In 2016, Dartmouth professor Mukul Sharma thought that bringing down carbon emissions fast enough to meet international goals sounded impossible.
It was the year after the Paris Agreement was signed – an international treaty on climate change that aims to hold the global average temperature increase to less than 2 degrees Celsius.
As he studied the Marcellus Shale, a major source of fracked gas for the United States, he started thinking up solutions.
He found that there was an intimate relationship between the carbon in that shale and clay, which had lived together for hundreds of millions of years after being deposited underwater.
The process that created a massive repository for fossil fuel, Sharma thought, could provide insight into how humans might start removing carbon from the atmosphere. So he started experimenting with an idea: what if humans sprinkled clay dust on the surface of the ocean?
“Removal of CO2 from the atmosphere is super critical,” Sharma said. “A large solution is removing it in the ocean. And one of the ways we can do it is by enhancing the biological pump.”
Tiny plants and clay
The ocean has already been working overtime to help earth mitigate climate change. It has absorbed about 90% of the heat humans have generated through greenhouse gas emissions, and absorbs around a quarter of all carbon dioxide emissions.
The biological pump is the ocean’s natural process for securing carbon. Tiny plants, called phytoplankton, work kind of like trees. They photosynthesize and take up carbon dioxide – and they can store that carbon at great depths.
But, Sharma says, that pump is not very efficient. Unlike trees, phytoplankton only live for about 20 days. And when they die, bacteria in the ocean eat them.
“So as a result, essentially all the carbon that the phytoplankton have taken in gets released back,” he said.
Sharma knew that clay can easily absorb carbon. So his team started experimenting, putting clay into water and finding that it picked up organic carbon that phytoplankton produce.
In lab experiments and studies using water and plankton from the Gulf of Maine, they also found that when bacteria are present, they attach to the clay and the carbon.
“They want to stick to it,” Sharma said. “And the first thing they do is produce gobs and gobs of very gooey material.”
The goop entangles phytoplankton, too. And the sticky blobs fall down through the water, heavy with clay and other materials they collect as they drop. Then, they become a food source for zooplankton – tiny animals that live deep in the ocean, but swim up during the night time to feed.
“Anything that is raining down which is organic, they’re going to eat it,” he said. “Then they move back down, and they are pooping out the stuff that they have ingested.”
Their poops are heavier because of the clay, and they move faster towards the bottom of the ocean, potentially securing carbon deep under the surface.
Sharma says more research is needed to understand how much carbon could be sequestered using clay and to understand any other consequences of adding clay to parts of the ocean. One possible side effect is that parts of the ocean could lose oxygen, becoming anoxic.
But, he says, the process is following nature’s guidance.
“This is how nature removed carbon,” he said. “ All these very large deposits of oil and gas that you see around have – by very similar processes – been produced over millions of years.”
There are also more modern examples. The Sahara desert blows dust into the Atlantic Ocean, which other researchers say increases carbon sequestration.
Humans continue putting carbon into the atmosphere – almost 40 billion tons a year. To keep it from heating up the atmosphere, Sharma says, we need to find somewhere else for it to go.
His team is planning to do a field experiment off the coast of Southern California next.
“One has to always move with baby steps here,” he said. “It’s like going to the moon. You want to make sure that you get there and the rocket doesn’t explode halfway through and you can come back.”
This story was originally published and shared as part of the New England News Collaborative.
