United States

Environmental Protection 

Agency

March 2008

EPA530-F-08-009 

www.epa.gov/osw Agricultural Uses for Flue Gas 

Desulfurization (FGD) Gypsum 

What Is Gypsum?

Gypsum is calcium sulfate dihydrate, or CaSO4•2H2O, which can come from a 

number of sources. Mined gypsum is a common mineral found around the world 

in sedimentary rock formations, from which it is mined or quarried. FGD gypsum 

is a synthetic material of identical chemical structure produced as a byproduct from 

coal-fired electric utilities. Other sources of gypsum include phosphogypsum, 

citrogypsum and fluorogypsum, which are byproducts of different chemical 

manufacturing processes1.

Gypsum has many beneficial uses, including agricultural applications, wallboard 

products for residential and commercial buildings, as an ingredient in portland cement 

manufacturing, and as a filler ingredient in some foods and toothpaste. Because of its 

relatively high degree of purity, FGD gypsum can be used as a substitute for mined 

gypsum in many uses, while also realizing important environmental benefits that 

result from recycling this byproduct material.

Gypsum in Agriculture

Both mined and FGD gypsum can be used as a soil amendment in a range of soil 

and hydrogeologic conditions. Gypsum can be used as a nutrient source for crops; as 

a conditioner to improve soil physical properties, and water infiltration and storage; to 

remediate sodic (high sodium) soils; and to reduce nutrient and sediment movement 

to surface waters, among other uses. The United States Environmental Protection 

Agency (USEPA) and the United States Department of Agriculture (USDA) support 

the use of FGD gypsum in appropriate soil and hydrogeologic conditions as an 

effective method of soil conservation and industrial material recycling. However, 

before applying any fertilizer or other soil amendment, including FGD gypsum, it 

is important to first assess the amendment material and soil conditions to determine 

compatibility and appropriate application rates.

1 This brochure does not address these sources of gypsum.
FGD Gypsum

FGD gypsum is created by forced oxidation scrubbers attached to coal-fired 

power plants to limit emissions of the sulfur which is released when coal is burned. 

The scrubbers spray liquid lime or limestone slurry into the flue gas path, where it 

reacts with sulfur in the gas to form calcium sulfite, an intermediate product with 

little practical value. However, when the chemical reaction is pushed further by 

the introduction of air into the FGD absorber tank, the calcium sulfite reacts to 

become gypsum. The material is then dewatered and processed; the end product is a 

consistent, finely divided powder. This process is known as flue gas desulfurization 

(FGD), and the gypsum produced is known as FGD gypsum. 

The term FGD gypsum is the name most often used by generators of the material. 

Other names include recaptured gypsum, byproduct gypsum, and synthetic gypsum. 

All of these terms refer to the same material produced by the forced oxidation 

process. The gypsum in both FGD gypsum and mined gypsum has the same basic 

chemical makeup— CaSO4•2H2O; however, the amount and types of trace materials 

and unreacted sorbents found in the gypsum can vary among power plants and among 

mines2. If you are considering using FGD gypsum products as a soil amendment, it is 

appropriate that the chemical analysis of the material be provided by all commercial 

sources to support decision-making in their use, as States may have regulations and 

standards that need to be followed. To this end, it is advisable to contact your State’s 

department of agriculture or State extension service before FGD gypsum is used as a 

soil amendment. 

The Future of FGD Gypsum

According to the American Coal Ash Association’s annual Coal Combustion 

Product Production and Use Survey, total production of FGD gypsum in 2006 

was approximately 12 million tons. Close to 9 million tons of FGD gypsum was 

put to beneficial use, while the remainder was landfilled. Of the amount used, 

approximately 80 percent was used in wallboard products, and about 2 percent 

(168,190 tons) was used in agriculture, with most of the rest being used in concrete 

and cement applications. In the future, FGD gypsum may find more use as filler 

in plastics and fiberglass, as well as in reducing mine subsidence, re-contouring 

landforms, and improving soil conditions at mining sites.

2 Information about constituent concentrations in mined and FGD gypsum may 

be found at http://www.epa.gov/epawaste/partnerships/c2p2/ccps/fgd.htm.
Current Uses of Gypsum in Agriculture 

Nutrient Source

Gypsum is rich in calcium and sulfur, two nutrients essential to all crops. The 

most common application of gypsum is to crops that have high calcium requirements, 

or to areas that have calcium-poor soils. Peanuts have particularly high calcium 

requirements, and gypsum often is added to peanut fields to increase yield and quality 

of the crop. Many fruits, vegetables, and cereals also can benefit from increased 

calcium availability; in particular, fruits such as tomatoes and cantaloupes need 

calcium for skin strength, and growers may add calcium to produce fewer blemishes 

and a longer shelf life. 

