Part I: Glass is Magic and Infinitely Recyclable

by Thom Zaremba, shareholder at Roetzel & Andress

My last few blogs have reported on International Building Code (IBC) developments regarding the glass industry’s efforts to increase the safety of schools from armed intruders. However, that was a temporary departure from a series of blogs that dealt with the resiliency of glass in buildings. In them, I described how the types of glass found in the windows and doors of a building can be used as a “litmus test” to predict whether significant upgrades might be required to restore the resiliency of the entire building in the event of a natural disaster. Today, we will look at the resiliency of glass when buildings end their valuable lives.

I’ve said it before and will repeat it—GLASS IS MAGIC. And when it comes to recycling, glass must be magic! It can be recycled infinitely. At the end of its useful life, the glass used in windows and doors can be crushed into cullet and made back into glass repeatedly. No matter how many times it is converted from the glass we see in windows and doors back to its molten state and then back again into glass, it never loses its integrity as glass. One might accurately say that glass is glass forever.

However, its magic has a cost. Once sand, soda ash and limestone are melted, the resulting glass is probably one of the most environmentally stable products ever made. For example, glass remains perfectly stable in all types of weather throughout the entire life of a building. Even when the building has reached the end of its useful life, the glass usually remains unchanged from the day of its manufacture. Indeed, when the building is finally demolished and its glass is sent to a landfill, that glass will be there, as glass, literally, forever.

Unfortunately, glass never degrades in landfills. Indeed, some experts suggest that it would take at least a million years or more for a simple glass bottle to degrade fully under normal landfill conditions.

Despite being one of the best candidates for recycling and one of the worst for being sent to a landfill, the U.S. disposes of enough glass every two weeks to fill a skyscraper comparable in size to the 1,350-foot-tall World Trade Center towers.

What in the world is going on?

In a word, the culprit is impurities. But before probing why impurities impede recycling, we must look at aluminum, a second candidate for recycling sainthood. Like glass, aluminum can be infinitely recycled. So, what’s the problem?

The problem is that glass and aluminum (and sometimes steel and other metal products) often go together like a hand and a glove as building components. The windows and doors found in buildings usually use aluminum frames. That brings the glass into intimate contact with the aluminum. Why is that a problem? It can result in impurities in the glass when the time comes to recycle it.

Virtually all the architectural glass now is float glass. Before its invention in the 1950s by Sir Alastair Pilkington, flat glass had to be ground and polished after it cooled to make it smooth enough and uniformly flat enough for use in making windows and doors.

While the float process reduced the time, labor and waste involved in making flat glass, it also made the process of making glass a bit fussy. In that regard, impurities in almost any amount, especially aluminum, nickel and other types of metal that aren’t fully absorbed into the glass when melted, can contaminate the entire bath on which the glass floats during manufacture. Once it gets into the bath, getting it out is complicated and expensive.

Once even a slight, nearly invisible impurity gets into the mix of ingredients used to make float glass, it is virtually impossible to get it out. Once it contaminates the float bath, it will likely halt the entire manufacturing process. For that reason, glass companies are extremely hesitant, or will rightfully refuse, to introduce any glass recovered from buildings back into their manufacturing process.

Does this mean that glass can’t be recycled? Not at all. Glass cullet recovered from buildings can still be recycled into many different things. However, without the extensive processing and inspections necessary to remove all impurities, it won’t be used to manufacture float glass.

The types of things that glass recovered from the end of its life in a building are usually made into something, which will have to wait for my next blog to be explored. Please stay tuned.