A typical pair of running shoes generates 30 pounds of carbon dioxide emissions, equivalent to a 100 watt light bulb a week, according to a new assessment of the MIT-based life cycle. But what is surprising to the researchers is not the size of the carbon footprint from a shoe, but where comes from the majority of that footprint.
The researchers found that more than two-thirds of the impact of carbon of a running shoe can come from manufacturing processes, with one lower percentage of derivatives of the acquisition or the extraction of raw materials. This breakdown is expected for products more complex such as electronics, where the energy that enters in the manufacture of integrated circuits with fine, can compensate for the energy expended in the processing of raw materials. But for "less advanced" products, particularly those that do not require electronic components - not usually the case.
So why a pair of sneakers, that may seem like a relatively simple product, emit carbon dioxide much more in its production phase? A team led by Randolph Kirchain, principal investigator at the MIT materials systems laboratory, and the researcher Elsa Olivetti broke down the various steps involved in the extraction of materials and manufacture of a pair of sneakers to identify hot spots of emissions of greenhouse gases. The Group found that much of the impact of the carbon came from feed manufacturing plants: an important part of shoemakers in the world are in China, where coal is the main source of electrical power. Coal is also typically used to generate steam or run other processes in the plant itself.
A typical pair of sneakers consists of 65 discrete parts that require more than 360 steps to assemble, sewing and cutting for injection molding, foam processing heating. Olivetti, Kirchain and his colleagues found that for these components reduced such processes are energy-intensive and therefore, carbon, compared to the energy-intensive that enters the production of footwear, such as polyester and polyurethane materials.
The results of the group, says Kirchain, will help shoe designers identify ways to improve designs and reduce the carbon footprint of the shoes. It adds that the results may also help industries to assess the impact of similar products more efficient carbon. "The environmental footprint of understanding is resource consumption. The key is, you have to put your analytical effort in areas that are important, "says Kirchain. "In general, we found if you have a product that has a relatively high number of parts and phases of the process, and that is relatively light [weight], then you want to make sure that you remember to manufacturing."
The sum of the parts of the shoe
In 2010, shoes nearly 25 billion were bought in the world, most of them manufactured in China and other developing countries. As Kirchain and his co-authors write in his book, "an industry that scale and geographic footprint has come under great pressure in terms of its social and environmental impact".
In response, companies have begun to take into account the contributions of greenhouse gas from their products, in part by measuring the amount of carbon dioxide associated with each process throughout the life cycle of a product. One of those companies, ASICS, a Japan-based sports equipment company, approached Kirchain to conduct an assessment of the life cycle for a made in China running shoe.
The team took a "cradle to grave" approach, breaking every step possible greenhouse gas emissions: from the point in which extracted raw materials to the disappearance of shoes shoes, because it is burned, deposited in landfills or recycling.
The researchers divided the life cycle of the shoes in five main stages: materials, manufacturing, use, transportation and life. These last three stages, found, contributed very little to the carbon footprint of the product. For example, shoes for running, unlike electronics, require very little energy to use, apart from the energy required to wash frequently shoes.
Most of the emissions, they found, came from manufacturing. While part of the manufacturing footprint is attributable to the installation source, other emissions came from processes such as foam and the molding of the sole of a sneaker, who spends large amounts of energy in the manufacture of small, light pieces. As explains Kirchain, "you have a lot of effort in the molding of the material, but will only get a very small part of that process."
"What was this burden of manufacturing are on par with the materials, that we had not seen in similar products," adds Olivetti. "Part of that is because it is a synthetic product. "If we were in a leather shoe, would be much more based on materials due to the carbon intensity of leather production."
Better design
In a tally of carbon emissions for each part of the life cycle of a running shoe, the researchers also could points places where reductions could be made. For example, noted that manufacturing facilities tend to get rid of unused material. On the other hand, Kirchain and colleagues suggest these waste recycling, as well as the combination of certain parts of the shoe to eliminate steps of cutting and welding. Print certain features in a shoe, rather than fixing of different fabrics, would also streamline the Assembly process.
Kirchain and Olivetti see their results as a guide for companies seeking to assess the impact of similar products. "When people try to streamline approaches [life cycle assessments], often emphasizing the impact of materials, which makes perfect sense," said Olivetti. "But we have tried to identify a set of characteristics that are designated to ensure that it also sought on the manufacturing side, when it matters."
Vikas Khanna, Professor of civil and environmental engineering at the University of Pittsburgh, says focusing on the impact of the carbon in the manufacture of a product is required, though difficult, fit for the business life cycle. "We are often restricted to quantify the environmental impacts of production material, since the manufacturing data are not readily available or landlord," said Khanna, who was not involved in the research.
He adds that know the contribution of manufacturing can help companies find more effective ways to reduce the carbon footprint of a product. "It is important to note that strategies of substitution of materials alone may not be sufficient to reduce the environmental impact of products," said Khanna. "For example, switch to renewable materials may not be sufficient for products that involve high production energy requirements."
