Study finds the bulk of shoes' carbon footprint comes from manufacturing processes

May 22, 2013 by Jennifer Chu
Study finds the bulk of shoes’ carbon footprint comes from manufacturing processes

A typical pair of running shoes generates 30 pounds of carbon dioxide emissions, equivalent to keeping a 100-watt light bulb on for one week, according to a new MIT-led lifecycle assessment. But what's surprising to researchers isn't the size of a shoe's carbon footprint, but where the majority of that footprint comes from.

The researchers found that more than two-thirds of a running shoe's carbon impact can come from , with a smaller percentage arising from acquiring or extracting raw materials. This breakdown is expected for more complex products such as electronics, where the energy that goes into manufacturing fine, can outweigh the energy expended in processing raw materials. But for "less-advanced" products—particularly those that don't require electronic components—the opposite is often the case.

So why does a pair of sneakers, which may seem like a relatively simple product, emit so much more carbon dioxide in its manufacturing phase?

A team led by Randolph Kirchain, principal research scientist in MIT's Materials Systems Laboratory, and research scientist Elsa Olivetti broke down the various steps involved in both materials extraction and manufacturing of one pair of to identify hotspots of greenhouse-gas emissions. The group found that much of the carbon impact came from powering : A significant portion of the world's shoe manufacturers are located in China, where coal is the dominant source of electricity. Coal is also typically used to generate steam or run other processes in the plant itself.

A typical pair of running shoes comprises 65 discrete parts requiring more than 360 processing steps to assemble, from sewing and cutting to injection molding, foaming and heating. Olivetti, Kirchain and their colleagues found that for these small, light components such processes are energy-intensive—and therefore, carbon-intensive—compared with the energy that goes into making shoe materials, such as polyester and polyurethane.

The group's results, Kirchain says, will help shoe designers identify ways to improve designs and reduce shoes' carbon footprint. He adds that the findings may also help industries assess the carbon impact of similar consumer products more efficiently.

"Understanding environmental footprint is resource intensive. The key is, you need to put your analytical effort into the areas that matter," Kirchain says. "In general, we found that if you have a product that has a relatively high number of parts and process steps, and that is relatively light [weight], then you want to make sure you don't overlook manufacturing."

Kirchain and his colleagues have published their results in the Journal of Cleaner Production.

The sum of a shoe's parts

In 2010, nearly 25 billion shoes were purchased around the world, the majority of them manufactured in China and other developing countries. As Kirchain and his co-authors write in their paper, "An industry of that scale and geographic footprint has come under great pressure regarding its social and environmental impact."

In response, companies have started to take account of their products' greenhouse-gas contributions, in part by measuring the amount of carbon dioxide associated with every process throughout a product's lifecycle. One such company, ASICS, an athletic equipment company based in Japan, approached Kirchain to perform a lifecycle assessment for a running shoe manufactured in China.

The team took a "cradle-to-grave" approach, breaking down every possible greenhouse gas-emitting step: from the point at which the shoes' raw materials are extracted to the shoes' demise, whether burned, landfilled or recycled.

The researchers divided the shoes' lifecycle into five major stages: materials, manufacturing, usage, transportation and end-of-life. These last three stages, they found, contributed very little to the product's carbon footprint. For example, running shoes, unlike electronics, require very little energy to use, aside from the energy needed to infrequently wash the shoes.

The bulk of emissions, they found, came from manufacturing. While part of the manufacturing footprint is attributable to a facility's energy source, other emissions came from processes such as foaming and of parts of a sneaker's sole, which expend large amounts of energy in the manufacture of small, lightweight parts. As Kirchain explains it, "You have a lot of effort going into the molding of the material, but you're only getting a very small part out of that process."

"What stood out was this manufacturing burden being on par with materials, which we hadn't seen in similar products," Olivetti adds. "Part of that is because it's a synthetic product. If we were looking at a leather shoe, it would be much more materials-driven because of the carbon intensity of leather production."

An improved design

In tallying the carbon emissions from every part of a running shoe's lifecycle, the researchers were also able to spot places where reductions might be made. For example, they observed that manufacturing facilities tend to throw out unused material. Instead, Kirchain and his colleagues suggest recycling these scraps, as well as combining certain parts of the shoe to eliminate cutting and welding steps. Printing certain features onto a shoe, instead of affixing them as separate fabrics, would also streamline the assembly process.

Kirchain and Olivetti view their results as a guide for companies looking to evaluate the impact of similar products.

"When people are trying for streamlined approaches to [lifecycle assessments], often they put emphasis on the materials impact, which makes a lot of sense," Olivetti says. "But we tried to identify a set of characteristics that would point you to making sure you were also looking at the manufacturing side—when it matters."

Vikas Khanna, assistant professor of civil and environmental engineering at the University of Pittsburgh, says focusing on the carbon impact from a product's manufacturing is a needed, though difficult, adjustment for the lifecycle business.

"We are often restricted to quantifying the environmental impacts of material production only, since the manufacturing data is either not readily available or proprietary," says Khanna, who did not participate in the research.

He adds that knowing the manufacturing contribution may help companies find more effective ways to reduce a product's .

"It is important to keep in mind that material substitution strategies alone may not be sufficient in reducing the environmental impact of products," Khanna says. "For example, switching to renewable material sources may alone not be sufficient for products that involve high energy requirements."

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User comments : 17

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StarGazer2011
1.7 / 5 (11) May 22, 2013
First: Wow, someone spent money on this?
Second: Because it doesnt take into account the CO2 emitted to make the machines that make the machines that make the machines that make the shoes its totally fatuous, but a good example of how overfunded climate research is.
Jack_J_Smith
1.7 / 5 (11) May 22, 2013
Physics.org believes and promotes the Hippie Apocalypse of Global Warming - oops now they call it Climate Change -- "Carbon footprint" is the biggest scam since Cold Fusion.

