Nearly a billion tons of it lie stacked on Florida soil. It's a problem that a new law won't solve.

When a 150-foot-deep sinkhole ripped the middle out of an 80-million-ton pile of radioactive waste in Central Florida two years ago, it grabbed the public's attention.

To those flying over the cave-in, it was "planet Earth's first moon crater."

To the wags living near it, it was "Disney's World's newest attraction: Journey to the Center of the Earth."

FSU Oceanographer Dr. Bill Burnett surveys the crater-like summit of Florida's largest GYP stack at IMC-Agrico in Polk County

But to Bill Burnett, a professor of oceanography at Florida State University, the cave-in at the IMC-Agrico plant in Polk County near Mulberry was yet another striking example of why Florida must change the way it deals with one of the state's biggest hazardous-waste problems: phosphogypsum. "By the year 2,000, Florida will have close to a billion tons of this stuff sitting around," says Burnett (Ph.D, Hawaii). "That's enough to give every man, woman and child in China a ton of it."

Where does it all come from? Phosphogypsum is created as a waste byproduct when fertilizer is made. And since Florida produces 90 percent of the nation's (and 30 percent of the world's) phosphate ore-a chemical used to make agricultural fertilizers-it also produces an abundance of phosphogypsum. About 30 million tons a year, to be exact.

Because it contains minute traces of radioactive byproducts of uranium, found naturally in phosphate-bearing ore, the phosphogypsum is largely considered useless in this country. For years, Florida's 13 phosphate-mining companies have simply stacked the stuff up in piles, usually right beside their processing plants. The result is a landscape dotted with about 20 man-made mountains, an oddity for Florida to be sure. One stack can cover as many as 500 acres, roughly the size of the footprint of the sinkhole stack at IMC-Agrico, one of the largest of all. That monster pile caved in when the earth beneath it buckled for unknown reasons. Quips Burnett: "What can you see that's man- made from outer space? The Great Wall of China, the Pyramids and the Florida gyp-stacks."

After four years of research, however, the professor says he numbers among those who are convinced that phosphogypsum can be turned into something safe and useful. Over the years, a number of ideas have cropped up-from building roadbeds with the stuff to mixing it with cement to build artificial reefs-but for various reasons most have gone nowhere. Burnett insists there's an answer, and it may be to turn the material into a sulfur-rich fertilizer, he says.

"This stuff isn't nuclear waste," Burnett says. "This is a beautiful example of a problem that's solvable."

The kicker, however, is that the state already has established a way to deal with the huge stacks, and it doesn't leave much room-or industry money- to explore any alternative approaches, Burnett says. After years of struggling to get the rule into place, Florida regulators say they're satisfied that the state's requirements are the best way to deal with the problem.

And there is still another obstacle Burnett must overcome: the concerns of some environmentalists. ManaSota 88, an active, grassroots environmental group in central Florida, balks at any alternative use of the phosphogypsum.

"It's a radioactive, corrosive hazardous waste, in our opinion," says Tom Reese, an environmental attorney with ManaSota 88. "These stacks need to be capped. They're unlined, and as long as they remain uncapped they pose a potential contamination threat to our groundwater."

Along with the radioactive elements of uranium and radium, the phosphogypsum also contains trace amounts of arsenic, cadmium and other heavy metals, Reese says.

Gypsum, a common mineral formed naturally during the evaporation of ancient seas, has many commercial uses, from plaster of Paris to wallboard. But phosphogypsum, a chemically produced byproduct containing radionuclides-radium on its way to becoming radon-does not.

Because of phosphogypsum's radon emissions, the federal Environmental Protection Agency has banned most commercial uses of it, and requires the industry to store it in stacks. State regulators, however, have been concerned for more than a decade that simply stacking the phosphogypsum up was not protective enough of Florida's fragile environment. Since 1985, at least a dozen of Florida's gyp-stacks have been cited for violating pollution standards. In at least one case, a leaking stack was linked to contaminated water in nearby wells, according to a report last year by U.S. News and World Report.

