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  • Circular Indiana

Glass Recycling, Explained

Updated: Jul 29, 2022

Welcome to the circular world of glass recycling! Glass embodies more than one aspect of the circular economy, and there’s more to glass than just recycling it right. From your bin to the product’s next life, we break down the basics on how glass recycling works.

Multi-colored glass cullet in recycling machinery

Glass & the Circular Economy

Glass is a valuable part of the circular economy, and was one of Indiana’s first major manufacturing products, along with aluminum and steel. Actually, its value extends to multiple levels of the circular economy. Glass is non-toxic, is infinitely recyclable, and embodies an especially important part of the circular economy—other “R” words like reuse and refill.

Since the 1900s, the glass industry has been a critical piece of Indiana manufacturing. Today, Indiana continues to be a glass manufacturing powerhouse—Indiana is one of the top container glass producing states in the US—and also is a primary end-user for recycled glass. In fact, while Indiana only recycles about 10 tons of glass each year (Glass Packaging Institute), Indiana manufacturers use over 150,000 tons of recycled glass to make new products.

Glass is Non-toxic

One of the most impressive features of glass is that it is completely non-toxic, both during use and when it breaks down. The reason for this is that glass is “inert,” or chemically inactive, meaning that it does not interact with other substances. This is great for keeping the flavor of last week’s tuna casserole out of this week’s guacamole, but it’s even more helpful in the event that glass is discarded. Unlike other materials that can leave toxic substances behind when they break down, glass just breaks into smaller and smaller pieces until it forms a sand-like substance.

Glass is Infinitely Recyclable

Glass can be recycled endlessly without loss in quality or purity. There are many benefits of using recycled glass to make new glass. Because glass melts at a lower temperature than raw materials, using recycled glass as a feedstock in the glassmaking process decreases the energy needed to run the furnaces. Less energy means fewer greenhouse gas emissions, which contribute to climate change. Additionally, recycled glass can be substituted for up to 95% of the raw materials used to make new glass, such as sand, soda ash, limestone, and feldspar. These valuable resources may seem unlimited, but some are actually running out—there is currently a global sand shortage. Sand is the second most used resource after water, but without proper management, supplies could dwindle.

By using recycled glass to make new glass, the need for finite natural resources can be substantially reduced—thereby lessening the environmental impacts of mining those materials.

Of course, not all glass is recycled into new containers—much of the glass recycling that occurs today is made into other products, like fiberglass insulation, reflective roadway paint, abrasives, and more. These products are typically the end of life for the glass used to make them, but they still play a vital role in reducing the impact of our waste and keeping glass out of landfills and incinerators.

Glass is refillable and reusable

Glass recycling is valuable, but the circular economy prioritizes reducing or reusing materials before recycling. Because the quality of glass does not degrade over time, this makes glass durable for reuse. Items made of glass can be easily washed and refilled, without concerns of contamination or leaching into whatever is stored inside. In fact, the first commercially-produced glass containers manufactured in the US (many of which were made in Indiana) were specifically designed to be refilled and reused over and over again because glass was expensive to make. As industrialization lowered manufacturing costs and disposability became the cultural norm, we shifted away from reuse and towards glass recycling. However, glass’s unique qualities still make it an ideal choice for reducing waste.

Glass Container Recycling Loop: 1. Recyclables are placed in curbside bins; 2. Recyclables are collected; 3. Recyclables are delivered to a Material Recovery Facility; 4. Recyclables are separated by material types; 5. Glass from the MRF and drop-off locations is sent to a glass processing company; 6. Glass is separated from trash and other contaminants, then sorted by color; 7. Recycled glass is sold to manufacturers and made into new bottles and jars; 8. Consumers purchase food and beverages in glass packages. And the cycle continues!

How Glass Recycling Works

The process of making new products from your recycled glass has 6 basic stages. Follow our step-by-step guide for detailed information on this process, or watch this NPR Planet Money segment.

1. Collection & Sortation

Glass recycling starts when you put glass in your recycling bin. In Indiana, we have two ways of collecting glass: in a curbside bin with other recyclables or in a separate glass-only bin. The recycling process is generally the same for both collection methods, but glass-only collection tends to be much cleaner because it is not mixed with other items that can cause contamination. Because it is cleaner, separate glass collection tends to have a greater value for manufacturers than glass from a mixed-material, curbside recycling bin.

Definition: a materials recovery facility (MRF) is a sortation plant that separates the different materials in your recycling bin, like paper, glass, metal, and plastic.

If you’re recycling glass in your curbside bin,* your recycling is collected and taken to a material recovery facility (MRF) where the glass is sorted from other materials like paper or metal and sometimes by type. This may seem simple, but there are a variety of kinds of glass, and not all of them are recyclable. Glass may also be sorted by color, separating clear glass from clear, green, or amber.

*If you’re recycling your glass via a separate glass collection program, your glass may be transported directly to the processor, skipping the MRF altogether.

