I cleaned out the firebox of the big bourry box kiln that Donovan Palmquist built for us at Pinecroft. The kiln uses between 3 and 4 bush cords per firing. I looked up the weight of a cord of wood and of course it depends on the type of wood and whether it is green or not. I figure ours is around 4000 lbs per cord. To illustrate how efficient that firebox is look at the amount of ash I cleaned out. I don't have enough to fill a 5 gallon pail. I spent the day chain sawing and moving the 4 cords and it hit me like a ton of bricks. I was in bed at 8 and slept till 7. I ached where I used to play. I have to remind myself that I'm not 36 anymore. Going this morning to fill the pickup with some ash boards that we use to fire the first 8-10 hours.