X
Innovation

How waste from copper mines can help the roofing industry

Waste from Upper Michigan's copper mines is a treasure for area roofers who can use stamp sand to make cheaper shingles from recycled material.
Written by Christina Hernandez Sherwood, Contributing Writer

Waste from Upper Michigan's copper mines is a treasure for area roofers who can use stamp sand to make cheaper shingles from recycled material. Ralph Hodek, an associate professor of civil and environmental engineering at Michigan Technological University, spoke with me recently about this material -- and about the additive he developed to further improve the process.

What is stamp sand?

Stamp sand is a generic term. You start out with rock. In order to liberate a metallic, you take the metallic rich rock and run it through a so-called stamp. It's strictly a mechanical process. It works because the metallic material is already in the metal form. We're talking about metallic copper as you would see in copper pennies. There are only a few places in the world where metallic copper occurs and one is in the copper country in Upper Michigan. It's not uncommon for you to walk on the road and see pieces of metallic copper in there.

Stamp sand is the result of a copper-rich basalt rock which is broken up mechanically in a stamp mill. It's a very mechanical process, just as you might do if you were making gravel in the quarry. We're breaking this rock down in to a small enough size that the pieces of metal -- in this case, copper -- are liberated. They come apart from them rock. Once you've got the material broken down, we use gravity [to] float off that rock and the copper goes to the bottom.

What do we do with the ground up or stamped rock after we've taken out the copper? We dispose of it. In the old days, not so long ago, we just dumped it any place. In our particular property, we had about 90 million cubic yards of stamp sand. A particular particle is going to be smaller than a quarter inch in diameter. Most of it is large enough that you can see with the naked eye the individual particles.

Why is it ideal for making roofing shingles?

Roofing shingles are one of the value-added products we're interested in pursuing. The important thing about roofing shingles is that they're angular, they will stick to the asphalt and they have enough toxicity in the rock so you don't grow moss and algae. Asphalt shingles normally have to have copper added to the sand that they use in order to make the shingles last for 20 or 25 years without being filled with growth.

You've created a new additive and process to make it work even better? Talk about that.

Naturally, there's just enough copper remaining in this sand to give it a little bit of algaecide behavior. Rather than the shingle manufacturers having to buy very expensive copper oxides and add them, this stamp sand already has enough copper in it to inhibit the growth of moss and algae and so forth. That's natural.

It is important to the shingle manufacturer that the sand sticks to the asphalt. A shingle is made up of tar paper, a coating of asphalt and some sand, essentially. If you've ever noticed when your asphalt shingle roof starts seeing its age, the sand starts coming off. In order to make the sand stick very well to the asphalt beneath it, we have developed a proprietary coating which bonds the sand to the asphalt. The coating itself is a mono-molecular layer that we put onto the sand. It doesn't inhibit the algaecide behavior of the sand, but it does increase the adhesion between the sand and the underlying asphalt. Instead of having a mechanical bond between the sand and the asphalt, we have a chemical bond. The university has patented this. It's a major step forward in the shingle sand industry.

What's the next step?

We are working with some prospective clients who are interested in putting up a shingle mill in the area. These are very expensive projects. We're also negotiating with some of the existing shingle makers to use our sand. In that case, we would treat this sand at our facility and then ship it down to either Chicago or Detroit or Cleveland, anywhere on the Great Lakes. [The Illinois Department of Transportation has certified our stamp sand as being acceptable as sand for their new asphalt pavement specification.]

Do you have anything else to add?

This material was put on the shore of Lake Superior from about 1890 to about 1945. It was strictly a waste product. We're starting with the right-sized material and a material that does not need an additive to make it an algaecide. We don't have to put in an additive, so that means money saved. All of the mining and the crushing which we would otherwise have to do has been done for us. It's a very 'green' material because we're saving so much energy by recycling it.

Photo: Ralph Hodek with stamp sand

This post was originally published on Smartplanet.com

Editorial standards