Question

what happen in 4R -principle -the 4th R -recover does not come in major role

Answer 1

The 4R principle is the best way of decomposing materials that are not naturally degradable. It follows 4 steps
1. reduce: the waste is reduced by the minimal usage
2. reuse: the material is broken down and again made to be used again
3. recycle:  The product is changed into some other new product
4. recover: The conversion of waste materials for the recovery of the energy values

As there are not many products that can be used as energy purposes so this step doesn't count as much