System Design (facility layout, capacity planning, etc,)
Process Planning
Operation Scheduling and Control
Advanced Planning and Scheduling (APS), etc.

Decisions on Facilities (facility location, capacity determination, etc.)
Decisions on Transportation (network design, vehicle routing and scheduling, etc.)
Decisions on Inventory location and allocation
Information Systems (MRP, ERP, APS..), etc

Design and Operation of Collection Networks
Design and Operation of Remanufacturing Systems
Disassembly Process Planning
Design for Environment, etc.

Optimization Techniques (Linear programming, Integer programming, Network theory, etc.)
Meta heuristics or AI techniques
Probability and Statistics
Coding Language or Simulation, etc.