I pass a tire distributor on my commute and they always are getting rid of pallets. There were four equal sized beauties that no one seemed to want so I stopped for them as I was running out of 4x4s for stacking on. Usually I can pick em up and toss em in but these were solid oak with angle iron bolsters. They must weigh 250 lbs a piece. I'll stack on them and then get some btus out of them.
I used to find these massive 4 x 8 skids. Like a double pallet only with 8 foot long beams. Got these cut up and dried for when it really hits the fan. They were incredibly heavy...... likely 300-400 lbs. Enjoy the dismantling, watch for the hardware!
Nice! I stack on hardwood eight footers, but not quite as stout as what you've got there - mine have 2x4 rails underneath. The weight difference between the hardwood and pine pallets is tremendous!
I get anywhere from 3-12 pallets at work every week, I pick and choose the best ones, which have some combination of hardwood runners and/or slats, close slat spacing, and nothing broken. The rest I leave for anyone else to take, but they usually go to the brush dump. I don't have time to take the pine ones apart for firewood, although I do burn pallet pieces in my fire pit. The good ones, I may get one to five, come home for stacking firewood on them.