Stack Free:
What is the Future for Phosphogypsum?

There are at least 80 countries in the world with phosphogypsum (PG) stacks and they are grappling with many of the same questions and concerns that Florida does in dealing with the more than 20 phosphogypsum stacks in this state.

The questions and concerns are coming from a growing sense of environmental responsibility worldwide that is putting pressure on industries in other countries. It is similar to what happened in the 1960s and 1970s in America when a public concern about pollution brought about the formation of the U.S. Environmental Protection Agency (EPA).

These countries are looking to Florida and the Florida Institute of Phosphate Research (FIPR) for advice gained through technical experience with the issues, environmental regulations and research concerning phosphogypsum.

Public and private sectors in the U.S. have struggled for more than two decades with environmental and liability issues related to the by-product created when the phosphate industry converts the phosphate rock it mines to the soluble phosphoric acid that is needed to make fertilizer.

In response to the interest in Florida expertise, FIPR has provided partial funding and is joining with other organizations worldwide in a project to look at phosphogypsum. Researchers in the project – Stack Free by 53? - are gathering data in the U.S. and throughout the world. The intent is to build an understanding of the properties of phosphogypsum in different countries and regions of the world and how the material is stored, disposed of or used in these localities.

A number of groups are interested in joining the project. The International Fertilizer Industry Association (IFA) has indicated support for the survey of the international membership. Other organizations wanting to be involved include: the World Phosphate Institute (IMPHOS), the Arab Fertilizer Association (AFA), Mosaic Company, the Organization for Economic Cooperation and Development (OECD), the International Atomic Energy Agency (IAEA), and Rothamsted Research Center. Project leaders have also had discussions with several companies and organizations from China, Pakistan, Tunisia, Finland, South Africa, Morocco and Bulgaria.

Researchers will evaluate potential large-scale uses of PG, especially in agriculture, on the basis of risk and marketability. The goal is to determine whether PG has environmentally safe and economical applications, or that stacking is the best practice. The project will hopefully help define answers for Florida stacks and help other countries seek environmental answers that fit their communities and needs.

Through the years, most American phosphogypsum has accumulated in large stacks, and when these stacks are no longer active, they are closed according to regulations.

Florida stacks cover up to 400 acres each. They rise as high as 200 feet into the air and store billions of gallons of acidic water in cooling ponds on top and at the foot of the stack. There are more than billion tons of phosphogypsum currently stacked in Florida stacks and another 30 million tons are produced annually.

FIPR research indicates that a beneficial, commercially appropriate and environmental neutral use for PG would be preferable to dumping or perpetual storage in stacks.

Why is it that the U.S. EPA has banned phosphogypsum’s use?

Phosphate rock when mined is naturally slightly radioactive – the level is typically a little higher than the naturally occurring radioactivity in almost all soils worldwide. US regulators in the 1980s took the view that it would be safer to store the phosphogypsum in stacks, rather than continuing to use the substance in construction and agriculture. In 1992 EPA promulgated a Rule that in effect made stacking mandatory.

EPA banned phosphogypsum use based on the following scenario. It assumed that the by-product was used in road building or as an agricultural amendment and 100 years later a house was built on the farm field or the abandoned road. If the homeowner lived in the house 70 years, staying in the house 18 hours a day, the homeowner's risk of radon-related health concerns exceeded the EPA's acceptable limits.

Technical debates about the safety and environmental impact of stacking phosphogypsum have been ongoing since 1992. Recently these debates have moved into the public arena as one company declared bankruptcy and abandoned three phosphogypsum stacks with cooling ponds full of acidic water on top and another has had spills from ponds into the environment, killing aquatic life in surrounding surface water systems.

Finding environmentally safe and economically feasible ways to use phosphogypsum has been a top research area for FIPR since the Florida legislature created it in 1978 to study phosphate issues that impact the state’s citizens, environment and economy and to be a phosphate information resource. Currently FIPR is also aggressively seeking ways to improve the quality and reduce the quantity of acidic water used to transport the phosphogypsum from the processing plant to cooling ponds on top of stacks.

January 2006