Fabricating Strong and Stiff Bioplastics from Whole Spirulina Cells

Abstract Since the 1950s, 8.3 billion tonnes (Bt) of virgin plastics have been produced, of which around 5 Bt have accumulated as waste in oceans and other natural environments, posing severe threats to entire ecosystems. The need for sustainable bio‐based alternatives to traditional petroleum‐derived plastics is evident. Bioplastics produced from unprocessed biological materials have thus far suffered from heterogeneous and non‐cohesive morphologies, which lead to weak mechanical properties and lack of processability, hindering their industrial integration. Here, a fast, simple, and scalable process is presented to transform raw microalgae into a self‐bonded, recyclable, and backyard‐compostable bioplastic with attractive mechanical properties surpassing those of other biobased plastics such as thermoplastic starch. Upon hot‐pressing, the abundant and photosynthetic algae spirulina forms cohesive bioplastics with flexural modulus and strength in the range 3–5 GPa and 25.5–57 MPa, respectively, depending on pre‐processing conditions and the addition of nanofillers. The machinability of these bioplastics, along with self‐extinguishing properties, make them promising candidates for consumer plastics. Mechanical recycling and fast biodegradation in soil are demonstrated as end‐of‐life options. Finally, the environmental impacts are discussed in terms of global warming potential, highlighting the benefits of using a carbon‐negative feedstock such as spirulina to fabricate plastics.