Methodology
How OPF Trace calculates your product's carbon footprint
System Boundary
OPF Trace calculates a cradle-to-gate product carbon footprint (PCF). This boundary encompasses:
- Materials: extraction, processing, and production of raw materials used in your product, including packaging (packaging is tracked as a material category, not a separate step)
- Manufacturing energy: electricity and fuel (including natural gas) consumed at the production facility
- Transport: shipping of materials to the factory and the finished product to the customer's location
- Consumables & wastes: select waste-treatment inputs (and optionally other consumables like chemicals) you record for materials that don't become part of the finished product (e.g., glass sent to landfill during manufacturing, sodium hydroxide used in processing) — these contribute CO₂e but are excluded from the product's mass
Out of scope: end-of-life of the finished product (disposal, recycling), consumer use, and return logistics. Waste-treatment and consumables emissions are included only for the specific consumables & wastes rows you add — Trace does not model disposal of the product itself.
Calculation Formulas
Materials
Every bill-of-materials row — including packaging, which is a material category rather than its own step — is calculated by multiplying its weight by the material's lifecycle emission factor, then summed. Consumables & wastes rows (e.g., glass sent to landfill) use the same weight × factor formula and are included in this total, but their weight is excluded from the product's mass and from the materials-weight mismatch check.
Manufacturing Energy
Manufacturing energy emissions depend on:
- Energy consumption: you provide kWh per product, or we estimate based on product type and weight if unknown
- Electricity factor: varies by country and energy source (national grid mix and "I don't know" use your country's grid factor; renewable uses a fixed constant of 0.026 kg CO₂e/kWh); alternatively you may supply a custom emission factor (kg CO₂e/kWh) if you know your facility's actual electricity carbon intensity, which is used in place of the grid/renewable lookup
- Natural gas: if your facility also burns natural gas, enter the amount in MJ; it is converted at a fixed 0.0503 kg CO₂e/MJ (derived from EPA 5.31 kg CO₂e/therm ÷ 105.4804 MJ/therm, US EPA GHG Emission Factors Hub, Stationary Combustion) and added to the electricity contribution
Transport
Each transport leg (e.g., raw materials to factory, finished goods to customer) is calculated by multiplying the transported weight, distance, and mode-specific emission factor. Mode factors are from DEFRA 2025 and vary by transport type (road, rail, sea, air). Distance includes a circuity factor to account for actual routing vs. straight-line distances.
Total Footprint
Emission Factor Sources
All factors are publicly available and traceable to their source. Below is our complete provenance manifest:
| Source ID | Publisher | Version/Year | License | URL |
|---|---|---|---|---|
| S1 | DEFRA/DESNZ UK Government | 2025 | UK Open Government Licence v3.0 | gov.uk |
| S2 | Ember (via Our World in Data) | 2026 (country data 2022–2025) | CC BY 4.0 | OWID |
| S4 | ICE Database, University of Bath | v2.0 (2011) | © University of Bath; freely published | PDF mirror |
| S5 | Cotton Incorporated / PE International | 2012 | Freely published | cottoninc.com |
| S6 | Textile Exchange | 2026 (published March 2026) | Freely published; ISO 14044:2006-conformant study with independent critical review panel | textileexchange.org |
| S7 | PET Recycling Team GmbH / ALPLA | 2023 | Industry report; attributed | Packaging Europe |
| S8 | Li, Sun, Zhang et al. (2024) | 2024 (peer-reviewed journal) | SAGE Publications; fair use | SAGE |
| S9 | FEFCO / Cepi ContainerBoard | 2021 | Industry data; attributed | Packaging Europe |
| S10 | CEPI Eurokraft | 2021 | Industry data; attributed | cepi-eurokraft.org |
| S11 | APEAL | 2023 | Industry LCA; attributed | apeal.org |
| S12 | US EPA ENERGY STAR | Textile Industry Guidebook | Public domain | energystar.gov |
| S13 | Ratnasingam et al. (2016) | 2016 (peer-reviewed journal) | BioResources; open access | bioresources.cnr.ncsu.edu |
| S14 | IPCC AR5 WG3 | 2014 | Freely available publication | ipcc.ch |
| S15 | US EPA GHG Emission Factors Hub (Stationary Combustion) | 2024 edition | US Government public domain | epa.gov |
Disclaimers and Transparency
Self-Declared
OPF Trace is a self-declared calculator. We do not seek independent verification or certification of our results. Users are responsible for the accuracy of their input data. This calculator shall only be used for educational purposes. It is not intended to produce standardized, verified, or commercially useful LCA or PCF results.
ISO-Informed, Not ISO-Certified
Our methodology is informed by ISO 14040 (Life Cycle Assessment — Principles and Framework) and ISO 14067 (Greenhouse Gases — Quantification and Reporting of Product Carbon Footprints). We follow many of their principles but do not undergo the full ISO certification process.
Data Quality Guidance
OPF Trace displays a data-quality indicator for each section (Materials, Energy, Transport) in your results:
- User data: you provided a value (e.g., measured energy consumption, specific transport distance)
- Fallback default: Trace estimated the value (e.g., you selected "I don't know" for energy consumption, so we used product-type average energy intensity)
To improve the accuracy of your footprint, provide specific data wherever possible. Measured or vendor-supplied figures are always more reliable than category averages.
Questions?
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