Researchers Believe Power Plant Waste Is Key For Nutrient Removal

A waste product from coal-fired power plants may be useful in fighting water pollution.

Researchers are probing how gypsum, a power-plant byproduct, can be used to treat fertilizer runoff on farms, which threatens waterways with phosphorus pollution.

“It’s an old concept. U.S. farmers have been treating fields with gypsum since George Washington was president. In part, that’s because sulfate in the gypsum binds with magnesium in the soil, helping the soil hold water. But pollution specialists are more interested in the calcium in the gypsum; it binds with phosphate in soil, forming a larger particle that resists being washed away,” Science reported.

“Researchers saw a possible comeback for gypsum as nutrient pollution problems grew and coal-fired power plants proliferated,” the report said.

Francisco Arriaga, a soil scientist at the University of Wisconsin (UW) in Madison, is exploring the pollution-fighting potential of gypsum. He has set up three study sites at farms and is working in cooperation with an energy company that runs a coal-fired power plant.

A farm run by Dan Johnson is one of the sites. Johnson began applying gypsum to his soil two years ago.

“Preliminary results — which Arriaga will present at a Soil Science Society of America conference [in November] — suggest gypsum is helping keep phosphorus in Johnson’s soils. And previous field experiments, including projects in Georgia and Ohio, have found that the mineral can also can reduce levels of toxic aluminum and pathogens in soils, as well as provide a source of calcium and sulfur, two nutrients plants need to grow. (Now that power plants emit less sulfur, which used to fall back to land in the form of acid precipitation and dust, some soils are deficient in that nutrient),” the report said.

The appeal of using power-plant gypsum on farms is that it is cheaper than mined gypsum, in part because the location of a power plant may be closer than the location of the gypsum mine. The report noted that power plant gypsum often ends up in landfills.

“A ton of mined gypsum can cost as much as $140, whereas a ton of FGD gypsum costs $38,” the report said.

Preliminary results of a previous study by a scientist in Ohio State University’s College of Food, Agricultural, and Environmental Sciences found that fields treated with gypsum appear to have 55 percent less soluble phosphorus runoff in the trials up to this point, according to Ohio Ag Net. The researchers took water samples from field drainage tiles.

Where is mined gypsum found? The Gypsum Association explains: "Natural gypsum occurs in sedimentary rock formations and is found in over 85 countries. The United States, Canada and Mexico have some of the largest reserves of high-quality gypsum. Gypsum is mined in 17 states. Iowa, Texas, Utah, and New Mexico are particularly important producers."

To read more about nutrient removal visit Water Online’s Nutrient Removal Solutions Center.