What’s the Carbon Footprint of Sunglasses? Plastic, Metal, Cheap Sunglasses Emissions

Understanding the Carbon Footprint of Sunglasses

The carbon footprint of sunglasses is the sum of all the greenhouse gas (GHG) emissions produced during the lifespan of a single pair!³⁰

It begins with the collection and processing of the raw materials, continues to build through manufacturing, transport, and packaging, and eventually includes the degradation of the product at the end of its lifetime.

Carbon footprint calculation is achieved by adding up all of the carbon dioxide equivalent (CO₂e) emissions produced at each stage of a product’s life cycle, accounting for both direct and indirect sources.

To give an example: the heating and melting of plastics during manufacturing would be a direct source of emissions while emissions produced by employees commuting to and from the manufacturing plant would be considered an indirect source (see “Scope 1 and Scope 2 Inventory Guidance” and “Scope 3 Inventory Guidance”). ^31,32

An accurate calculation requires careful consideration of all relevant factors, and this is why relatively few companies have managed to provide life cycle analyses of their products.

There are many types and makes of sunglasses on the market, and many factors affect the carbon footprint of a given pair of sunglasses. Whatever type of frame a pair of sunglasses boasts, all sunglasses have lenses that are constructed from either glass or plastic.

Traditionally, glass lenses were favored for eyeglasses due to their clarity, focus, and scratch resistance. However, glass lenses are no longer the mainstream option for eyeglasses, as glass is more expensive, heavier, and more susceptible to breakage than the more versatile plastic lenses.

While many people still prefer and opt for glass lenses, unfortunately, there is not any readily available life cycle data on glass lenses for eyeglasses at this time.

Lenses are more commonly made from one of several types of plastic nowadays. Plastics such as CR-39,³⁴ polycarbonate, nylon, or acrylic are all popular lens materials.

A 2019 life cycle analysis (LCA) study by the Netherlands-based glasses company, Ace & Tate, examined the environmental impact of glasses made with CR-39 plastic lenses. The lenses, optical, sun, and plano (clear) averaged 7.5 in net weight.

Estimating for end-of-life treatment and excluding the consumer use phase (cleaning, maintenance), the study found that their optical lenses generated approximately .2 kg of CO₂e and their plano/sun lenses generated approximately .06 kg of CO₂e.¹¹ This is about the equivalent of driving one-tenth (.1) of a mile in a gasoline-powered vehicle.⁹

Plastic lenses can be treated and tinted to produce a variety of appearances and effects: blue light, gradient, mirrored, photochromatic, polarized, and solid tint.²⁰ Added steps in the manufacturing process and additional materials will marginally increase the overall footprint of the product.

Each of these varieties has its unique characteristics and advantages:

• Blue Light Lens: Filters out blue-violet light emanating from the sun and digital devices to protect the eye from strain and damage.⁶ The lens is created by adding a thiophene/benzene compound to divert blue light to the monomer (plastic).¹

• Gradient Lens: A darker tint at the top of the lens provides extra protection from overhead sunlight and the gradient makes transitioning between indoors and outdoors more pleasant.⁸ They are produced by adding a metal oxide to the monomer.²⁹

• Mirrored Lens: A mirror coating reflects light, decreasing glare and improving clarity.²⁷ The mirrored coatings are made from powdered oxides and lacquered plastics and vacuum sealed to the lenses.¹²

• Photochromic Lens: Reactive lenses darken in ultraviolet light and lighten in its absence. This effect is produced by embedding silver halides in glass lenses and naphthopyrans/spirooxazines (photochromic molecules) in plastic lenses.¹⁵

• Polarized Lens: A chemical treatment of polyvinyl alcohol (PVA) applied to the lenses helps to reduce glare.²

• Solid Tint Lens: A dark tint provides protection from UV rays. The tint is sometimes achieved via dying and sometimes through bonding a tinted film to the lens.¹⁰

More on Eyeglasses With Sunglasses

Some people who regularly wear eyeglasses prefer to use photochromic, or transition lenses, which allow them to combine their eyeglasses with sunglasses. These are more convenient as the individual isn’t forced to continually carry two pairs of glasses on their person.²⁵