The pollution problems led regulators to impose more stringent rules. About three years ago, the state decided the old stacks must be capped.

"Once the stack reaches its useful life-both its economic and physical life- you now have to close it," says Phillip Coram, an industrial-waste engineer with Florida's Department of Environmental Protection. "Closing it means you have to cover it."

Most stacks are closed when they reach about 200 feet in height, Coram says. Once closed, a plastic cover is dropped over the huge mound to prevent chemicals from leaching out from around the pile when it rains. Soil is then spread over the cap, and plants are grown.

At least one old stack has already been capped, Coram says, and two others are in the process of being closed. But it's not cheap. Depending on the stack's size, the price tag to cap a stack ranges from $10 million to $20 million, Coram says.

And there's the rub, says Burnett. When the industry is forced to make such enormous investments in closing the stacks, it's not as inclined to look for alternative uses for them.

Yet conversion to a useful product, even without a significant profit margin, is much preferable to the huge expense and endless monitoring required for environmental isolation of the phosphogypsum, Burnett believes.

"My opinion is that they ought to delay these closures," Burnett says. "There's a much better alternative to treating it like a nuclear waste. As a scientist, I would rather take a more optimistic approach. As an example, let's look at the Merseberg solution."

For years, Burnett says, the Merseberg process-named after the German city where it was invented in the mid-19th century-has been used to make a sulfur-rich fertilizer, ammonium sulfate, from the naturally occurring mineral, gypsum. Burnett proposes using the same process to do the same thing with phosphogypsum.

His study, sponsored by the Florida Institute of Phosphate Research, is the first to document what happens to the radioactive elements in phosphogypsum during this waste-to-fertilizer process. Done with post-doc researcher C.D. Hull and grad student Michael Schultz, the FSU investigation showed that the resulting radioactivity in the ammonium sulfate product is very low.

The first step in the process is to react the phosphogypsum with ammonium carbonate, to make ammonium sulfate. Also created, as a waste byproduct, is calcium carbonate. The radioactive elements concentrate in the calcium carbonate, so it's not usable. But the good news here is that you end up with a much smaller amount of radioactive waste than you started with-anywhere from 30 percent to 60 percent less, plus a very useful product is produced, says Burnett.

"You still have waste material, but you have decreased the volume considerably," he said.

The smaller waste product is about three times more radioactive than the original, which makes a five-pound bucket of it about a third as radioactive as a typical home smoke detector, says Burnett. But when it comes to radioactive waste, he says he'd "rather have a hill of this stuff than a mountain of the other."

The Merseberg process has been used in Asia to convert phosphogypsum into fertilizer, on a small scale. But not for environmental reasons.

"In Asia, the situation is different because sulfur is more expensive," Burnett says. "So recycling the phosphogypsum is more practical there. For them, it was a decision based on economic choice-it made good economic sense.

"But for the U.S. today, it doesn't, at least that's what people keep telling me."

Traditionally, there's been little demand for sulfur-rich fertilizer in the U.S. But Burnett sees that changing in the not-too-distant future. The price for ammonium sulfate is going up, and if it continues to increase, Burnett believes it may become much more economically attractive to recycle phosphogypsum into a useable, sulfur-rich fertilizer.

Although sulfur is an essential nutrient for plants and triggers increased crop yields, it has for years been left out of fertilizer. Burnett said that's because the fertilizer industry has for several decades believed that it wasn't necessary to add sulfur to the soil. Leaving it out also, of course, reduced production costs.

And the industry may have been right to omit it, for scientists now say that acid rain was indeed inadvertently adding sulfur to American soil. Today's tougher clean-air regulations, however, have significantly reduced the amount of sulfur-laced rain that crops receive.

Add that to today's increased demand for crops, and you've got a "sulfur gap," Burnett says. There's growing evidence that lack of sulfur is responsible for lower crop productivity in developing countries and in more than 35 states in the U.S.-including Florida.

With the evidence mounting, and the projected cost of capping and monitoring the Florida's strange man-made mountain range, the only logical solution seems to be to continue to search for some alternative uses, he feels.