BSEE-JUL21-P08 Environmental Awareness_Layout 1 08/06/2021 10:43 Page 8
BSEE
Silicone is a bit like concrete. It’s everywhere. It’s invaluable. But unless you’re working directly with the material no one ever really stops to think about it. And like concrete helps to keep a building standing, so silicone (or more precisely, silicone extrusions) help to keep the contents within that building working. That’s because in our modern, technological world, we are increasingly reliant on machines and dynamic systems with moving parts. And silicone extrusions are key to keeping those moving parts operational.
T
he food processing industry is no exception. Various types of silicone tubes, cords, strips, profiles and gaskets co-exist all
throughout food production. And silicone’s low density makes it perfect for compression seals and dampening on food production lines. Specialist FDA-approved grades are required to do this. And because it has certain advantages over competing materials that extrusions are made of, it has come to dominate much of the food processing industry.
For example, silicone is more flame resistant than natural rubber, making it safer in the event of fire. It also has a wider tolerance for more extreme temperatures (hot or cold) and is more resistant to chemical weathering and ultraviolet radiation. Yet despite all of these industrial advantages, there is a problem with the general culture around how we treat silicone once it has served its purpose, and how we treat it in comparison to other chemicals.
Silicone and recycling
The truth is, not much silicone produced today gets recycled. Silicone is somewhat difficult to recycle because it can be hard to break down. But this stubbornness is also what makes it environmentally friendly in a way. Silicone does not break up into microplastics like plastic does. It doesn’t react with any other chemicals. It resists biodegradability, and this is actually beneficial because it means silicone does not disperse throughout the environment.
As a general trend across all the industrialised nations, the silicone we produce en masse is kind of just accumulating or sitting around. It would take about 500 years for silicone to eventually start breaking down. So that means all of the silicone not already recycled or reused is still out there today. This may be due to a lack of urgency. There is little evidence that silicone is harming the environment, so there is little motivation to do something about it. But silicone usage is increasing across multiple industries, and especially in food processing and production.
These weather-resistant properties are what makes silicone recycling more difficult, which is another factor
which may be behind the delay in the mass mobilisation of recycling efforts. There are many companies that already specialise in silicone recycling, yet I have heard arguments from within the industry that to properly recycle silicone would involve having it carried away by “the tonne-load”. This way of thinking must be changed. And we should also work across the wider industry to implement a wider strategy of networking and accessibility that makes mass recycling or silicone desirable, feasible, and affordable. Currently, methods to break silicone down include tearing it into little pieces and then exposing it to both high saline and high- temperature environmental conditions — in which deliberate chemical reactions begin to break down the silicone’s bonds. But even if silicone isn’t recycled it can be repurposed and reused. For example shredded silicone can be used as rubber mats.
Silicone and siloxanes… are they a problem?
Silicone is one of the preferred materials to use in the food processing industry, because it is practical and cost-effective. Importantly, FDA-grade silicone is considered very safe for use in food processing. But inevitably, like all materials, it’s possible for trace elements of silicone (siloxanes) to “crossover” into the food products themselves. And this can understandably cause concern. This crossover is more likely to happen in silicone-food packaging and if the food itself has a high fat content — not necessarily with silicone extrusions in an industrial setting. Most of the crossover siloxanes are cyclic type siloxanes. They are odourless and colourless, and are sometimes added deliberately to creams and
8 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JULY 2021
moisturisers. There is no real world evidence to suggest they are harmful to human health and the environment. But naturally, people still worry about them and in some cases crossover levels are close to the “1000 Dalton limit”, which is the general limit for absorption of molecules in the stomach. Anxieties about silicone has resulted in the European Chemicals Agency (ECHA) and the European Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) limiting three types of silicone — D4, D5, and D6 to either 0.1 per cent by weight in products or to ban them
altogether. This decision is currently being challenged by the Global Silicones Council, who believe the EU came to the decision by flawed reasoning. The EU is the only place where such a ban has come into force.
So what can be done to put these fears to rest? Well, while the Silicones Council and EU battle it out, there are things that could be done in the meantime. According to a study by the Technical University of Denmark, the answer is more intense curing. Silicone rubber “curing” is the process of turning it from a liquid state into a solid. To me, the answer to this problem is obvious. It involves more transparent and better regulatory standards to ensure the curing process is carried out to higher standards that will snuff out siloxane crossover.
In the meantime, the industry will need to keep monitoring siloxanes and to comply with the current regulations imposed by law where they operate. And despite the tightened EU regulations, it could be the stimulus the industry needs to help it find silicone alternatives to D4, D5 and D6 that satisfy everyone with their safety, including the EU.
Conclusion
With a rapidly growing food processing industry, and increasing reliance on silicone to service that industry, it seems clear that silicone is here to stay. There is no real world evidence that it is harmful, but not everyone is convinced. Hence the EU’s current stance is more of a “precautionary principle” than anything.
But silicone is a very important raw material for future development. And especially if we are to reduce our carbon emissions footprint on Earth. It has been estimated that for every tonne of C02 that is used to produce silicone, its application ends up saving more than nine tonnes in the long run.
The key then, is putting to bed once and for all environmental fears. And that means working to find types of silicone that are absolutely safe, so that everyone is satisfied. And remaking our lackadaisical culture from one that isn’t all that keen on recycling, into one that is.
ENVIRONMENTAL AWARENESS
Working to make silicone safer and more sustainable in the food industry
About the author
This article was written by Matthew Bishop, Operations Manager at Viking Extrusions, a company that manufactures extrusions, including those of the rubber silicone type. Their products can be found throughout and in virtually all industries.
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www.bsee.co.uk
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