Propane BTU burner question

[Marj]

This is my first year tapping and I am collecting sap from ten black walnut trees. Although I know black walnuts don't yield as much sap as maples, collection is going well so far. I live on a 20 acre wooded property so my plan was to use wood as my fuel source, however I don't have enough dry wood set aside this spring for boiling the sap so I've decided to use propane. I've found a lot of information here about tanks, burner types, etc. but am not sure how many BTU's the burner should have as I've seen outdoor burners range from 65,000 - 200,000 BTU's. I will be boiling about 20 gallons of sap at a time. I also plan to have two 10 pound tanks of propane on hand to boil the 20 gallons of sap, which I think should be enough. Any thoughts or recommendations are much appreciated!

[Gissert]

While it takes BTUs to boil, its more of an issue of surface area that is important.You'll get more evaporation for a wide and shallow pan than you will a turkey fryer pot. I have a double burner camp chef propane cooker that I use to finish syrup that comes off my 2 foot by 4 foot evaporator pan. I had a pan built to fit the cooker, and it works well to finish on, but I'd go broke in a hurry if I used it to cook raw sap to finish. That said, if its just 20 gallons, you should be fine.