Many customers use the meat or share it with friends. If there is no interest in that option, you can bury or compost/recycle them. If you have the equipment to dig a hole, that is probably your best option, as it keeps the smell down as they decay. If you're composting/recycling them, you will want to drag them downwind and as far away from areas where you spend time (house, gardens, etc.) as practical. We also recommend "opening" the pig's belly so scavengers can make faster work of the carcass.
Do not dispose of the hogs near a water source or where livestock could be birthing. Dead pigs disposed closely to birthing areas will cause vultures and predators to visit more frequently. Check with your state water regulatory agency to get specific state laws on the disposal and environment.