Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Footwear’s (carbon) footprint

23.05.2013
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 manufacturing processes, 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, integrated circuits 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 running shoes to identify hotspots of greenhouse-gas emissions. The group found that much of the carbon impact came from powering manufacturing plants: 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 injection molding 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.”

Written by: Jennifer Chu, MIT News Office

Sarah McDonnell | EurekAlert!
Further information:
http://www.mit.edu

More articles from Studies and Analyses:

nachricht Study relating to materials testing Detecting damages in non-magnetic steel through magnetism
23.07.2018 | Technische Universität Kaiserslautern

nachricht Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Air pollution leads to cardiovascular diseases

21.08.2018 | Ecology, The Environment and Conservation

Researchers target protein that protects bacteria's DNA 'recipes'

21.08.2018 | Life Sciences

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>