PG Questions & Answers

Phosphogypsum (PG) is a by-product of phosphate fertilizer manufacturing. 30+ years ago, the EPA required PG be stored in stacks based on very conservative risk exposure guidelines. Today, science tells us a different story.

1What is phosphate?
Florida’s abundant phosphate reserves formed millions of years ago when the area was covered by nutrient rich ocean waters, with sediments forming a layer of phosphate ore. Phosphorus is an essential nutrient that is derived from the phosphate minerals typically found in that ore. Phosphate promotes healthy plant growth and has no synthetic substitute. Typically, it enters the food cycle through the soil where it nourishes crops, and in turn, nourishes people and animals when those crops are eaten.
2How is phosphorus made and manufactured?
Once an operations site is permitted and environmental preservation and reclamation plans have been submitted, machines called draglines are used to extract the “matrix” which can be found approximately 40 feet below the earth’s surface. The “matrix” that contains phosphate rock is mixed and becomes a slurry when water is added to enable it to be pumped to a separation plant. Here, the phosphate is separated from other materials and later transported by rail, truck or ship to a fertilizer manufacturing plant. The fertilizer plant transforms the phosphate into a water-soluble form that plants and animals can use. The basic process involves mixes an acid with the matrix. During the process, the calcium from the matrix combines with the sulfur in the acid to produce calcium sulfate. Calcium sulfate is gypsum – a common industrial mineral. In the fertilizer industry this calcium sulfate byproduct is called phosphogypsum, or “PG” is created. That PG is stored in gypstacks. Fertilizer produced with Florida made phosphate is then shipped to farmers and used to grow the food that the world needs.
3What is phosphogypsum (PG)?
Phosphogypsum, or PG for short, is calcium sulfate, a product created during the phosphate manufacturing process. For every ton of phosphorus produced, approximately five tons of PG is made. PG is a durable product and its stacked while wet and later hardens to hold its shape. In the US, PG use has been limited to certain agricultural applications and scientific research. Other countries, however, looked at phosphogypsum as a beneficial material that can be used in agriculture, forestry, building materials, concrete and more.
4Why is PG stored in stacks in the US?

Over 30 years ago, the Environmental Protection Agency (EPA) required PG storage in stacks based on very conservative radioactivity risk exposure – science based on decades of additional research now tells a different story. PG contains NORM, naturally occurring radioactive materials. According to the International Atomic Energy Agency (IAEA), PG is considered a NORM residue – meaning it is a material that remains from a process and contains NORM. During manufacturing, once the phosphate is removed, these materials are more concentrated, but maintain the same low-level of radiation. PG can be further classified as TeNORM, meaning it is technologically enhanced during the manufacturing process.

IAEA confirms that commercial use of PG has been restricted in the US because of concerns about its NORM content, even though such concerns appear to be without scientific foundation. Outside of the US, countries are already beneficially using their PG and at least 55 different uses have been researched worldwide.

5Are gypstacks a safe way to store phosphogypsum?
Gypstacks are heavily regulated, safe structures that can span many acres and reach up to 500 feet tall. The permitting process is very thorough, often taking years for State and County governments to approve. An important component of the modern permitting process includes extensive reporting and monitoring requirements during a stack’s active life and for 50 years after it is closed. Today, phosphate producers build and maintain stacks that are equipped with the latest technology and geotechnical monitoring devices that allow for a stack to be studied inside and out. Over time, gypstacks experience settling and consolidation that require periodic maintenance identified through inspection, monitoring and the multitude of available data. While gypstacks were considered by experts to be a safe way to store PG when the regulations were put in place in the 1980’s, volume and long-term management were not considered. Finding innovative ways to beneficially use PG may eventually reduce the size of existing stacks and mitigate their long-term environmental impact.
6How many gypstacks are there in the United States and Florida?
In Florida, there are 25 total gypstacks that store PG produced during the state’s long history of producing phosphate to grow healthy crops in the US and around the world. Of these, 21 stacks are closed, in closure or are idled, where PG sits ready to be put to productive use. Four are currently active and support phosphate manufacturing operations. There are active stacks in Polk County, Hillsborough County, and Hamilton County. Nationwide, gypstacks can also be found in Louisiana, North Carolina, Idaho, Iowa, Illinois, Minnesota, Mississippi, Wyoming and Utah.
7What happens when a stack is at capacity?
When a gypstack has reached the end of its useful life it is prepared for closure, a process that may take many years. Process water stored on the stack is treated to meet strict standards for water quality before it is discharged into permitted areas. Once process water has been removed, a high-density polyethylene liner is installed at the top of the stack followed by backfilling with soil and planting grass. After closure, the stack and any residual process water is managed in accordance with State and Local regulations. Rainfall and other water drained from the stack is treated and discharged, subject to rigorous standards identified in permits. Today, permits require long-term care for up to 50 years after a gypstack is closed and includes a significant, ongoing investment by producers to cover the full cost of stack maintenance and inspections.
8Could what happened in March 2021 at Piney Point in Florida’s Manatee County occur at an active gypstack used by the phosphate industry in Florida today?

