This is a typical unit of twin shaft shredders.
The requirement is to have a very simple model of the twin shaft shredder with possibly two motors of may be 5 KW each geared to reduce speed of the rollers for effective cutting of waste materials for reduction of particle size.
There are heavy machines that are available but they are not affordable to implement every where.
The two rotors are in opposite direction at different speeds to accomplish ease of operation.
Reduction gear options may be the kind of differential gears of cars / mini truck / truck / and / or designed specifically for the purpose.
The reason of option of gears is the availability of the same at very low cost.