Since substances break down much faster under aerobic conditions, as oxygen helps break the molecules apart, in a process called oxidation, biodegradation that actually takes place does so slowly that effects may not be visible in decades after a product was buried, if even then.
When an item is raised, the work is done in opposition to gravity. When an item is worked on, energy is transmitted to it, and it develops gravitational potential energy. If the same thing falls from that height, gravity must do the same amount of effort to bring it back to the Earth's surface.
