A mass balance attribution chain-of-custody model for biomass-attributed PET has been adopted by a nine-partner industry consortium led by Fashion for Good, marking a concrete step toward brand-driven decarbonisation in apparel. The project addresses a critical gap: biosynthetics remain a small fraction of 2030 material projections because dedicated commercial-scale infrastructure is not yet fully developed, keeping production volumes low and costs prohibitively high.
- Biosynthetic materials have demonstrated technical performance parity, but lack of commercial-scale infrastructure has kept production volumes low and costs too high for widespread industry transition.
- The mass balance attribution model, borrowed from renewable energy and sustainable forestry sectors, allows renewable and fossil-based feedstocks to be physically mixed within the same production system.
- Renewable feedstock inputs are carefully measured, recorded through a verified accounting system, and proportionally allocated to outputs — strictly controlled so no renewable attribution can be double-counted.
- The initiative positions the project as a blueprint for scaling biomass-attributed PET across the apparel value chain.
THE TRIGGER: A nine-partner consortium assembled by Fashion for Good set out to close the gap between industry appetite for biosynthetics and the commercial frameworks needed to support adoption at scale. The project was structured to build impact evidence, commercial proof points, and the feedback loops required for the mass balance attribution model to scale with integrity across apparel supply chains.
- The consortium brings together Bestseller, Beyond Yoga (Levi Strauss & Co.), On, Paradise Textiles, Environmental Resources Management (ERM), Indorama Ventures, ISCC, UPM Biochemicals, and Textile Exchange.
- Fashion for Good designed the initiative to demonstrate that existing manufacturing systems can integrate renewable feedstocks today, without waiting for dedicated biosynthetic infrastructure to mature.
- Bestseller noted that polyester is its second largest fibre by volume, citing the project as an opportunity to build direct experience with mass balance attribution and bio-attributed polyester.
- The consortium was designed not only to demonstrate what is possible today but to generate insights the wider industry can build on now and in the future, with Bestseller citing ambitions to initiate pathways that support scaling of renewable feedstocks going forward.
WHAT THE DATA SHOWS: The mass balance attribution model, borrowed from renewable energy and sustainable wood and paper industries, allows renewable and fossil-based feedstocks to be physically mixed within shared infrastructure. A verified accounting system tracks how much renewable input enters the production system and proportionally allocates that amount to outputs, accounting for process losses and conversion factors throughout.
- A chemical manufacturer introduces renewable feedstocks — such as agricultural residues or used cooking oil — into a production system that also processes fossil-based feedstocks.
- By the time feedstocks become resin, they are chemically indistinguishable; the renewable share is tracked through verified accounting rather than physical separation.
- If 30 per cent of feedstock entering the system is renewable, a corresponding share of output can carry a renewable attribution — in this project, biomass-attributed PET.
- Producers cannot allocate more renewable attribution than the amount of renewable feedstock entering the system, and once attributed, certified attributes cannot be counted again elsewhere.
- The model could also be applied to other fibres beyond PET, with nylon cited as a further potential application.
RIPPLE EFFECTS: The Mass Balance Demonstrator project is structured around four interconnected objectives designed to generate evidence and tools the broader industry can act on. Beyond producing biomass-attributed materials, the consortium committed to quantifying climate impact, developing a scale-up blueprint, and feeding insights into the standard-setting bodies that govern climate frameworks across the sector.
- The project will physically produce biomass-attributed resin and yarns, with the source explicitly stating the real-world output is expected to match performance parity with conventional materials.
- A cradle-to-grave greenhouse gas emissions model will be developed for the produced materials, delivering science-based insights into their decarbonisation potential and overall environmental footprint.
- The consortium will deliver a practical roadmap for scaling biomass-attributed PET, identifying key supply chain actors and evaluating the techno-economic feasibility of market deployment.
- Lifecycle accounting approaches for different chain-of-custody models will be assessed as part of the scale-up blueprint, strengthening the evidence base for wider industry transition.
- Insights from the project will be shared with climate initiatives and standard-setting bodies to support credible guidance on mass balance attribution across the sector.
WHAT THEY SAID
We are at a point where the industry wants to move and adopt biosynthetics, but the production frameworks and commercial infrastructure haven't caught up. The Mass Balance Demonstrator project is about closing that gap: building the impact and commercial evidence, the blueprint, and the feedback loops that will allow the MBA model to scale with integrity.
— Katrin Ley
Managing Director
Fashion for Good
Polyester is our second biggest fiber by volume in Bestseller, that means we are continuously investigating improvements in this category. By taking part in this project we as a company are building experience within mass balance attribution and bio-attributed polyester. Hopefully, as we collaborate with other great partners, this can initiate pathways that can support scaling of renewable feedstocks going forward.
— Anders Schorling Overgård
Material Research Lead
Bestseller
