Packaging Matters

Glass Packaging (II)

Glass Packaging (II)

In this post, I’ll comment on glass packaging sustainability (LCAs and recyclability ), and a few recent innovations.

Please check  part I for the history of glass packaging, a summary of  the main manufacturing process, and some curious examples of glass bottles.


Glass is the preferred packaging for many products ampng other reasons for keeping the integrity of the contents, having a nearly zero rate of chemical interaction,  and therefore preserving the flavors and aromas. This fact contributes to avoid food waste (more on packaging and food waste on the first post of this blog).

So let’s begin to consider the pros and cons of glass packaging from a sustainability point of view, and the review a few LCAs for more through review:


  • Glass bottles can be remolded in to new containers an infinite number of times.
  • Glass packaging keeps products fresh. Products that are packaged in glass retain their pure form because glass in non-porous and impermeable it will not compromise the taste and aroma of the products inside.
  • Cullet (recycled glass) is added ( up to 50% or more. An additional advantage is that cullet  lowers the melting temperature of glass contributing to reduce the energy spent in creating the containers.
  • 80% of the glass that is recovered is made into new glass bottles and other products.
  • Glass is the safest material to use in a microwave or to reheat food items. Other packaging products have the potential to emit harmful chemicals or additives when heated to certain levels.


  • The high weight of glass can significantly raise transportation costs and its carbon footprint. The transportation disadvantage is twofold: 1) It is not possible to avoid sending empty containers to the bottling plant (as in the case of preforms  or  a wall to wall supply as in he case of PET bottles, or transport reels as in the case of cartons).  2) Once filled the final product is very heavy so sometimes it’s not possible to take advantage of the truck’s total volume (since the maximum weight is reached before this). Products that are packaged in glass cannot be packed as tightly as those with aluminum or plastic packaging, which means it requires more energy to transport glass.
  • Glass is brittle and susceptible to breakage from internal pressure, impact, or thermal shock. This characteristic increases the secondary packaging requirement for glass bottles (i.e. crates, cushioning, etc.) during transportation and storage.
  • Glass has to be melt to manufacture the contains, the high temperatures needed in the process make it very energy-intensive (usually burning  high quantities of natural gas).

In short: glass is heavy and needs a lot of energy to be produced.

Let’s see what the LCAs say:


I’ll show the main conclusions of some Life Cycle Analyses comparing glass bottles to other types of packaging:

– Glass vs. Plastic: Life Cycle Assessment of Extra-Virgin Olive Oil Bottles across Global Supply Chains (R. Accorsi, L.Versari and R. Manzini. Department of Industrial Engineering, University of Bolognia, 2015)

According to this analysis, glass less impactful than in PET, due to high fractions of package waste devoted to recycling (over 40%). Recycled PET (R-PET) has the lowest impact on global warming given all of the potential EOL (end of life) strategies, because the efficient supply of packaging couples with a good response to recycling. Even knowing the performances and practices of current waste management chains tends to support the adoption of glass bottles, there is still great room for advances and improvements in PET recycling processes, regulations and EVOO stakeholders’ practices.

LCA of Container Glass and comparison with PET, Beverage Carton, Pouch and Al Can AIGMF (All India Glass Manufacturers’ Federation, 2012.)

Here’s a table from this LCA comparing several scenarios for all the materials studied: 

Only PET shows worse results than glass for human toxicity and Photochemical Ozone Creation Potential.

-Life Cycle Assessment on Aluminium Can and Glass Bottle for Packaging 500 ml Beer (Rajat Nag, UCD School of Biosystems and Food Engineering, Dublin, 2015).

Hera the glass bottle seems to be more environmental friendly in terms of greenhouse gas emission. Use of more natural gas and less use of oil and electricity created the difference. The hotspot for the analysis is the natural gas  and electricity necessary for aluminium electrolysis.

