Plant-Based Sunglasses
- What Are They Made From Really?
This page was last updated in 2023.
When I first saw the term plant-based sunglasses, I was thinking would be rubbery, spongy glasses that could hold their shape in normal circumstances but would be completely useless if thrown around or placed in water.
Plant-based sunglasses are nothing like that.
I also thought plant-based meant that the frames were made from wood, bamboo or cork.
That’s not the case either. Although these types of sunglasses do exist.
When a company is claiming their sunglasses are plant-based it is typically because the sunglass frame is made from bio acetate. Bio acetate behaves just like traditional acetate frames however it is made without the injection of petrochemicals and is biodegradable at the end of its life.
Still a mystery and want to know more? Well, here I get into:
What is bio acetate?
Bio acetate is formed when cellulose is combined with acetic acids, acetic anhydride and a catalyst like sulfuric acid, to form cellulose acetate. A vegetable-based plasticiser is added to turn this into the final plastic-like substance known as bio acetate.
The product’s base is cellulose – a natural polymer that underpins the natural world, typically taken from tree pulp. Cellulose can be digested by a large number of microorganisms because it is a naturally occurring product.
The addition of chemicals like acetic acids, acetic anhydride and sulfuric acid, turns cellulose into cellulose acetate. This changes the biostability associated with cellulose but the substance is still recognised as a biodegradable polymer at this point.
Plasticisers are added to improve the plasticity and workability of the substance. The most efficient known plasticisers for cellulose acetate are petrochemical-based. Typically manufacturers use diethyl phthalate (DEP), glycerol triacetate (GTA) and triethyl citrate (TEC).
The resulting product is still known as cellulose acetate after the plasticisers have been added. Whether this is biodegradable or not is discussed below.
After the plasticisers have been added, the material is finished and ready to use. It is then shaped, cut and moulded into sunglass frames.
Bio acetate is made the same way. But the key difference between regular cellulose acetate and bio acetate is the fact that a vegetable-based plasticiser is used to turn the acetate into a plastic-like material.
Don’t believe this is possible?
Have a look at this neat little YouTube video which shows how plant-based materials found in your kitchen pantry can be used to make plastic:
In this example, glycerine is used as the plasticiser.
As mentioned, in traditional acetate production petrochemicals are used as the plasticiser. In bio acetate, vegetable-based plasticisers are used.
Manufacturers are silent on what vegetables are used to make bio acetate (trade secret presumable) however scientific reports reveal that natural-based plasticisers can come from vegetable oils like soybean oil, linseed oil, castor oil, sunflower oil, and fatty acid esters (FAEs).
Dyes are added to the bio acetate to give it its colour. And it can be mixed with other bio acetate sheets to form the patterns you see in sunglass frames.
Here is a video that shows how M40 bioplastic is created:
M49 is really a bio acetate (not bioplastic) and it is manufactured by the Italian company Mazzucchelli, a family business that has been making acetates for the sunglass industry for many years. They are the source material for many plant-based sunglasses on the market.
Are plant-based sunglasses truly plant-based?
Plant-based sunglasses made from bio acetate are not exactly 100% plant-based if you take the words “plant-based” to mean that the product has a high percentage of organic carbon. At best, by all published accounts, plant-based sunglasses are around 70% plant-based.
Surprised? I must admit I was very surprised to find that “plant-based” does not mean that the products are made entirely of natural products.
And how could it? It is unreasonable to expect something that looks, feels and acts like plastic to be close to 100% natural.
However, bio acetate is more plant-based when compared to traditional plastic or cellulose acetate frames.
A standardised test can be used to determine how “natural” a product is.
Reference test ASTM D6866 is a standardised test that determines the biobased carbon content in solids, liquids and gases. Bio-based means materials where the carbon source was directly in equilibrium with carbon dioxide in the atmosphere at the time of harvesting the crop.
This means that it tests how much of the product contains materials that are still in the form they were when they were present in the natural environment. These tests can report back what percentage of the product is still in its natural form and what percentage has been altered from the natural state.
They do this through 14C radiocarbon dating. Carbon derived from fossil fuels contains the 14C isotope, while carbon from natural sources lacks this isotope.
As mentioned, M49 bio acetate is frequently used in the sustainable sunglass market and the company that makes this material is more transparent than most about the composition of their products. They note on their website that their products have gone through ASTM D6866 testing and independent testing has confirmed that 68% of the carbon in M49 bio acetate is attributed to its natural origins.
Another manufacturer, Hong Kong-based Biotate, has reported their product contains 76% bio-based content.
The rest of the carbon in the product is attributed to carbon from fossil fuels.
Disappointed? Don’t be, because it’s not too bad compared to alternatives in the market.
