In this guide, we outline whether glass might be more sustainable than plastic, and vice versa.
We compare some of the key factors involved in the production, usage and waste management of each.
Summary – Is Glass More Sustainable Than Plastic?
Breaking Down Which Might Be More Sustainable
There’s a few main points to consider when is comes to comparing the sustainability of glass and plastic …
Glass tends to come from renewable and abundant resources like limestone, sand, soda ash, and other source materials
Plastic on the other hand comes from mainly non renewable petrochemicals and other additives
Plastic might be cheaper and has less of an eco footprint to produce compared to glass
Plastic does have an energy footprint to produce, and may use additives like plasticisers
Glass needs to be melted at high temperatures in a furnace, which might use a lot of energy
Recycled glass, waste glass, broken glass and glass cullet can reduce the environmental impact of producing glass (i.e. reduce the energy consumption and carbon footprint during production), but, there are challenges and costs involved with obtaining suitable and reasonably priced recycled glass, along with glass recycling presenting other issues to do with mixing glass, contamination, and so on
In countries like Australia for example, it’s also worth noting that reports from dirtcheaprubbishremoval.com.au and waster.com.au indicate that it’s cheaper to import some glass items like glass bottles than it is to recycle glass or recreate it, and glass ends up stockpiled, or in landfill, because there’s no viable market for the glass
Plastic may have a lower transport footprint than glass due to it’s weight
There’s also practical considerations such as glass being more prone to breaking than plastic, and not being as flexible of a material
Both are waterproof though when sealed
4. Waste Management (Disposal, & Recycling)
Plastic is recycled at a lower rate in general than glass in some countries (but it depends on the country, and type of glass or plastic item in question)
Glass can be recycled infinitely whilst plastic can only be recycled a certain amount of times before it may experience problems with losing it’s integrity and quality.
waster.com.au also indicates that some glass can be crushed and repurposed for use as glass sand in building materials and construction
Plastic pollution in the environment may be a more significant issue than glass pollution in the environment
Both materials take an extremely long time to break down, but plastic can break into micro and nano plastics that get into food and water supplies, and plastic can absorb and transport organic pollutants as litter or ocean debris
From an environmental perspective, how sustainable glass and plastic are might depend on the exact environmental indicator you are measuring (greenhouse emissions, energy use, water use, waste generated, etc), what stage of the product or material lifecycle you are referring to, the item you are talking about (a bottle, a container, etc.), the country you are referring to (the US, UK, a european country, and so on), and other variables.
Food and beverage type glass especially probably has more potential to be a material that is part of a circular economy compared to plastic, but in some countries, the recycling and waste management systems aren’t set up to optimise glass recycling.
Outside of environmental indicators and measurements of sustainability, plastic tends to cost less and be easier in general for businesses to produce and transport as part of their products.
Plastic is probably the more profitable material for most businesses to use.
Plastic may present issues to human health in terms of leaching of BPA and other chemicals when used in plastic bottles, containers, etc., plus potential issues with micro and nano plastics. Glass presents less of these issues.
Plastic may also lead to ingestion by, and entanglement for wild life and marine life.
Glass doesn’t seem to lead to as many problems for wild life.
Specifically with drink bottles, a high quality glass bottle that is re-used hundreds of times and can be recycled effectively and in a cost effective manner might be more sustainable in some ways than a single use plastic bottle
Glass vs Plastic: Comparison
General Sustainability Of Each Material
– What They Are Made Of
Glass is sourced from sand, soda ash, limestone and other additives.
Recycled glass can also be used in the form of glass waste/broken glass/cullet.
Glass is therefore mostly made from renewable and natural source materials.
It should be noted though that limestone usually has to be quarried, which has some environmental concerns
Plastic on the other hand mostly comes from non-renewable petrochemical feed stock such as crude oil and natural gas
From oberk.com: [Glass is made from raw materials where] Silica (sand), soda ash, limestone, and cullet (furnace-ready, recycled glass) are combined
[… glass comes from mostly natural abundant materials, but these materials may need to be quarried – such as limestone] (earth911.com)
Glass is a resource efficient material which is made of abundant natural raw material such as sand and glass waste (cullets) (glassallianceeurope.eu)
– Energy Used, & Greenhouse Gas Emissions In Production
Glass can be energy intensive because of a high heat furnace used to melt glass, and fossil fuels that can be used to provide energy for heating and melting.
