June 3, 2010
Sand has been used for thousands of years as a metalcasting medium, with other natural materials added to allow the sand grains to adhere to each other. The sands and clays that make up more than 95 percent of most metalcasting facility sands are naturally occurring materials mined from the earth. Until the advent of the Resource Conservation and Recovery Act (RCRA) in the early 1970’s, facilities simply discarded their used sands on their own properties, sent them to local landfills, or gave them away to be used as fill materials on other properties. There are many properties in older industrial areas built on top of foundry sand, which is generally an excellent fill material providing strong structural support. This practice came to a halt with the advent of RCRA.
Under RCRA, metalcasting facility sands are regulated as solid wastes, requiring disposal in lined landfills. All natural aggregates, soils and clays contain metallic elements from the earth’s crust. The sand and clay portions of metalcasting facility sands therefore contain similar levels of naturally occurring metals. Additional metals or organics may be introduced at low levels through the metalcasting process. Many research studies have shown that the vast majority of metalcasting facility sands are non-hazardous, the exception being sands from brass or bronze facilities using leaded alloys.
More than 90 percent of metalcasting volume is comprised of ferrous (iron and steel) and aluminum castings, so most research studies have focused on sands from these processes. Over the past two decades, the industry has cooperated with researchers at major research universities such as the Ohio State University, the Pennsylvania State University, Purdue University, Michigan Technological University and the University of Wisconsin. Research consistently shows that these sands, when uncontaminated with common garbage, solvents or non-sand materials, are safe for use as aggregate substitutes outside the metalcasting facility. Copies of the resulting reports can be found in the AFS Library. Primary sources are listed under Environmental References in the Tools & Resources section.
Research from leading universities was pivotal in encouraging many state regulatory agencies to establish beneficial use rules for metalcasting sands. But in most instances, the research was confined to facilities in a particular state and other state regulators were often reluctant to accept the results or adopt rules from other states.
Penn State Characterization Study (2004)
In 1998, AFS and state metalcasting associations established a task force to focus on multi-state issues relating to the reuse and recycling of discarded metalcasting sands. The task force evolved into FIRST, which received 501 (c) 3 non-profit status in 2001, and which was reorganized as AFS-FIRST in 2009. AFS and FIRST recognized that multi-state third party research efforts were needed to provide additional information to Federal and state regulators, many of whom had little experience with metalcasting sands. Some regulators erroneously believed that the majority of metalcasting sands were hazardous materials, in contradiction to both industry data and academic research studies. At that time, there was little data in the public domain addressing the question of whether these sands might vary significantly from facility to facility, or vary over time from the same facility. Lack of knowledge and transparent data were believed to be significant impediments in establishing a comfort level with the use of metalcasting sands as construction materials in many states.
With support from the AFS Research Board, the Pennsylvania State University (PSU) developed a proposal for funding from the U.S. Department of Energy’s Metalcasting Industries of the Future program. The Pennsylvania Transportation Institute, based at PSU, has performed many research projects for the Pennsylvania Department of Transportation assessing the suitability of recycled materials for highway construction projects. Other researchers at PSU had experience researching various aspects of foundry sand characterization and performance.
DOE research funding supported a multi-phase research project conducted by the Pennsylvania State University and the University of Wisconsin. As part of the study, nearly 400 foundry sand data sets were analyzed for potential environmental impacts. The multi-year research project had three primary objectives:
- a statistically sound evaluation of the characterization of foundry sand;
- a laboratory investigation to qualify foundry sand as a major component in controlled low-strength material (CLSM);
- the identification of the best methods for using metalcasting sand as a replacement for natural aggregates for construction purposes, specifically in asphalt paving materials.
The exhaustive research performed through this project is detailed in a 486-page report submitted to the Department of Energy in October of 2004. The report, titled “Excess Foundry Sand Characterization and Experimental Investigation in Controlled Low-Strength Material and Hot-Mixing Asphalt,” can be downloaded from the AFS Library.
For the sand characterization part of the research, PSU collected multiple datasets from third-party laboratory analyses of foundry sands. The datasets were randomly selected by PSU to span a wide range of foundry processes and metal types, without regard for whether or not the sands might be deemed suitable for beneficial reuse. These datasets were loaded into a database, which was then subjected to a detailed statistical analysis. It is important to note that the PSU analysis included datasets from copper-based sands, which may contain certain elements exceeding regulatory limits, but which are less than 3 percent of total tonnage of castings produced.
