Iron Fertilization: A FE-asible Policy Solution?

This article was originally published on the SERC website in May 2019.

Iron fertilization is part of the burgeoning movement of geoengineering – the idea that humans can purposefully shape natural processes on a global scale, most notably to combat climate change. It’s a controversial idea that is universally recognized to need significantly more testing to work. One of the most promising ideas to emerge from the geoengineering field is that of iron fertilization, something that has the capacity to drastically reduce our net greenhouse emissions.

To understand iron fertilization, one must first understand phytoplankton. Phytoplankton is a term used to describe a group of microscopic plankton species that photosynthesize throughout the world’s oceans, from the poles to the tropics. They are arguably the most important living things on the planet, as they produce a majority of the world’s oxygen, consume almost half the world’s carbon dioxide, and are the absolute base of the marine food web. Every living thing in the ocean gets it energy either directly or indirectly from phytoplankton. As oceans have gotten warmer and more acidic, global phytoplankton populations have decreased by around 40%, reducing the Earth’s capacity to absorb carbon dioxide in a vicious positive feedback loop. This is where iron fertilization comes in, which is effectively a form of controlled eutrophication.

Eutrophication is a phenomenon in which fertilizers enter a water source and trigger a spontaneous algae bloom. The algae bloom quickly chokes the life out of whatever is living near it, and then dies after consuming all the fertilizer, creating a dead-zone of biohazardous water. This is called a Harmful Algae Bloom (HAB) and is a common occurrence in water sources near farms and ranches. With iron fertilization, the goal is to create a sustainable, non-toxic bloom that can be integrated into the ecosystem and sequester huge amounts of carbon dioxide.

The first step in iron fertilization is choosing a location. The ideal location for this would be in open waters to avoid coastal wash ups, away from bio-infrastructure like reefs, and outside popular trade routes. It also needs to have a fair amount of fish in the area in order to regulate the population. Once a location is selected, the fertilizing compounds are introduced either through direct application or cloud impregnation. Iron compounds are used because they don’t affect the pH of the water, eliminating the threat of acid rain and ocean acidification. Once fertilized, the bloom is closely watched to insure a healthy growth rate, and to make sure that it is being fed off of. This is the crucial part of iron fertilization, and what separates it from eutrophication. As the fish eat the plankton, they effectively take the carbon that has been collected by the plankton out of the carbon cycle, because once they pass it or are killed, all that carbon gets locked in the seafloor for hundreds of thousands of years. Additionally, healthy algae swarms can create areas of high pH water, serving as a localized break from the looming threat of ocean acidification.

It’s a potent idea: if the global population of phytoplankton was increased by just 5%, it would offset the carbon emissions of the entire U.S. West Coast. Additionally, research has shown that large swarms of phytoplankton can create clouds above them to block out the sun (using a similar process; reverse cloud fertilization), which naturally increases the total albedo, or reflectiveness, of Earth.

It’s not without its problems, however. The main concern scientists and policymakers have with this project is the lack of variable control. It’s effectively impossible to guarantee that the bloom won’t die, grow out of control, pass over a reef, run into a coast, or a host of other catastrophic events that would do far more harm than good. Additionally, any large-scale project would need to be carried out in international waters, which means it’s difficult to find someone willing to foot the bill if they don’t see it as their problem. One promising avenue is the introduction of climate supercomputers, which can model the Earth’s atmospheric and oceanic changes with increasing accuracy. Supercomputers could theoretically identify ideal locations for blooms, and create a risk assessment of possible outcomes.

Another argument against iron fertilization is that it is largely untested, although recently that claim has been somewhat rebutted. The University of New Zealand carried out a large-scale controlled Algae Bloom off the coast of Argentina, and the results were surprising. The bloom was 100 miles long and 2 miles wide, and in the 2 weeks they kept it running, it absorbed 3300 tons of carbon dioxide, and was successfully allowed to die without any negative environmental impacts.

This is a promising start, and it proves that iron fertilization has a bright future ahead of it. A study in the Norwegian research publication Gemini concluded that geoengineering by itself cannot meet the Paris Climate goals, even if technology and funding increased in the coming years. It seems like a realistic application of this technology would involve pairing it with greenhouse gas reductions, possibly using revenue from a Pigouvian corrective tax to fund the venture. While it is absolutely a field in need of more study, iron fertilization is a promising way humans might be able to have a positive impact on the planet.