(Edited from a Greenbuild 2003 paper by Robert S. Hedin and Evan J. Verbanic of Iron Oxide Recovery, Inc.)
For decades, water pollution was considered an unavoidable consequence of coal mining. This belief resulted in the degradation of thousands of streams, rivers and lakes, with water pollution continuing in most cases long after the mines responsible for it had been closed and abandoned. An estimated 2,500 miles of streams in Pennsylvania are adversely impacted by acid mine drainage (AMD), which is one of the most significant environmental impacts of coal mining. AMD-related impacts are the reason that over half of the streams in Pennsylvania do not meet water quality standards.
Beginning in the 1960s, a number of measures were initiated to address the growing problem of AMD, including the construction of several chemical treatment plants. While these chemical treatment schemes were largely successful, the cost to operate and maintain them was substantial and they lacked long-term legal accountability. In addition, an unavoidable consequence of mine drainage treatment is the production of metal-rich sludge, which adds to the expensive chemical treatment systems due to the cost of its management and disposal. In contrast, passive methods of treating mine water generally require more land area, but use less pricey reagents and don’t require as much operational attention and maintenance. Passive systems are typically constructed with years of sludge storage capacity, thereby eliminating the need for regular sludge management.
In 1994, Hedin Environmental, Inc. received a Small Business Innovation Research award from the U.S. Department of Agriculture to investigate the feasibility of manufacturing a marketable product from AMD. The ensuing study revealed that, under certain chemical conditions, the formation of iron oxide sludge compared favorably with natural iron oxide ores mined and marketed for pigmentary characteristics. Five years later a patent was granted for the manufacture of pigment-grade iron oxide from AMD and early in 2000 a potential customer was identified. At the same time, a “proof-of-principal” project was initiated to determine whether this unfinished product could be made from an abandoned mine site using off-the-shelf dewatering and processing technologies. Iron Oxide Recovery, Inc. was formed in 2001 to pursue the profitable production of iron oxide goods from AMD.
Such oxides are used in a variety of industrial and manufacturing applications, and are valued for their pigmentary, catalytic and magnetic properties. They are produced in two principal ways: through the mining of natural ores and by a variety of synthetic, chemical processes.
The output of finished natural iron oxide pigments sold by U.S. processors in 2001 was 69,900 metric tons, accounting for 52% of total tonnage and 17% of the value of total pigment output. In comparison, synthetic production of iron oxide pigments was 64,700 metric tons, accounting for 48% of total tonnage and 82% of total value. The largest end-use categories for both natural and synthetic output in the U.S. in 2001 were construction (35%) and coatings (20%).
Like other natural iron oxide pigments, EnvironOxide is non-toxic, colorfast and weather-resistant. Once recovered, unfinished EnvironOxide “ore” is dewatered, dried and milled into a finished product. In its original form, this ore is goethite, a yellow iron oxide; when heated, it becomes hematite, a red iron oxide. These pigments can then be used as earth tone colorants in a broad range of building materials, including paint, wood stain, concrete, clay plaster, and wall and paving brick. They are also produced as part of the mitigation of one of the most significant water quality issues in Pennsylvania and elsewhere.
To-date, EnvironOxide pigments have been used in building projects seeking LEEDTM certification and others of an environmental or restorative nature. Locally it has been used on the District Mining Office of the Pennsylvania Department of Environmental Protection in California, PA (LEED Certification pending), the Center for Conservation Education in Westmoreland County, and the historic Keystone Viaduct in Meyersdale, Pennsylvania. From the greening of governmental agencies and universities to the emerging field of heritage tourism and environmental art exhibits, the use of this pigment exemplifies “resource recovery” in a myriad of applications.