To decrease our dependence on fossil depletable feedstocks and to increase the use of renewable sources for PET yarns and fibers, a mass balance approach is a step forward to reach fossil-free future. Indorama Ventures developed an integrated supply chain that delivers bio-PET yarns and fibers based on mass balance approach. This supply chain allows reaching substantial progresses toward a Net Zero carbon footprint vs. its fossil version without compromising on the product quality. The lecture shares Indorama Ventures experience on the challenges for building the supply chain, how bio-based PET solution based on mass balance approach can improve the carbon footprint and why it is important to adopt a mass balance approach.