Glass may take more energy during production than plastic.
[The production process and melting of flat glass uses fossil fuels and results in greenhouse gas emissions in the form of CO2, but also air pollution in the form of sulphur dioxide, nitrogen dioxide, and particles] …
Other environmental issues are water pollution, the use of non-renewable natural raw materials such as sand and minerals, production of solid waste and emission of volatile organic compounds (used in production of mirrors and coatings) …
A glass furnace runs 24/7 and cannot be stopped and cooled down during its lifetime (15-18 years). Most technologies can therefore only be installed during a furnace rebuild …
[… development of environmental techniques to minimise environmental impact are ongoing]
… fossil fuels [are] required to generate the very high temperatures needed to manufacture glass
Glass takes twice as much energy to produce [compared to plastic]
Despite the melting process for glass, some studies indicate ‘manufacturing [a] low weight PET bottle is [the] equivalent to manufacturing a glass bottle, which is heavier, causing carbon emission that’s similar to a PET plastic bottle’ (drkarenslee.com)
From oberk.com: [Raw materials used to make glass are melted at very high temperatures in a furnace, which uses a lot of energy]
– Using Recycled Glass To Cut Production Energy Consumption & Carbon Footprint
The production and use of glass has a number of environmental impacts …
New glass is made from four main ingredients: sand, soda ash, limestone and other additives for colour or special treatments. Although there is no shortage of these raw materials as yet, they all have to be quarried, which can damage the landscape, affect the environment and use more energy …
The addition of domestic waste glass (known as cullet) to a furnace in the glass manufacturing process, substantially reduces the energy requirement and decreases CO2 emissions
From cen.acs.org: [Using recycled glass in the form of] cullet [with new ingredient for new glass] benefits glassmakers, the environment, and consumers.
50% of the energy is used to recycle glass compared to making a new glass (drkarenslee.com)
Glass is a heavier material than plastic
– Transport & Delivery
Because of the weight and properties of glass, glass may be more expensive, use more fuel, emit more GHGs, and be less efficient with packing and transport space – all leading to a higher environmental footprint for the transport of glass products and containers than lighter materials like plastic
– Recycling Rate
Glass has a higher recycling rate at around an average of 33% for all types of glass containers and bottles in the US in 2015 (cen.acs.org, and gpi.org), compared to plastic which had a recycling rate of 9.1% in 2015 in the US (thebalancesmb.com).
In the UK, different glass types are recycled at different rates – soda lime silica glass is recycled at a far higher rate than other glass types like borosilicate glass, lead glass and glass fibre, that aren’t widely recycled (recyclenow.com via bettermeetsreality.com).
Windows, ovenware, Pyrex, crystal and other types of glass can’t be cross contaminated with food and beverage glass for recycling (gpi.org).
In some countries, glass has an average 90% recycling rate, and the turnaround for putting a glass container or bottle from the recycling bin back on the shelf as a new glass product can be as little as 1 month (several sources via bettermeetsreality.com)
– How Many Times Each Can Be Recycled
Plastic can only be recycled a finite number of times before needing to be downcycled, or sent to landfill, or incinerated. Plastic loses it’s economic value and quality after being recycled a certain amount of times. Glass in comparison, can be recycled an infinite amount of times
From cen.acs.org: [Glass has] an unlimited life and can be melted and recycled endlessly to make new glass products with no loss in quality.
– Ease Of, Efficiency Of, & Value Of Recycling
Different types of both glass and plastic can be difficult to recycle, can be inefficient to recycle, and both tend to have lower value as recycled material compared to other recycled materials like metal in current waste management systems with current facilities and technology.
Some challenges with recycling glass can be overcome, whilst some challenges are too costly or inefficient to fix.
