If you’re an avid follower of the news, you may have heard of a company called Planktos that’s trying to fight global warming and make a profit at the same time through a process called "ocean fertilization".
The concept is simple: phytoplankton (tiny one-celled algae) take up carbon dioxide (CO2) during photosynthesis. Fertilizing the ocean encourages growth of phytoplankton, and increases the rate at which CO2 is consumed – presumably leading to less CO2 in the atmosphere. Since ocean photosynthesis is often limited by lack of iron, the idea is to dump iron into the ocean and watch the phytoplankton bloom. Planktos sees this as an economic opportunity: Increase CO2 uptake in the ocean, and sell it as an offset to carbon emitters. (I talked more about how offsets work in a previous post on land-based offsets.)
Ocean fertilization may sound like a good idea, but it has some very serious problems. Here’s why.