years before the algae market is big enough to be truly competitive.

"That might sound like a long time, but drilling off the coast would take just as long to get started," he said.

Once commercial-scale facilities are built, Byrne thinks that algae production will rapidly become more efficient, just as ethanol production has.

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