From a construction industry perspective, foundry sands would need to perform comparably to conventional construction materials, with no significant environmental impacts. Conventional construction materials include excavated soils and aggregates, as well as concrete, cement and asphalt. Chapters 3, 4 and 5 of the report detail the data characterization analysis, including a comparison to background soil levels. The researchers concluded:
The comparison between background concentration of soil and average bulk analysis of foundry sand suggests the degree of environmental impact waste streams may pose. The comparison is summarized in Table 5-12, supported by data in Tables 5-13 through 5-16. While excess metalcasting sands contain higher levels of metallic elements (aluminum, copper, and iron), the concentrations of most regulated metallic elements are less than or in the same level as those of soil. This illustrates that excess foundry sands do not pose greater threats to the environment than soil.” (Chapter 5.6, page 123).
The Penn State study confirmed the industry’s long-term experience that ferrous and aluminum foundry sands can be safely used as construction materials. States such as Wisconsin, Ohio, Indiana and Pennsylvania had already developed beneficial use regulations allowing for such use.
U.S. EPA Foundry Sand Assessments
For some years, AFS has had a good working relationship with US EPA through the agency’s Sector Strategies program (since disbanded). The agency and the industry had worked on many technical assistance projects together. After FIRST was formed, industry representatives held meetings with US EPA to discuss ways to increase the reuse and recycling of metalcasting sands. The industry expressed concern that some state regulators continued to believe that these sands could have detrimental environmental impacts and were therefore reluctant to approve their use in unbound applications. As non-hazardous “wastes,” most metalcasting sands are regulated by individual state environmental agencies, with the result that regulations vary greatly from state to state.
This situation dramatically constrained the market development potential for metalcasting sands, because the “real world” experience in states with progressive regulations showed that the higher volume uses for foundry sands are in construction projects such as road bases, structural fills and embankments. In those applications, the structural integrity in the foundry sands provides an engineering advantage over conventional construction materials. In contrast, bound applications such as cement and concrete often have technical limitations to how much foundry sand can be used as substitutions for conventional aggregates.
Industry representatives supplied prior research reports as well as proprietary industry data to EPA staff, and Penn State supplied the data generated through its research project. The industry asked US EPA to assess this information, focusing on ferrous and aluminum facility sands. Many state regulators also asked the agency to make a clear and unambiguous statement about the reuse and recycling of metalcasting sands. AFS-FIRST representatives emphasized that other nonferrous sand types may also meet state environmental regulations, but felt it was important to develop a comfort level first with the overwhelming volume of metalcasting sands.
Following a three-year internal evaluation, US EPA released its first Foundry Sand Statement in April 2007. At that time, the agency was intently following the USDA Foundry Sand Initiative, and knew that research project would provide more data on the environmental profile of foundry sands in soils-based applications. US EPA has indicated that it will revise the Foundry Sand Statement in accordance with the findings of the USDA research and subsequent risk assessment, which is expected to be finalized in 2010.
As part of its overall industrial materials program, US EPA’s risk assessors and economists also undertook a review of the costs and benefits of recycling foundry sand, using methodologies normalized for a number of materials. The purpose of these reports is to provide an initial assessment of the market dynamics that affect the generation, disposal, recovery, and beneficial use of these materials; and to provide a preliminary life cycle analysis of the beneficial impact of these materials. The resulting report was completed in February 2008 “Waste and Materials-Flow Benchmark Sector Report: Beneficial Use of Secondary Materials–Foundry Sand.”
The benchmarking report uses several modeling techniques to extrapolate the environmental benefits of reusing metalcasting sands in multiple scenarios, most of them common construction uses and manufactured soils. Page 33 of the report states, “. . . current beneficial use of metalcasting sand results in positive environmental impacts for all beneficial use applications that can be measured. The most significant impacts include energy savings and water use reductions associated with avoided extraction of virgin sands.” The report goes on to calculate the potential for savings in energy and greenhouse gas (GHS) emissions attributable to the industry’s 50% recycling goal in 2015.
