Slowly...... VERY slowly cooking down maple sap into maple syrup. About 40 gallons will yield about 1 gallon of syrup, and will take about 20 hours to cook down. I am using the top of an old gas grill, taken off it's stand, and placed on the ground. I make 2 fires, 1 on each side, and use the middle to add wood. I used 2 old canning kettles that needed replacement as the containers to boil down the sap.
Gas grill was literally garbage, and the wood I am using is from 3 maple trees that came from our rental property. They were dropping limbs onto the roof and needed to be taken down. I was going to be charged $750 to haul the wood away, so I split it myself and hauled it to my home. I figure it is about 5 or 6 full cords.
Total cost was the gas to split and haul it, but I "saved" $750 by taking the wood instead of paying to have it hauled away.
I must admit it feels a little cannibalistic to make maple syrup with maple wood, but what a great day outdoors, and maple syrup...YUM :)