Land Application of Biosolids

Related Information

Use and Disposal Management Practices

Land application is the spraying, spreading, incorporation, or injection of sewage sludge into or onto the land to either condition the soil or fertilize crops or vegetation grown in the soil. 

The terms “biosolids” and “sewage sludge” are often used interchangeably by the public; however, the EPA typically uses the term “biosolids” to mean sewage sludge that has been treated to meet the requirements in the EPA’s regulation entitled, “Standards for the Use or Disposal of Sewage Sludge,” promulgated at 40 C.F.R. Part 503, and intended to be applied to land as a soil conditioner or fertilizer. 

Biosolids can be used on agricultural land, forests, rangelands, disturbed land in need of reclamation, or nonagricultural lands like parks, golf courses, and home lawns and gardens. Land application of sewage sludge can have environmental benefits including improved soil health, carbon sequestration, and reduced demand on non-renewable resources like phosphorus. Land application also generates reduced emissions of greenhouse gases compared to other management practices. 

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Types of Biosolids Land Application

Agriculture

Agricultural land application is the most common type of land application. Biosolids are often applied to grasses or grain for animal feed, wheat, soy and turfgrass, among other agricultural products.

Reclamation Sites

Biosolids have been used successfully to establish sustainable vegetation, reduce the bioavailability of toxic substances often found in soils, control soil erosion, and regenerate soil layers at sites that have damaged soils. Soil regeneration is very important for reclaiming sites with little or no topsoil. Examples of reclamation sites include overgrazed pasture and mines. 

Forestry

Biosolids have been found to promote rapid timber growth, allowing quicker and more efficient harvest of an important natural resource.

Lawns and Home Gardens

Biosolids that meet the most stringent pollutant, pathogen and vector attraction reduction requirements may be purchased by the public from hardware stores, home and garden centers or their local wastewater treatment plant. 

Classes of Biosolids

Existing requirements and guidance help ensure that biosolids are processed, handled, and land-applied in a manner that minimizes potential risk to human health.  Biosolids are divided into “Class A” and “Class B” designations based on pathogen treatment methods. The different classes also have specified requirements for vector attraction reduction, as well as general requirements and management practices. The third class, Class A EQ, has regulatory requirements for both pathogen treatment and chemical pollutant limits.

Individual states, Tribes, or localities may have more stringent requirements and additional criteria. For more information about classes of biosolids and land application in your area, please contact your regional EPA office and state department of environment.

Class B Biosolids

Class B treatment processes significantly reduce, but do not eliminate, pathogens in sewage sludge. Generally, pathogens may exist when requirements are met under Part 503 for Class B biosolids, which is why there are additional requirements when Class B biosolids are land applied including they may not be applied to lands with high potential for human exposure, limiting site access for humans and grazing animals, and harvesting restrictions, which allow time for further pathogen degradation.

Class A Biosolids

The Part 503 requirements for Class A are designed to further reduce the risk from pathogens present in treated sewage sludge. Thus, there are fewer additional requirements for land application of Class A biosolids and therefore Class A biosolids are often land applied to sites like parks and golf courses. 

Class A-EQ Biosolids

Though not explicitly named in Part 503, Class A “Exceptional Quality” or “EQ” sludge is treated sewage sludge that meets the most stringent pollutant, pathogen, and vector attraction reduction limits in Part 503. Class A EQ biosolids are those that meet the “ceiling concentrations in Table 1 of § 503.13 and the pollutant concentrations in Table 3 of § 503.13; the Class A pathogen requirements in § 503.32(a); and one of the vector attraction reduction requirements in § 503.33(b)(1) through (b)(8).” Once biosolids are treated to be Class A EQ there are no additional requirements for land application. Thus, Class A EQ biosolids are often sold directly to the public for use in home gardens and on lawns in stores or directly from the wastewater treatment plant. 

Potential Odors

Biosolids may emit a distinctive odor depending on the treatment process and methods used. The odorous compounds generated and detected most often are ammonia, amines, and reduced sulfur-containing compounds. Meteorological conditions such as wind speed and direction, relative humidity, and temperature can impact nuisance odors. The presence of biosolids odors does not mean that the biosolids pose harm to human health and the environment.

EPA Documents about Land Application of Biosolids

Biosolids

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Last updated on January 6, 2025