Spunding is a process often used by lager brewers to naturally carbonate their beer. A device called a spunding valve is attached to the tank late in fermentation, when most of the sugars in the wort have been processed by the yeast.
The spunding valve carefully controls the release of CO2, keeping the tank pressurized and producing a desired effervescence and mouthfeel. The spunding method’s advantages are considerable. Naturally carbonated beers often have brighter flavours and a more consistent mouthfeel.