And finally,  a review of several LCAs, from which I’ll show some interesting graphics:

Beverage Container Review . Final Report.  (T. H. Owen, K. Boyd. Thompson Rivers University. July 2013 )

Glass bottles have more impact in all stages:

However, glass seems more environmentally friendly than aluminum and PET if we consider these parameters:

Here’s the literature review studied in this report:

PET seems to be the best option in 3 of the 5 studies. Only one considers glass bottles (refillable) the most sustainable packaging.

The energy consumed in the manufacturing process, and the weight of the final product, are the main issues of glass packaging regarding sustainability.

Besides recycling, reuse is a key strategy to reduce glass container’s environmental impact. Systems to organize bottles collection, like Ecovidrio’s HORECA programme in Spain (for glass bottles waste from hotels, restaurants and caterers, which generate almost 50% of single use glass packaging waste) can increase dramatically the number of bottles recycled.


Regarding weight, lighter containers can be achieved by strengthening glass through new surface treatment. New technologies such as Narrow Neck Press and Blow (NNPB) forming process can help in such light-weighting efforts.

Let’s see what this process consists of:

As seen in part I, during the traditional Blow & Blow process, molten ‘gobs’ of glass are delivered into a mold known as a ‘blank’ or parison mold where the neck finish is formed. This partially formed bottle or parison is then blown  by a blast of compressed air to form the ‘parison’ of pre-form for the bottle against the walls of the parison mold cavity.

Source: The Future of Glass Forming Technology for the Manufacture of Lightweight Containers (Waste & Resources Action Program, 2008)

The thick-walled parison is then transferred to the final mold while the surface of the glass ‘reheats’ and softens again enough to allow the final container shape to be fully formed inside the final mold (by the application of either compressed air or vacuum). The container is then transferred to an annealing oven where it is reheated to remove the stresses produced during the previous stage sand then cooled under carefully controlled conditions

In the Press and Blow Method, the molten ‘gobs’ of glass are delivered into the parison mold and a plunger is used to press the glass into the parison shape. The final mold stage of the process is the same as in the Blow and Blow Process. Due to the use of a plunger, the overall glass distribution is better controlled.

NNPB is basically the same as the press and blow process. Using an improved plunger material – capable of withstanding higher temperatures – it became possible to make the plungers thinner,  in order to penetrate the narrow necks of the bottle’s parison. Parison pressing allows better glass distribution, and therefore better wall thickness equality. NNPB was one of the major process improvements in recent bottle production leading to potential weight reductions.

Here’s a video about NNPB:

Glass Recycling


The collection and conversion of cullet has been constantly developing over the years, to ensure as much glass as possible is distributed back into the production process. Cullet has a much lower melting temperature than its original constituents and therefore requires around 40% less energy to create the molten glass that forms the containers. In Europe in 2011, this meant the emission of more than 7m tonnes of CO2 was avoided, the equivalent of taking four million cars off the road.

For every 10 percent increase in the amount of recycled glass, or cullet, that is used to make containers, COemissions go down 5% and the amount of energy needed goes down 3 percent (see article).

It is difficult to separate from other materials collected in single-stream recycling bins, particularly if it is not removed early in the sorting process. Amazingly, up to half the glass collected in single-stream recycling is unsalvageable mainly due to contamination. Glass is also heavy to transport, a potential hazard to haulers, complicated by different colors and hard on equipment. Furthermore, it often involves paying someone to process, especially when contaminated with other materials.

Glass recycling. Source:

In the US  single-stream recycling programs  (in which all recyclables, are placed in a single bin) are quite commom. However conveninet, thiis system has mayor drawbacjs for glass recycling. Putting glass in that bin was really problematic.Glass is a very abrasive material so it does not perform well on conveyor belts and damages the equipment. But more importantly, it contaminates other materials. For instance, paper bales leave the sorting facilities with piles of glass embedded into the paper. There’s no real mechanical way to get the glass separated from all the other materials, just like there’s no real mechanical way to get other material separated from the glass.

