Achieving carbon-neutral fiber-composite materials by reducing the thermosetting matrix system’s global warming potential

Motivated by the demand for sustainable thermoset matrix systems, this study proposes several approaches; the most effective combines flax fibers, furan resin, and biochar filler into a low-impact material system. Eco-mechanical performance was experimentally assessed at the material level via four-point bending and at the structural level via axial compression tests, using global warming potential as the sustainability metric considering LCA module A1, with estimates extended to cradle-to-gate (A1–A3). Incorporating 19.1 wt% biochar achieved A1 carbon neutrality, with 15.1% and 16.3% reductions in mass-specific flexural modulus and strength, respectively. Up to 27.6 wt% biochar was implemented in (hybrid) coreless filament-wound structures, while maintaining processability and adequate mechanical performance. In flax–epoxy systems, biochar addition improved eco-mechanical performance but could not achieve A1 carbon neutrality. The proposed flax–furan–biochar system offers a fully renewable, carbon-neutral/carbon-negative, mechanically viable solution for fiber-composite lightweight structural applications.