Other eyeglass wearers may opt for clip-on or magnetized sunglasses that easily attach to their eyeglasses. Because eyeglasses require an energy-intensive edging process that sunglass lenses do not usually need, the carbon emissions from eyeglasses may be higher than most people would expect.¹¹

Understanding the carbon footprint of sunglass lenses is the first step to appreciating the environmental impact of this popular accessory. The following sections look at the different types of sunglass frames, what they are made of, and how they are made to determine which stage of the sunglasses’ journey contributes most to its environmental impact.

 The Carbon Footprint of Wood Sunglasses

Wood sunglasses are touted as a more environmentally friendly option as wood is a natural and renewable resource that biodegrades in nature. Both of these things are true.

But while there is no life cycle data available for wood frames at this time, this does not mean that wooden glasses are carbon neutral; they pack their own carbon footprint, too. This is because although a single pair of sunglasses does not require a large amount of wood, no one ever cuts down only one part of a tree.

Ideally, all parts of a tree, once felled, would be utilized and not wasted. However, there is invariable waste during the cutting process and after as wood is cut to the size and specifications required for various products.

Scrap parts may be incinerated, left to decompose, or incorporated into other products. When wood rots or burns, the embodied carbon it contains is released into the atmosphere, contributing to CO₂e emissions. Additionally, the machines typically used for cutting timber are primarily reliant on fossil fuel combustion which is extremely carbon-intensive.

On the upside, wooden sunglasses are durable, don’t require as many chemicals and synthetic materials, and don’t contribute to the same degree to the problem of “forever plastic.”¹⁹  Furthermore, wooden sunglasses are often hand-crafted, reducing carbon emissions from machine processing!

The Carbon Footprint of Metal Sunglasses

Metal frames have long been used for reading glasses, and many popular styles of sunglasses, such as the aviators and navigators, are also constructed with metal rims.

Frames can be made from several types of metal, such as aluminum, stainless steel, or titanium.  Note that most metal frames contain some small plastic parts, usually from acetate.

As all types of sunglasses share the same variety of lenses (mirrored, photochromic, polarized, etc.), evaluating the carbon footprint of the frames themselves is the surest way to compare metal sunglasses to their companions.¹⁷

The Ace & Tate LCA investigative report mentioned earlier evaluated two of their popular types of glasses: a metal-rimmed pair and a plastic-rimmed pair.

The metal-rimmed glasses examined here were made from a combination of stainless steel and copper/nickel, with small plastic and silicone parts. The manufacturing of the metal frames with plastic parts, including materials sourcing, accounted for approximately .8 kg of CO₂e.¹¹

The Carbon Footprint of Plastic Sunglasses

Plastic sunglasses are, by far, the most versatile and affordable variety of sunglasses. Yet, they are also more difficult to recycle and dispose of properly than their wooden or metal counterparts.

The most common plastic used in plastic frames is cellulose acetate,³³ or Zyl, followed by propionate.²³

The Ace & Tate study mentioned above also examined a pair of sunglasses with plastic frames made from cellulose acetate. The production of frames along with materials sourcing accounted for approximately 3.65 kg of CO₂e, a huge chunk of the overall product footprint.¹¹

What Is a Carbon Footprint?

People are still seeking to better understand “What is a carbon footprint?” and learning how to calculate carbon footprint manually. “Carbon footprint” is the term that expresses the environmental impact of a given source by evaluating the greenhouse gas emissions produced by that source.

Every human, company, activity, and entity in the world has a carbon footprint which can be measured by looking at all direct and indirect sources of emissions.⁴ Many carbon emissions calculators are available online that can provide reasonable estimates of carbon footprints in various domains.

What Every Person Should Know About Sustainable Sunglasses

Environmentally-minded individuals who have ever had to replace a pair of sunglasses prematurely may find themselves questioning the ethics of this type of purchase and wondering about more sustainable options.

