Frequent Questions about EPA's Risk Assessment of Spent Foundry Sands in Soil Related Applications
The answers below address frequent questions posed about EPA's Risk Assessment of Spent Foundry Sands in Soil Related Applications. Click on a question from the list to learn more.
On this page:
- What is spent foundry sand?
- Does EPA support beneficial uses of silica-based spent foundry sand?
- What spent foundry sand applications did EPA evaluate in the risk assessment?
- What are manufactured soils and soil-less potting media?
- How much spent foundry sand is generated in the United States and how is it beneficially used?
- How much spent foundry sand is beneficially used in manufactured soils and road construction?
- Why beneficially use spent foundry sands?
- Were any materials that are left over from foundry operations not covered in the risk assessment?
- What is the role of the EPA and States in regulating and/or evaluating various beneficial uses of spent foundry sand?
- Is EPA evaluating other beneficial uses of spent foundry sands?
- Will products with silica based spent foundry sand be sold at my local garden centers and hardware stores?
- If I use manufactured soil containing silica-based spent foundry sand in my vegetable garden, are the vegetables safe to eat?
Foundries purchase virgin sand to create metal casting molds and cores. The sand is reused numerous times within the foundry operation itself. The term “spent foundry sands” applies only to molding and core sands that have been subjected to the metalcasting process. Not included in the term “spent foundry sand” are other foundry wastes, such as unused and broken cores, core room sweepings, cupola slag, scrubber sludge, baghouse dust, and shotblast fines.
Based on the conclusions of the risk assessment and the available environmental and economic benefits, the EPA supports the beneficial use of silica-based spent foundry sands specifically from iron, steel and aluminum foundries, when used in manufactured soils, soil-less potting media, and roadway construction as subbase. Only silica-based spent foundry sands from iron, steel and aluminum foundries are evaluated in this risk assessment. In contrast, spent foundry sands from leaded brass and bronze foundries are often regulated as hazardous waste. Spent foundry sands from non-leaded brass foundries and spent foundry sands containing olivine sand are also not evaluated in this risk assessment.
The Agency addressed three applications: manufactured soils, soil-less potting media, and road subbase, which is a foundation layer underneath a road. The Agency quantitatively evaluated the use of silica-based spent foundry sands in manufactured soil and also applied those findings to soil-less potting media and road subbase.
Manufactured soils are blends of soil, soil components and soil-like material used in horticulture/ landscape applications and site restoration (i.e., large volume applications). Using manufactured soils allows for “tailoring” of soil properties to specific need. Soil-less potting media is a sterile mix of natural ingredients processed according to certain specifications and used to raise plants in controlled conditions, like greenhouses and cuttings beds. To most of us it means a bag of potting soil. Gardening with soil-less potting mix does not include the use of soil. Some of the most common soil-less growing mediums include peat moss, perlite, vermiculite, and sand. Generally, these mediums are mixed together rather than used alone, as each usually provides its own function.
Approximately 10 million tons of spent foundry sands are produced annually; only 26 percent is beneficially used. The markets for spent foundry sands can be divided into three general groups: highway and construction uses, aggregate substitutes, and manufactured soils. The table below shows the current overall beneficial uses of spent foundry sand in the United States. In this table, the term “road construction” is synonymous with road base.
|BENEFICIAL USE APPLICATION
|QUANTITY BENEFICIALLY USED (TONS)
|Top soil mix/horticulture
|Reuse at another foundryb
Based on the August 2007 AFS survey with 244 total respondents, or a 24 percent completion rate. Survey respondents had the option of selecting more than one beneficial use application. Beneficial use quantities have been extrapolated to reflect beneficial use in the entire metal casting industry.
a. Construction fill includes both structural fill and flowable fill.
b. Spent foundry sand is transferred from one foundry to another for use in on-site construction projects or other application.
c. AFS excludes landfill daily cover as a beneficial use application from the total beneficial use quantity (2,645,427 tons).
The EPA’s most recent study (from 2008) estimates that over 220,000 tons of spent foundry sands are used in manufactured soil and 144,288 tons are used in road construction. The expectation, based on the findings of the risk assessment, is that the beneficial uses of spent foundry sands studied in the risk assessment should increase.
|BENEFICIAL USE APPLICATION
|QUANTITY BENEFICIALLY USED (TONS)
|Top soil mix/horticulture
The beneficial use of spent foundry sand, when conducted in an environmentally sound manner, can have positive environmental and economic benefits, particularly in the area of reducing impacts associated with food production and in the construction of roads and other infrastructure. Environmental benefits include energy savings, reduction in greenhouse gas emissions, and water savings. Economic benefits include job creations in the beneficial use industry, reduced costs associated with spent foundry sand disposal, increased revenue from the sale of spent foundry sand, and savings from using spent foundry sands in place of more costly materials.
A 2008 EPA analysis provides estimates of the environmental benefits that can be achieved with the beneficial applications that were studied in this risk assessment. Environmental benefits from using spent foundry sand in soil-related applications and road base include:
- The energy savings equivalent to the annual electricity consumption of 800 homes;
- Water savings equivalent to the amount of water to fill 12 Olympic swimming pools; and
- Carbon dioxide emissions reductions equivalent to removing 840 cars from the road from one year.
|Environmental Benefits of Spent Foundry Sands Beneficial Use
|Road Base Use
|Manufactured Soil Use
|Total avoided impacts
|Annual electricity consumption of 800 homes
|7.8 million gallons
|Amount of water to fill 12 Olympic swimming pools
|4,000 metric tons
|Removing 840 cars from the road for one year
8. Were any Materials that are left over from foundry operations not covered in the risk assessment?
In addition to spent foundry sands, foundries can generate numerous other wastes (e.g., unused and broken cores, core room sweepings, cupola slag, scrubber sludge, baghouse dust, shotblast fines). This assessment, however, applies only to molding and core sands that have been subjected to the metalcasting process and can no longer be used to manufacture molds and cores. To the extent that other foundry wastes are mixed with spent foundry sands, the conclusions drawn by this assessment may not be applicable.
9. What is the role of EPA and states in regulating and/or evaluating various beneficial uses of spent foundry sand?
The Resource Conservation and Recovery Act (RCRA) encourages environmentally sound materials management practices that maximize the use of recoverable materials and fosters resource recovery. The EPA strives to motivate behavioral change to improve materials management through both regulatory and non-regulatory approaches. The EPA’s primary role in non-hazardous solid waste management, including evaluating beneficial uses, is providing national leadership and technical assistance. Under RCRA, non-hazardous solid wastes, including non-hazardous industrial materials, are predominately regulated by state and local governments. Many states have beneficial use programs, and should be consulted to determine whether beneficial uses of spent foundry sands are allowed within a specific state.
EPA is not planning to evaluate other uses of spent foundry sands or other beneficial uses of industrial materials. We are, however, currently developing a broad-based framework and several tools that others can use to evaluate beneficial uses of industrial materials.
Manufactured soils (potting mixes) are sold at garden centers and hardware stores, so it is possible that potting soils and similar products would contain silica-based spent foundry sands.
12. If I use manufactured soil containing silica-based spent foundry sand in my vegetable garden, are the vegetables safe to eat?
Yes. EPA and USDA are encouraging the beneficial use of silica-based spent foundry sand in manufactured soils and other soil-related applications because the soil is safe when used for its intended purpose. This risk assessment demonstrates that the constituent concentrations found in silica-based spent foundry sands are below agency health and environmental benchmarks, including the metal concentrations.