By: Weez


When considering glass packaging, it can be helpful to have an idea of the costs: both monetary and environmental. There are a lot of proponents and debunkers out there, and I found that there’s more to the glass issue than meets the eye. So, I dug up some information that just might shed some light on the surprisingly complex issue of manufacturing glass packaging materials.

First, let’s make sure we’re clear on glass (yep, I totally went there). There are two main types: 

  • Virgin glass is made from newly collected, raw materials and it is made up of three primary ingredients: soda ash, sand, and limestone.
  • Recycled glass is made from previously used sources that have been crushed down into cullet. Recycled glass may contain a mixture of cullet and virgin materials, and in fact, often does.

Each type of glass has its own manufacturing process from material extraction/collection through end of life. Virgin glass requires raw material extraction whereas recycled glass requires, well, recycled glass. Raw material extraction is generally more cost effective than the collection of recycled materials, but the land use and destruction caused by raw material extraction is an environmental red flag to some who would rather pay (or get paid) to collect recycled glass and thereby “save the planet.” 

Both virgin and recycled glass require the use of fossil fuels throughout their manufacturing process: procurement, transportation, and production. Procurement and transportation help to take up about 25% of the total energy requirements of glass manufacture and melting glass accounts for 75%. This means that production is a huge deal, and if we are to focus on reducing any negative impacts of this industry, this would be a good place to target. 

Glassmaking furnaces are designed to use natural gas, oil, and some electricity. They run continuously over the course of their lifetime, which is generally 10 years or more, and tend to operate at 50%-60% efficiency. Depending on their size they can produce up to 1.4 million tons of glass over their lifespan (1,000 tons per square foot of melter surface) and up to 650,000 tons of CO2 per year. Furnaces and other components are cooled with water, and it is estimated that it takes over 18,000 gallons to produce 1 ton of glass.

Raw virgin materials require 1500˚C in order to melt, and some components (like limestone) produce CO2 when exposed to these high temperatures. Per ton of virgin glass, about 8 tons of CO2 is emitted. Recycled material (cullet) requires 1000˚C in order to melt and does not produce CO2 when heated. Per ton of recycled glass, about 1.5 tons of CO2 is emitted. Cullet lowers the melting point required to make materials molten, thereby producing a 30% energy savings. And if 100% cullet is used it could allow for up to 50% emission reduction when compared with glass made strictly from raw virgin materials. All of this implies that in choosing between the two types, recycled glass is clearly a better option (ooh, gotcha again). 

Here’s the kicker: there’s virtually no such thing as virgin glass any more. Glass producers know the cost-saving benefits of using less heat per batch (i.e. less fuel required), and many of them know the environment-saving benefits too (less CO2 produced, less land used), so most glass today is made with at least 30% cullet.

So why are we even talking about virgin glass? Well, it’s more about the materials than the final product. In the U.S. only about 30% of glass packaging products are recycled. So, if we wanted to have a truly closed loop in which we only make new glass from recycled glass, we’re about 70% off the mark. This is one reason that virgin raw materials are still used. 

Now, don’t get me wrong, this is not simply a matter of raising awareness and getting more people to recycle – although, that would help. Rather, this is often a matter of infrastructure and cost. Many recycling programs in the U.S. have cut glass from their menu entirely, and often when cullet is available, complications remain in using it. Here are a couple of the many reasons why:

  • Our single-stream approach to recycling is inefficient and therefore expensive. Aluminum, plastic, and glass are put in bins together, so they must be sorted before recycling can occur. Glass must be further sorted by color: clear, green, and blue. Multi-stream recycling (where each material has its own bin), results in 90% of the glass it collects being recycled, versus 40% recycling rates for single-stream systems where glass is often contaminated. 
  • Distances between facilities, suppliers, and buyers are great and this leads to costly transportation fees that are often deemed “not worth it.” 
  • If the price of cullet is too high, procurement companies won’t buy it. And if the quality of cullet is too low, glass companies won’t buy it no matter what the price is. In this way, the cullet market suffers from the goldilocks effect. There is also the matter of availability. Some glass producers require only blue cullet, others green, and still others clear, while some require mixed-color cullet. The single colors are undoubtedly the most difficult to supply, as quality sorted materials add steps to the process, and in a single-stream recycling system contamination of all available glass is a prominent issue, so mixed-color cullet can suffer the same quality problems as individual colors.

So, we find ourselves in a bit of a pickle jar (points for the attempt on that one?). There are so many benefits to making glass from 100% recycled materials. Unfortunately, here in the U.S., we’re not spinning that wheel because the price isn’t right.


  • For every 10% of cullet substituted in glassmaking mixtures, CO2 emissions decrease by about 5%. So, theoretically, if we used 100% cullet to make glass, we would reduce overall glassmaking CO2 emissions by 50%. 
  • Glass can be recycled infinitely without any loss of quality.
  • The use of cullet improves the glassmaking mixture and results in finer quality glass.
  • One ton of CO2 emissions are eliminated for every six tons of recycled glass used.
  • Recycled glass does not end up in landfills where it lasts for millions of years and takes up acres of space on its own. (Fun fact: every month we throw out enough recyclable glass to fill a skyscraper. This is literally like throwing money in the dump.) 
  • Recycling glass can reduce (or eventually eliminate) the need for mining raw virgin materials, which reduces (or eliminates) land use and destruction.
  • It is estimated that 500 jobs are created for every 100,000 tons of glass collected for recycling. 
  • Glass made from 100% cullet represents a closed loop system, which is ideal from an environmental standpoint. 


Not all glass is recyclable, and just 5 grams of non-compatible glass will contaminate an entire ton of recyclable glass. Glass packaging cannot be mixed with non-recyclable glass like drinking glasses or heat-treated glass (i.e. Pyrex), window glass, light bulbs, stained glass, opaque (white) glass, or auto glass. But you might be surprised how often well-meaning people toss these things in with their recyclable glass. It happens so frequently there’s a term for it: wish-cycling. When folks don’t know where it goes, they chuck it in the recycling bucket at wish for the best.

In a perfect world all glass would be recycled, and the manufacturing process would be non-resource intensive. Unfortunately, this is not the current reality. For all its benefits, glass is still an energy-intensive end environmentally expensive product that presents challenges throughout its lifecycle. This is practically the same case for other packaging materials, but each has its own unique circumstances. So, when considering packaging material in general, it seems to me that glass isn’t necessarily the clear winner (gotcha again – for the win!) and the best thing we can do is seek as much information as possible and make the choice that feels best to each of us. 

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