A new way to combat global warming? Scientists want to fertilize the oceans with the help of nanoparticles

Researchers want to make even better use of the oceans to combat climate catastrophe. How? They propose to develop special nanoparticles that will stimulate the growth of phytoplankton so that they absorb as much carbon dioxide as possible.

How do you remove excess greenhouse gases from the atmosphere, especially carbon dioxide, which drives global warming? One method is to use so-called carbon sinks. This term is used to describe anything that is able to bind carbon-containing chemicals for an indefinite period of time. And thus permanently remove this element from circulation.

A carbon sink, for example, is vegetation, which in the process of photosynthesis takes in CO2 from the air and gives off oxygen. The carbon stays bound in plant tissues for a long time. Later, in a process that takes millions of years, the biomass turns into fossil fuels.

This is also the function of the oceans, which contain phytoplankton. The microscopic plant organisms that comprise it feed in the same way as land plants: they absorb CO2 and produce oxygen. After they die, they sink to the bottom of the ocean, “taking” much of the bound carbon there with them.

How to stop global warming

The process has long been the subject of high hopes among all those who are looking for new ways to remove the excessive amounts of CO2 released into the atmosphere since the beginning of the industrial era. One controversial idea is to speed up the growth of phytoplankton.

To this end, some scientists are advocating so-called fertilization of the oceans. That is, releasing into their waters such substances that would stimulate the growth of phytoplankton. And then they would accelerate the removal of carbon dioxide from the air and the storage of carbon on the bottom.

Unfortunately, fertilizing the oceans with iron compounds, for example, carries enormous risks. This is because it is possible to lead to blooms, i.e. massive growth of phytoplankton.

Blooms are a huge modern ecological problem. Sewage and fertilizer runoff from the mainland drives plankton growth and results in regular blooms. The dense layer of microorganisms on the surface can firstly lead to water poisoning by toxins produced by certain species of cyanobacteria. Second, it leads to the formation of “death zones” — huge areas of water deprived of oxygen. It is estimated that the area of the “death zone” in the Baltic is already approx. 60 thousand sq. km.

How to fertilize the ocean safely?

All this means that fertilization of the oceans can only be done through scientific experiments. Such as, for example, dumping iron-containing sand into the water and checking how this will affect the development of phytoplankton. Such research was started a year ago by British researchers at Cambridge University’s Climate Remediation Center.

Instead, a group of scientists from the Department of Energy’s Pacific Northwest National Laboratory has a different idea. The team, headed by Michael Hochella, has just published a paper in the scientific journal Nature Nanotechnology, in which they argue for an improved method of fertilizing the oceans. To do this, according to the scientists, specially designed nanoparticles should be used. Their use is expected to offset the disadvantages of traditional fertilization methods.

“To date, 13 field experiments have been conducted involving the addition of iron (Fe2+) to the ocean. Several studies monitoring the fertilization of the ocean with iron naturally have also been done. We found that although intentional dissolution of iron can stimulate significant phytoplankton blooms, its efficiency in removing carbon dioxide is lower than in natural processes,” the researchers wrote in their paper.

Tailor-made nanoparticles

So how to fertilize the oceans safely? The researchers analyzed 123 articles describing various nanoparticles that stimulate phytoplankton growth. They found those containing iron, silicon dioxide or aluminum oxide to be the most promising. And although fertilizing the oceans with their help is 2–5 times more expensive than traditional methods, the nanoparticles have some unique advantages.

First, they can be tailored to specific environments. In some places, fertilizers with carbon-containing nanoparticles will have a better effect, in others silicon. Second, the process is much more efficient. The nanoparticles can be designed to be more easily absorbed and remain available to phytoplankton longer. This is expected to result in the formation of more biomass, which will sink to the ocean floor and store carbon there.

“The whole idea is based on taking advantage of a natural process”, says Michael Hochella. — “Humans have been fertilizing the soil for crops for centuries. We can also learn how to fertilize the oceans responsibly”, the researcher adds.

Source: phys.org, Nature Nanotechnology

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