Green Fuel From Green Slime

  • Roger Ruan directs the Center for BioRefining at the University of Minnesota. He's experimenting with algae that grow quickly in the nutrients in wastewater. He says the oil-rich algae are a potential source of biodiesel. (Photo by Stephanie Hemphill)

When people talk about bio-fuels,
they usually mean ethanol from corn or diesel
fuel from soybeans. But there are lots of
possibilities. One of them is algae. Algae
contains a lot of oil. The US Department of
Energy experimented with algae for nearly
twenty years after the oil crisis of the 1970s.
But with fuel prices so high, scientists around
the world are looking at algae again. Stephanie
Hemphill reports one researcher thinks
he’s figured out how to grow lots of algae, fast:

Transcript

When people talk about bio-fuels,
they usually mean ethanol from corn or diesel
fuel from soybeans. But there are lots of
possibilities. One of them is algae. Algae
contains a lot of oil. The US Department of
Energy experimented with algae for nearly
twenty years after the oil crisis of the 1970s.
But with fuel prices so high, scientists around
the world are looking at algae again. Stephanie
Hemphill reports one researcher thinks
he’s figured out how to grow lots of algae, fast:

Roger Ruan has been trying for years to figure out how to turn algae into diesel,
economically. He’s the director of the Center for BioRefining at the University of
Minnesota.

Ruan says there’s no question it can be done; some people are already producing algae
oil. They’re growing it in open ponds. It’s used for pharmaceuticals, food supplements,
and cosmetics.

“Right now, based on an open pond system, per acre per year, you can easily get 5,000
gallons of oil, and soybean would probably give you 50. That’s 100 times difference.”

So algae can be far more efficient at producing diesel fuel than soybeans. But how do
you grow enough algae to make a dent in the nation’s energy demand?

Ruan is turning to an unlikely partner: the local sewage treatment plant.

“Wastewater has lot of nutrients: phosphorus, nitrogen, are all available in wastewater,
and actually you spend lot of money to remove these from wastewater, so if we can kill
two birds with one stone, that would be the best, and that’s what we’re hoping to do.”

(sound of treatment plant)

St. Paul, Minnesota’s sewage treatment plant sits on the bank of the Mississippi River.
The basement of the building where the solids are separated from the liquids is a
brightly lit space. It’s filled with big steel pipes and valves and tanks.

Off to one side, Ruan’s team is setting up a rack of aquariums – the future home of juicy
green algae. When everything is ready, some of the partially-treated waste will be
diverted into the tanks, where it will feed the algae.

The waste is still full of stuff that’s bad for the river, but good for algae.

“It’s got a fair amount of phosphorus, and some ammonia nitrogen that the algae are
going to need.”

Bob Polta is manager of research and development at the treatment plant.

It’s easy to see why he likes this idea: every day the facility has to remove 4 tons of
phosphorus and more than 16 tons of nitrogen from the waste stream.

The algae experiment, if it works, will allow them to do some of that removal in a more
cost-effective way. And this could be the answer to Roger Ruan’s problem of trying to
create enough algae to make enough oil to compete with petroleum diesel.

Polta says there’s a big potential, both for cleaning wastewater and for producing
energy in the same place.

“All the wastewater treatment ponds in the small communities around the state are
essentially using algae to treat wastewater; it’s just that they’re not being harvested. It’s
just that we’re getting two goals together here, and two research groups, one is essentially taking algae and
harvesting the oil and making biodiesel, and the other is using algae as a treatment
scheme, and to see if we can make this thing really fit.”

Polta expects by the end of the year he’ll know more about whether this is a practical
idea.

Roger Ruan says within six-to-ten years someone, somewhere, will be producing diesel
from algae on a commercial scale.

For The Environment Report, I’m Stephanie Hemphill.

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