Membranes already have important applications in artificial organs, the processing of biotechnological products, food manufacture, waste water treatment, and seawater desalination. Their uses in gaseous mixture separations are, however, far from achieving their full potential. Separation of air components, natural gas dehumidification and sweeting, separation and recovery of CO₂ from biogas, and H₂ from refinery gases are all examples of current industrial applications. The use of membranes for reducing the greenhouse effect and improving energy efficiency has also...