Sustainable sunglasses can take many forms, but generally, manufacturers are striving to make frames for sunglasses from more eco-friendly materials while minimizing chemical use and CO₂e emissions in production. Many manufacturers are using a combination of plant-based materials and recycled plastics to directly address the growing plastic pollution problem around the globe.¹³

Biodegradable sunglasses may have wood or bamboo frames which will degrade in time. Others are made from bio-acetate, a plant-derived substance that can be made into plastic.

While this plant-based plastic biodegrades faster than petroleum-based plastics, consumers should always read the fine print. Even bio-acetate is very slow to degrade in landfill-type environments, so sunglasses disposed of improperly can still become a significant waste problem.^{7, 16, 22}

The market for eco-friendly sunglasses is certainly expanding, and it is fantastic to see plastic waste being cleaned up and used to make new products and research uncovering more sustainable ways to make beloved products.

However, for all of this to work, consumers must do their part. A circular economy relies on consumers to dispose of/recycle glasses properly to ensure that materials can be reused and do not end up in landfills and oceans.

What Recycled Sunglasses Are Made Of

Companies are getting creative in their approaches to eco-eyewear, and consumers can now buy sunglasses made from a variety of recycled items.

The most abundant source of materials for recycled sunglasses is marine plastic. Various companies and programs are using plastics cleaned from the ocean to create new sunglasses which then help to support the cleanup of more ocean areas.

Plastics from fish nets, plastic jugs and bottles, plastic caps, and even chip packets are being melted down and used to construct eco frames for new pairs of sunglasses and eyeglasses.^14,28

The downside is that plastics cannot be indefinitely recycled, as the materials begin to seriously degrade after a few cycles. Thus, eliminating single-use plastics should still be the goal for manufacturers and consumers.

The Carbon Footprint of Eco-Friendly Sunglasses

Several sustainability-oriented companies have made it their mission to craft products that address the problem of climate change. Eco-friendly sunglasses are one way that companies are making a difference.

By pinpointing the areas that produce the most CO₂e emissions and finding cleaner materials and methods, companies are reducing their products’ carbon footprints.

Karün Eyewear reports that its sunglasses made from recycled materials average 1.69 kg CO₂e lifetime carbon footprint, including the glasses case.⁵ Eco-Eyewear reports 1.703 kg for their biobased shades, 1.447 kg for recycled metal glasses, and 1.296 kg for their sunglasses made from marine plastic.³

Comparing these numbers to the Ace & Tate analysis reporting 3.65 kg of CO₂e for just raw materials and production of non-recycled plastic frames (no lenses, no transportation, no case, no retail, etc.), the climate benefit of eco-friendly lenses is readily apparent!

Other Tips For Reducing the Carbon Footprint of Sunglasses

The preceding sections discuss the merit of swapping conventional sunglasses for eco glasses which are designed with the environment in mind.

And while this is undoubtedly the best way to reduce the carbon footprint of sunglasses, it is not the only way!

Here are a few other suggestions:²⁶

1. Opt for metal, wooden, or recycled plastic frames over new plastic sunglasses.
2. Extend the longevity of a pair of sunglasses by treating them with care and performing regular cleaning and maintenance.
3. Repair scratched or broken lenses at home or pay a professional to replace old lenses.
4. Donate gently used sunglasses and eyeglasses to local charities.
5. Research local sunglasses recycling facilities for old eyewear that is not salvageable. Contact optometrists in the area to ascertain whether they collect used frames.
6. And of course, plant trees and/or donate to conservation efforts to help offset additional carbon emissions.

The average American relies upon sunglasses to protect their vision, and in 2023, sunglasses in the United States generated more than 5 billion dollars.¹⁸

With so many types of sunglasses on the market and variability in manufacturing operations and processes, it is difficult to nail down precise numbers to represent the climate impact of an individual pair of sunglasses.

It is, however, apparent that the manufacturing phase of plastic sunglasses is the largest contributor to the carbon footprint of sunglasses, and manufacturers and consumers can ameliorate the environmental burden of sunglasses by turning to alternate and recycled materials.

Frequently Asked Questions About the Carbon Footprint of Sunglasses