Other U.S. EPA efforts to increase the use of foundry sand are described under Tools & Resources/U.S. Resources/U.S. EPA Foundry Sand Initiatives. Prominent among them is the development and execution of a Foundry Sand Multi-Stakeholder Action Plan (MAP). The Foundry Sand MAP is a collaborative effort involving Federal, state and private sector stakeholders. Following a series of stakeholder meetings in 2008, a number of Challenges were identified and various Priority Actions described. A core planning group, facilitated by staff in US EPA’s Region 5 office, meets on a quarterly basis to monitor the Priority Action Items. As part of the Foundry Sand Multi-Stakeholder Action Plan, a number of fact sheets are being developed, one of which is Environmental Evaluation of Foundry Sand.
U.S. EPA and the U.S. Department of Agriculture conducted a multi-pathway risk assessment for foundry sands, building on research conducted by USDA-ARS in its Foundry Sand Initiative. The document is undergoing peer review. U.S. EPA officials have spoken about the risk assessment in several public venues. EPA officials have stated that they believe that properly managed iron, steel and aluminum metalcasting facility sands are safe for use in manufactured topsoils and roadbases (some sand types, including olivine sands and nonferrous sands, may require further assessment). Presentations on the risk assessment conclusions can be accessed through the Conferences and Events page under Tools and Resources.
U.S. Department of Agriculture-Agricultural Research Service Foundry Sand Initiative
Most soils used for landscaping and horticulture in the United States are actually manufactured soils, blended with combinations of virgin and recycled materials. Metalcasting sand has captured the interest of some soil blending companies because of its texture and local availability. However, most state regulators have been reluctant to approve this use, lacking the research capability to determine that metalcasting sand is safe for use in this application.
At the urging of the metalcasting industry, USDA’s Agricultural Research Service (ARS) undertook a five-year research program to assess the safety and suitability of metalcasting sands in horticultural and agricultural applications. This research complemented a history of ARS byproduct utilization research that has been incorporated into U.S. EPA policies and regulations. U.S. EPA and ASTSWMO representatives had inputs to the research plan and received regular briefings on its progress. The results were very favorable for properly screened iron, steel and aluminum metalcasting sands. USDA cooperated with US EPA to produce the Foundry Sand Risk Assessment described elsewhere.
Background for this project, as well as additional research and references concerning the use of metalcasting sand as an agricultural and horticultural soil amendment, is provided in the Soils Overview.
The ARS foundry sand research was subjected to rigorous internal and external scientific peer review at each step along the way. The results of each phase of the project were submitted to peer-reviewed technical journals; a listing of journal articles is included under Soils References. There is no summary report covering the entire research project, but some of the conclusions are stated in various journal articles:
Overall, it is unlikely that spent sands from iron, aluminum, and steel foundries will present a risk to environmental receptors when beneficially used in soil-related applications. Concentrations of PCDD/PCDFs and PCBs in spent foundry sands. Chemosphere. 75:1232-1235
Based upon the earthworm mortality and metal accumulation data, our study suggests that waste sands from the iron, aluminum and steel foundries do not pose an ecotoxicological or metal transfer risk. Metals in waste foundry sands: Assessment with earthworms. Journal of Residuals Science & Technology. 3:177-184
Through collaborative research agreements, ARS also supported foundry sand research projects at the Ohio State University, the Pennsylvania State University and Purdue University. Descriptions of each research project along with annual reports can be found on the ARS website:
- A Practical Study on Foundry Sand: Literature Review, Inventory, Blending Guidelines, and Interaction with Nursery Industry Representatives
- Use of Foundry Sand: Assessment of Transport and Availability of Trace Metal and Organic Contaminants and Nutrient Dynamics in Topsoil
- Mineral Characteristics of Foundry Sand: Impacts on Soil Hydraulic Conductivity, Erosion and Plant Growth
- Risk Assessment and Remediation of Soil and Amendment Trace Elements
A number of peer-reviewed journal articles resulted from the foundry sand project; a listing of most of them can be found by accessing the publication page of Dr. Robert Dungan, lead ARS scientist for the project, at http://www.ars.usda.gov/pandp/people/publications.htm?personid=34560. In addition to the journal articles, ARS soil scientists have given a number of public presentations on the research results and conclusions, the most recent of which can be found under the Agriculture II session at http://www.beneficialusesummit.com/2008/2008presentations.html