Modern gypstack design, operation, closure and long-term care plans are subject to stringent standards. Today’s phosphate producers have invested in technologies and methods that have proven to mitigate risks associated with gypstacks. The gypstack at Piney Point last operated 20 years ago and was constructed before current regulations were in effect. The more recent use of the Piney Point stack was for purposes unrelated to the phosphate industry. Thus, the events that occurred at Piney Point are neither reflective of phosphate manufacturing practices, nor the required process for closing a gypstack.

Innovative and beneficial use opportunities for PG stored in gypstacks have been extensively studied and reviewed by EPA for use in projects like road construction and limited agricultural applications. Recycling opportunities would reduce the amount of land needed to store PG, reduce the carbon footprint of mining other natural minerals for which PG could substitute, and contribute to a circular, more sustainable economy. PG reuse, that is permissible in many parts of the world, is a more sustainable approach to fertilizer production using more components of the phosphate matrix.

9 How do gypstacks and the process water they contain hold up in Florida’s unique geology and its notorious weather events?
A generation ago, very few Americans recycled. Today, almost everyone does. As Americans learned more about the environment, we became better at protecting it. That’s how it worked for the phosphate manufacturing industry, too. Historically, Florida’s geology and weather have had an impact on gypstacks. After a record-setting four hurricanes battered Florida in 2004, our industry developed and implemented new safeguards designed to strengthen the integrity of gypstacks and maintain process water on site. Accounting for Florida’s unique geology, significant investments have been made to incorporate technologies into gypstacks that provide early indication of potential geological activity such as sinkholes. Process water is managed in a way that accounts for hurricanes or other significant rainfall events. Readiness, mitigation and training plans are continuously reviewed and improved. Today, gypstacks hold up well against the challenges that Florida’s environment presents.
10What is process water and is it hazardous?
Water is a key component of the manufacturing process. Gypstacks collect and retain rainfall and “process water” which is circulated in ponds on top of active gypstacks for reuse in plant operations and it transport of PG to stacks. Process water contains some elements that have been dissolved out of the phosphate matrix. Like the phosphate matrix obtained in phosphate manufacturing operations, process water contains low levels of Naturally Occurring Radioactive Materials, sodium and sulfate. Process water is not considered hazardous, but nonetheless based on its characteristics is highly regulated and is managed appropriately to protect human health and environment. Only treated process water that meets the permitted discharge water quality standards can be released through permitted and monitored points.
11Can process water be unintentionally released into groundwater or water bodies?
Water management practices are regulated and engineered to maintain all process water on site. Gypstacks are designed with comprehensive groundwater monitoring systems, drainage systems and recovery wells to detect irregular conditions and ensure process water remains on the stack. Rigorous field inspection requirements are also in place to monitor the integrity of the overall system. Modern gypstacks are lined with an impermeable barrier that is routinely monitored for integrity. The industry can use recovery wells that act like a giant straw that collects any impacted groundwater and keeps it in the system. Innovative practices, procedures and planning methods are constantly being evaluated to mitigate risk from unforeseen geological or severe weather events.
12Is process water and PG radioactive?

Phosphate ore contains some naturally occurring radioactive materials called NORM. Process water used in the manufacturing process comes into contact with these materials leaving it with low levels of NORM. The water it comes into contact with and the byproduct PG does, too. During manufacturing, once the phosphate is removed, these materials are more concentrated, but maintain the same low-level of radiation. PG can be further classified as TeNORM, meaning it is technologically enhanced during the manufacturing process.

Everyone is exposed to natural sources of NORM on a daily basis. Our bodies naturally contain it, and virtually everything we come into contact with has some level of NORM. Scientists are more concerned about the degree of exposure, than the fact that it is present. Common sources of NORM include the granite countertops in our kitchens, ceramics, and even foods we eat like bananas. Risk associated with NORM from process water and PG are low, even for those working near or with it daily.

Potential exposure to NORM from PG if it were to be incorporated into road base has been found to be safe by the EPA. In fact, data and analysis has demonstrated maximum lifetime exposure – even for road construction workers – is well below the EPA risk threshold.

