Today in 2005, US Patent 6843391 B2 was issued, an invention of Glyn Jones, for his “Gas Reclamation System.” Here’s the Abstract:

A gas reclamation system for use in a beverage dispensing system. The system includes a valve for releasable connection to a used beverage container containing a pressurized gas, the valve allowing release of gas from the container. A filter for removal of particulate matter from the gas and a sterilizer for removal of bacteria from the gas are also provided, together with a compressor to re-pressurize the filtered and sterilized gas for supply to the beverage dispensing system. The system may be used for carbon dioxide recovery from beverage containers, reducing the consumption of carbon dioxide from beverage dispensing systems.