Fashion for Good Launches Mass Balance Project to Scale Bio-Based PET

Fashion for Good has introduced the Mass Balance Demonstrator project, a collaborative initiative focused on advancing the adoption of the mass balance attribution (MBA) chain-of-custody model for biomass-attributed PET in textile applications. The project is intended to support brand-led decarbonisation efforts across the apparel sector.

Although both preferred existing and next-generation materials offer potential pathways for reducing emissions, biosynthetics are expected to represent only a limited share of materials by 20301. Dedicated large-scale infrastructure for biosynthetic production remains underdeveloped, resulting in low production volumes and high costs despite proven technical performance.

The mass balance attribution model, used in sectors such as renewable energy and sustainable wood and paper, allows renewable and fossil-based feedstocks to be processed together. The system tracks the volume of renewable inputs entering production and allocates that share proportionally to outputs, supported by audits and certification mechanisms.

In practice, a chemical manufacturer introduces renewable feedstocks such as agricultural residues or used cooking oil into a production system alongside fossil-based inputs. These materials pass through the same processes and become chemically indistinguishable at the resin stage. The quantity of renewable input is measured and recorded, accounting for process losses and conversion factors.

This recorded input is then allocated to outputs using mass balance principles. For example, if 30% of the feedstock is renewable, a corresponding proportion of output can carry renewable attribution. In this project, the focus is on biomass-attributed polyester (PET), although the model can also apply to other fibres such as nylon. The attribution reflects the assigned share of renewable input rather than the physical composition of each product. The system ensures that renewable inputs are not over-allocated and that certified attributes are not counted more than once.

“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 at Fashion for Good.

The project brings together a consortium including BESTSELLER, Beyond Yoga (Levi Strauss & Co.), ON, Paradise Textiles, Environmental Resources Management (ERM), Indorama Ventures, ISCC, UPM Biochemicals, and Textile Exchange. The initiative aims to generate practical insights for broader industry adoption.

“Polyester is our second biggest fiber by volume in BESTSELLER, which 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 (or inputs) going forward.” Anders Schorling Overgård, Material Research Lead at BESTSELLER

The project focuses on four main objectives. It will produce biomass-attributed resin and yarns to demonstrate real-world application and performance. It will also develop a cradle-to-grave greenhouse gas (GHG) emissions model to assess environmental impact. In addition, the initiative aims to create a roadmap for scaling biomass-attributed PET by identifying supply chain stakeholders and evaluating lifecycle and economic factors. Finally, findings from the project will be shared with climate initiatives and standard-setting bodies to support the development of guidance on mass balance attribution.