This FIPR research area concentrates on issues pertaining to the chemical processing of phosphate rock into fertilizer products - an industry that has grown dramatically during the past 50 years.

History of Phosphate Chemical Processing and Phosphogypsum in Florida

Until the 1950s fertilizer manufacturing facilities were relatively small and produced fertilizers tailored to the soil needs of areas farmers, commonly within as 100-mile radius. Prior to 1950, only 4 million tons of primary nutrients were produced yearly. But in the late 1940's this began to change. Domestic agriculture and industry, as well as European and Western Pacific markets devastated in World War II, increasingly requested these nutrients. The demand to deliver more phosphate to the farmers at lower costs changed the way fertilizers were produced. In the 1960s phosphoric acid replaced normal super phosphate as the primary fertilizer commodity, turning what had been strictly a mining business into chemical production. This was especially true in Florida, which produces approximately 75% of the phosphate rock mined in the U.S. Phosphate rock is no longer sold for fertilizer manufacture. It is exclusively used to make phosphoric acid, almost all of which is used in the production of phosphate fertilizers.

Overview of Phosphate Chemical Processing and Phosphogypsum in Florida

After the phosphate is separated from the sand and clay at the beneficiation plant it goes, along with the phosphate pebble from the washer, to the chemical processing plant. There it is reacted with sulfuric acid to create the phosphoric acid needed to make fertilizer. The principal fertilizer product of the industry is diammonium phosphate (DAP), made by reacting ammonia with the phosphoric acid. Chemical processing is necessary because phosphate rock is not soluble in water. The DAP fertilizer is water-soluble and will be available for the plants to take up through their roots.

When sulfuric acid is reacted with phosphate rock to produce phosphoric acid, a by-product calcium sulfate (gypsum) is also produced. This byproduct gypsum is called phosphogypsum. There are approximately five tons of phosphogypsum produced for every ton of phosphoric acid product produced. Phosphogypsum must be stockpiled in stacks after a 1989 US Environmental Protection Agency (EPA) rule banning its use based upon the trace amount of radioactivity it contains.

There are currently about 1 billion tons of phosphogypsum stockpiled in about 25 stacks in Florida. About 30 million new tons of phosphogypsum are created each year. FIPR has funded much research into finding safe, environmentally sound ways to use this byproduct and reduce the amount that is stacked.

FIPR's Research in Phosphate Chemical Processing and Phosphogypsum

In 2002 FIPR made a related topic a high priority research focus when the Florida Department of Environmental Protection (DEP) and phosphate companies asked the Institute to spearhead an effort to improve the quality and reduce the quantity of acidic process water stored around and on top of the stacks.

While FIPR had done research on process water over the years, the topic became more critical after the Florida Department of Environmental Protection (DEP) had to take on responsibility for three phosphogypsum stacks with full ponds when Mulberry Corporation (a chemical processing company) declared bankruptcy in January 2001. The company had two stacks in Mulberry in Polk County and one at Piney Point in Manatee County. A spill from the Mulberry stack would endanger the Alafia River and a spill from Piney Point would endanger Bishops Harbor, a prized estuary.

Over the years regulations on how phosphogypsum is stacked have strengthened to protect groundwater seepage. There are also strict standards companies must meet before they can release any of the process water into the environment, but human error and natural occurrences such as heavy rains can cause the acidic water to spill. Even if there is never another spill, however, there is still a need to handle the billions of gallons of water stored in and around a stack during the rainy season and when the stack is eventually closed.

Since opening in 1978, FIPR has funded research to understand phosphogypsum's engineering properties, environmental impacts, and potential use as a roadbase material, a commercial sulfur source, an agricultural soil amendment, a construction material and a covering for landfills that would hasten decomposition and extend the landfill's life.

The Institute has also put on three international symposiums on phosphogypsum, two workshops on by-products of the phosphate industry and a Fact-Finding Forum in December 1995 to generate discussion among decision makers on the risks and benefits of putting phosphogypsum to use rather that having it remain in stacks. FIPR routinely provides scientific input and data to the ongoing technical dialogue with the US EPA to resolve issues associated with the agency current rules requiring phosphogypsum to be stacked.

Examples of other issues that have been investigated in this area include: controlling dust connected to fertilizer processing and transportation, minimizing the impact of magnesium on the processing of rock being mined to the south where there is a high concentration of dolomite, finding more efficient and environmentally friendly ways to transport materials, developing process controls and techniques that reduce the amount of phosphogypsum and increase the quality of phosphoric acid produced.

Mike Lloyd has directed this area of research since 1982. Before coming to FIPR, Mike worked at Agrico Chemical Company and held positions in research, process engineering and production of fertilizers, phosphorus and both wet and furnace phosphoric acid. He received a BChE degree for Clemson University in 1950.