13What are some common gypstack myths?
Many unfounded myths are associated with gypstacks and all of them have been dismissed by extensive independent studies, conducted by third-parties. In reality gypstacks do not emit high levels of radiation that would affect human health. PG is delivered to stacks using process water, which then dries and hardens, preventing wind from transporting PG beyond property lines by air. Wetlands and aquifers near gypstacks are monitored using hundreds of wells and regular sampling to confirm the cleanliness of groundwater. Only treated and clean water that meets the strictest government quality standards leaves a facility.
14Why are there different regulations in the US that require phosphogypsum to primarily be stacked compared to the rest of the world?
More than 30-year-old Federal regulations from the 1980’s require PG be stored in gypstacks based on a very conservative risk exposure because less was known about PG at the time. The original ruling was amended to include two other uses for PG – limited agriculture use and research. A petition process for approving additional uses was established. At that time, the volume of stacking, and the environmental and public concerns that come with long-term stacking was not recognized, nor the full range of beneficial uses that would be discovered. Globally, many safe uses for PG have been recognized. In fact, around the world PG is being beneficially used in over 20 countries and has over 55 different researched uses.
15What changed that would now allow PG to be safely used in other applications, when for years we were told it was dangerous and needed to be retained in stacks?
Science once told us that PG must be stacked and stored away from people, but after more than 30 years of research the science now tells us a different story. The EPA and industry’s extensive review of PG use included a thorough assessment of the risk in using PG in road construction under various scenarios including road construction workers handling PG, truck drivers transporting PG, residents living near roads that contain small amounts of PG and utility workers performing work on utilities under or near roads. The assessment looked at the amount of PG that would be used in road construction and calculated the risk for the reasonably maximally exposed individual – confirming it was no more than 0.5 in 10,000 – for comparison, EPA has a risk threshold of less than 3 in 10,000 in determining whether a product is safe for use. Consequently, the risk of using PG in road construction is low and would be at least as protective as keeping it in stacks.
16What makes PG a useful product? What are some of the common uses of PG globally?
PG is a useful product as a road material because it’s durable and multi-purpose. PG is being used in over 20 countries around the world – in fact, multiple countries are using 100 percent of their PG. In Canada, it is used for agriculture afforestation and carbon sequestration while in Spain it is used as soil amendment for crop growth; Finland uses it in roads, forestry and agriculture. Worldwide, over 20 countries have approved PG for beneficial uses.
17When will PG start to be used as a road material in the US?

Under Clean Air Act regulations, the EPA may approve a request for a specific use of PG if it is determined that the proposed use is at least as protective of human health as storage in a gypstack. The phosphate industry has petitioned the EPA for a review of PG use in road construction projects that use appropriate, generally-accepted road construction standards and specifications. That review is underway, and the industry is working with federal regulators to make available all information that such a request must contain.

If approval is obtained, PG will only be used as part of government construction of paved roads. Such construction projects will have specific limitations on how much PG is used, its makeup, qualifiers on setback from edge-of-road and that roads constructed with PG may not be abandoned or used for non-road purposes. Any unused PG would be returned to gypstacks. Public notice will be provided with a planned road will use PG, along with workers involved in construction and provided with appropriate protective equipment. Records must be maintained indefinitely which will be made available by regulators for public review.

As part of their studies on beneficial use of waste products, researchers at the University of Florida are developing road specifications for the Department of Transportation to be implemented in future PG road construction projects in Florida and Louisiana. This research will also be used to support the EPA authorized-use petition process.

18If PG is approved for other uses, does this mean gypstacks in Florida will get smaller or won’t be needed anymore?
28 million new tons of PG is produced per year in the US, with about 5 tons of PG being made per ton of phosphate used. Right now, about 1.7 billion tons of PG is stored in gypstacks in the US. Even if additional PG uses are approved, the supply far exceeds the demand and therefore stacking will still be necessary to support current fertilizer production levels. Long-term, if use of PG becomes commonplace, the need for PG storage in gypstacks will greatly diminish and eventually reduce their size and environmental footprint.
19Are there other PG use opportunities being explored in the US beyond road base?

Other countries are recycling PG into useful products. If they can do it, so can the United States. Productive use of PG guarantees and essential domestic industry’s future, providing employment to thousands of Floridians and delivers essential nutrients that help farmers grow crops and put food on our tables. PG is being used in over 20 countries around the world – in fact, multiple countries are using 100 percent of their PG. Recycling this byproduct into useful products will help the United States maintain its competitive edge and be consistent with more sustainable production practices.

There are many other potential uses for PG, with 55 different beneficial uses discovered - so far. PG also contains about 0.04 to 1.6 percent of rare earth elements (REE); and extraction of these elements from PG stacks could support U.S. efforts to strengthen domestic supply chains for these types of materials. The current primary source is China.

20Why is recycling PG beneficial?
It’s a key part of achieving a sustainable economy in which what once was discounted as a byproduct is revisited. In the case of phosphogypsum, it has been found beneficial on a multitude of fronts, including to the environment, which could make stacking both outdated and unnecessary. As an essential American industry, discovering more innovative uses for PG offers our domestic phosphate industry a way to reduce waste and stay competitive with global producers who often do not face the same strict regulations or costs associated with stacking and storing PG. It is time for the US to view recycling as a matter of course and storage in gypstacks as a last resort by beneficially using PG.

Expand / Collapse All