Turning Glass into Aggregate Opens
Glass aggregate, made from collected containers and other scrap, can offer new markets for the glass recycler.
Pulverizing glass to a size of three-eighth inch or less in diameter creates a safe end product by turning it into sand. This glass sand can then be used in the same way sand can be used and in other applications.
For about eight years the city of Abilene, Texas has been pulverizing glass and using it in projects around the city and county. Bill Brock, the city's waste reduction and recycling coordinator, said that using glass aggregate started with the Texas Department of Transportation doing research on material uses in roadways. Abilene was selected as the state's testing ground in using glass aggregate in its roadbase, called flexbase. The city received a grant to purchase a glass pulverizer and started creating the aggregate.
"Once the testing was done," said Mr. Brock, "we were left with a lot of glass. Our local engineers started planning projects to use the aggregate. We still use the glass flexbase in our roads and use it in parking lots."
Mr. Brock said the city also has separated brown glass and pulverized it to use in golf course sand traps.
"The glass sand allows for excellent drainage," he added. "The glass is used for sand filters, pipe bedding markers, around pipes in the ground, in leachate fields and septic system liners."
Mr. Brock continued, "In leach fields, sand has some absorbency and glass doesn't. Personally, I think the glass works better as particulates stick to the glass better and clean water is percolated down to the soil."
The city does not always make the glass as small as sand.
"Some of it we pulverize to about three-quarters of an inch around. This is good for the roadways. The glass is going to retain its shape for years," Mr. Brock said. "We've also used it for landscaping and walkways. We have glass walkways in our composting site. We take off our shoes and socks and walk on it barefoot to show people it's not sharp. We are in the process of creating a large nature walk using the glass."
Mr. Brock said one of the best things about pulverizing glass is that it allows him to set up a collection of co-mingled glass. The city of Abilene has about 112,000 people with several collection container drop-off sites. It also allows other communities to bring glass to him without separating the colors.
"Many of the surrounding counties only have about 5,000 residents each. By allowing them to bring their glass here without color separation allows them to have a glass collection and allows them to recycle it," said Mr. Brock. "I have people as far as 90 miles away bring glass in quantity."
Mr. Brock said the city stockpiles the glass after it has been pulverized so it is available when needed for projects. He added that he usually allows people who want to use the glass in a project to do so. If someone wishes to buy the glass, he takes the going rate for sand and cuts it in half.
"We like to see the recycled material get used," he said. "We sell it as a base for swimming pools and it also is used in sand filtration systems to clean swimming pool water."
With the nearest glass market about 250 miles away, making glass into sand was the only glass recycling alternative for Stutzman Refuse Disposal in South Hutchinson, Kansas. Owner John Stutzman explained that South Hutchinson is in the middle of Kansas.
"There are recyclers in the area, and what they get for the glass cullet is eaten up in the freight to get it to the glass manufacturer," he said.
Stutzman Refuse contracts with the city for refuse hauling and recycling pickup. The city of South Hutchinson has about 40,000 residents.
"We collect our recyclables in a co-mingled form. We put the recycling collection through our glass pulverizer from Andela and it separates out the glass and the rest of the co-mingled recyclabes come through. What is handy is that you don't have to worry about people getting cut sorting the glass. Its already removed from the stream," Mr. Stutzman explained.
The company pulverizes about 11 tons of glass per month. So far they have used all of it internally. "In two-and-a-half years we haven't had to find a market for the glass sand. We make a fill grade sand and gravel for a coarser grade. We've been using it internally or we allow our employees to use it. Most of it is used as fill sand when someone does concrete work. If it gets to the point where we have to find a market, it's not going to be a problem," he added confidently. "Many of our local builders are interested. I'm not worried about having to get rid of it."
In Madison County, New York, glass aggregate is being used for all kinds of applications at the landfill. James Zecca is the director of the Madison County Department of Solid Waste and Sanitation. The department runs the local municipal landfill and recycling center for the county, which has about 70,000 residents.
Mr. Zecca said the glass aggregate is one of the best materials to use in the trenches and around the pipes for methane gas collection. He said new York state regulations and federal regulations now require that new landfill cells collect the methane gas that is created as garbage breaks down. The gas must be collected and vented and burned through a flare or used for energy.
"To collect the gas, trenches are dug that lead down to vacuum pipes. We use the glass aggregate in the trenches and around the pipes instead of using a coarse gravel or sand. The gravel is a new material and is expensive to buy. With the glass aggregate, we are using a recycled product, a free product and it works better. The sand and gravel can plug up very easily. This creates a nice passageway, and there are cost savings benefits," said Mr. Zecca.
Temporary roads are made throughout the landfill and the glass aggregate is used to make these roads.
"We have a clay soil here that gets very wet and sloppy. We add the glass aggregate and it firms the road. It performs very well," he explained. "We also use it in the mix for permanent roads. The tractor-trailers travel the road to our materials recovery facility (MRF) and the road has held up very nicely," he said.
The county also used to use the glass instead of sand in the leachate fields for the landfill instead of sand.
"Sand is the least desirable material to use for leachate fields. Glass is a good material and a good product to use, but we started using tire chips and have found them to be the best product for the leachate field filtration," Mr. Zecca explained.
In Madison County the MRF is run by the county's local Association for Retarded Citizens (ARC). The county still separates unbroken clear glass containers to make into glass cullet. All other green and brown glass and any broken glass are made into aggregate. This way workers have very little contact with broken or dirty glass.
"We stockpile the glass as we need to. Since we are building a new landfill cell, we haven't had any to stockpile. We have had to use some outside sources of glass, which we get for free, on this project as well. The cell is seven acres, which is not a very big landfill area and we have used up the entire stockpile in building this cell. It doesn't hurt to stockpile the glass because it doesn't contaminate anything," Mr. Zecca added.
He said the state of New York also has approved the use of glass aggregate as a daily landfill cover. While he hasn't used it for that, he said it would be a good alternative for urban areas that have to truck in soil to use.
The town of Ocean City, Maryland, uses glass aggregate as the material in its asphalt base for roads.
John Bruch, recycling coordinator for Ocean City said that the glass aggregate is stockpiled and then added to the asphalt mix by the company that has the contract to do road construction.
"Right now we give it to them. It's better than landfilling the glass," said Mr. Bruch. "We used to sort glass by color and sell it, but that market went away. There is no market for the waste. We came up with this solution for handling our collected glass and it keeps the glass out of the waste stream."
Ocean City has a town ordinance that all establishments with a liquor license must recycle all glass and aluminum containers. The city provides the collection containers and collection. About 900 tons of glass a year is collected in the city.
He said pulverizing the glass into glass aggregate not only gives them a material they can use but also has been much easier than separating the glass by color.
"We get a mix of all colors and also window glass and some ceramic. With such a variety, this method has been an ideal situation for us," Mr. Bruch said.