Is Your Silicone Spatula Sustainable?
The story of those colourful kitchen accessories starts in a surprising place: a sand mine.
Have you checked out your local home-goods store’s baking section lately? You may have noticed a rainbow of cooking utensils—baking molds, cupcake liners, baby bottles, you name it—lining the shelves. Made from the soft, rubber-like material we know as silicone, these items are easy to use, easy to clean, and easy on the eyes. And they’re made from an element that comes straight from the earth: silicon.
From the earth to your kitchen
Silicon (pronounced SIH-la-kun) is the 14th element on the periodic table. It’s also the building block of that mixing spoon you’re holding. Despite being the second most abundant element on Earth (it makes up about 27% of the Earth’s crust), silicon is never found on its own. It’s usually bound to oxygen as a compound we call silica.
What we think of as sand is usually silica. It’s extracted from the earth by quarrying (or open-pit mining)—a process that disrupts natural features and habitats, like lakes, rivers, and shorelines.
Then, there are some ancillary environmental effects. Moving silica to a silicone manufacturing plant requires some form of transportation, which releases greenhouse gases into the atmosphere. And the furnace that heats the raw silica in order to separate out the silicon requires a lot of energy input. As with all materials, the production process is cleaner if that energy comes from a renewable source.
To understand how sandy silicon becomes rubbery silicones, we have to briefly go back to chemistry class. When making silicone (rhymes with “bone”), scientists have to isolate the silicon from silica by melting it with carbon in a very hot (upwards of 1700oC) furnace. The carbon and oxygen combine to produce carbon dioxide, separating out the silicon. This means that a greenhouse gas is a byproduct in the isolation of silicon. But whether it’s released into the atmosphere or captured in the process depends on the manufacturer.
To make the silicone we use at home, raw silicon is combined with oxygen, hydrogen, and carbon, explains Michael Brook, who holds the chair in sustainable silicone polymers at McMaster University’s faculty of science in Hamilton, ON. To integrate the four elements, silicon is combined with a chemical called methyl chloride—which itself is created through a reaction of methanol and hydrochloric acid—in a reaction known as the Rochow Process. The product is a liquid form of silicone, also known as a “silicone oil.” Next, cool liquid silicone is either injected under pressure into heated molds or poured into hot compression molds. The heat cures the silicone into the final product—like your kitchen spoon.
Baby bottles make their mark
Scientists have been experimenting with silicone for decades. Though the term was coined in the late 1920s, it gained popularity during World War II, when scientists began looking for alternatives to natural rubber as supplies were cut off during the war. By the 1960s, silicones were used in baby bottle nipples, which, Brook says, was transformational for the material. People started to think, “If it’s safe enough for my kid to suck on, it might be safe for a consumer product,” he says.
The first silicone spatula showed up around the 1990s. This food-grade silicone—meaning it has to adhere to health and safety regulations—gained popularity for its many useful properties in cooking. It’s durable, flexible, liquid-proof, resistant to high temperatures and stains, and free of harmful fillers like bisphenol A (BPA), which are often added to plastics to enhance their properties and reduce costs, but can have devastating health effects.
Brook says he doesn’t see any human safety issues with food-grade silicone. “I think that silicones offer a lot of advantages,” he says. “One of them is that they’ve been around for a long time. And food-contact silicones are not the same as the silicones you would use in your bathtub to seal it to the tile, for example.”
Experts at Health Canada agree. They note: “There are no known health hazards associated with use of silicone cookware. Silicone rubber does not react with food or beverages, or produce any hazardous fumes.”
One thing Brook says to watch out for is the dyes used in cookware products. “Silicones are clear,” he says. So if you’ve got pastel-coloured cupcake molds, or a bright red spatula, that means something’s been added to the product—not necessarily something harmful, but something you might not know the properties of.
He adds that silicone oil, which is part of the manufacturing process, can sometimes leach out of silicone products over time, though it happens in such small quantities that you’re unlikely to notice, and it’s perceived to be safe for human consumption at those levels.
An alternative to plastic?
Silicone culinary tools like molds or utensils are meant to replace items made from plastic and metal. “As someone who has tried to clean rusty bread tins and basically given up in disgust because you can never get them clean,” Brook thinks silicone in the kitchen is a worthwhile investment.
He also mentions that silicones are more thermally stable than most plastics, especially the cheap plastics we sometimes find in the kitchen, which means silicone products will ultimately last longer with regular use.
But not all silicones are created equal. Look for products that are marked food-grade or GRAS (Generally Recognized As Safe). And, to check whether the silicone in your shopping cart has harmful fillers in it, give it a twist. If the colour changes, it’s likely got something else in there. Pure silicone doesn’t change its colour, even when twisted.
From your kitchen to the bin
When it comes to disposal, silicone can be recycled, but not in your everyday blue bin—it needs to be sent to a recycling facility that can handle silicone, like commercial recycler TerraCycle, which accepts hard-to-recycle materials mailed in by individuals. And even then, it’s usually downcycled into a lower-grade product. Recycling facilities mechanically break down used silicone before mixing it with fresh silicone to make products such as recycled silicone molds, playground mulch, or building insulation.
But since the recycling process isn’t available on doorsteps, many people toss old silicone products into their garbage cans, where they could potentially become an issue, because silicone rubber isn’t biodegradable.
The best way to keep your kitchen green is by asking yourself whether you really need a new product, and buying secondhand when you do. If you ultimately do go with silicone, give it another life by finding a recycling facility when you’re done with it.
Print Issue: Summer/Fall 2022
Print Title: The Story of Silicone