Science

The wastewater disaster in Florida is a symptom of how we grow our food

Fearing a 20-foot “tidal wave” of contaminated wastewater breaking free from a giant industrial waste pile, Florida officials told hundreds of residents to evacuate their homes in Manatee County over Easter weekend.

Since then, authorities have furiously drained more than a 170 million gallons of wastewater to alleviate the pressure that might have otherwise overwhelmed containment walls. The most dangerous water (which picked up contaminants as it leaked through the breach) was trucked away to be processed — but the rest has been intentionally drained into Tampa Bay, where it could cause more problems.

It’s a string of potential disasters that can be traced back to the area’s legacy of mining phosphate rock, which the agricultural industry relies on for fertilizer. The crisis is unfolding at the former Piney Point phosphate plant, where phosphate was mined and then turned into fertilizer for decades until the site was abandoned in 2001. What’s left in its wake are three towering phosphogypsum “stacks” — flat-topped hills of radioactive industrial waste with wastewater ponds at the center.

This isn’t the first time phosphogypsum stacks have suddenly released slurries of water and waste — and it probably won’t be the last. Another crisis like the one at Piney Point could easily happen again unless we rethink the way we grow our food, some environmental advocates say.

“The damage that occurs from just producing fertilizer — not even using it, but just producing fertilizer — is profound,” says Rachael Curran, an environmental attorney in Florida.

A big mess

Florida supplies a quarter of the world’s phosphate and 80 percent of all the phosphate used in the US. Most of it goes into fertilizer.

But before it can be used to help crops grow, the phosphate goes through a chemical process that leaves behind a big mess. Once phosphate ore is dug up, sulfuric acid dissolves it into a “slurry.” The stuff used in fertilizer is separated out from the slurry, leaving behind phosphogypsum as a byproduct. For every ton of desirable phosphoric acid produced for fertilizer, more than five tons of phosphogypsum waste remains.

Phosphogypsum has been used as a construction material in other countries, like China, which produces the most phosphate in the world (the US ranks third). But in the US, the Environmental Protection Agency banned using the material in construction in 1989 because of its radioactivity, albeit at relatively low levels. (Phosphate ore contains some uranium, thorium, and radium.)

Last year, the EPA gave the greenlight to use phosphogypsum with low levels of radioactivity to build roads (it followed a landslide of environmental rollbacks under the Trump administration). But Curran still worries about that — instead of piling the risk all in one place, she worries, that’s just spreading it around.

Since it isn’t typically used for anything, the phosphate industry pumps its leftover “slurry” into phosphogypsum stacks. Water pools on the top while solids settle and are used to form the containment walls. These “stacks” grow into mountains over time — with some reaching nearly as tall as a 20-story building and as wide as 600 football fields. There are more than two dozen phosphogypsum stacks strewn across Florida.

These giants are vulnerable. Much of Florida is built on porous rock, which makes it susceptible to sinkholes. In 2016, one opened up underneath a 120-foot tall phosphogypsum stack, sending contaminated water and waste into a major drinking water aquifer. Another sinkhole did something similar to another stack in 1994. And in 1997, the wall of another stack collapsed and sent more than 50 million gallons of contaminated water into the Alafia River. Piney Point itself spilled 170 million gallons of wastewater when the lining of its stacks ripped in 2011.

Luckily, there’s little risk that the waste from Piney Point will reach the aquifer and affect drinking water this time, officials say — although they’ve provided bottled water to affected residents.

The slight radioactivity of wastewater in phosphogypsum stacks isn’t likely to cause major problems for wildlife or people, according to Matt Pasek, a geoscience professor at the University of South Florida. “It won’t kill you to get splashed with it,” Pasek says. “But it’s not something you would want to swim in or drink.”

Still, there are other problems at Piney Point. The stacks are the highest point in the area, which is one reason why a cascade of wastewater from the site threatened to wipe out homes this week. Officials decided that the potential “tidal wave” posed a greater threat than letting water drain into Tampa Bay. But environmentalists and people in the fishing industry are worried that the wastewater, laced with nitrogen and phosphorous, could trigger harmful algae blooms that use up much of the oxygen in the water, choking local marine life.

