Photo: STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY

Green Machines: Phytoplankton, a type of algae, are at the base of most aquatic food chains. If the organisms die without being eaten, they sink to the ocean bottom. In the Southern Ocean, their growth is limited by the availability of iron.

Climate Engineering

As the 20th century waned and dot-com fever went criti­cal, the flow of hallucinatory business plans became a mad torrent. Shortly before it all went down the drain, observers pointed with alarm at the millions of dollars thrown at plans for using a plastic cat to track people while they surfed the Internet, for offering virtual “sticky notes” to be attached to Web sites, and for selling a USB device that emitted odors corresponding to whatever was on the ­computer monitor.

Now, in the early 21st century, it seems that “green” energy and climate change are making a bid to replace the Internet as a subject of feverish fixation and flimsy business plans. And the wackiness has shifted accordingly.

Consider Russ George. He is the chief executive of both D²Fusion, of Foster City, Calif., a “deuterium ­solutions” company that unabashedly champions cold fusion, and Planktos, which grows forests to be sold as carbon offsets to those wishing to ­counterbalance their greenhouse-gas emissions. But that ­forest-­growing business is just a ­sideline: Foster City–based Planktos’s main goal is to spread iron dust over great swaths of the ocean, where it will feed vast blooms of ­surface phytoplankton that will suck carbon dioxide out of the seawater, which would later be replaced by carbon dioxide from the atmosphere.

Most recently, Planktos has nudged itself into the spotlight with its quirky plans to provide offsets, free of charge, for both Vatican City and for a newborn girl by growing separate forests in Hungary to make the state and the infant carbon-neutral. It is not clear how the baby, born last 20 August in Budapest, was chosen.

The idea behind the iron-dust scheme is that the element is the pivotal ingredient that determines how much phytoplankton can grow on some regions of the ocean’s ­surface. Phytoplankton are the microscopic plants on which most of the marine food chain is based. As phyto­plankton grow, they pull carbon dioxide from the atmosphere and convert it into organic carbon, and it’s this part of the process that interests environmental engineers. The tiny plants feed marine animals, and those creatures’ fecal matter sinks and gets conveniently tucked away in the depths of the ocean. Where cold fusion would have heralded an era of plentiful, free energy, now carbon extracted from the atmosphere through iron fertilization holds the promise of solving the problem of climate change.

Or at least some of it does. Ocean­ographers differ in their assessments of how much organic carbon actually sinks into deeper waters and how much of it is taken up by other organisms or swept along by ocean currents. Nevertheless, if iron is dumped in all the world’s waters that are conducive to phytoplankton growth, “the most you could possibly sequester is about 1 gigaton of carbon per year, and that’s if you wish away all the problems,” says David Archer, a geophysicist at the University of Chicago who studies the carbon cycle. Other oceanographers contacted for this story agreed with that metric. That quantity, Archer estimates, would cover less than one-tenth of annual world emissions of carbon dioxide.

“If the trade-off is having to alter the biology of a big chunk of the ocean and what I get is a gigaton a year” of carbon uptake, “then I’m not interested,” says John Cullen, an oceanographer at Dalhousie University, in Halifax, N.S., Canada. Others are less dismissive and see carefully conducted iron fertilization as a promising component of climate change mitigation, once ocean scientists have worked out the details—but not before then, and certainly not right now.

By design, iron fertilization would modify the biological processes at work in the ocean, and the list of potential, though unproven, side effects is long and daunting. High on that list, says Louis Codispoti, a research professor at the Horn Point Laboratory of the University of Maryland Center for Environmental Science, in Cambridge, Md., is the possibility that an increase in carbon sequestration might cause other parts of the ocean to release more nitrous oxide—a greenhouse gas that is 300 times as potent as carbon dioxide.

But it’s hard to know for sure what the presence of more iron might do to the ocean because it is extremely difficult to monitor the movement of particles—over weeks let alone over decades. So keeping track of how much carbon actually sinks is at best an imprecise science. Compare iron fertilization with planting a forest to sequester carbon. Trees, just like phytoplankton, use carbon dioxide from the atmosphere. Even with forests, though, it is not at all straightforward to set up a mechanism for validating and auditing the greenhouse-gas reductions attributable to those trees. For example, depending on whether you plant a forest in the snowy subarctic or in old volcanic ash, you could increase or decrease the local albedo, which is an indication of how much heat is absorbed by the Earth’s surface by virtue of the amount of sunlight it reflects. In other words, depending on where you’ve put that forest, it may end up soaking up more heat from the sun than that patch of land would have done without the forest, and perhaps lead to localized warming.