Incorporating Microalgae and Cyanobacterial Pigments into Biopolymers to Develop Attractive Bio-Based Materials for the Built Environment

Delivering net-zero CO 2 emissions by 2050 requires rapid, large-scale carbon sequestration. Global photosynthesis, driven by cyanobacteria, microalgae, and higher plants, captures CO 2 and constitutes the dominant natural carbon sink (biomass). The built environment represents a second major sink. Large-scale microalgal cultivation and the integration of its bioproducts into building materials offers a pathway to capture and store CO 2 in built infrastructure. Colourful sustainably produced biopolymers offer one such route for carbon sequestration. Although pigments have a minor direct contribution, their coloration potential can accelerate the adoption of C-containing materials to increase architectural carbon sequestration. Here, we blended (individually and in combination) a range of structurally different pigments; the carotenoids—lutein (yellow) and astaxanthin (red), a water-soluble chlorophyll derivative—sodium copper chlorophyllin (green), and a water-soluble protein (phycocyanin, blue) into two biopolymers, polyhydroxybutyrate-hydroxyhexanoate and polycaprolactone with melting points of 135 °C and 60 °C, respectively. Six blending processes were evaluated for homogeneous coloured biopolymer production. UV resistance of coloured biopolymers was evaluated and enhanced by the application of a UV-protective coating. The best of the coloured biopolymer samples were integrated into a small-scale curved architectural structure to gain insight into the use and performance of the translucent materials produced for exhibition.