Parameter Tree:
EARTH SCIENCE > HUMAN DIMENSIONS > SOCIAL BEHAVIOR > RECYCLING

Definition:
Involves processing used materials into new products to prevent waste of potentially useful materials, reduce the consumption of fresh raw materials, reduce energy usage, reduce air pollution, and water pollution by reducing the need for "conventional" waste disposal, and lower greenhouse gas emissions as compared to virgin production. Recycling is a key component of modern waste reduction.

Reference:
http://en.wikipedia.org/wiki/Recycling