Some curb side recycling organisations and facilities are choosing not to deal with glass because of increased processing costs and because they don’t have the proper equipment to clean glass properly [they choose not to or can’t upgrade recycling facilities and equipment] … but others are choosing to recycle glass
… glass recycling rates can be dependent on the city … [but] viability of the material, end markets, economics, supply and processing costs [all have to be considered with glass before recycling it].
There are some claims around glass recycling that broken and mixed glass are problematic, glass must be washed and cleaned, glass can contaminate other materials, and glass has no end market.
But, [in some markets] Demand for recycled glass exceeds supply, [and many issues surrounding glass recycling can be fixed with the right glass recycling equipment]
Glass can be more expensive to recycle than plastic (blog.theplasticbottlescompany.com)
– Secondary Uses
Both plastic and glass, if not able to be recycled, can have secondary uses across a range of applications.
Plastic can be incinerated for waste to energy (with technology that captures CO2 and air pollutants preferably)
– Environmental Impact Of Recycling & Other Disposal Options
Glass recycling may have some benefits in terms of energy and carbon footprint savings.
However, some reports indicate glass recycling might pollute more than plastic.
… glass recycling [can help save] significant amounts of raw materials … [and] natural resources …
Glass recycling also helps in saving energy [during the melting process] as cullets melt at a lower temperature than raw materials.
More pollution is created in the manufacture, shipping and recycling of glass [than plastic] (blog.theplasticbottlescompany.com)
Glass is more fragile and brittle than plastic, and is more prone to breaking.
Hard plastic may last longer than most types of glass, and increase it’s sustainability footprint from re-use (but, it depends on the type of glass and type of product or item in question)
Broken glass can be a health and safety issue in general, where as plastic tends not to be as much of a safety issue in general use (unless leaching, or even micro plastics is/are an issue)
– Human Health
– Impact On Wildlife
– Pollution Waste Created
More pollution is created in the manufacture, shipping and recycling of glass [than plastic] (blog.theplasticbottlescompany.com via bettermeetsreality.com)
– Litter & Pollution In The Environment
– Break Down & Degradation
– Carbon Footprint
Several publications indicate glass has a higher footprint than plastic – ‘Glass creates more than 6 times the global warming gases than plastic’ (blog.theplasticbottlescompany.com)
But that footprint can be lowered with re-use of the glass item and the use of recycled glass partially replacing virgin glass (blog.theplasticbottlescompany.com and tappwater.co, via bettermeetsreality.com).
One source indicates ‘for every six tons of recycled glass used, the carbon dioxide emissions drop a ton’ (inquirer.com)
– Eco Impact Per Gram
Glass has a lower eco impact per gram for abiotic materials, water use, and GHG emissions indicators during production. But, glass is heavier, so the totals for final glass bottles compared to plastic bottles for example tend to favor plastic [i.e. similar plastic and glass items tend to favour plastic because of it’s weight](giynow.com)
– Eco Impact For Reusable Materials
Reusable glass is better environmentally across abiotic materials, water use, and GHG emissions during manufacturing compared to reusable plastic (giynow.com)
– Improvements In Each Material
Both materials have been getting lighter over the past few decades, as well as more eco friendly across various measurements.
So, there could be further improvements in the future environmentally for each material based on this trend continuing
Plastic vs Glass Bottles
When looking at bottles as an example, the more sustainable material can come down to several factors such as the types of glass and plastic used, how many times the bottle is re-used, what is used to make the bottle, how the bottle is disposed of, and other factors
The Sustainability Of Plastic
Read more about the sustainability of plastic in this guide
Other Factors To Consider
– Just as there are different types of plastic, there are different types of glass.
Each different type of glass can have a different sustainability footprint
– Using recycled glass like cullet makes a difference to sustainability compared to using glass purely from virgin resources
– The waste management systems, facilities and technology in a given country or State make a difference to the sustainability not just of different materials, but different waste items and products (because of how different waste materials and items are processed among the different disposal options at different rates)
– How long a glass product or item lasts, or how many times it can be used/re-used before being thrown out, impacts it’s sustainability footprint