Algae will grow using the nutrients from sewage in the Spanish trial. Photograph: Patrick Pleul/AFP/Getty Images
There's not much that's more renewable than sewage. So the idea of
turning human waste into algae and then into biofuel is an attractive
one and is now going to be put to the test on a commercial scale in
southern Spain.
The €12m project will see the sunny skies of Cadiz
beaming down on open ponds in which algae suck up the nutrients from
the waste water. If all goes to plan over the next five years, the plant
will produce about three tonnes of algae a day from 10 hectares of
ponds, enough to run about 200 vehicles.
The project is led by Aqualia,
the third largest private water company in the world, with six other
technology and academic partners providing expertise. The European Commission has provided €7m of the €12m funding.
Aqualia's
Frank Rogalla says the project would turn the sewage treatment facility
from a consumer of energy to a producer of energy, very much like the fuel-cell technology I wrote about last week.
First,
much of the organic matter will be anaerobically digested to produce
methane, another fuel source. This is already done on in some tropical
countries and for special waste waters, such as that from breweries. The
reason for the pre-treatment is so the algae don't have to battle it
out with bacteria for the organics. Instead, the carbon dioxide produced
alongside the methane is pumped back into the waste water, to feed the
algae.
A key advantage of the proposal is that the waster water is
already full of the nutrients - nitrogen and phosphorus - that the
algae need to grow. "We would get the nutrients for free, when today we
get paid to destroy them," says Rogalla. He says 30% of the costs for
commercial algae growers is buying in nutrients.
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