Are sunglasses biodegradable?
On the whole, typical sunglass frames are not biodegradable. Moulded sunglasses using polymers of plastic (such as nylon) and metal framed sunglasses are not biodegradable, although they can be recycled. Sunglasses made from cellulose acetate are not certified biodegradable, but they can decompose under certain circumstances.
According to the International Union of Pure and Applied Chemistry (IUPAC): “Biodegradation is the degradation of the materials into environmentally acceptable products such as water, carbon dioxide, and biomass by the action of naturally available microorganisms under normal environmental conditions.”
This is generally what I am referring to when here when I refer to biodegradability.
Plastic sunglasses are traditionally moulded from polymers of plastics. “Polymers” is a really broad term.
In the sunglass world that usually means nylon and sometimes polycarbonate. Cheaper-quality sunglasses may use other types of plastics. All in all, being true plastics, they are made from fossil fuels and are not biodegradable.
Metal frames are typically made from stainless steel, titanium, nickel, beryllium and copper. Metals are also not biodegradable since it can take 50 – 200 years for metals to break down.
Lenses are made from either plastic (polycarbonate) or glass. And glass is also not considered biodegradable since it can last a long time without degrading naturally.
None of these materials is considered biodegradable. So by extension, your typical sunglasses are not going to naturally biodegrade.
But there is a possible exception – sunglasses made from cellulose acetate.
There are a large number of plastic sunglasses that are made from cellulose acetate. The most common name for acetates in sunglasses is Zylonite or Zyl. If you see this listed as the frame material, it means the frames were made from cellulose acetate.
The question of whether cellulose acetate is biodegradable or not is a complicated one to answer.
A scientific literature review on this topic depicted the problems in the diagram below:
It is widely understood that cellulose acetate is biodegradable, however, the degree of biodegradability can vary depending on structural and environmental parameters. That means the chemical structure of the acetate and the conditions that the acetate is placed in at the end of its life are the two main factors that will decide whether the acetate will degrade or not.
Cellulose acetate can be made in several ways, so its chemical structure can vary. The study noted above found that cellulose acetate requires a high degree of acetylation for good thermoplastic properties. This means more changes to the structure of cellulose are needed to get it to act like plastic. Unfortunately, this high degree of acetylation lowers the degradation potential.
There are ways to accelerate degradation, but this involves chemical intervention.
In the end, the study was largely inconclusive stating:
Biopolymers are inherently degradable in common natural environments although the time-frame differs greatly depending on the actual condition…
There is need for more systematic studies with thorough molecular level characterization of original structures and changes taking place under different environmental conditions to understand structure-environment-degradation relationships.
But they do note “general “environmental degradability” cannot be guaranteed”
What does this all mean? Well, it is biodegradable under certain circumstances but on the whole, there is no guarantee that it can degrade in the natural environment.
So I would say sunglass frames made from cellulose acetate are not biodegradable in the way we would want them to be.
But it’s a different story for bio acetate.
Are plant-based sunglasses biodegradable and compostable?
The key manufacturers of bio acetate have had their products independently tested and they have confirmed bio acetate is biodegradable. This has been tested against international standards which look at biodegradability in the natural environment. One company can also claim that their bio acetate is also compostable.
Three manufacturers of bio acetate were found online – Mazzucchelli M49, Bio Acetate S70 and Biotate. All three have been tested under ISO-14855 international standards for biodegradability.
According to the International Organization for Standardization, the term biodegradable is used to define any material that can be broken down by the enzymatic activity of microorganisms, sunlight and other environmental physical agents, into simple chemical compounds such as water, carbon dioxide and methane. Biodegradation is influenced by the chemical nature of the material to be biodegraded and by the biodegradation environment. In order to define a plastic material as biodegradable, the degree of biodegradation must reach 90% in an incubation time of no more than 6 months.
The degree of biodegradation of M49 exceeds 90% after 115 days of incubation and is therefore biodegradable. The S70 bio acetate manufacturers don’t give details of how quickly their material biodegrades, however they do meet the international standard. Likewise Biotate.
Furthermore, Mazzucchelli claims their M49 bio acetate is compostable.
There is a difference between being biodegradable and compostable as explained so clearly by Mazzucchelli:
Under the international standard ISO 17088: 2012, a substance is compostable if:
- At least 90% biodegradation occurs within 6 months.
- More than 90% is disintegrated – the residual mass with dimensions greater than 2mm must be less than 10% of the initial mass.
- The resulting compost has low content of heavy metals and no ecoatoxicological effect on plant growth.
- Absence of negative effects in the composting phase.
And M49 bio plastic meets this standard.
So plant-based sunglasses can be biodegradable and compostable.
