Living textile biocomposites deliver enhanced carbon dioxide capture

Over 110 million tonnes of textile fibres and apparel are produced annually, ultimately ending with significant quantities of waste textiles. One route for upcycling end-of-life textiles is to repurpose the materials for atmospheric carbon dioxide (CO ₂ ) removal by integrating microalgae (single celled photosynthetic organisms) to form ‘living’ biocomposites. In this study we demonstrate the CO ₂ capture performance of prototype living algae biocomposites that use textiles as a solid substrate. Chlorella vulgaris was attached to 100% cotton and 100% polyester sheets, of which half were coated with kappa-carrageenan (a natural polymer derived from seaweed) as a gel topcoat to enhance microalgae retention. The biocomposites were investigated in 28 days semi-batch CO ₂ absorption tests using a 5% v/v CO ₂ /air gas mixture. They absorbed significantly more CO ₂ than suspension microalgae culture controls, with the highest CO ₂ absorption rate being 1.82 ± 0.10 g CO ₂ g ⁻¹ _biomass d ⁻¹ from the coated cotton biocomposites, followed by 1.55 ± 0.27 g CO ₂ g ⁻¹ _biomass d ⁻¹ from the uncoated cotton biocomposites. The coated and uncoated polyester biocomposites had comparatively lower CO ₂ absorption rates (0.49 ± 0.04 and 0.42 ± 0.03 g CO ₂ g ⁻¹ _biomass d ⁻¹ respectively), likely due to the surface charges of the materials affecting microalgae adhesion and retention. A two weeks attachment test on cotton/polyester blends revealed some deterioration of the cotton which could limit the longevity of the biocomposites. Despite these issues, the CO ₂ abatement values compare favourably with other Chlorella CO ₂ capture studies with the added benefit of much reduced water usage and a reduced land requirement.