Australians call them “runners." The British know them as “trainers."
Americans refer to them as “tennis shoes” or “sneakers."
Whatever you call them, these rubber-soled, casual shoes
are worn by billions of people around the world.
Originally invented in the late 19th century,
these simple canvas and rubber creations have changed a lot
since they first hit the pavement.
Today, sneaker consumption is at an all-time high.
No country buys more sneakers than the United States,
where people purchase 3 pairs a year on average.
To meet this demand, roughly 23 billion shoes are produced each year,
mostly in factories across China and Southeast Asia.
But making shoes has become more complicated, more labor-intensive,
and in some ways, more dangerous,
for the workers involved and for our planet.
Shoe manufacturing accounts for roughly one-fifth
of the fashion industry’s carbon emissions.
Sneakers alone generate 313 million metric tons of carbon dioxide every year,
which is equivalent to the annual emissions of 66 million cars.
To better understand your shoe’s carbon footprint,
let’s dive into the anatomy of a sneaker.
For starters, the heel, insole, midsole, and upper layer
are usually made from synthetic textiles like polyester, nylon, latex,
and polyurethane.
Mining the fossil fuels that make up these materials emits tons of greenhouse gases.
And processing those raw ingredients into synthetic textiles
also uses a lot of energy, further compounding that pollution.
Some sneaker tops are made from natural sources like leather,
but tanning this material relies on chromium;
a carcinogenic chemical that can damage freshwater ecosystems.
The outer soles of most shoes are made of rubber
that’s gone through a process called vulcanization.
This technique adds sulfur to superheated raw rubber to create a material
that’s both elastic and sturdy.
Until recently, sneakers used natural rubber for this process.
But today, most outer soles are made with a synthetic blend of natural rubber
and byproducts from coal and oil.
Producing these materials accounts for 20% of a sneaker’s carbon footprint.
But more than two-thirds of the shoe’s carbon impact comes from the next step:
manufacturing.
A typical sneaker is comprised of 65 discrete parts,
each of which is produced by specialized machinery.
This means it’s cheaper for factories to mass-produce each piece separately
rather than manufacturing every part under one roof.
But the transportation required to ship these pieces
to one assembly plant emits even more CO2.
Once the components arrive at the assembly line,
they undergo cutting, pouring, melting, baking, cooling, and gluing,
before the final products can be stitched together.
The assembly of a typical sneaker requires more than 360 steps,
and accounts for the remaining 20% of a sneaker’s environmental impact.
The dispersion of factories fuels another problem as well: labor abuse.
Most brands don’t own or operate their factories,
so the plants they work with are in countries
with little to no worker protection laws.
As a result, many laborers earn below the living wage,
and are exposed to harmful chemicals, like toxic glue fumes.
When manufacturing is complete,
the shoes are packaged and transported to stores around the globe.
For many, these shoes could last years.
But for someone running 20 miles a week,
a pair of running shoes will start wearing out after roughly 6 months.
Since the shoes are made of so many different materials,
they’re almost impossible to break down into recyclable components.
20% of these shoes are incinerated, while the rest are tossed into landfills
where they can take up to 1,000 years to degrade.
So, how can we balance our love of sneakers
with the need for sustainability?
First, designers should streamline design elements
and focus on eco-friendly materials.
Factories need to develop energy efficient manufacturing processes
that consolidate steps and sneaker parts.
And consumers should support companies using clean energy
and ethical manufacturing processes.
We can also buy fewer shoes, wear them for longer,
and donate those we no longer need.
So no matter what your style, we can all take steps towards a sustainable future.