Yeah but; so if they are not biodegradeable in a landfill, just where are they going to be biodegradable? Much, maybe most, of what goes into landfills does not break down due to biological processes, anyway. Uses for old tires have been explored, mainly by burning to recover the energy locked in them. But, they are still limited. They don't "compost" old tires, either. So, if you live where practical recycling alternatives are not readily available, then dispose of them using approximately the same method many of them are by approved tire-disposal companies. That is-- cut them up(going around the outer edge of the sidewall on both sides) with a good sharp utility knife, and dumpster them. This will cost you much less than a round trip to a tire shop & $3+ each.