Synthetic Footwear (Athletic / Sneaker)

Material Composition Assumptions

The default reference product is a pair of athletic sneakers weighing approximately 0.75 kg, composed of:

• Upper materials: Polyester mesh, synthetic leather (PU-coated textile), and/or engineered knit fabric — approximately 0.25 kg. Typical composition is 60-80% polyester with nylon reinforcement.
• Midsole: Ethylene-vinyl acetate (EVA) foam or thermoplastic polyurethane (TPU) — approximately 0.2-0.25 kg. EVA is the dominant midsole material in athletic footwear.
• Outsole: Styrene-butadiene rubber (SBR) or natural/synthetic rubber blend — approximately 0.15-0.2 kg.
• Adhesives: Solvent-based polyurethane or water-based adhesives — approximately 10-15 g.
• Other: Insole, laces, tongue padding, heel counter, toe cap, eyelets — approximately 0.05-0.1 kg.
• Packaging: Shoebox (corrugated cardboard), tissue paper, silica gel packets — approximately 0.3 kg.

Synthetic footwear is heavily petroleum-dependent. The upper, midsole, outsole, and adhesives are all derived from petrochemical feedstocks, making the material production stage the dominant emission driver.

Manufacturing Geography

The default manufacturing scenario is based on Southeast and East Asian production: material production in China, South Korea, and Taiwan, with shoe assembly in Vietnam, China, and Indonesia.

• Grid intensity (China): 565 gCO2e/kWh (IEA 2024). China is the world’s largest footwear producer (~60% of global output).
• Grid intensity (Vietnam): 480 gCO2e/kWh (IEA 2024). Second-largest athletic shoe exporter, hosting major Nike and adidas suppliers.
• Grid intensity (Indonesia): ~720 gCO2e/kWh (IEA 2024). Third-largest footwear exporter, with a coal-heavy electricity grid.
• Rationale: Athletic shoe assembly involves approximately 200-300 discrete manufacturing steps. Key energy-intensive steps include rubber compounding and vulcanization (180-220 degC), EVA foam injection molding, cement activation (heat tunnels), and press lasting. Assembly factories typically draw significant electricity for conveyorized production lines.

Regional Variation

Manufacturing Region	Grid Intensity	Estimated CCI Score	Adjustment vs Default
China (default)	~565 gCO2e/kWh	14.0 kgCO2e	Baseline
Vietnam	~480 gCO2e/kWh	13.4 kgCO2e	-4%
Indonesia	~720 gCO2e/kWh	15.1 kgCO2e	+8%
EU (Portugal, Romania)	~300 gCO2e/kWh	12.1 kgCO2e	-14%
USA	~390 gCO2e/kWh	12.7 kgCO2e	-9%

Note: Scope 2 represents approximately 26% of total emissions for synthetic footwear, making grid intensity a moderately important factor. Material production (Scope 3 upstream) is the largest contributor and is relatively independent of assembly location.

Provenance Override Guidance

A supplier or brand may override the default CCI score by submitting:

1. Environmental Product Declaration (EPD) or Product Carbon Footprint (PCF) per ISO 14067 covering materials through finished shoe.
2. Material composition data specifying recycled content. Recycled polyester uppers can reduce material-stage emissions by 30-40%. Bio-based EVA (sugarcane-derived) can reduce midsole emissions.
3. Factory energy data from Tier 1 assembly and Tier 2 material suppliers, including renewable energy procurement (PPAs, RECs/GOs).
4. Higg FEM verified data from SAC-participating facilities.
5. Sole material data: Natural rubber from certified sustainable sources or recycled rubber can reduce sole-stage emissions.

Methodology Notes

• CCI score of 14 kgCO2e per pair represents a conservative estimate consistent with FDRA/Quantis benchmark data (11-14 kgCO2e) for athletic footwear manufactured in Asia with coal-intensive grids.
• Scope breakdown: Scope 3 dominates at 71% (10.0 kgCO2e), driven by petrochemical-derived material production and upstream chemical manufacturing. Scope 2 is 26% (3.6 kgCO2e) from factory electricity for assembly, molding, and vulcanization. Scope 1 is 3% (0.4 kgCO2e) from on-site thermal energy.
• Functional unit: One pair of athletic sneakers (~0.75 kg excluding box), cradle to gate through finished packaged product.
• Use-phase: Excluded. Athletic shoes are rarely washed in machines; use-phase emissions are minimal.
• End-of-life: Excluded. Athletic shoes have very low recycling rates (<5%) due to the difficulty of separating bonded multi-material construction.
• Data gaps: Wide variation exists between basic athletic shoes and premium performance models. Specialized features (air units, carbon fiber plates, engineered knit uppers) can add 20-50% to material-stage emissions. The default score represents a mid-range athletic shoe.