Florida lawmakers have proposed spending $200 million on “the complete cleanup and closure” of Piney Point. The state senate will consider the budget amendment today. “When it’s all said and done, those stacks will be emptied and sealed. So I’m thrilled about that,” Manatee County Commission Chair Vanessa Baugh said during a briefing on Piney Point yesterday. The county board of commissioners authorized the use of a deep injection well to store the remaining wastewater from Piney Point once it’s been treated.

Curran still worries that those actions won’t prevent another phosphogypsum stack collapse or leak in the state. Heavier rainfall and more intense storms as a result of climate change are putting already vulnerable stacks in an even more precarious situation, she adds. A 2004 hurricane caused another breach at another stack that spilled 65 million gallons of wastewater into Tampa Bay.

“There is no safe way to manage these stacks, that’s been made clear so the solution is really to stop generating the waste in the first place,” says Curran. “That ultimately means we need to change the way we grow food.”

A new landscape?

Changing our agricultural system is a tall order. Phosphate is, after all, a building block for life. It forms the “backbone” of DNA strands. Phosphorous is one of the three primary nutrients plants need to grow, along with potassium and nitrogen.

A Mosaic Co. dragline carves out phosphate matrix in Tampa, Florida, US, on Friday, Dec. 2nd, 2011. Mosaic Co. is the world’s largest producer of phosphate and second-largest producer of potash — two crop nutrients which are primary ingredients in producing fertilizer.
Jim Stem / Bloomberg via Getty Images

After World War II devastated agriculture and industry across much of Europe and Asia, demand for these nutrients in fertilizer grew (there were also nitrate factories readily available that had previously been used to make munitions). Fertilizers increased crop yields as the population of Earth grew, and they became an integral part of industrialized agriculture.

“Phosphate is not a sort of vanity mining industry, something that you want for jewelry or things like that,” says Pasek. Because of its important role in agriculture, Pasek says an end to phosphate mining “is not feasible, let’s put it that way.”

Some farmers, however, are putting that to the test. They’re doing things differently by returning to some of the ways farming was done before there were industrial fertilizers. There’s a growing movement toward so-called “regenerative” farming. Instead of applying fertilizer and tilling soil — breaking it up — between cash crops, they’re planting other crops that replenish nutrients in the soil. Radishes, for example, have been shown to increase phosphorus in soil.

“There are a lot of farmers out there that have completely done away with synthetic fertilizer, and are doing fine,” says Rick Haney, a soil scientist with the USDA.

Even if it’s too soon to throw out synthetic fertilizers altogether, there are opportunities to use a lot less of it. Some researchers are trying to tap into the legacy of phosphate fertilizers that’s already trapped in soil. Sometimes phosphorus reacts with other minerals in soil to form compounds that modern crops have a harder time soaking up. Farmers traditionally solved this dilemma by turning to more phosphate fertilizer. As an alternative, crops can be bred to become better at making use of those trapped nutrients.

And while phosphorus might be a building block for life, phosphate rock used to make synthetic fertilizer is a finite resource that could one day be depleted. That’s adding to the growing momentum for regenerative farming.

“In 20 years it’s going to be a very different farming system. I think that we’re going to have to move in that direction because it just makes more sense,” says Haney. “Why would you work against nature when you can work with it?”

But changing people’s mindset when it comes to fertilizer is still slow-going. “It’s like trying to turn the Titanic with a tugboat,” Haney says.

In the meantime, residents like those evacuated down the hill from Piney Point will keep shouldering the risks posed by industrial fertilizers. Mountainous piles of waste from phosphate mining will keep growing because no one really knows what else to do with it except put it into piles or bury it.

People who evacuated were allowed to return to their homes last night. The risk of an imminent catastrophic phosphogypsum stack collapse has passed, at least for now. The stacks still loom in the distance, dominating the landscape.

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