Dump corn stalks at sea to slow global warming?

And river's-end dump sites already receive a fair amount of vegetable matter that flows down river. So any ecological effect would likely be minimized compared with other parts of the deep ocean. Still, the duo continues, there is much to learn about potential ecological effects. So they make a pitch for more-intense research to cover that base.

Yes, but ...

Gentlemen, meet Robert Carney. He's a biological oceanographer at Louisiana State University in Baton Rouge. He's heard about the proposal. And he offers some cautions (which Strand and Benford recognize in their paper):

Among them:

Residence time: The Gulf of Mexico is an odd beast. It's known as a silled basin. Water glides in from the Caribbean through the relatively shallow Yucatan Straight, then moves over that sill and into the Gulf's basin. Although the estimate is somewhat controversial, Dr. Carney says, the Gulf is small enough and circulation vigorous enough to give deep water there a residence time from 200 to 300 years before it resurfaces.

Ecological changes: Meanwhile, his own experiments placing containers of rabbit food (a.k.a compressed alfalfa) on the deep-sea floor suggest that over several years, the presence of high concentrations of crop-like nutrients allow colonies of deep-sea chemosynthetic worms to take hold.  Even without them, bacterial will break down the vegetable matter, with CO2 as a byproduct. Assuming the sea-water residence estimate holds up, that falls short of the millennial time scales needed for keeping the carbon out of the atmosphere.

And society may have other ways it wants to value crop residue, adds James Dooley, a senior scientist at the Joint Global Change Research Institute. It's a joint project of the US Department of Energy and the University of Maryland.

He cites cost or sustainability as two other values society might place on the same crop residue.

"Our research tells us that, over time, society tends to use things for their highest-value uses," he explains in an email exchange.

Other metrics besides efficiency

In other words, as policies are adopted that make high-carbon fossil fuels more expensive, biofuels made from renewable crop residue will become relatively cheaper; it has a far lighter carbon footprint than fossil fuels.  Consumers will go for the cheap(er) stuff. And if biofuels come to provide the energy to make electricity, especially if the generating stations are equipped with carbon-capture and storage, the value of crop residue for energy generation rises even further.

So as a consumer (individual or corporate), one might then ask: Why dump this stuff in the ocean if I can use it to reduce the growth in emissions (perhaps at a less efficient rate than pure dumping) and keep my motor-fuel or electricity bills lower than they otherwise would have been?

Such are the discussions surrounding a range of semi-natural or steel-and-concrete sequestration approaches.

But if they are not ready for prime time, or even late-night, they are concepts that we may not want to discard entirely.

Some scientists -- most recently, noted atmospheric chemist Susan Solomon -- are making an increasingly vocal case that when we finally come to stabilize greenhouse-gas concentrations in the atmosphere at whatever level (especially CO2), that level will remain essentially constant for 1,000 years or more. You can read more about it here.

If emissions aren't brought essentially to zero fast enough to avoid the more-dire emissions trajectories (zero emissions are needed to stabilize atmospheric concentrations),  minimizing the effects later may require some approach to recapturing that carbon from the air and squirreling it away for a very long time.

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