Green Goo for Biodiesel:
By Sarah Curry
With diesel fuel retailing at over $4.75
per gallon, algae-based oil sources are
beginning to look better than cost-effective.
More than 50 companies in the United States
are now working to commercialize algae-generated biodiesel.
Most start-ups begin with the findings of
the Aquatic Species Program, which ran at
the National Renewable Energy Lab (NREL)
from 1978 to 1996. The lab collected and
screened more than 3,000 algal strains,
looking for species that naturally produce
a useful quantity of oil. After narrowing
the collection down to 300 strains, mainly
green algae and diatoms, NREL grew the
algae in test ponds in Roswell, N.M., for a
year. They also studied the process for lipid
extraction and conversion to biodiesel. In
the last few years of the program, they
worked to genetically modify the algae to
produce more oil.
Microalgae are fast-growing beasts with a
voracious appetite for carbon dioxide. They
have the potential to produce more oil per acre
than any other feedstock being used to make
biodiesel, and they can be grown on land
that’s unsuitable for food crops.
In theory, producing algadiesel should be
easy: Just separate CO2 from a coal plant’s
exhaust, bubble it through an algae tank,
squeeze out the oil and pipe it into a refinery. As part of their photosynthetic process,
the algae also “exhale” oxygen.
According to Al Darzins, group manager
of NREL’s National Bioenergy Center, some
algal strains can produce upwards of 50 to 60
percent of their total body weight in oil. But
to do that, they must be stressed. Researchers
usually remove a nutrient, such as nitrogen,
to induce this stress.
“It’s the same reason we turn excess
food and store it as fat on various areas of
our body,” said Doug Henston, CEO of Solix
Biofuels in Fort Collins, Colo. “When the
algae feel like they’re going into an environment where they’re not going to have readily available nutrients, they start to produce
oil to store energy.”
Stress reduces growth rate, so the trick is
to find a balance between growth and oiliness that optimizes oil output. At that optimum stress, Darzins says, algae can produce
more than 5,000 gallons of oil per acre per
year (soybeans produce about 50 gallons per
acre). If diesel sells for $5 per gallon, the
annual retail value of the algae crop is $16
million per square mile. That’s rich enough
for oil companies to pay attention.
The Energy Security Act of 2007 calls for
36 billion gallons of domestic biofuels to be
produced each year by the year 2022. The act
mandates that 20 billion gallons must come
from “advanced” biofuels, meaning non-corn-based biofuels. Companies are working
hard to make algae-based biodiesel available
as an “advanced” biofuel. Twenty billion gallons might be grown on about 1. 5 percent of
American real estate.
Doing it in a lab and doing it on an industrial scale are two very different things. It’s a
matter of maintaining just the right environmental conditions, on a large scale, while
facilitating rapid harvesting.
“There’s a lot of challenges and technical
barriers that need to be overcome,” Darzins