Destruction of Benzene, VOCs and Odors from Metal Casting

This page updated January 25, 2006.

Gregg Industries, Inc.

Destruction of Benzene, VOCs and Odors from Metal Casting

The statements and conclusions in this Report are those of the grantee and not necessarily those of the California Air Resources Board. The mention of commercial products, their source, or their use in connection with material reported herein is not to be construed as actual or implied endorsement of such products.

Foundry casting operations may produce odor-causing compounds, volatile organic compounds (VOCs) and particulate matter. VOCs are regulated compounds under federal and state laws. Odors lead to nuisance complaints that may eventually lead to fines. Technology is needed to ensure compliance with VOC regulations and to eliminate odors from odor-causing compounds.
Project Objectives
The objectives of this demonstration project were to determine 1) the effectiveness of the Sonoperoxone®-Scrubber (see photo) in reducing odors and VOCs from gaseous effluents generated from core making and sand handling operations and 2) the overall technical and economic feasibility of the integrated system, specifically whether savings from the use of Sonoperoxone® Systems in sand handling operations can justify the cost of the odor and VOC scrubbing technology.

Sonoperoxone®-Scrubber System

Technology Description
The innovative integrated systems approach involved installing a Sonoperoxone® Clearwater System to treat the water used in foundry sand systems with high powered acoustics, ozone and hydrogen peroxide to lower VOC emissions; a Sonoperoxone® Blackwater System that adds a solids separation system to recycle coal and clay separated from silica by acoustic energy; and the Scrubber System that removes odors and pollutants using wet phase scrubber sections with sonocatalytically reacted water, ozone and hydrogen peroxide in conjunction with ultraviolet oxidation chambers. The first two systems in addition to lowering VOC emissions, improve casting quality, reduce scrap and reclaim costly materials, all leading to an overall energy saving for the plant; the last system reduces pollutants and removes odors. No other technology provides similar energy and environmental benefits,
The project was complete on August 31, 2004 and continues to operate at the Gregg Industries' facility. The final report is on file with the complete technical details of the project. The project began on June 26, 2002. The entire system was installed by July 2003. Large scale pre- and post-installation testing was completed by February 2004. Two minor problems, permitting delays and excessive sampling and analytical costs, were resolved quickly and did not impact the results of the project.
A. Odor-Causing Compounds Five compounds were identified as representative foundry odiferous compounds. An evaluation of emissions data collected following installation of the Sonoperoxone®-Scrubber System eliminated consideration of 1-methylnaphthalene and toluene as odor-causing compounds as the values for these two compounds exiting the stack were far below odor threshold limits. The 50 ppm odor threshold of acetaldehyde was exceeded by only 1 ppb under maximum production conditions (mpc), but was almost 40% below the threshold under average production conditions (apc). 0-Cresol exceeded the odor threshold under mpc (58.6 ppb vs. the 40 ppb standard) but was substantially lower (11.7 ppb) under apc. In terms of mass removal (lb/hr), 0-cresol levels were reduced by 56.5% (mpc) and 79.4% (apc). Phenol, measured at three times the threshold level in the baseline study, increased to five times the threshold level under mpc, but decreased to two times the threshold level under apc. In terms of mass removal, phenol levels were reduced by 32.8% (mpc) and 54.8% (apc). Since installation of the technology, off-site odor complaints have gone from 200 to 2 and these two complaints were found not to be related to Gregg Industries operations.
B. VOCs Total VOC concentrations were reduced by 19.9% under mpc and by 46.5% under apc. In terms of pounds of VOCs per ton on iron poured, the reduction was 45.9% (mpc) and 41.3% (apc). The project met or exceeded all objectives and goals. No performance tradeoffs were required nor resulted from the technology.
As a result of installing the Sonoperoxone®-Scrubber System, the following benefits have been realized: 1) odor complaints have been eliminated; 2) the odor-causing compounds have been reduced and with an additional minor system modification can be reduced even further; 3) VOC emissions have been reduced; 4) energy use is down 20%; 5) scrap rate is down 50%; 6) raw material use has decreased (sand 9%, carbon 15.5%, and clay 19%); 7) the number of man hours per ton of metal poured has decreased approximately 20%; and 8) the quality of the castings has improved. Potential emissions reduction are from 1.0 to 1.8 lbs/hr of VOCs for a foundry operating a single shift (2000 hr/yr), or 1.1 to 1.8 tons of VOCs per year; reductions double if two shifts are employed. If five of the estimated 30 similar  types of foundries in the L.A. Basin employ the technology, reduction in VOCs could range from 5-9 tons/year (single shift) to 10-18 tons per year (double shift). An anticipated benefit was a reduction in odor complaints by 90-95%; actual reduction was 99-100%. VOC reductions between 30-40% were expected; results ranged from 41-46%. While odor-causing compounds and VOCs were reduced, no environmental problems were created. In fact, dust levels in the plant decreased (visual observation).
Commercialization and Applications
The Sonoperoxone®-Scrubber System is available for installation at any foundry where odors or pollutant emissions are a problem. The cost of future delivered systems will decrease, as this was the initial model installed. Estimated market size is 30 foundries in the Los Angeles Basin plus more than 200 foundries statewide. Nationally the market may exceed 1,000 foundries. In addition, with slight modifications, the technology can be used to solve similar odor / pollution problems in other industries, including chemical, petroleum, and pharmaceutical. The Sonoperoxone®-Scrubber System is commercially ready; minor modifications will be made in future units to increase the scrubber efficiency.

Funding Source

Funding Amount





South Coast Air Quality
Management District


Click here for the entire final report.

ICAT Funded Projects