Engineers come up with an ambitious plan to bury excess carbon at the bottom of the ocean

Our inability to decisively mitigating climate change is prompting researchers to examine more drastic approaches, such as ocean fertilization to combat climate change. massive excess of carbon dioxide in our tunes.

“At this stage, time is running out”, said Michael Hochella, Earth scientist at the US Department of Energy’s Pacific Northwest National Laboratory.

“To fight against rising temperatures, we must reduce CO₂ levels globally. Looking at all of our options, including using the oceans as CO₂ sinking, gives us the best chance of cooling the planet.”

Phytoplanktonthe photosynthetic variety of microorganisms that float on the surface of the ocean, are one of the main components of the carbon cycle biological pump who takes CO₂ out of the air to be stored in the depths of the ocean.

Tiny organisms need minerals like iron to grow and multiply, but there is only a fixed amount floating on the surface of the waters with them, which limits the amount of phytoplankton that can bloom..

So just as fertilizers can help photosynthetic organisms thrive on land, the same help could – theoretically – be offered to the sun-eaters floating on our seas.

Whales once did a huge part of natural ocean fertilization, feeding the plankton nutrients otherwise out of reach via giant plumes of poo. Before industrial whaling drastically reduced whale numbers, whales helped remove nearly 2 million tons of carbon dioxide per year through this process; now it’s closer to 200,000 tonnes.

So, by artificially adding this missing fertilizer, we could stimulate these microbes to grow and reproduce, suck in more CO₂ of heaven and carry it with them until their death. CO₂ is stored in the ocean floor at this point, where most of the excess has been released through human activities.

This poetic completion of the cycle that we have broken could sequester this carbon for hundreds of thousands of years, as fossil fuels did before them.

The larger, soluble forms of the necessary nutrients don’t tend to linger near the surface long enough to be consumed by phytoplankton, the team explains. The researchers therefore turned to nanoparticles. Nanoparticles such as iron oxides and iron oxyhydroxides are natural ocean fertilizers from sources such as volcanic ash and soil sediments.

“The idea is to augment existing processes,” said Hochella. “Humans have fertilized the land to grow crops for centuries. We can learn how to responsibly fertilize the oceans.”

Reviewing 123 studies, University of Leeds biogeochemist Peyman Babakhani and his colleagues found engineered nanoparticles that could be candidates for safely fertilizing phytoplankton growth.

Artificial ocean fertilization should occur at a level that increases the number of microalgae, but not enough to risk toxicity.

Some of the studies evaluated by the team achieved a 35-756% increase in algae growth and abundance compared to controls.

Additionally, it appears that the nanoparticle’s affinity with cell surfaces (in this case, phytoplankton) dictates the amount absorbed, rather than the concentrations, so it could be released at levels equivalent to those already present. in sea water.

Some experiments have shown that growing phytoplankton blooms using ocean fertilizers eventually depletes other surrounding nutrients that were not artificially supplied. This stunted their growth, which means future fertilizers may need to incorporate more minerals.

“If considerable CO₂ knockdown is achieved using engineered nanoparticles, this may enable applications of the approach as a carbon dioxide removal technology at smaller scales or at specific locations,” the team explains in their article“and thereby allay some of the concerns about the risks of geo-engineering the entire marine ecosystem and downstream ‘nutrient theft’.”

As with any large-scale manipulation of the environment, this proposal is not without significant risks, as is the use of land-based fertilizers.

“While natural nanoparticles exist in most ocean environments, the potential negative environmental risks of adding [engineered nanoparticles] to the ocean require rigorous assessment,” Babakhani and his colleagues prevent.

None of these particles has been the subject of a targeted study under realistic conditions, so this idea is still at the brainstorming stage.

The long-term impact of nanoparticles on ocean biogeochemistry is unknown, particularly in light of their tendency to aggregate over time in marine ecosystems, potentially suffocating life below the ocean surface.

The researchers outline a plan to begin addressing the many concerns. But they believe that although designing the correct nanoparticles would be much more expensive than using existing materials, it would give us the ability to tailor them to the needs of specific environments (those that need more silicon or iron, for example). example), making them more effective.

As the need for such extreme interventions becomes increasingly likely, researchers recognize that they must be approached with extreme caution. In the meantime, we already have reliable and much better understood methods geo-engineering: protecting and restoring lost and degraded ecosystems.

This research was published in Nature’s nanotechnology.