Operation Recolonize was the plan enacted by the BnL Corporation to clean the excessive amounts of garbage off the Earth's surface, and eventually resettle humanity upon its homeworld. Much of the cleanup operations were handled by WALL•E and incinerator units. WALL•Es collected and packed the trash into solid cubes and incinerators incinerated them. After a few years, however, the operation was deemed a failure by Shelby Forthright, BnL's CEO. He declared Earth too toxic to ever support life again (that, and the WALL•E's were failing), shut down the reclamation efforts, and secretly sent Directive A-113 to the Auto units aboard human-carrying spacecraft.
Little did Forthright know that Operation Recolonize actually was successful, as plant life began to grow amongst the ruins of cities. Once the humans aboard the Axiom came back home after 700 years away from Earth, they quickly adapted to the environment, began farming, and flourished once again.