Is silk a safe, biodegradable alternative to microplastics? Study says yes

Written by on July 25, 2022

Scientists may have found a new material that could act as a substitute for microplastics: Silk. 

According to a recent study, published in the peer-reviewed academic journal Small, this relatively simple material, something that has been known to humanity for thousands of years, may be able to be used in various items ranging from paint to agriculture products instead of microplastics.

This comes as nonbiodegradable microplastics have become an increasingly problematic issue around the world and after the European Union declared that they must be eliminated by 2025.

What are microplastics?

Microplastics, as their name implies, are extremely tiny particles of plastic. Specifically, according to both the European Chemicals Agency and the US National Oceanic and Atmospheric Administration (NOAA), it refers to any type of plastic fragment less than 5 millimeters in length, which would put it around the same size as an individual sesame seed.

Having said that, they aren’t all uniform and they can vary in size – so long as they are smaller than five millimeters – and shape.

View of Empty plastic bottles on the Dead Sea beach, on November 5, 2020. (credit: YONATAN SINDEL/FLASH90)

They are notably distinct in this regard from macroplastics, which just refers to any larger plastic waste like a plastic milk carton.

Microplastics can originate in many different ways, and they can be largely brought into two categories. These are:

  • Primary microplastics: Plastic fragments that are made to be five millimeters long or less
  • Secondary microplastics: Fragments from larger preexisting macroplastics. 

The second category makes sense since they’re just fragments of something larger that broke off. The first category, however, refers to those that are intentionally made that way.

This is because microplastics actually have a wide range of industrial and commercial uses.

What are microplastics used for?

Microplastics can be found in a number of products and industries. For example, skin care products often use microplastics as a natural “scrubber” to help with exfoliation. 

One type of microplastic in particular, known as microbeads, has been used in this regard, although they have also been used in some medications to make it easier for them to swallow.

Another type of microplastic, microfiber, is regularly used in a number of textile products for furnishing, cleaning, apparel and more.

For instance, microfiber towels are used to wash cars. Athletic clothing often has large amounts of microfabric inside it. They are also often used as a substitute for leather in certain clothing and accessories.

This is important because it showcases a large amount of benefits microplastics can have. For example, microfibers are known for their unique quality to essentially repel water rather than absorb it, as well as softness, durability and more. This makes them ideal athletic clothing, for instance, since it keeps sweat away from the body, letting it evaporate and cool down those who wear it. Microfiber-made accessories have advantages over leather since it can be more cosmeticized, is very durable, lightweight and essentially waterproof.

But a major use of microplastics can be seen in air blasting, which, among other things, helps remove rust and paint.

Overall, these uses – especially from microfiber textiles – are where most microplastic pollution comes from, along with fragmentation from tires that accumulate considerable wear and tare over time.

Why are microplastics bad?

Microplastic pollution has become a massive problem over the years. This is due to a combination of how widespread they are used and because plastic isn’t biodegradable, meaning it will only degrade over the course of hundreds and even thousands of years. 

As such, when microplastic items are thrown away for whatever reason, fragments will end up polluting the environment and staying there.

In fact, they are currently present in every single part of the environment.

Any source of pollution is something risky and worrying, and while microplastics and their environmental impacts are still emerging fields of research, the worry is present and evidence has already pointed at some serious dangers. 

And the worry of microplastic pollution has only gotten more prominent in recent years – since, indeed, this is nothing new and many experts have warned about it for several years – as the amount of pollution has only continued to grow and accumulate.

Most of these dangers can be seen in the water, as microplastics have had ongoing widespread accumulation in marine environments, continuing to buildup and reshaping the ecosystem’s landscape. 

Already, this has manifested in the considerable amount of microplastics that marine life consumed.

In fact, microplastics have been consumed by many different life forms – including humans. This is in part due to how microplastics don’t degrade easily, so if an animal consumes microplastics and that animal is then eaten, the microplastics are passed on to them.

While some cases of microplastics in animals have had noted ramifications, like how it can essentially slow down the digestive process in some animals or get stuck forever, there is still much further research to be done to see exactly how much this impacts life.

But there are other risks than just this pollution. For one thing, despite the many benefits of microfibers mentioned earlier, there also cons – specifically, they are often flammable. Not only that, but when they burn, they emit toxic gases.

This in turn leads to another problematic risk of microplastic. While they aren’t biodegradable and only degrade over extremely long periods of time, they do still degrade eventually, which can also result in releasing toxic compounds.

As such, it isn’t too surprising that calls for a replacement for microplastics are becoming louder.

Enter silk.

“The only way to have an impact is where we can not only replace a synthetic polymer with a biodegradable counterpart, but also achieve performance that is the same, if not better.”

Benedetto Marelli

The study

The researchers behind the study sought to look at a possible alternative to microplastics that will also be biodegradable. 

This saw them look at various alternatives that can be found, specifically based on silk. 

Silk is an incredibly versatile material and has been used by humanity in various capacities for thousands of years. Here, though, there may be other possible uses in the realm of microplastics.

Having said that, silk tends to be extensive. This can be seen in the high price tag on fabrics containing silk threads. This is because the process to make these fabrics can be very expensive to do, involving the incredibly painstaking taking apart silkworm cocoons.

But this doesn’t nearly require as careful of a process. Cocoons that aren’t of textile quality, for example, are perfectly usable in this context. It can also make use of discarded silk fabric. 

In fact, it is so simple and easy to do that not only will it be affordable, but the researchers think it can also readily be adapted for use in the preexisting equipment, meaning industries won’t need to shell out massive amounts of money to completely refurbish themselves for new material.

Another benefit of this product is that silk isn’t toxic or dangerous like plastic. It can be used safely in food and medicine and will naturally degrade in the body. 

But more importantly, not only is this a safer alternative to synthetic microplastics, but it’s also just as, if not more, efficient, according to the tests the researchers carried out. It also can be tailored to specific needs, with the silk-based material being able to be water-repelling and water-attracting depending on the need.

“The only way to have an impact is where we can not only replace a synthetic polymer with a biodegradable counterpart but also achieve performance that is the same, if not better,” explained Benedetto Marelli, a professor of civil and environmental engineering at Massachusetts Institute of Technology (MIT) who was involved in the study.

The benefit can also go further than that. Silk is, of course, made possible due to silkworms, and silkworm breeding and production had essentially been perfected thousands of years ago already. These small animals are very easy to culture and raise and exclusively eat just one thing: Mulberry leaves. These leaves come from mulberry trees, a fast-growing plant that has actually become an invasive species in some parts of the world like the US and Brazil.

There are some issues with silkworm farming, as the industrial process behind it nowadays uses considerable energy to produce the optimal heat. However, it should be noted that some places get this heat by burning mulberry trees, which means the food needed for silk cultivation itself can also act as the needed fuel.

Currently, the vast majority of silk production in the world is in China, where the practice originated in the first place. However, it is possible to export it elsewhere, especially since the incredibly difficult process to extract fine silk won’t be needed here.

The solution isn’t perfect, however, and it won’t fix all of the pollution or even all of the microplastic pollution. But it is still a major step in the right direction.

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