Polyester Shirt (Synthetic)

Material Composition Assumptions

The default reference garment is a 100% polyester shirt weighing approximately 150 g, composed of:

• Polyester fiber: 100% virgin polyethylene terephthalate (PET) polyester, produced from purified terephthalic acid (PTA) and monoethylene glycol (MEG), both derived from petroleum feedstocks — approximately 150 g finished weight (raw fiber input ~165 g accounting for cutting waste)
• Dyes and chemicals: Disperse dye system with carrier chemicals, heat-setting agents, and finishing chemicals — approximately 3-8 g chemical input per garment
• Thread and trim: Polyester sewing thread, woven care label, printed hang tag — approximately 3-5 g
• Packaging: Polybag, cardboard insert, shipping carton (allocated per unit) — approximately 20 g

Virgin PET polyester production is a petrochemical process. The two primary monomers, terephthalic acid and ethylene glycol, are derived from paraxylene and ethylene respectively, both sourced from crude oil or natural gas refining. The embedded fossil carbon in PET polymer is approximately 62% by weight, though this is not released as CO2 unless the material is incinerated at end of life.

Manufacturing Geography

The default manufacturing region is China, which produces approximately 65% of global polyester fiber and is home to the largest PET resin-to-garment integrated supply chains.

• Grid intensity (China): 565 gCO2e/kWh (IEA Emissions Factors 2024). China is the dominant location for PET polymerization, fiber extrusion, and textile manufacturing.
• Grid intensity (Vietnam): Estimated ~500 gCO2e/kWh. Vietnam is a growing garment assembly hub.
• Grid intensity (Indonesia): Estimated ~700 gCO2e/kWh. Indonesia has a coal-heavy grid and is a significant polyester textile producer.
• Rationale: Polyester fiber production is energy-intensive at both the chemical (PET resin) and physical (melt extrusion, drawing, texturizing) stages. Unlike cotton, the raw material (PET resin) is produced in chemical plants rather than on farms, concentrating upstream emissions in industrial facilities that are sensitive to grid carbon intensity and process fuel choice. Approximately 25% of the polyester value chain’s emissions occur during fiber extrusion and yarn spinning, primarily from electricity use.

Regional Variation

Manufacturing Region	Grid Intensity	Estimated CCI Score	Adjustment vs Default
China (default)	~565 gCO2e/kWh	7.0 kgCO2e	Baseline
Indonesia	~700 gCO2e/kWh	7.5 kgCO2e	+7%
Vietnam	~500 gCO2e/kWh	6.7 kgCO2e	-4%
EU (average)	~300 gCO2e/kWh	5.9 kgCO2e	-16%
USA	~390 gCO2e/kWh	6.2 kgCO2e	-11%
India	~708 gCO2e/kWh	7.6 kgCO2e	+9%

Note: Scope 2 (factory electricity) represents approximately 21% of the total footprint. Grid intensity variation has a moderate impact because Scope 3 upstream emissions (PET resin production, petrochemical feedstock processing) are driven by chemical process energy and feedstock carbon, which are less sensitive to local grid mix. However, fiber extrusion is highly electricity-intensive, so grid decarbonization in China would meaningfully reduce the total score.

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) certified by an accredited third party per ISO 14067, PAS 2050, or the EU Product Environmental Footprint (PEF) method.
2. Fiber sourcing data specifying whether virgin PET, mechanically recycled rPET, or chemically recycled rPET is used. Mechanically recycled polyester from post-consumer PET bottles can reduce the fiber production hotspot by up to 79% (from ~2.5 to ~0.45 kgCO2/kg of fiber).
3. Mill-level energy data for polymerization, extrusion, texturizing, knitting/weaving, and dyeing facilities, including fuel mix and renewable energy procurement.
4. Recycled content certification such as Global Recycled Standard (GRS) or Recycled Claim Standard (RCS) with chain-of-custody documentation.
5. Transport mode and distance data for finished goods distribution to point of sale.

Brands using certified recycled polyester (GRS-certified, minimum 50% post-consumer rPET) with verified mill energy data may qualify for a score reduction of 20-35% depending on the recycled content percentage and manufacturing location.

Methodology Notes

• CCI score of 7 kgCO2e represents a conservative estimate for a virgin polyester garment manufactured in China. This aligns with the lower-to-mid range of published LCA values. The score is lower than the cotton t-shirt (10 kgCO2e) primarily because polyester fiber production is less carbon-intensive per kg than the combined cotton cultivation and processing chain, and the polyester garment is lighter (150 g vs. 200 g).
• Scope breakdown: Scope 3 dominates at 76% (5.3 kgCO2e), driven by PET resin production from petrochemical feedstocks and energy-intensive fiber extrusion at upstream supplier facilities. Scope 2 (factory electricity for knitting, dyeing, and garment assembly) is 21% (1.5 kgCO2e). Scope 1 (direct emissions from on-site thermal processes) is 3% (0.2 kgCO2e).
• Functional unit: One polyester shirt (~150 g), cradle-to-gate, including PET resin production, fiber extrusion, texturizing, yarn spinning, fabric knitting, dyeing, finishing, cutting, sewing, and packaging. The gate is the finished packaged garment ready for distribution.
• PET resin baseline: Virgin fossil-based PET resin is assumed at approximately 2.5 kgCO2e per kg (2020 industry average), which includes both process energy and embedded feedstock energy allocated to the product system.
• Use-phase emissions (laundering over garment lifetime) are excluded from the CCI score. Polyester garments typically require less frequent washing and lower drying energy than cotton, adding approximately 2-5 kgCO2e over a garment’s useful life depending on care practices.
• Microplastic shedding: Environmental impacts of microplastic fiber release during washing are a recognized concern for synthetic textiles but are not captured in the kgCO2e metric and are therefore excluded from the CCI score.
• End-of-life: No credit or debit is included for end-of-life disposal or recycling. Polyester is technically recyclable but global textile-to-textile recycling rates remain below 1%. If incinerated, the embedded fossil carbon (~62% of polymer weight) is released as CO2, adding approximately 2.3 kgCO2 per kg of polyester burned.
• Data gaps: PET resin production emissions vary by facility age, energy source, and process efficiency. The estimate uses an industry-average value. Specific supplier data from PET producers (e.g., Indorama Ventures, Reliance Industries) would improve accuracy.