Recycle Silicone: How to do it?

Silicone is a synthetic polymer derived from silica, and it is being touted as an eco-friendly alternative to traditional plastic. Silicone is a cross between synthetic rubber and plastic and can be used to make soft rubber-like items, hard resins, and fluids.

Chemically, silicone is polysiloxane, which means it has a silicon-oxygen backbone. What backbone? Like plastic and silicone, polymers are made of repeating molecules, called monomers, joining to form a polymer.

This polymer structure is what gives plastics their durability and strength. The backbone is the main molecule in a polymer, bound by other side chains. Now plastics are made up of hydrocarbon monomers- molecules consisting of carbon, hydrogen, and oxygen- so they have carbon-carbon backbones.

The silicon-oxygen backbone of silicones comes from silica, sand, and quartz and is the most abundant mineral on planet earth. In contrast, plastics are derived from the petroleum refining process and are linked to the use of fossil fuels.

But silicone does have hydrocarbon side chains that give it its plastic-like properties. The silicon structure also means that silicones can theoretically return to the soil when thrown away, but it is much more complicated than that. We will talk about it later in the article.

The process of creating silicones is energy-intensive. Turning silicon dioxide (silica) into silicon requires a large amount of heat and carbon. Then why is silicone so popular?

Why is Silicone Popular?

Silicone is an elastomer, which means it has elastic properties. It thus acts like rubber, but its strength and resilience are far greater than natural rubber. Silicone creates a perfect water seal, so it can be used to waterproof or seal various items. It, however, allows many gasses to pass through. 

Silicone does not support microbial growth and can be easily sterilized due to its heat resistance, making it a prime material for medical devices that need air to pass through.

But the most useful property of silicone is probably its heat resistance: Silicone is thermally stable through temperatures ranging from -100 to 250 degrees Celsius.

Unlike a carbon-carbon backbone that is prone to distortion and disruption by heat, an inorganic silicon-oxygen backbone is far more resilient. This heat resistance also gives silicone another of its most valuable properties: insulation.

Silicone is an excellent thermal and electrical insulator, meaning it does not allow heat or electricity to pass through.

On top of that, silicone is claimed to be chemically inert and resistant to chemical action. While most plastics leach out harmful chemical substances, silicone is said not to leach anything under normal temperature ranges.

This, combined with its non-stick and non-staining properties, makes silicone very useful in cooking, serving, or storing foodstuffs.

Uses of Silicone

Medical uses:

Due to its inert nature, silicone is highly biocompatible- it does not cause any reactions when it comes in contact with biological tissues. This quality is beneficial for making medical equipment like seals, gaskets, coverings, tubes, etc.

Apart from manufacturing medical equipment, silicone’s biocompatibility makes it the material of choice for use in gel form in cosmetic surgery as breast implants, pectoral implants, testicle implants, and contact lenses.

“Medical grade” silicone is the best and most inert grade of silicone. Apart from the above uses, it is also used as an oil to replace the fluid inside the eye following a surgery to remove said fluid and treat scars.

Personal care:

Silicones have significant applications in the cosmetic and personal care industry. Silicones are added as ingredients to skincare, haircare, and other products, like hair conditioners and hair coloring agents.

Silicone is also used to make menstrual cups. Thanks to silicone’s inertness and thermal stability, these cups can be cleaned and sterilized after each use multiple times.

Using a menstrual cup can greatly reduce the use of disposable sanitary pads that need to be thrown away after each use and pollute the environment. This can also cut down the cost of personal hygiene for many women worldwide.

Baby bottle nipples and pacifier teats are also silicone because of the same qualities. 

Cooking:

Silicone is becoming more and more popular in the cooking landscape as a material to make lids, pots, containers, spatulas, and much other stuff.

Chemical inertness, non-stick and non-staining properties make silicone helpful in making storage containers. Supreme water resistance allows for creating near-perfect seals for making lids. Heat resistance is useful in making spatulas and microwavable cookware that can withstand temperature extremes.

According to Health Canada: “There are no known health hazards associated with silicone cookware. Silicone rubber does not react with food or beverages or produce any hazardous fumes.”

And back in 1979, the U.S. Food and Drug Administration (FDA) determined that silicon dioxides, essentially the core ingredient in silicone, were generally recognized as safe to use even in food-grade contexts.

So, authorities generally consider silicone to be safe for use in cooking and storing food. However, there have been some concerns over silicones leaking chemicals into the food they were used for cooking or storing.

One study found that siloxanes from silicone can leak into food, especially fattier foods, and at higher temperatures, above 300 degrees.

There are also concerns that the use of silicone in food preparation may lead to infertility, hormone disorders, and even cause cancers.

These fears are increased because the FDA had not published any other guidelines after 1979, which was a decade before the first consumer-grade silicone cooking products hit the market. This raises the question of whether the guidelines apply to modern-day products.

We recommend avoiding microwaving or cooking oily or fatty food in silicone containers. Spatulas and brushes aren’t so much of a problem because they come into contact with hot food for only a short time. Try using glass or metal utensils. 

