Geoengineering vs. climate change: fertilizing oceans with iron

Not sold on that artificial volcano idea as a method of modifying our climate? Here's something else to try: dumping massive amounts of iron into the oceans to spur algae blooms that suck carbon out of the atmosphere. Ocean fertilization, as it's called, isn't a new idea, but newly published experimental results suggest that it might actually make sense.

If you want to take carbon out of the atmosphere, you have to have somewhere to put it. Trees are a popular place: they turn CO2 into O2 and C, and the C hangs around for a long time as wood, where it doesn't contribute to climate change. You can do the same thing with algae, which are tiny little plants that live in the ocean. They may be small, but there are a lot of them, and they're much faster and easier to cultivate than trees are: all you have to do is feed them some iron, and they go absolutely bonkers.

Most of the time, algal growth is limited by iron, since not enough of it is naturally available in the ocean to support all of the algae that want it. Adding even a modest amount of iron to the water causes an algal bloom, where you'll get hundreds or thousands or even millions of individual algae cells per milliliter of water, each one of them responsible for taking a little bit of carbon out of the atmosphere. When the bloom recedes after a few weeks and all the algae die off, their little bodies sink down to the bottom o' the sea, where they (and their carbon) stay for a long, long time.

Or at least, that's what's supposed to happen. Folks have tried this before with varying degrees of success. In the last major study, they were able to make a giant bloom with iron fertilization, but a bunch of shrimp just came along and ate it all. This is bad, because it keeps the carbon in the food chain when you really want it to be removed from the picture entirely.

A new report on the results of an iron seeding experiment that took place back in 2004 suggests that when done properly, ocean fertilization might actually be something worth doing. The Eifex trial went exactly as it was supposed to, generating an algae bloom using iron that persisted for three weeks and then died off and sank. This method is appealing because iron is cheap and available, dumping it into the ocean is relatively easy, and since algae are at the bottom of the food chain, having a big population of them is also good news for other marine life.

A global program of ocean fertilization has the potential to remove anywhere from one to three gigatons of carbon from the atmosphere per year, which is between 10% and 30% of the carbon emissions that we produce. This would require something like sixteen supertankers full of iron at a cost of about $25 billion or so, but considering the cost and consequences of not doing anything, $25 billion seems like a relatively paltry sum considering the benefit that could be provided.

Via New Scientist

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