This is a question we hear all the time at Tavern Service. Roasters and coffee shops want to know how much Nitrogen they will use when pouring and nitrogenating coffee.
Of course that depends. What size is the nitrogen tank? What is the volume of coffee being served? What nitrogen pressure does the roaster want the coffee dispensed at in order to get the optimal head? For the sake of this article, I’ll assume the nitrogen tank will be a 14 CF cylinder (just under 18” tall, fits in a kegerator), the coffee keg is 5 gallons (most everyone uses either a 5 gallon ball lock or 5.16 gallon 1/6 barrel keg), and the roaster wants to dispense the coffee at 35 pounds per square inch (35 psi on the top gauge of the regulator).
Micromatic, one of the leading beer equipment manufacturers says that a 5 pound CO2 tank will dispense 15 to 22 5-gallon kegs of beer. (http://www.micromatic.com/beer-questions/how-many-beer-kegs-dispensed-out-co2-tank) We have observed the same thing with our own beer and with our beer customers. A 14 CF nitrogen tank is just a 5 pound CO2 tank that has a nitrogen valve and is filled with a different gas.
One major difference is that CO2 is a combination of liquid and gas when in the cylinder and nitrogen is all gas. This means that the pressure in a CO2 tank will not drop until all the liquid is used up. A 20 pound sized cylinder holds 55 cubic feet of nitrogen at 1800 psi or 175 cubic feet of CO2 when filled to 20 pounds. Put another way, the same cylinder will push a little over 3 times as much liquid with CO2 as with Nitrogen.
The other major difference is that beer is normally dispensed at 10-12 psi. That can change with factors such as volumes of carbonation, altitude brewed, and distance from the keg to the faucet, but most direct draw kegs are fine at 12 psi. Nitro coffee will be served at 30-45 psi, depending on the roaster’s specs. It will take three times as much gas to push the same volume of coffee at 36 psi as at 12 psi.
CO2 is more soluble in beer than nitrogen is in coffee. That offsets some of the difference in the volume of gas. Between the regulator pressure and the use of nitrogen instead of CO2, cold brew coffee will only get maybe 12-20% of the “push” as beer for the same size tank.
Number of Kegs Dispensed per Nitrogen Cylinder
(1800 CF full dispensed at 36 psi)
14 cubic feet (small 5#) 2-3
28 cubic feet (medium 10#) 4-6
55 cubic feet (large 20#) 8-12