Sulfur fertilization also is required for many crops, and gypsum can be an 

effective sulfur source. There is a growing need for sulfur addition to soils, since 

atmospheric deposition of sulfur has decreased, and most nitrogen and phosphorus 

fertilizers no longer contain significant amounts of sulfur. Sulfur is sometimes a 

constituent of nitrogen and phosphorus fertilizers, but gypsum also can be an effective 

sulfur source for some crops. In addition to calcium and sulfur, gypsum, depending 

on its source, may provide essential micronutrients to plants. 

Soil Improvement

Gypsum is helpful in treating sodic soils and soils suffering from crusting and 

other structural problems. Gypsum is more readily soluble in water than other 

calcium-rich soil amendments such as limestone, and therefore moves throughout 

the soil column more easily. Calcium ions from gypsum displace excess sodium 

Over the next ten years, annual production of FGD gypsum may double as more 

coal-fired power plants come online, and as scrubbers are added to existing power 

plants to comply with the EPA’s Clean Air Interstate Rule and other requirements. It 

is anticipated that the majority of the new scrubbers will produce FGD gypsum, 

although in some parts of the country power plants may select dry scrubbers, 

resulting in materials 

other than FGD gypsum. 

This increased supply is 

an opportunity to explore 

the expanded use of FGD 

gypsum as a soil 

amendment. Ongoing 

and future research and 

demonstration projects 

will be able to assist 

people in making 

decisions about the use of 

FGD gypsum.

Agricultural Applications of Gypsum

There are three general uses of gypsum in agricultural 

applications:

• A source of nutrients for plants

• Improvement of soil physical and chemical 

properties

• Reduction in the transport of nutrients, sediment, 

pesticides and other contaminants to surface waters 

Agricultural Applications of Gypsum

There are three general uses of gypsum in agricultural 

applications:

• A source of nutrients for plants

• Improvement of soil physical and chemical 

properties

• Reduction in the transport of nutrients, sediment, 

pesticides and other contaminants to surface waters 
and other ions, which then become mobile and diffuse. The calcium ions reduce 

dispersion of soil particles by promoting the aggregation of clay particles. This 

improves soil structure and stability and prevents soil crusting. Reduced crusting 

and better particle aggregation allow for greater water infiltration and storage in soil, 

thereby reducing runoff and erosion. These soil structural improvements also ease 

the emergence of seedlings and allow roots to penetrate further into the soil to take 

advantage of the additional stored moisture.

Mitigation of Contaminant Transport to Surface Water

In addition to water quality benefits associated with reduced runoff and erosion, 

FGD gypsum application can reduce the solubility of nutrients such as phosphorus in 

livestock and poultry manure and soils treated with manure. Gypsum converts readily 

soluble phosphorus to less-soluble forms, which can reduce the runoff of phosphorus 

into adjacent streams, lakes, or ground water. Excess phosphorus in runoff leads to 

water quality problems, including algal blooms and eutrophication of water bodies. 

 

Gypsum Decisions in Agriculture

Recycling coal combustion products (CCPs) and other industrial materials 

can result in significant environmental benefits, including reduced greenhouse gas 

emissions, less use of virgin materials, and decreased use of landfills. The USEPA’s 

Coal Combustion Products Partnership (C2P2) (http://www.epa.gov/c2p2)

aims to increase recycling of CCPs, including FGD gypsum. In addition to its

environmental benefits, FGD gypsum may be less expensive for users than mined

gypsum, although transportation costs can be a factor in evaluating the 

practicality of using FGD gypsum as a gypsum source. 

As with any fertilizer or chemical additive, there are a range of considerations 

that should be kept in mind when deciding whether to apply gypsum. Gypsum is 

not suitable for all soil types, soil conditions or crops. Appropriate application rates 

should be determined to accomplish specific soil improvement goals, while not 

exceeding state limits on the use of individual constituents. In general, application 

rates of up to two tons per acre should be sufficient to accomplish most agronomic 

and horticultural objectives3. 

In situations where there is excess sulfur in the soil, the amount of gypsum to be 

added should be balanced against copper nutrition in animals, as high levels of sulfur 

in feed can interfere with copper absorption. Boron concentrations in FGD gypsum 

typically are higher than in natural gypsum sources; therefore, crops sensitive to 

boron uptake such as cherry, peach and kidney bean may require lower application 

rates. The high calcium and sulfur content of gypsum can cause an imbalance in 

other soil nutrients, such as magnesium; therefore, soil nutrient characteristics, 

and potential plant and animal uptake, of these and other constituents should be 

understood and considered before deciding whether to use any gypsum product. 

