A few small orange flags stuck in the dirt are the only markers that distinguish Kwesi Joseph’s kale and collard plantings from the rows of other lush vegetables at the Hands and Heart Community Garden on New Lots Avenue in East New York.

But Joseph, an urban gardens specialist for the Cornell Cooperative Extension, is conducting a low-tech and audacious experiment with those vegetables.

His thesis is simple – crushed basalt rock mixed with soil and compost in this Brooklyn garden will both capture more carbon from the air and also help plants grow bigger, thus increasing the potential yield of fruits and vegetables.

“If urban gardens can assist in sequestering carbon, why not?” Joseph said.

The experiment is his own twist on ongoing research that Ben Houlton, dean of Cornell University’s College of Agriculture and Life Sciences, is currently conducting to glean what the potential is for using rock dust as a tool for carbon capture.

It’s an idea already in practice in other places like Davis, California and Northampton, Massachusetts, said Joanna Campe, executive director of Remineralize the Earth, a sustainable agriculture nonprofit based in Northampton. She noted that Joseph’s experiment is likely among the first time rock dust’s impact on plant nutrients has been studied in an urban garden.

“Even in organic agriculture, the minerals are often missing that we need. And minerals are absolutely important for us to utilize all the other nutrients, so we can increase the nutrients in our food supply by adding rock dust,” Campe said. “And it increases the biological activity, so it's also food for the micro-organisms, so to speak.”

Basalt and other silicate rocks naturally react with carbon dioxide in the air, sequestering it out of the atmosphere and turning it into a solid that gets stuck in the ground. Studies show that this process, known as enhanced rock weathering, can also remove acids from soil and sop up nitrogen pollution caused by fertilizers.

Basalt rock is also sustainable, given that it is produced by volcanic lava and is the most common type of rock in the Earth’s crust.

“The idea is if farmers apply this rock dust to soils around the world, then we can convert a significant portion of CO2 [carbon dioxide] that would enter our atmosphere into bicarbonate or carbonate, which are stable and below ground and really all good things for solutions for our climate,” said Garrett Boudinot, a research associate at Cornell’s Department of Ecology and Evolutionary Biology who’s assisting Joseph with the Brooklyn garden project.

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