One of the most advanced glass material recovery facilities in the country is the Rumpke Waste and Recycling facility in Dayton, Ohio. Rumpke is a waste and recycling company servicing residential and commercial customers in Ohio, Indiana, Kentucky, and West Virginia. The company recently earned a gold-level Glass Certification, an award given out by the Glass Recycling Coalition. Rumpke values glass as a commodity and is committed to recycling it. To ensure more recyclable glass, their Dayton facility has a pre-cleaning process to remove glass early in the sortation process, which creates a cleaner, more recyclable product. The sorted glass is then taken to their glass processing sites for further cleaning, sorting by color, and distributing to manufacturing customers.


2. Transportation

After sorting, the glass is transported to a processing facility, which will transform the MRF glass into cullet—the product used in making new glass products.

Definition: glass cullet is glass that has been crushed into small pieces, with different grades of cullet for different colors and sizes of glass pieces.

In Indiana, glass is transported to the largest glass processing company in North America—Strategic Materials, Inc (SMI). With over 50 locations in the US, SMI plays an important role in the glass recycling process and is a critical partner in providing clean glass cullet to manufacturers across Indiana. The company prioritizes passionate advocacy, operational excellence, and collaborative partnership to convert recyclable glass into valuable products.


3. Preparation & Cleaning

Once at the Strategic Materials, Inc. facility, the glass goes through a cleaning process to remove any lingering contamination, and is sorted again. Magnets and charged currents remove metals while air vacuums remove light materials like paper, plastic, or organics. Any contamination that is recyclable elsewhere, like most metals, is also recycled.


4. Sortation

Optical sorters are then used to separate the glass by color and also remove non-recyclable glass materials like ceramics. There are three primary colors of glass used in packaging—green, amber, and flint. Clear glass is known as flint and is primarily used for food packaging. Amber glass is most used to make beverage bottles - especially beer - for the UV protection it provides. Green glass is often used for packaging wine and olive oil.


5. Crushing & Screening

After cleaning and sorting, glass recyclables are crushed into cullet and sorted using screens with different sized holes. Different sizes of cullet have different uses—larger pieces which are 5/8 inches are used to make new glass containers. Cullet smaller than5/8inches is often ground into a fine powder, which can be made into other glass products like fiberglass or abrasives. After processing the glass into cullet, SMI sends the cullet to manufacturers across Indiana to make brand new products from your recyclables.


6. Making New Glass Products

Indiana has many companies that use recycled glass to make new products. Some examples of these companies include Knauf Insulation which makes fiberglass insulation; Owens-Illinois, which manufactures glass containers; and Ardagh, which manufactures glass containers.

Knauf Insulation

One user for the glass cullet is Knauf Insulation, a leader in sustainability, the circular economy, and glass recycling in Indiana. Since 1978, they have employed hundreds of Hoosiers at their plant in Shelbyville, Indiana. Knauf Insulation’s EcoBatt fiberglass insulation is made from thousands of tons of recycled glass cullet (about 10 railcars of glass, every day!), along with an eco-friendly binder made out of plants. In addition to their use of recycled materials, Knauf Insulation is committed to promoting the circular economy, increasing energy efficiency, and becoming zero-waste across their operations.


Another Indiana user of glass cullet is Owens-Illinois (O-I), located in Lapel, Indiana, a leading producer of container glass. The plant was built in the 1890s and was purchased by O-I in 1988. Many of O-I glass plants use recycled content to make new glass bottles and jars, with an average of 40% of the raw materials being glass cullet. In addition to using recycled glass, O-I also promotes circularity through designing and manufacturing refillable glass bottles, which can reduce waste even more. O-I recognizes that many communities have limited glass recycling options, and therefore has targeted initiatives aimed at growing and improving glass recycling.

Ardagh Group

Ardagh Group, is a glass packaging company with its North America group headquartered in Fishers, Indiana. Their manufacturing facility in Dunkirk, Indiana uses recycled glass to make products, with glass cullet ranging from 10 to 60 percent of raw ingredients. The facility was built in 1889, making it one of the oldest continuously operating glass manufacturing plants in the country. Ardagh Group values glass packaging as a sustainable way to contain food and beverages, both because glass is considered highly safe for food packaging and because of its recyclability.

Closing the Loop

Glass recycling is a valuable part of the circular economy, and it’s happening right here in Indiana! Indiana’s manufacturing industry has a large demand for recycled glass cullet because using recycled glass instead of raw materials provides many benefits. Manufacturers save energy and cost when using recycled glass cullet, which also can extend the lifespan of furnaces due to operating at lower temperatures. Additionally, using locally recycled glass makes supply chains more resilient. Because the materials are closer to the facility, transportation and procurement costs are minimized.

In fact, Indiana manufacturers demand so much recycled glass that if every Hoosier individual, business, or organization recycled all their glass, it would be used to make new products close to home. Despite the great need for recycled glass, Indiana is currently not capturing enough of it for recycling—but you can help by recycling all the glass you can and encouraging others to do the same. You can also support organizations, like Circular Indiana, who are advocating for policy changes to support glass recycling.


To learn more about the different commodities, how they fit into the circular economy, and the organizations doing circular work in Indiana, make sure you subscribe to our newsletter and follow @CircularIndiana on social media!

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