Utilization of FGD Gypsum in Agriculture for Environmental Benefits.

This paper will discuss the utilization of FGD gypsum in agriculture for environmental benefits. Gypsum (CaSO₄ .2H₂O) has been used as an agricultural soil amendment for over 250 years. It is a soluble source of calcium and sulfur for crops and has been shown to improve soil physical and chemical properties. Flue gas desulfurization (FGD) gypsum is a manufactured gypsum by-product of the coal-fired combustion process. FGD gypsum is formed by scrubbers that remove sulfur dioxide (SO₂) from the flue gas stream when coal is burned to generate electricity so it does not become an atmospheric pollutant. As a result, the availability of gypsum as an agriculture amendment has greatly increased over the last few years. Currently, FGD gypsum is undergoing “Risk Evaluation” to determine any potential environmental concern with its utilization, but several studies have shown that gypsum can be used to reduce environmental degradation from agriculture. The environmental benefits to be discussed include reduced erosion losses and reduced soluble P and As in runoff from agricultural fields, especially fields which receive poultry litter. For example, a rainfall simulation study on a Coastal Plains soil has shown a 51% reduction in total dissolved P load. New techniques to reduce P contamination utilizing gypsum will also be discussed. This includes a gypsum “in-ditch filter” system, which demonstrated a 22% reduction in total dissolved P and preliminary data for a “gypsum curtain filter” system.