The study shows that green clay tennis courts in the United States, built with metabasalt, can sequester substantial amounts of carbon dioxide via enhanced rock weathering. Researchers analysed a database of court locations and surface types and modelled 17,178 green clay courts. Their carbon removal estimates incorporated the type of basalt, crushed-rock grain size, court temperature and chemical composition. Similar models were used to estimate emissions from hard courts for comparison.
The method calculated both gross and net sequestration and accounted for emissions during mining and processing, transport of materials to court sites, court construction and ongoing maintenance. The authors estimate total removal of about 25,000 metric tons of CO2 per year. They found that 80% of courts reach net zero emissions in fewer than 10 years, 92% in fewer than 20 years, and the median time to become net negative is roughly 3.5 years. By contrast, hard courts made of concrete do not remove carbon through weathering, and clay court construction emissions are 1.6 to 3 times lower than hard-court emissions even before weathering is counted.
Location and temperature strongly influenced sequestration: the warmest sites and courts nearest the primary basalt processing site in Virginia showed the highest removal rates. Nineteen courts in the coldest and most distant regions are unlikely to reach net zero. The authors conclude that this approach offers a practical way to reduce emissions and that adjustments to crushed rock composition and better tracking of maintenance could increase verifiable carbon removal. The research appears in Applied Geochemistry (source: NYU).
Difficult words
- sequester — to remove and store carbon dioxide
- sequestration — process of removing and storing carbon dioxide
- metabasalt — a type of basalt rock used on courts
- enhanced rock weathering — chemical breakdown of rock that removes carbon
- net zero — when total emissions balance total removals
- verifiable — possible to measure and prove accurately
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Discussion questions
- What practical challenges could prevent some courts from reaching net zero, based on the article?
- How might changing crushed-rock composition and better maintenance tracking increase verifiable carbon removal?
- Would you support using metabasalt on local tennis courts to reduce emissions? Why or why not?
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