But of course, this doesn’t apply to the whole sunglasses, just the frame.
And it should be noted that bio acetate is not the only substance that ticks these boxes. Frames made from wood and bamboo are also biodegradable and compostable.
But that’s another story.
Are plant-based plastics a better choice?
Bio acetate, as a plant-based plastic, is a sustainable alternative to traditional cellulose acetates or plastic frames. It is bio-based (the end product is mostly natural) and biodegradable (it decomposes into simple chemicals when exposed to microorganisms, sunlight and other natural conditions).
However, it is not a completely clean product and there are other aspects to consider.
Here’s what to like about bio acetate:
- Rather than using fossil fuel-based plasticisers, it uses plant-based plasticisers
- The plants grown to support the production of bio acetates are able to sequester carbon (see the diagram below depicting this)
- The substance is phthalate free. Phthalate is used as a plasticiser in cellulose acetate frames. The health issues were not covered here but health organisations note that some types of phthalates affect the reproductive system in animals. The effect on human health is not as clear
- The majority of the material is plant-based
- The material is biodegradable when compared to alternatives like cellulose acetate
- Biodegradation is essentially clean and does not harm the environment further
- There are compostable products available (M4 bioplastic)
Here’s what’s not to like:
- It is not always clear where the plants are sourced from and if they are sustainably produced
- There are reports that there are cheap eyewear factories in China that produce frames using bio acetate however they use harmful chemicals such as acetone to polish and glue the glasses together. The concern here is the harm to factory workers.
- The process involves the use of harmful chemicals (such as sulfuric acid)
- The end product is not completely natural and plant-based
It’s clearly not perfect. But it’s not all bad.
What to look out for when purchasing products made from bio acetate
There are ways to ensure the bio acetate used in your sunglasses meets the highest standard. The easiest way is to look out for trusted certifications.
Some of these include ensuring:
- The product is bio-based as determined under ASTM D6866
- The product is bio-degradable as determined under ISO 14855
- It is free of harmful plastiziers such as Diethyl Phthalate (DEP)
- It is manufactured in a regulated environment (for example under the Europeans Unions REACH chemical guidelines)
The manufacturers of M49, S70 and Biotate bio acetate met these standards.
As a consumer, you may not be able to check for all this yourself since a lot of brands don’t advertise where they get their source materials from.
Most brands that use M49 tend to mention it in their product specifications. Some of these brands are mentioned here: 9 Sustainable Sunglass Brands Worth Checking Out.
But generally, brands don’t mention where they get their materials from. So it can be hard to know whether a company is truly using sustainable materials.
If this matters to you, here’s a list of questions you may want to ask a brand that claims its frames are plant-based:
- Who manufactures the plant-based materials?
- What country is the frame produced in and what ethical work standards are in place?
- Where are the plant-based materials sourced?
- Are they sourced sustainably?
- Are the frame certified bio-based?
- Are the frame certified biodegradable?
Perfection is an ideal that is often unattainable. And when it comes to making sustainable consumer choices, it can leave you paralysed.
If your options are already limited, don’t feel paralysed by what has been discussed above. This was not meant to paralyse you or stop you from buying anything that does not meet the high bar discussed above.
Rather it’s been provided so you know what options are out there and what is possible. So you can keep your eyes open for products that are really worth supporting.
In the end, we have to do what is easy and works, but let’s do it with our eyes open.
xxx Tahsin
After more information? You may be interested in....
Don’t Throw Them Away – Practical Uses for Your Old Glasses – if you have old eyewear, don’t trash it! Explore this guide, which covers options to repair, reuse and recycle glasses.
Sustainable Sunglasses – Know What to Look Out For – learn about the different options available to make your sunglass purchase a sustainable one.
9 Sustainable Sunglass Brands Worth Checking Out – for a list of Australian brands making sunglasses from sustainable materials and a summary of the pros and cons of each.
Sustainable Choices for Your Eyewear – Your Options Covered – for information on reusing old frames and lenses and where to get glasses second-hand.
Replacing New Lenses in Your Old Frames – Is it Worth it? – for further information about getting new lenses into your existing frames, in particular, how much this will cost
7 Sustainable Eyewear Brands Worth Checking Out – for a list of Australian brands making prescription glasses from sustainable materials.
Recycled Plastic Sunglasses – Innovations Worth Supporting – learn about the types of recycled plastics used in sunglasses and the different brands that sell this sustainable option.
A Close Look At Bamboo Sunglasses – Sustainable or Not? – for a great overview of bamboo as a material source, allowing you to judge whether it is a sustainable option or not.
Recycled Metal Sunglasses – From Waste to Wearable – discover the unusual source materials used in recycled metal sunglasses and the studies that show they are a sustainable option.
