Recycling or salvaging is the word covering both reuse (use for the same purpose) and reclamation/recovery of materials or energy.
The reasons for implementing recycling may change depending on national and local conditions, and the key ideas in the arguments for recycling may be:
detoxification of hazardous waste when high environmental standards are set by the authorities
resource recovery in low income areas
reduction of volume in areas where landfilling is predominant
energy recovery in areas where conversion of waste to energy can replace fossil fuel (coal, natural gas, crude oil and so on) for energy production.