More than 60% of glass products manufactured in the US are made from clear (flint) glass. This is usually favored by manufacturers, since their products can be clearly seen through the glass, but light exposure can cause products in clear glass containers to degrade. Also, generally, used clear glass products are recycled into further clear glass products and colored glass recycled into further colored glass products. This is why recycling centers require that clear glass be separated from colored glass.

Around 31% of glass containers produced in the US are brown or amber in color. Carbon, nickel and sulfur are added to molten clear glass to achieve the color. Brown and amber glass can only be recycled into further brown or amber products. Brown glass protects its contents from degradation due to sunlight, preserving flavor and freshness. Brown glass is the most common color of beer bottles.

Commonly used for wine bottles, green glass accounts for seven percent of the glass containers made in the US. Iron and copper or chromium are added to molten clear glass to produce green glass. As with brown glass, green glass can only be recycled into further green glass products. Green glass protects its contents from temperature changes and sunlight.

Unfortunately within the recycling industry, as colours of glass must be separated, a lot of recycled glass ends up in asphalt production, rather than as new glass products. This is a huge challenge to the industry and one that must be tackled if glass is to live up to its potential as an environmentally friendly option

Here’s a video about glass color sorting:

A study from WRAP in the UK  shows that most consumers would accept the move from clear to green glass (with a higher recycled content)

Source: The Case for Green Glass Containers, WARP

So the use of  gives businesses more confidence to use mixed-color recycled glass, which could strengthen the market and demand for recycled glass while reducing the amount of glass separation and sorting that takes place.

WRAP is also planning a larger-scale trial for mixed-color glass. The group is looking for assistance in developing and testing infrastructure for annually turning 30,000 tonnes of mixed-color cullet into bottles with more than 90% recycled content. The trial will look at packaging for a variety of products and hopes to uncover any roadblocks in sourcing, processing and manufacturing high-recycled-content bottles.

In the US  single-stream recycling programs sorting the glass by color won’t help — it will all still be thrown into the same recycling truck on pick-up day. An alternative is taking the sorted glass to a local drop-off location on your own. There are also local and specific coleection systems for glass, like this one for beer bottles, or this other onne from Innovative Glass Works to recycle 100% of the glass recovered in Quebec:


Most innovations in glass packaging are not very flashy. Most of them are related to bottle lightweighting (which only presents a real sustaibability imporvement if it doesn’t involve an increase in secondary packaging).

So I’ll just comment the ones I consider more remarkabale.

Functional shapes

Owens-Illinois, (or O-I for short) is a of glass pacakging company frquently appearing on innovation news. They have developed containers with a shape that optimizes funtionallity (pouring or dippping). See some examples below:

From left to right: Versaflow™, MyPour™, and Versaflip™ containers by O-I.  Source:

3D labels

Although not strictly speaking a glass packaging innovation, OI‘s EXPRESSIONS technology introduces photo-realistic and three-dimensional digital print to the container glass industry:


Source: Source:



An interesting curiosity. Online spirits retailer Master of Malt  launched in 2015 the world’s first single malt whiskies featuring “experimental” glass closures. The “innovative” closure is thought to eliminate the “undesirable aromas and flavours” resulting from cork, and are more “attractive and functional” than screw tops. The line was  discontinued in 2016.

The result of a four-year collaboration between OI and the the Portuguese cork manufacturer Amorim, the Helix cork  features a series of grooves that fit perfectly the threads inside the neck of the Helix glass bottle, enabling the user to remove the cork effortless, simply by holding and twisting the top. After opening, the stopper can also be re-inserted in the bottle in the same way.

In my opinion, reuse is the key factor to improve glass sustainability, however, it requires some effort to improve the bottle collection logistics. In the 70s and 80s, it was common in many countries to carry the empty bottle to the supermarket to get a discount. Let’s see if new technologies used in automatic collection points are a way to promoting glass collection and reuse.

September 2019,  Bruno Rey – The Packaging Blog –

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