Manufacturing-focused emissions reductions in footwear production

What is the burden upon your feet? With sales of running and jogging shoes in the world averaging a nontrivial 25 billion shoes per year, or 34 million per day, the impact of the footwear industry represents a significant portion of the apparel sector’s environmental burden. This study analyzed the carbon footprint of a familiar consumer product, a pair of running shoes. A single shoe can contain 65 discrete parts that require 360 processing steps for assembly. While brand name companies dictate product design and material specifications, the actual manufacturing of footwear is typically contracted to manufacturers based in emerging economies. Using life cycle assessment methodology, this effort quantified the global warming potential burden of a pair of shoes and mitigation strategies were proposed focusing on high leverage aspects of the life cycle. Using this approach, it was estimated that the carbon footprint of a typical pair of running shoes made of synthetic materials is 14 ± 2.7 kg CO2‐equivalent. The vast majority of this impact is incurred during the materials processing and manufacturing stages, which make up around 29% and 68% of the total impact, respectively. By comparison, a person emits the equivalent amount of carbon by using a 100‐watt light bulb for a week. For consumer products not requiring electricity during use, the intensity of emissions in the manufacturing phase is atypical; most commonly, materials make up the biggest percentage of impact. This distinction highlighted the importance of identifying mitigation strategies within the manufacturing process, and the need to evaluate the emissions reduction efficacy of each potential strategy. By postulating the causes of manufacturing dominance in the global warming potential assessment of this product, this study described the characteristics of a product that would lead to high manufacturing impact. Thereby, the work explored how relying solely on the bill of materials information for product life cycle assessment may underestimate life cycle burden and ignore potentially high impact mitigation strategies.