When you step onto a Har-Tru green clay court, you probably notice the cooler surface and the joint-forgiving slide. But beneath your feet, something incredible is happening: the surface you’re playing on is actively helping to save the planet.

A groundbreaking new study published in the journal Applied Geochemistry by scientists from NYU and the University of Washington has revealed that green clay tennis courts across the United States are quietly absorbing massive amounts of carbon dioxide.

It turns out, the materials we choose for our communities matter—not just for your game, but for the long-term health of our environment.

The Science Behind the Surface

How exactly does a tennis court trap greenhouse gases? It comes down to a natural geological process known as "enhanced rock weathering."

Metabasalt, a natural green stone found in the Blue Ridge Mountains of Virginia

Har-Tru green clay is created from metabasalt, a specific type of naturally occurring volcanic rock. When rainfall interacts with this crushed silicate material on the court, a chemical reaction occurs that pulls carbon dioxide directly out of the atmosphere and safely locks it away.

While climate scientists have been utilizing this rock-weathering process in agriculture and coastal management, the new research confirms that the material you slide and hit on is doing the exact same crucial environmental work.

HAR-TRU green clay courts at the USTA National Campus in Lake Nona, Orlando, Florida

By the Numbers: A Remarkable Impact

To understand the scale of this benefit, researchers analyzed data from over 17,000 green clay courts across the country. They factored in every step of a court's lifecycle—from mining and transportation to construction and routine sweeping.

The findings are astonishing.

• 25,000 Metric Tons Removed: That is the estimated amount of CO₂ these courts collectively pull from the atmosphere every single year. (For perspective, that is the equivalent of taking thousands of cars off the road annually).
• Net-Negative in 3.5 Years: On average, it takes just three and a half years for a newly constructed green clay court to reach a "net negative" carbon footprint—meaning it absorbs more emissions than it took to build it.
• Lower Starting Emissions: Even before the carbon-trapping begins, the initial construction of a clay court generates 1.6 to 3 times fewer emissions than pouring a standard concrete hard court. 

The study also found that an incredible 92% of green clay courts reach net-zero emissions in less than two decades.

Building Better Places to Play

For communities, schools, and local parks, building or resurfacing a tennis court is a major investment. Traditionally, those decisions have been weighed entirely on cost, maintenance, and how the ball bounces.

What this study highlights is that environmental impact is officially part of that conversation. Choosing a playing surface isn’t just about how the court performs today; it’s about the value it delivers to the community over the next twenty years or longer. Every time it rains, a green clay court is quietly working to clean the air.

Want to dive into the data? You can read the full study at Applied Chemistry.