Footwear

Material Composition Assumptions

The default CCI score covers a representative pair of general-purpose footwear with a reference mass of approximately 700 g per pair (two shoes). Material composition varies significantly by product type; the default bill of materials represents a mid-market casual or athletic shoe:

• Upper: Leather (~30-40% of mass) or synthetic textile combination (polyester mesh, nylon, TPU overlays). Leather uppers carry the largest single-material footprint due to the emissions-intensive cattle supply chain and chrome tanning.
• Outsole: Carbon black rubber or EVA (ethylene-vinyl acetate) foam. Rubber vulcanization is energy-intensive; carbon black production is a significant ancillary emission source.
• Midsole: EVA foam or polyurethane (PU) foam. Foaming agents and isocyanate precursors for PU carry upstream chemical process emissions.
• Insole and lining: Foam or textile insole; fabric lining (polyester or cotton). Lower mass fraction; modest emission contribution.
• Adhesives and finishing: Solvent-based polyurethane adhesives used extensively in assembly. Some facilities use water-based alternatives, but solvent adhesives remain common in lower-cost supply chains.
• Accessories: Laces, eyelets, zippers, decorative elements. Typically steel or plastic; minor contribution.

Leather vs. synthetic uppers is the most significant material variable. A fully leather shoe may have a footprint 20-40% higher than an equivalent synthetic-upper model on a per-pair basis, due to the cattle-sourced leather supply chain.

Manufacturing Geography

The default manufacturing region reflects the global distribution of footwear production:

• China: Produces approximately 55% of global footwear by volume (APICCAPS 2023). Grid intensity ~565 gCO2e/kWh. Primary centre for both athletic and leather footwear.
• Vietnam: Approximately 10% of global production; preferred by Nike, adidas, and Puma. Grid intensity ~520 gCO2e/kWh, increasingly supplemented by solar capacity.
• Indonesia: Approximately 5% global share; major Nike and New Balance supplier. Grid intensity ~780 gCO2e/kWh (coal-dominated). Higher than China default.
• India: Significant leather footwear producer (Agra cluster). Grid intensity ~700 gCO2e/kWh.

Most luxury leather footwear (Italy, Portugal, Spain) is manufactured in lower-carbon electricity environments but carries similar upstream leather supply chain emissions.

Regional Variation

Assembly Region	Grid Intensity	Estimated Score Adjustment
China (default)	~565 gCO2e/kWh	Baseline
Vietnam	~520 gCO2e/kWh	-8% on Scope 2 (saves ~0.2 kgCO2e)
Indonesia	~780 gCO2e/kWh	+38% on Scope 2 (adds ~1.2 kgCO2e)
India	~700 gCO2e/kWh	+24% on Scope 2 (adds ~0.7 kgCO2e)
Italy / Portugal	~230 gCO2e/kWh	-59% on Scope 2 (saves ~1.8 kgCO2e)
EU average	~300 gCO2e/kWh	-47% on Scope 2 (saves ~1.4 kgCO2e)

Note: Because Scope 3 (materials, tanning, component manufacturing) represents ~75% of total emissions, assembly location grid intensity has a proportionally modest effect on the total score. Leather vs. synthetic upper choice is a more impactful variable than assembly country for most product configurations.

Provenance Override Guidance

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

1. Product Carbon Footprint (PCF) certified per ISO 14067 or compliant with the PEFCR for Apparel and Footwear, covering cradle-to-gate or cradle-to-grave with explicit material-level emission factors.
2. Published brand LCA: Nike, adidas, Timberland, and other major brands have published model-specific carbon footprints. These qualify as overrides when product-specific and third-party verified.
3. Leather traceability data: Leather Working Group (LWG) Gold or Silver-rated tannery certification, combined with cattle sourcing data and land-use assessments, may support a reduced leather-component emission factor.
4. Sole and material certifications: bluesign, OEKO-TEX, or Cradle-to-Cradle certification for specific sole or upper materials when accompanied by audited emission factors.
5. Assembly facility energy data: Renewable energy certificates (RECs) or power purchase agreements (PPAs) for the final assembly plant, with verified energy consumption per pair.
6. Recycled material content: Documented use of recycled rubber, recycled polyester, or ocean plastic uppers with verified LCA data (e.g., adidas Parley, Allbirds SweetFoam) supports a provenance override for material-stage emissions.

Methodology Notes

• CCI score of 14 kgCO2e per pair represents the median estimate from peer-reviewed literature and published brand LCA reports for general-purpose footwear. The per-kg intensity of ~20 kgCO2e/kg is derived from a reference mass of 700 g per pair.
• Scope breakdown: Scope 3 dominates at ~71% (10 kgCO2e), driven by leather tanning and supply chain, rubber and EVA production, synthetic textile components, and logistics. Scope 2 is ~21% (3 kgCO2e) from adhesive curing, lasting, and factory electricity. Scope 1 is ~7% (1 kgCO2e) from on-site solvent use and minor process combustion.
• Functional unit: One pair of footwear (two shoes), cradle to gate, with packaging. Consumer use phase (cleaning, resoling if applicable) and end-of-life are excluded.
• Leather allocation: The cattle supply chain emission factor used for leather is based on economic allocation between beef and leather co-products. Mass allocation would assign a lower share to leather; economic allocation assigns approximately 5-10% of total cattle system emissions to leather. This is a significant methodological choice that can shift the footwear footprint by ±20%.
• Product type variation: Footwear footprints vary widely by category — basic canvas/vulcanised shoes (~5-6 kgCO2e/pair), casual leather shoes (~15-18 kgCO2e/pair), running shoes with multi-component foam midsoles (~12-18 kgCO2e/pair), leather boots (~20-30 kgCO2e/pair). The default 14 kgCO2e represents a general mid-range estimate.
• Data gaps: Leather supply chain emissions are sensitive to cattle system (feedlot vs. pasture), country of origin, deforestation risk (Brazilian cattle versus European), and tannery process type (chrome vs. vegetable tanning). This contributes materially to the medium confidence rating.
• Comparison context: Footwear has a higher per-kg footprint (~20 kgCO2e/kg) than many apparel categories due to the multi-material construction and adhesive-heavy assembly process. However, durability varies considerably: a resoleable leather boot may serve 15+ years, while a fashion-athletic shoe may have an 18-month service life.