Beneficial Uses of Phosphogypsum?
There is growing consensus in the global phosphate industry that it is at a turning point: it is not yet clear where it might best turn. Phosphogypsum (PG) is pivotal to that decision, world-wide.
Phosphogypsum per se is not a new problem. For every ton of phosphoric acid produced by the wet process method, some four to five tons of phosphogypsum are also manufactured. The most obvious problem consists in what to do with it. Currently, for a mixture of reasons that vary quite widely from country to country manufacturing plant to manufacturing plant, and PG type to PG type, a high proportion of the phosphogypsum is either dumped or stacked. The decision to dump is partly affected by the relative leniency of environmental laws in producing countries where PG is seen as essentially safe, but of no value; the decision to stack is partly affected, notably in the United States, by regulations which describe PG as radioactive and hence subject to use only under permit. Stacks are a particular issue in Florida, which has some 20; but there are many other stacks in the US, and many other countries, world-wide which also have stacks. While the stacking regimen is held by many experts to be unnecessary, and prohibitive of potentially beneficial uses, notably in agriculture, it has the force of being the current norm. Both disposal methods are increasingly seen as problems rather than solutions, since the one leaves an unacceptable legacy on the land and immediate environs of the stack, the other has unknown consequences for the wider ecosphere.
The visible impact of PG as a consequence of phosphoric acid production is shadowed by an issue of increasing concern to commercial producers, that of the risk of exposure to radiation whether to workers in the production process itself, or to others in the product "value chain" as a consequence of the product's use.
In both cases, the relative radiation risk to people or the environment from the production of phosphoric acid or from the management of PG falls below, mostly significantly below, the level of radiation to which we are exposed through naturally occurring radioactive materials (NORM). But when the precautionary principle is interpreted against a background of absolute risk measurement, then even the most marginal increase in risk may be held to be too much. This leads to the so-called "zero tolerance" approach, one that was especially popular with policy makers in the 1990s. It may be the case however, that, however well intentioned, the policy framework that led to the promulgation of rules for creating PG stacks has now run its course and that in the interests of a more adaptive, and ultimately environmentally more sustainable management regime, that a fresh look needs to be taken to the problem as a whole, and also from a global perspective.
The point of departure for the project outlined in this document is that a beneficial, commercially appropriate, use for PG, based on objective data, sensitivity to stakeholder requirements and best available practices, must surely be a more appropriate outcome than dumping into water courses or the oceans, or perpetual storage in "stacks". The project goal is to provide specific guidance as to what beneficial uses of PG may be contemplated going forward, and under what conditions, especially with regard to human and environmental health, but also with regard to commercial viability and the requirements of lifelong product stewardship. Given that the availability of phosphate fertilizers significantly determines the world's food production capacity, if this issue is not tackled successfully the penalty to be paid will levied well beyond the industry itself.