New synthetic-biological pathways for CO2 fixation: Photosynthesis fixes about 130 Gt C (about 477 Gt CO2) annually. This natural process thus plays a key role in the global carbon cycle. However, photosynthesis cannot fully compensate for anthropogenic CO2 emissions of about 10 Gt C per year. An important bottleneck of photosynthesis is CO2 uptake and conversion. Synthetic biology opens up the possibility of realising new enzymes and metabolic pathways for CO2 uptake that surpass the naturally evolved CO2 fixation pathways in efficiency. These solutions have the potential to improve photosynthesis by 20 to 200% and contribute to CO2 uptake and storage (for example in blue-green algae or crops) on a global scale if the scientific and societal challenges can be overcome.