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.
British researchers published findings in 2020 that show rock dust’s carbon capture potential while also increasing cereal crop yield by up to 20%. The project found that applying basalt to just over an acre of land could absorb 6 to 10 metric tons of carbon dioxide per acre over one to five years. The typical car produces about 4.6 metric tons of carbon dioxide annually in the U.S., according to the Environmental Protection Agency.
The implications are potentially big for both agriculture and climate change – farmers could have a simple and natural way to juice their crops without relying on expensive fertilizers, whose production creates 1% to 2% of the globe’s greenhouse gas, according to the Massachusetts Institute of Technology. Urban gardeners in New York could also play a sizable role in carbon sequestration. NYC Parks GreenThumb, the city’s community garden program, states that more than 550 urban gardens exist in the five boroughs, covering 100 acres.
Joseph noted one limitation of using rock dust was transportation of the heavy material, especially for individual gardeners who can’t pay $58 to ship a 40-pound bag of dust.
But he hopes that eventually the rock dust can be distributed cheaply by government organizations. “Transporting it is what makes it economically inefficient. But if it can be done on a large scale by a large organization, then why not?” Joseph said.
Joseph said he was inspired after seeing the effects from using rock dust in his own garden in Bedford-Stuyvesant. He started by “experimenting like crazy” in his backyard with an old, spindly rosebush that belonged to one of his wife’s family members.
”We kept it as a memento … and then I put the rock dust and this stuff started growing new limbs,” Joseph said. “It bloomed like crazy.”
Joseph’s experiment in East New York will measure the carbon capture and crop yield among three different types of garden beds: one using compost mixed with 3% rock dust, another using 30% rock dust, and control beds with no rock dust at all. Houlton’s lab at Cornell received grant funding from SGI, a rock mining company based in Maryland, which included support for Joseph’s garden experiment.
SGI, which mines basalt, sent a statement praising Joseph’s experiment as an example of “beneficial upcycling of our mined materials.”
“SGI is supporting this trial with funding and the supply of rock dust from our operations. After we realized the potential for our materials to capture CO2 and improve the nutrient density of soil, we partnered with researchers at Cornell University’s College of Agriculture and Life Sciences to further investigate and quantify these impacts,” the company said. Questions about the amount of funding were not answered.
Aside from his experiment, Joseph has also recently offered the rock dust to others at the community garden where gardeners like Earl “Al” Miller have grown crops for years.
“I got kale, tomato, pepper, cucumber, cabbage. I got a lot of stuff,” Miller said.
Thanks to the community’s long-standing ties to the garden, Joseph feels a sense of stewardship of the space and the residents who use it.
“This neighborhood has stayed West Indian throughout the years. And these are folks, they grow their local crops here. Like you know, the callaloo and stuff like that, and a lot of peppers,” Joseph said. “So I feel privileged to be able to be working in a community like this, to prove that this stuff can help these folks out.”
He’s hopeful the experiment will ultimately lead to more food resources and cleaner air, especially for gardeners in lower-income areas and farmers in developing countries.
“These are the type of people, especially in their home countries that need it most, that are spending a ton on fertilizer, or aren't getting the yields that they're accustomed to getting,” Joseph said, adding that – as climate change worsens – growing food efficiently with lower overhead costs will be critical.
“This is my way of trying to help,” he said. “And it could be applied to any and everywhere.”