Case Study: The Forestry (Logistics) Problem
Submitted: 3 Apr 2008
Application Areas: Logistics
Adapted from a real-world problem
A paper company own a number of mills that produce paper with different processes, e.g., the thermo-mechanical process (see Figure 1
), the cold caustic soda process, etc. They procure raw materials for each of their processing machines from a number of different suppliers.
Thermo-Mechanical Processing machine
Their suppliers consist of 3 forestry operations: Kaingaroa, NSW and Taupo. They also own a recycling plant where they receive waste paper.
They own mills at Kawerau (NZ), Boyer (Tasmania) and Albury (NSW). The following table summarises the processing machines at each mill:
The paper company purchases three types of raw materials: woodchips, pulp logs and waste paper. The thermo-mechanical, refiner-mechanical and cold caustic soda processes use woodchips, the stone groundwood process uses pulp logs and the recycled fibre process uses waste paper. The requirements (in tonnes) for their different machines are given below:
The supplies of the various raw material is given in the following table:
The transportation cost of the raw materials is given in the following table:
| $100/tonne of material
| Recycling Plant
Note that pulp logs can be "chipped" into woodchips (see Figure 2
) at the suppliers at a cost of $250/tonne and that waste paper can be "compacted" into woodchips at the recycling plant at a cost of $600/tonne. Any excess waste paper that is not used must be disposed of at a cost of $150/tonne.
The paper company want to know how to supply their mills at minimum cost.
For more detail see Supply Chain Optimisation in the Paper Industry, Philpott and Everett
Return to top
Extra for Experts
You can solve the Forestry Problem by creating the appropriate data file for
the nodes are a pair consisting of the location and raw material). Rather than create a data file for
by hand you can read in the data provided and generate the appropriate data file using a script file.
The model file [[forestry_expert.mod
]] creates the AMPL structures and the data file [[forestry_expert.dat
]] specifies the data for the Forestry Problem. Using thes two files, we can create the supply nodes using the following loop
Return to top
Return to top
- Solve the Forestry Problem. Write a management summary of your solution
What to hand in Your model, data and script files. Your management summary.
- Experts Only Modify your script file from Task 1 so that it uses [[forestry_expert.mod]] and [[forestry_expert.dat]] to get the forestry data and then generates the data for
transportation.mod dynamically. Write a management summary of your solution.
What to hand in Your modified script file. Your management summary.