We don't recycle very impressive numbers in the glass category. About one fourth of our 10.2 million tons of waste glass per year sees a return ride to the mill. Separation of colors is necessary for reusing glass for new bottles and jars. Mixed glass is not so easy to find a buyer for. One great way to use the mixed glass cullet is for sand replacement. It is far more forgiving of poor quality glass. One ceramic beer bottle cap can render an entire batch of cullet destined for remanufacturing and non-container glass also contaminates recycled container glass - not so on the beach.
There are a couple of ways that beach sand can be lost. In storms, it will be washed out and will form sand bars along the direction of the shoreline (the littoral direction). Not only does this protect the beach from further erosion during the storm, but less aggressive waves will later wash these sand bars back ashore, making sand out to look like a pretty smart mineral because it seems to have a mind for defense and repair. Of course, sand isn't really any smarter than your average rock. It is just one of the natural cycles that make the world work the way that it does.
Another way that sand can be lost from certain locations is more permanent. Called littoral drift, alongshore currents take your sand and give it to your neighbor. This is also a perfectly natural occurrence. Shorelines are dynamic - nature changes them all of the time. This can be slowed by engineered groins and jetties that jut out perpendicular to the shoreline to present hurdles to littoral movement of sand.
Whether it's coming back eventually on its own or lost to the neighbors, erosion presents a huge problem in the tourism and coastal real estate industries. The problem is that coastal stakeholders need the complete protection of the beach because beachfront property is very valuable. The beach protects the coastal properties from stormy waves, and threatens the structural stability of coastal buildings if the shoreline moves too close.
The smart answer is coastal retreat, but it isn't a very practical one. Coastal properties can't retreat now. The development behind them is pushing them out to sea like a Lucille Ball's bon-bon assembly line. There's no backing up now. That leads us to a process called beach nourishment. I have no idea why it would be called this, except that perhaps it sounds more politically correct than, "protecting my property value". Maybe I'm just being a cynic.
Beach tourism is worth a lot of money to our economy. It is estimated that 31.7% of the U.S. GNP, almost $1.3 trillion, originated in coastal counties. Foreign tourists spend about $80 billion of that, which results in a $26 billion tourism surplus. 50% of US population lives and works in those same counties. So, we 150 million drylanders pay the same tax dollar as the 150 million in coastal counties receiving $8 each, just to keep their beaches profitable for them.
Broward County, FL sees 10 million visitors a year to the 24 miles of Broward County shoreline who contribute about $8 .4 billion to their economy. The coastal properties are estimated to be increased in value by $1.4 billion by being at the beach. The $4 billion in properties need the beach to protect them from wave damage. Broward County collects about 9000 tons of broken and mixed glass in their recycling program each year. In 2005, one 12-mile beach used 2.5 million tons of sand. Obviously, dredged and mined sand is in no danger of being replaced by glass.
Beach nourishment uses a hundred thousand to a million dollars per mile of beach, at a cost of between $100 million and $150 million in Federal taxpayer money per year (65% share). The local governments are responsible for the other 35%. It is performed in one of two ways. One way uses pumps or scrapers to dredge offshore sand to the beach. The other is to purchase sand from a mine.
There are a few environmental consequences associated with near-shore dredging because you are destroying a benthic environment by relocating it to the beach from the sea floor and pile it on top of the beach organisms, so you are basically damaging two microenvironments.
If inland sand is mined for beach renourishment, this wreaks havoc on rivers and streams because you hardly ever find good beach sand just sitting around on the ground somewhere. It is more likely in the bottom of a river bed. You are also competing with other aggregate needs, like construction. Like offshore dredging, riverbed mining severely damages a riparian habitat. The exact size distribution and color of sand needs to be matched carefully because wildlife on the beach, like nesting sea turtles for instance, may not nest in sand that differs too much. With glass, you can mix up the exact color and particle size distribution that you need to match up. You can't always find a matching sand and gravel mine within a reasonable distance, so you may have to truck it from miles away inland. You lose a few carbon points for that move.
Back to glass: Even if we processed every used glass container that we can't use for recycled container glass, beneficial reuse of glass as sand will come nowhere near the needs of beaches. But it sure beats landfilling or incinerating and it could put up to a 7.5 million ton dent in the replacement sand needs. That would represent about $85 million worth of sand with substantially less cost to the environment.
Cheers,
Bob Peeples, PE