Other than these, silicone is also used to make lubricants, insulation for wires, thermal pastes, molds for making other items, dry-cleaning solvents, and brake fluid, among other things.

Yes, we use a lot of silicone, and that means we produce a lot of silicone as waste. That brings us to the next question.

Is Silicone Recyclable?

Yes, silicone is recyclable. Silicone products can theoretically be recycled at their end of life into new silicone products, and the process can be repeated. 

How to Recycle Silicone?

The way this is done is- old silicone products are shredded down into tiny pieces of silicone. These granules are then added to a mold for making new silicone products. Fresh silicone is then added to the recycled silicone, and the whole material sticks together.

While this does not have the same quality as new silicone, and recycling silicone is almost always considered downcycling, the structural integrity of silicone is mostly preserved.

So while silicone cannot be recycled an infinite number of times in practice, it can still be recycled enough to make a difference.

The Problem with Silicone Recycling

But, silicone recycling is costly. This is primarily because silicone is relatively new, and as such, recycling plants for silicone are novel and different from those recycling plastic.

While a recycler may have the capacity for dealing with plastic waste, recycling silicone means they will have to buy a costly and specialized machine.

That is why most curbside recyclers in the U.S. and worldwide do not accept silicone for recycling. It’s only possible if you find a specialized recycler who accepts silicone.

Otherwise, you will have to rely on take-back programs by companies that sell silicone products or use recycling programs from providers such as TerraCycle to properly recycle your old silicone items.

Recycling silicone properly so that it can be made into silicone products of quality similar to the new ones is even more costly. Thus almost all of the silicone that is sent for recycling is downcycled into stuff like playground mulch, insulation, and lubricant oils. 

However, with research and development ongoing, silicone recycling will hopefully soon be cost-effective. With time, the cost of setting up a silicone recycling plant will decrease, making more recycling opportunities available to the public.

But what happens to silicone that does not get recycled? Let’s check out the next section.

Is silicone biodegradable?

No. Not in the way glass or paper is. Plastics and related materials such as silicone are not naturally occurring, and we, humans, created these materials and started producing them a mere 100 years ago. 

While nature will probably eventually come up with a method to break down plastic, it will take millions of years for that to happen. So, for now, any discarded silicone that goes to the landfill will stay there, taking space and polluting the environment for hundreds or thousands of years.

However, silicone has an advantage over traditional plastics: it is generally not known to leak any toxic chemicals as plastic does. So the chances of soil and water pollution are lower.

Also, silicon does not break into fine beads as plastic does, and these microplastics are increasingly proving to be a health and environmental hazard. Even if silicone does break down, the end products are silica, naturally occurring.

Combine this with silicone items that usually last longer than plastic ones, and silicone does come out as a more eco-friendly option. However, do not let the green marketing from the silicone industry fool you into complacency.

Silicone does not belong in a landfill, it needs to be recycled, and producers need to invest in both recycling and research to make recycling silicone economically viable. 

Can Silicone be Incinerated?

Incinerating silicone is less polluting than incinerating plastics. Plastics give off soot and carbon dioxide, which is a greenhouse gas contributing to the earth’s rising temperatures, along with several toxic compounds if the burning temperature is not high enough.

Silicone mainly gives off silicon dioxide and water during incineration thanks to its silicon-oxygen structure. Silicon dioxide exists naturally in the environment and is not considered a health or environmental hazard.

However, inhaling such fumes regularly for a long time can be dangerous. Also, while silicone’s polymer backbone is silicon-oxygen, it does contain hydrocarbon side chains. These hydrocarbon side chains can produce toxic and harmful fumes when silicone is burnt, albeit in a smaller amount when compared to regular plastic.

Yes, you could incinerate silicone to get rid of it, and it would be more environmentally friendly than incinerating plastic. But “more environmentally friendly” is a relative term- burning silicone wastes a large amount of material, material that was costly to make in the first place.

It is said that the furnaces at silicone production plants are never put out to maintain the high temperatures silicone needs for its production. Burning discarded silicone means wasting all this energy that goes into production.

Always try for more environmentally friendly options like metal or glass, or find a recycler that accepts silicone near you.

Silicone in the Seas

Silicon, in the form of silica, is abundant in the sea. But silicone is not silicon, and it is a synthetic derivative of silicon that doesn’t degrade naturally. 

When silicone finds its way into the earth’s oceans, it stays there. Since silicone has better resistance than plastic, it doesn’t easily break down into small pieces and floats in its original form for decades.

Since it is inert, silicone does not release toxic chemicals into the marine environment, nor does it lead to the formation of microplastics. 

That is not to say silicone is harmless to the oceans. Marine wildlife can mistake small silicone products for food and ingest them, harming their health.

Conclusion

Silicone is an eco-friendly option when compared to plastics. But it is still polluting and non-biodegradable, and discarded silicone can harm the environment for a long time if not properly recycled. 

Since silicone recycling is costly, only specialized recyclers accept silicone as of now, and curbside recyclers usually don’t. You will have to find a recycler that accepts silicone or sticks to materials like glass or metal.