Can Green Clay Tennis Courts Help Save the Planet?

Scientists at NYU make the case for more green clay tennis courts.

A new study shows the positive impact of green clay tennis courts. | IMAGO / ZUMA Press Wire

The more tennis courts, the better. However, there is a case to be made for a clay surface over a hard one — specifically green clay tennis courts. A recent study highlights how green clay courts absorb large amounts of carbon dioxide via enhanced rock weathering. 

Researchers Jonathan Lambert and Frank J. Pavia calculated gross and net carbon sequestration rates for 17,178 green clay courts and found that the courts collectively removed approximately 25,000 metric tons of carbon dioxide per year.

Among these courts, 80% of them reach net zero emissions in fewer than 10 years after construction, and 92% of the courts reach net zero in fewer than 20 years. The median time for a green clay court to become net negative for carbon dioxide emissions is approximately 3.5 years.

Serve On SI spoke with Jonathan Lambert, Ph.D., and Visiting Assistant Professor (Climate Change and Interdisciplinary Science at NYU Gallatin School of Individualized Study) about the positive environmental impact of green clay tennis courts.

The Charleston Open uses green clay courts. | IMAGO / ZUMA Press Wire

What inspired this study?

The idea for this study came about when our grad school tennis crew (four Columbia University geochemists, all rated around 4.5 NTRP) got plugged into a new climate change solution called "Enhanced Rock Weathering (ERW)."

About five years ago, multiple startups hit the scene planning to crush and spread a rock called basalt on agricultural fields in order to speed up the natural rock weathering process that draws down atmospheric carbon dioxide and can mitigate climate change. It turns out that this rock is very similar to what green clay tennis courts (aka Har-Tru or Rubico) are made of.

We made some back-of-the-envelope calculations about the carbon drawdown of individual green clay courts and saw they were potentially carbon negative. Then, in 2024, Qiyu Zhou published a paper advocating for ERW on golf courses, and at this point, we were fully inspired to do the same for tennis courts.

Maintenance of the courts at the Charleston Open. | IMAGO / ZUMA Press Wire

The Charleston Open features green clay courts. Do you see that becoming a trend?

In the paper, we show that ~17,000 green clay tennis courts across the U.S. combined sequester ~25,000 metric tons of carbon dioxide per year. This is equivalent to taking ~4,200 cars off the road. We also find that just the initial construction of a green clay court emits at least 1.6X less carbon dioxide than constructing a hard court.

This information was not available before, but now that it is, facilities like those in Charleston appear to be more carbon negative than hard-court facilities. With the USTA, ATP, WTA, and other organizations looking to reduce carbon emissions and raise awareness of climate change, there could be a future where green clay courts are more centered.

We aren't advocating for building large swaths of green clay courts, but if older facilities are renovating, we hope that they use this information when deciding their mix of hard and green clay courts.

Maintenance of the courts at the Charleston Open. | IMAGO / ZUMA Press Wire

Are there any clay court colors that are also helpful for the environment?

The key to green clay courts absorbing carbon dioxide is that they are made of basalt rock. Basalt can come in many different colors; however, because the suppliers of court material in the U.S. use "blue ridge metabasalt" from the Blue Ridge Mountains (which is green), green is the norm for these courts.

However, another key consideration for the environment is the reflectivity of materials. Lighter colors reflect sunlight and keep courts, players, and neighboring environs cool. This doesn't reduce carbon dioxide in the atmosphere, but it can help keep players and neighborhoods a bit cooler.

Is green the optimal color for absorbing carbon dioxide?

Carbon dioxide removal is about the chemistry of the court material used, so basalt of any color could sequester carbon dioxide as long as it has a high enough concentration of the right elements. However, it is important to note that red clay courts (like at Roland Garros) are usually made of crushed brick and not basalt, so they don't readily sequester carbon dioxide.

Some of the layers of material underneath the red clay (like calcium carbonate) can aid carbon sequestration, and a next step for us might be quantifying carbon sequestration on red clay courts.

Jessica Pegula at the 2026 Charleston Open. | IMAGO / ZUMA Press Wire

What can fans and casual players do to help promote the push for green clay courts?

We would love to get the word out to fans and casual players about the positive climate impact of these courts, since we think it is a fun and engaging way to talk about science and climate change. Just by their existence, green clay courts are helping mitigate climate change. And, just by playing on them, we are ever-so-slightly accelerating carbon drawdown by breaking down the rock into finer particles.

So, we would love to see signs posted on green clay tennis courts that say something like "these courts sequester carbon." So, if fans have the power to put a sign like this on their courts, we would see that as a win.