Eat My Carbon
November 3, 2009, 6:00 PM EST
What to do with the world's fossil fuel pollution? Why not feed it to plants?
If the world is going to make progress toward the goals to be discussed at the United Nations Climate Change Conference in Copenhagen this December, it's pretty clear that carbon dioxide, the most important greenhouse gas, must be captured. Fossil fuel produces nearly two-thirds of the world's electricity. All those power plants can't just be turned off.
But then what? Once carbon is captured, there are just a few places it can be sent. It can be piped thousands of feet underground into saline aquifers, it can be pumped into depleted oil and gas reservoirs, it can be used to help extract oil and gas, and it could be sent to the bottom of the ocean.
All of which is expensive. The cost of pressurizing captured carbon dioxide and injecting it underground or to the bottom of the ocean could be about $100 a ton. And that's not including the legal and insurance outlay it might take to convince (or force) local residents to allow it to be stored underneath them.
"That means you've taken $100 and shoved it underground," says Paul Woods, chief executive officer of Algenol, a Florida start-up that is developing an algae-to-ethanol technology. "It's much cheaper to capture it and give it to algae. It's not a little cheaper, it's a lot cheaper."
Like most other plants, photosynthetic algae feed on carbon dioxide. Using energy from sunlight, plants separate the carbon from carbon dioxide and reassemble it into energy molecules like sugars, starches and fats. Dozens of companies like Algenol are trying to get at those energy molecules and use them to push cars and planes around.
There are thousands of species of algae, and nearly as many ways of getting algae to produce fuel. Most companies are trying to coax algae to produce lots of fats. The algae are then harvested, and the fat is separated and refined into diesel or jet fuel. Craig Ventner's Synthetic Genomics, which is partnering with ExxonMobil, is trying to engineer strains of algae to produce ready-to-burn fuel.
Algenol's algae produce starches and ferment them into ethanol. Instead of being harvested, the algae are kept alive as they pump out fuel. Algenol and Dow Chemical are teaming to build a pilot "bioreactor" at a Dow plant in Freeport, Texas, that will produce 100,000 gallons of ethanol a year.
Feeding carbon dioxide to algae isn't quite like storing it underground for thousands of years. But algae proponents argue it at least displaces oil consumption--it prevents carbon that's already been underground for thousands of years from reaching the atmosphere.
The problem, again, is cost. Storing carbon underground may be expensive, but so far producing fuel from algae is expensive too. It’s tough even to reliably estimate what the future cost will be because both technologies are at such early stages that current costs are astronomical and future costs are based on assumptions that include heavy doses of hope.
Still, it would certainly help the algae fuel companies if carbon emitters paid them to take carbon dioxide away. And it would help carbon emitters to have a cheaper place to send carbon dioxide.
Another issue: scale. Philippe Joubert, who runs the power division of Alstom, the French maker of power plants and fast trains that is a leader in developing carbon capture and sequestration, agrees that algae could be a good place to sequester carbon dioxide. To a point. "This is a good model, it is absolutely feasible. The problem you have here is the quantity," he says. A big coal plant (1,000 megawatts) produces 2 million tons of carbon dioxide a year. "There's not an industry that could use that amount of carbon dioxide," he says. "I mean, we could put it in Champagne, too, but they just don't need very much."
Woods says stationary carbon dioxide emitters like power plants put out 3.6 trillion tons of carbon dioxide a year in the United States. If everything goes perfectly for Algenol, Woods says he'd be able to take 300 million tons. But first someone has to be willing to pay him to do it. For that he needs a carbon market. And that's up to Copenhagen and Congress.
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