When are these University liberals geeks going to stop the moralism of trying to tell us what to do and get back to real objective science?
TechnoCore
3.9 / 5 (7) May 22, 2013
@StarGazer
It says they conducted a life cycle assessment of the product, if you read the first sentence to the end. Imho it is a kind of silly to criticize a life cycle assessment for actually assessing the whole cycle of the product. But then again, maybe you got some of that one billion dollars the oil&coal industry pours into lobbying and disinformation every year.
TechnoCore
3.9 / 5 (7) May 22, 2013
@Jack J Smith
You call MIT a Hippie University? I feel sad for the humanity reading posts like yours, or then again maybe not.
antialias_physorg
2.6 / 5 (7) May 22, 2013
First: Wow, someone spent money on this?

Yes, because if you're going to devise strategies to lower the carbon footprint of products it's probably a good idea to start figuring out where you can save the biggest chunk with the least effort/cost. (sneakers are just a stand-in product for general low-tech items)

Second: Because it doesnt take into account the CO2 emitted to make the machines that make the machines

Firstly that is only a negligible amount (as you need only one machine, each to make many thousands of shoes - so the contribution to each shoe is very small)
Secondly that is covered when looking at high tech equipment itself - and can be addressed then.
antigoracle
1.7 / 5 (11) May 24, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.
Neinsense99
2.8 / 5 (11) May 26, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, reliability is a virtue. When, however, it is reliably failing to display even a shred of reason it is just pathetic. Prepare for the vituperative retort that will demonstrate my point.
antigoracle
1.7 / 5 (12) May 26, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, reliability is a virtue. When, however, it is reliably failing to display even a shred of reason it is just pathetic. Prepare for the vituperative retort that will demonstrate my point.

Hmmm... living up to your name NO SENSE. Put down the thesaurus and try to write English.
So tell me nosense, do you live barefoot in a cave or like your Vicar Gore, burning more power than most third world villages? Hypocrite.
deepsand
3.2 / 5 (13) May 27, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, reliability is a virtue. When, however, it is reliably failing to display even a shred of reason it is just pathetic. Prepare for the vituperative retort that will demonstrate my point.

Hmmm... living up to your name NO SENSE. Put down the thesaurus and try to write English.
So tell me nosense, do you live barefoot in a cave or like your Vicar Gore, burning more power than most third world villages? Hypocrite.

AO's just jealous of those with the ability to understand Science, to employ logic, and speak fluently.
antigoracle
1.4 / 5 (9) May 28, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, reliability is a virtue. When, however, it is reliably failing to display even a shred of reason it is just pathetic. Prepare for the vituperative retort that will demonstrate my point.

Hmmm... living up to your name NO SENSE. Put down the thesaurus and try to write English.
So tell me nosense, do you live barefoot in a cave or like your Vicar Gore, burning more power than most third world villages? Hypocrite.

AO's just jealous of those with the ability to understand Science, to employ logic, and speak fluently.

Is this middle school?
Are you a child or just plain stupid?
#rhetorical
deepsand
3 / 5 (12) May 28, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, reliability is a virtue. When, however, it is reliably failing to display even a shred of reason it is just pathetic. Prepare for the vituperative retort that will demonstrate my point.

Hmmm... living up to your name NO SENSE. Put down the thesaurus and try to write English.
So tell me nosense, do you live barefoot in a cave or like your Vicar Gore, burning more power than most third world villages? Hypocrite.

AO's just jealous of those with the ability to understand Science, to employ logic, and speak fluently.

Is this middle school?
Are you a child or just plain stupid?
#rhetorical

Wherein AO, as is usual for those of his age, fails to differentiate between toddlers such as himself and the adults charged with managing them.
antigoracle
1.4 / 5 (9) May 29, 2013
Number of AGW Alarmist boycotting shoes, in protest, ZERO. Why should they, when their Vicar Gore burns more power than most third world villages.

Normally, ... vituperative retort that will demonstrate my point.

Hmmm... living up to your name NO SENSE. Put down the thesaurus and try to write English.
So tell me nosense, do you live barefoot in a cave or like your Vicar Gore, burning more power than most third world villages? Hypocrite.

AO's just jealous of those with the ability to understand Science, to employ logic, and speak fluently.

Is this middle school?
Are you a child or just plain stupid?
#rhetorical

Wherein AO, as is usual for those of his age, fails to differentiate between toddlers such as himself and the adults charged with managing them.

Wherein deepsand confirms, he is just plain stupid.
deepsand
3 / 5 (12) May 29, 2013
Being the child that he is, AO has exhausted his vocabulary.
Neinsense99
3.2 / 5 (9) Jun 28, 2013
Being the child that he is, AO has exhausted his vocabulary.

But not sock puppets for down-voting, apparently.
deepsand
3.5 / 5 (8) Jun 29, 2013
A puppet with its own puppets?
ValeriaT
1 / 5 (5) Jun 29, 2013
From else the bulk of shoes' carbon footprint should come, if not from manufacturing processes? From else the bulk of carbon footprint of research should come, if not from silly studies trying to prove the obvious? Why we have so much of "duh" science?
deepsand
3.9 / 5 (7) Jun 30, 2013
From else the bulk of shoes' carbon footprint should come, if not from manufacturing processes? From else the bulk of carbon footprint of research should come, if not from silly studies trying to prove the obvious? Why we have http://science.sl...-science

A careful reading of the 2nd paragraph of the article will show that your intuitive conclusion does not hold for all products, that for "low tech" products" the energy used in the extraction of raw materials generally exceeds that consumed in manufacturing.

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