Phosphorus Lake: A Snapshot of Fertilizer Fallout

Strip-mining Florida to fertilize the nation

Join Our Community of Science Lovers!

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Phosphorus mining has a beneficial side and a disturbing side. It gives us ammonium phosphate, a key ingredient in the fertilizer used to grow abundant food. It also produces massive amounts of waste, depicted here.

The phosphorus comes from calcium phosphate rock that is strip-mined across several U.S. states and pulverized. Producers add sulfuric acid to form phosphoric acid, which is later converted to ammonium phosphate. Every ton of phosphoric acid generated creates five tons of a soil-like by-product, phosphogypsum. The white or gray substance emits radon gas and is therefore used in only a few applications, such as peanut farming. Most of the phosphogypsum is bulldozed for permanent storage into giant stacks that can reach 200 feet high and cover 400 acres or more. A gypstack contains one billion to three billion gallons of wastewater that gradually diffuses out, creating small lakes that shimmer blue or green as light bounces off bottom sediment. The water’s pH is between 1 and 2, corrosively acidic. The photograph shows the corner of one such stack in Florida and the lake beside it.

Florida generates 75 percent of the phosphorus that U.S. farmers use and about 20 percent of global supply. More than one billion tons of phosphogypsum lie piled in 25 stacks across the state; 28 million tons get added every year.

Subscribe to Support Independent Journalism

Great science journalism requires human expertise, time, effort and creativity. And it costs money. That’s why I and the journalists here at Scientific American hope you’ll join our community.

When you subscribe, you are supporting staff and freelance journalists who are passionate about telling science stories that are true, important and compelling. Our editors and reporters are often experts in their fields, which means they understand the nuances of big discoveries and can untangle the breakthroughs from the hype. With a subscription, you are also supporting rigorous fact-checking to ensure the words we publish are precise and accurate. And you’re supporting original illustrations, graphics and photos that bring you closer to an advanced laboratory, an ice sheet in Antarctica or a space mission in orbit. You’re helping us craft other types of high-quality journalism as well: Our newsletters are carefully written, edited and curated by staffers you have or will come to know and love. Our Science Quickly podcast is based on original reporting, collaboration with editors and scientists and exacting production.

Subscriptions keep this engine running so we can continue to deliver thoughtful, rigorous and independent science journalism to you. In an era of viral misinformation, this work is crucial. If you value what we do, I hope you’ll consider joining us as a subscriber

Thank you,

Jeanna Bryner, Editor in Chief, Scientific American