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Recycling Mining Tailings on Lake Superior

Imagine the “ideal” environmental success story. Perhaps it involves the removal of tons of solid waste from an otherwise pristine location, material that not only ruins the scenery but also dramatically affects the local ecology. Further, imagine that the removal of this waste somehow doesn’t cost the taxpayer a penny. And the waste isn’t just carted off to be buried in a landfill; it’s recycled as an important product used by millions. And while you’re at it, imagine that this product solves a major problem that affects many regions across the country, yet costs far less than current alternatives.

The preceding scenario isn’t just some environmentalist’s daydream; it’s the business plan for a small Michigan startup named GreenSand. And if they succeed, they will help restore miles of Lake Superior shoreline, while providing an economical solution to the common problem of algae stains on asphalt roofing shingles.

Mining Waste

The Great Lakes region has long been a productive area for mining various minerals and ores. For over a century, Michigan’s Keweenaw Peninsula has been the site of copper mining. This has resulted in approximately 500 million tons of tailings, fine sandlike material left over by the copper extraction process. These tailings exist in the form of large piles and dunes, drifting along waterways and shorelines. The particles still contain a certain amount of copper (approximately 0.3%), which acts as a natural algaecide. As a result, tailings have a significant impact on the local ecology, particularly at the bottom of the food chain. They also profoundly affect the use and value of the neighboring area. Unfortunately, the anticipated cost of removing such vast amounts of material has precluded cleanup of this waste.

GreenSand has devised a way to not only help remove these copper mining tailings, but also derive commercial value from this material. They are re-using the tailings as raw material for the manufacture of roofing shingles. This material, marketed under the name G-Sand, can be used as surface granules on shingles and possibly as filler material.

Algae and Asphalt Roofing Shingles

G-Sand could help prevent the growth of algae, which is a common problem for asphalt roofing shingles installed anywhere in the U.S that receives significant annual rainfall. This problem was initially confined largely to the Southeast, but in recent years it has expanded into regions as far north as Minnesota and New England.  Other areas affected by algae include the Mid-Atlantic and Midwest regions, as well as the Pacific Northwest.

Algae growth became a problem starting in the mid-1970s, when traditional natural cotton fibers became relatively scarce for the manufacture of roofing shingles, and polyester fiber was substituted. The artificial fibers are lighter than the natural fibers, so to meet shingle weight specifications (a minimum of 240 pounds per 100 square feet) calcium carbonate is added to the shingle as filler (or in some cases, dolomite [calcium magnesium carbonate] is also used ). The primary reason calcium carbonate is used is because it is cheap and plentiful. By the mid-1980s, homeowners began to discover that their shingles were turning black, due to algae growth. (It usually takes three to five years for the algae growth to become noticeable.) The algae, primarily Gloeocapsa magma, feeds on the calcium carbonate leaching out of the shingle surface.

Although this presents no structural issues, many homeowners are dissatisfied with the cosmetic appearance of the algae. Algae is the most common cause of appearance-related complaints reported to roofing contractors. Many homeowners mistake the dark stains caused by algae for faulty shingles. Although the algae streaks can be cleaned, the process can be expensive ($400 to $700), requires repeated applications, and may damage a roof and shorten the life of the shingles.

Shingle manufacturers typically address this problem by adding copper to the shingle granules. This provides effective anti-algae properties. Unfortunately, copper granules for asphalt roofing shingles can cost up to $800 per ton, which is roughly five times the cost of regular ceramic granules.

G-Sand

GreenSand’s plan is to remove the copper tailings from the environment and place it on roofing shingles, where its anti-algae properties can be put to good use. Processing the G-Sand material includes sorting out the particles of correct size (0.5 to 2 mm), grinding down oversized particles (approximately 40% of the material) to the proper size, applying a proprietary treatment which reduces water absorption by the particles (and provides other benefits), and sterilizing the material. Approximately 80% of the overall volume of tailings can be processed and used for roofing shingles. Processing will be done in a plant built near the site of the tailings.

G-Sand has been shown to be an effective anti-algae agent in tests.  Further testing is designed to demonstrate that G-Sand has a predictable and reliable leaching rate over a long period (10+ years), making it a potentially attractive alternative to copper granules. And if it can be additionally demonstrated that powdered G-Sand can effectively control algae when used as shingle filler in place of calcium carbonate, this could further expand its use within the shingle manufacturing industry.

Another major advantage of G-Sand may be cost. The building supply and construction industry typically operates on small profit margins, and manufacturers and end-users are constantly looking for low-cost alternatives to increase those margins.  As previously mentioned, copper granules are expensive. In addition, the ceramic material used for butt lap granules costs between $120 and $280 per ton.  G-Sand’s projected price is approximately $50 to $100 per ton, which represents a considerable potential cost reduction. So irrespective of its potential anti-algae properties, G-Sand could also find a market within the shingle industry based on price.

Then there’s the issue of “green” construction. Due to increasing awareness of environmental concerns, many homeowners are demanding products that use recycled materials. Groups such as the Green Building Council have been created to address this demand. G-Sand is made from 100% recycled material and likely requires considerably less energy to manufacture and process than other materials used in asphalt shingles.  Therefore G-Sand could be very attractive to manufacturers looking to serve the environmentally conscious consumer.

Challenges

A number of challenges remain before GreenSand can expect the $6 billion U.S. asphalt roofing industry to adopt their product on a large scale. For example, they obviously need to demonstrate that G-Sand is in fact effective for combating algae growth, in a predictable and reliable way over an extended period. This will ultimately require testing that simulates roofing shingles applied to actual roofs exposed to outside conditions for multiple years. The material would also need to fall within a very specific and consistent size range to be used as granules.

If used as filler, GreenSand would need to demonstrate to consumers that its material bonds well with fiberglass and other component materials of asphalt shingles.  They would also need to show that G-Sand is at least as strong as calcium carbonate, the material most commonly used as filler today. (The company believes it has addressed both issues. Testing by Michigan Technological University indicates that G-Sand’s bonding to asphalt is actually enhanced and stronger because of the proprietary treatment; and the basaltic rock from which the tailings material was originally mined is stronger than limestone.) In addition, a new algae-resistant material should be able to demonstrate that it is cost-effective compared to current technologies.

Finally a key characteristic is whether or not a new material is “machine friendly” – that is, whether or not equipment designed to manufacture shingles from current materials can handle the new material without modification. Manufactures will be unlikely to adopt a new technology, even one that performs well, if they must replace their current equipment to use it.

Going Forward

Assuming GreenSand can address these challenges, and raise the necessary capital for a large-scale processing operation, they could provide a latter-day example of the old adage “one person’s trash is another’s treasure.” They may also serve as a model for how, with a little creativity, a seemingly intractable environmental problem can be resolved in a way that provides additional — and even surprising and novel — benefits.

Dick McCarrick is an analyst with Foresight Science & Technology.

Dick McCarrick
Dick McCarrick is an analyst with Foresight Science & Technology.
 
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2 thoughts on “Recycling Mining Tailings on Lake Superior

  1. This material is made through recycling, but will these G-sand shingles be recyclable at the end of their useful life? Will this shingle last longer than conventional shingles? Many recycled shingles wind up in asphalt road applications. How about these shingles? Overall, I think this is great news, just hope someone is thinking about the questions that I am raising.

  2. Is there any health hazard in the use of G sand from tailings. There is potential danger in the use of some tailings in Arizona and Oklahoma through acid, lead and zinc.

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