Green machine: A new push for pond scum power

Green machine: A new push for pond scum power

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Pond scum. The term surfaces in every news report about the decades-long effort to get energy from algae. But more respect for the tiny creatures may soon be in order: industry and governments have started pouring billions into alga power.

Just the basic facts make you wonder why algae aren't powering our civilisation already. The single-celled phytoplankton produce half our planet's oxygen and are the fastest-growing green organisms known. In shallow seawater ponds on land, they can use sunlight and sewage to turn concentrated carbon dioxide – flue gas from coal burning, say – into

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Pond Scum and The Future

"Ten million hectares of algae could supply all US transportation fuel," says Greg Mitchell of the Scripps Institution of Oceanography in La Jolla, California. That's less than 3 per cent of the area farmed in the US – and algae can live in seawater in the desert.

Algae into diesel was all the rage back in the 80's!

Too good to be true? Until recently, it seemed so. After the 1970s fuel shocks, the US launched the Aquatic Species Program (ASP) to investigate algae. It eventually built 1000 square metres of ponds at Roswell, New Mexico, and found many promising algal strains. But it concluded in 1996 that diesel from algae would cost twice as much as diesel from oil – at least at oil prices then.

So the emphasis turned to corn ethanol but enthusiasm there has cooled because corn is more valuable as a food crop.

So the ASP ended, and focus shifted to bioethanol from maize. Enthusiasm for that has dimmed, however, as it conflicts with our need for farmland for food.

So now scientists are back to developing algae:

Algae can produce 10 times as much energy per hectare as land-grown oil crops, says Mark Hildebrand of Scripps, because "they float. They don't have to spend half their [energy] building stalks to support themselves."

Instead, they make more cells until they run out of nutrients such as nitrogen. Then they stop dividing, but keep photosynthesising, storing the results as an oil droplet that can eventually take up more than half the cell.

The payoffs for algae could be big but will require considerable further scientific study:

And ultimately, production will require suitable climate, land, water, nutrients and CO2, all at one site. Even using waste land, seawater, sewage and smokestack CO2, Benemann thinks this will limit the potential for algal biomass to the equivalent of 1 per cent of the CO2 now being released, or less. "But that's still a gargantuan amount. Let's hope we can do that much."

We won't without more long-term funding, says Mitchell. But he is sanguine about the pay-off. "The US has been subsidising corn ethanol at $5 billion a year. Half that amount for 15 years in algae could solve the water, fuel, energy, feed and farmland crises humanity faces."

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reply to post by plumranch


Algae represents a much better alternative than ethanol. The fuel needs of the entire country could be raised in a relatively small area of ponds and with considerably less environmental side effects such as runoff, fertilizers pesticides and chemicals.