3 Donstova et al. and other sources
In determining the environmental suitability of FGD gypsum for a particular location, 

you may find the USEPA’s Industrial Waste Management Evaluation Model 

(IWEM) and the chapter on land application (Chapter 7) in the associated Guide 

for Industrial Waste Management (http://www.epa.gov/epawaste/nonhaz/industrial/

guide/index.htm) to be useful resources. You should also consult with your State’s 

department of environmental protection to comply with any regulations pertaining 

to the management of CCPs. You may also find it helpful to consult with your 

State’s department of agriculture and agricultural extension service, and with the 

USDA Natural Resources Conservation Service.

FGD Gypsum Beneficial Use Considerations

Decision Things to Consider Resources

1. Is gypsum a good 

choice for my needs?

• Types of crops

• Nutrient requirements 

of crops

• Soil structure

• Soil chemical profile

• State department 

of agriculture/ag. 

extension agency

• USDA Natural 

Resources Conservation 

Service

2. If gypsum is a good 

choice, should I use 

FGD gypsum?

• Trace element 

sensitivity of crops

• Purity of available FGD 

gypsum

• Cost differential

• State department 

of agriculture/ag. 

extension agency

• Fertilizer supplier

3. Is the use of 

FGD gypsum 

environmentally 

protective?

• Ground water

• Direct exposure

• Ecosystem impacts

• Surface waters

• State departments 

of environmental 

protection

• EPA’s Guide for 

Industrial Waste 

Management

References and Websites

The references and Websites below provide additional information and studies 

about the uses of gypsum in agriculture.

Clark, R.B., K.D. Ritchey, and V.C. Baligar (1999) “Benefits and Constraints for 

use of FGD Products on Agricultural Land.” Fuel, 80:821-828. 

Donstsova, K., Y.B. Lee, B.K. Slater, J. M. Bigham (no date) Gypsum for 

Agricultural Use in Ohio – Sources and Quality of Available Products. Ohio State 

University Extension Fact Sheet. School of Natural Resources, The Ohio State 

University, Columbus, OH. Available online at: http://ohioline.osu.edu/anr-fact/0020.

html.

EPA (2003) Guide for Industrial Waste Management. U.S. Environmental 

Protection Agency. EPA530-R-03-001. February.

Korcak, R.F. Utilization of Coal Combustion By-Products in Agriculture and 

Horticulture. U.S. Department of Agriculture, Agricultural Research Service. 

Beltsville, Maryland.
OSU (2006) Gypsum for Agricultural Use in Ohio--Sources and Quality of 

Available Products. Ohio State University Extension Fact Sheet, ANR-20-05. 

Available online at: http://ohioline.osu.edu/anr-fact/0020.html. Accessed August, 

2007.

Smith, I. (2006) Management of FGD Residues. IEA Clean Coal Centre. 

London, United Kingdom. August.

Stout, W.L., J.L. Hern, R.F. Korcak, and C.W. Carlson (1988) Manual for 

Applying Fluidized Bed Combustion Residue to Agricultural Lands. RS-74. U.S. 

Department of Agriculture, Agricultural Research Service, Washington, DC.

USGS (2005) Major- and Trace-Element Concentrations in Soils from Two 

Continental-Scale Transects of the United States and Canada. Open-File Report 

2005-1253, U.S. Geological Survey. Available online at: http://pubs.usgs.gov/

of/2005/1253/. Accessed September 13, 2007.

For More Information

--USDA Natural Resources Conservation Service:

http://www.nrcs.usda.gov/partners/for_farmers.html

--USEPA C2P2 Website: http://www.epa.gov/c2p2

--USEPA Industrial Waste Management Website: 

http://www.epa.gov/epawaste/nonhaz/industrial/guide/index.htm

--FGD Products Website: http://www.fgdproducts.org/

--Information sheets on agricultural gypsum use from a leading distributor: 

http://www.gypsumsales.com/gyp_whitepapers.html

--A paper on agricultural gypsum use from a distributor: 

http://www.dktgypsum.com/news_content7.html

--Information sheet on FGD gypsum from the American Coal Ash 

Association: http://www.acaa-usa.org/PDF/EnvFocusFinal3g2.pdf

Acknowledgements

EPA gratefully acknowledges the following organizations for their contributions 

to its preparation:

-- United States Department of Agriculture

-- Agricultural Research Service

-- United States Department of Energy--National Energy Technology Laboratory

-- USEPA Office of Air and Radiation

-- USEPA Office of Research and Development

-- American Coal Ash Association

-- Electric Power Research Institute