Glass is a beautiful material that is believed to date back to 2400 BC. Glass is made of roughly 70% silica sand with other components, namely limestone (calcium carbonate) and soda ash (sodium carbonate). By heating these materials in a furnace above 2700 degrees Fahrenheit and then cooling, glass forms. Soda-lime glass is the most common and least expensive glass, accounting for about 90% of all manufactured glass. Thanks to glass recycling, cleaned, crushed used glass is frequently part of the heated mixture. The addition of recycled glass (cullet) reduces the number of raw materials and lowers the amount of carbon dioxide and other pollutants generated in the process. For every 10% of recycled glass blended into the mixture, the energy required for the furnace falls by 3%.
The collection of recyclable materials in a single bin is termed single-stream collection. It is the most common means of collecting glass (and other materials) for recycling in the US. At a materials recovery facility, recyclable materials are separated. The glass tends to be more contaminated than glass collected from multi-stream recycling programs, where each material is contained in its bin. About 90% of waste glass from multi-stream programs is recycled into new glass containers.
In comparison, about 40% of glass from the single-stream collection is clean enough to convert into new products. The companies that process waste glass (cullet producers) rely on crushers and sorters equipped with sensors. Other science/technology advancements automatically remove paper labels and metals and analyze about 100,000 pieces of glass every minute.
Approximately 33% of the 10 million tons of waste glass is recycled in the United States, compared to several countries in Europe that recycle over 90% of waste glass. States such as Maine and Oregon recycle over 70% of waste glass, while the glass recycling rate is as low as 10% in other states. Many people in the glass recycling industry believe that bottle deposit programs will heighten recycling rates. Also, there are signs that more people are changing their attitudes about the value of materials and want to live more sustainably. It is good to clean and recycle all your used glass bottles. The industry is hopeful that the US can achieve 50% recycling of waste glass shortly. Maybe we should aim for 90%!
Julie Peller Ph.D. is an environmental chemist (Professor of Chemistry at Valparaiso University ) and she leads the Environmental Ministry at Nativity of Our Savior in Portage IN. Julie has been writing a weekly column for church bulletins for the past ~6 years called the Green Junction and is helping to move the call of Laudato Si to action forward. Her Research Interests are in Advanced oxidation for aqueous solutions, water quality analyses, emerging contaminants, air quality analyses, Lake Michigan shoreline challenges (Cladophora, water, and sediment contaminants), student and citizen participation in environmental work