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Optimization approaches to tactical planning problems in the forest industry
Linköping University, Department of Mathematics, Optimization . Linköping University, The Institute of Technology.
2004 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

By using decision support tools based on operations research (OR) and optimization in the supply chain in the forest industry, the planning process can be improved and higher profitability can be obtained. The focus of this thesis is on modelling two real-life problems. The problems are united by the facts that they concern tactical (annual) planning in the forest industry, and that the models are developed and tested with real data at Swedish companies.

In the first paper, a problem of the supply chain of forest fuel is modelled and solved. The problem of deciding when and where forest residues are to be converted into forest fuel, and how the residues are to be t ransported and stored in order to satisfy demand at heating plants is studied. Decisions also include whether or not additional harvest areas and saw-mills are to be contracted. In addition, we consider the flow of products from saw-mills and import harbours, and address the question about which terminals to use. The planning horizon is one year and monthly time periods are considered. The test data is from Sydved Energileveranser AB.

The second paper is a case study from Södra Cell AB. A combined problem of terminal location and ship routing is studied. The objective is to minimize the costs of distributing pulp products from pulp mills to customers (paper mills). Shipping vessels chartered on short or long term are used to transport products to terminals in Europe. In addition, trains and lorries are used for direct transports to customers from mills. From each terminal, the products are transported to customers by lorry, train, or a combination of both. Decisions about which terminals to use, which shipping routes to use, and which other transportation possibilities to use are included.

In both problems, relatively large mixed integer programming (MIP) models have been developed and solved using a commercial lp (linear programming) solver. Heuristics have also been developed in both problems in order to obtain faster solutions. Several scenarios of the problems have been tested and evaluated.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 2004. , 17 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1071
National Category
Mathematics
Identifiers
URN: urn:nbn:se:liu:diva-32396Local ID: 18296ISBN: 91-7373-893-X (print)OAI: oai:DiVA.org:liu-32396DiVA: diva2:253218
Presentation
2004-02-11, Glashuset, Hus B, Linköpings Universitet, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-11-07
List of papers
1. Supply chain modelling of forest fuel
Open this publication in new window or tab >>Supply chain modelling of forest fuel
2004 (English)In: European Journal of Operational Research, ISSN 0377-2217, Vol. 158, no 1, 103-123 p.Article in journal (Refereed) Published
Abstract [en]

We study the problem of deciding when and where forest residues are to be converted into forest fuel, and how the residues are to be transported and stored in order to satisfy demand at heating plants. Decisions also include whether or not additional harvest areas and saw-mills are to be contracted. In addition, we consider the flow of products from saw-mills and import harbors, and address the question about which terminals to use. The planning horizon is one year and monthly time periods are considered. The supply chain problem is formulated as a large mixed integer linear programming model. In order to obtain solutions within reasonable time we have developed a heuristic solution approach. Computational results from a large Swedish supplying entrepreneur are reported.

Keyword
Supply chain management, Integer programming, Inventory, Transportation
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-14461 (URN)10.1016/S0377-2217(03)00354-0 (DOI)
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2013-11-07
2. A combined terminal location and ship routing problem
Open this publication in new window or tab >>A combined terminal location and ship routing problem
2006 (English)In: Journal of the Operational Research Society, ISSN 0160-5682, Vol. 57, no 8, 928-938 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we consider a combined terminal location and ship routing problem at Södra Cell AB. The purpose is to supply the customers' annual demand for pulp products while minimizing the distribution costs. Customers are supplied with various pulp products from pulp mills in Scandinavia by ships, trains, or lorries. The ship routes go from the pulp mills to terminals in Europe. From each terminal, the products are transported to customers by lorry, train, or barge. Some customers can be supplied directly from the pulp mills by trains or lorries. We have developed a mathematical model to select which terminals to use and, at the same time, determine the shipping routes. The mixed integer programming model was solved directly using a commercial solver. When the number of routes generated is large, the time required to obtain an optimal solution is too long. Hence, we have developed heuristics in order to obtain an acceptable solution in reasonable time. In addition to the basic case, five different scenarios were tested. Our heuristics provide solutions that are within 0.12% of the optimal ones.

Keyword
mixed integer programming, facility location, transportation, ship routing
National Category
Mathematics
Identifiers
urn:nbn:se:liu:diva-14462 (URN)10.1057/palgrave.jors.2602057 (DOI)
Available from: 2007-05-14 Created: 2007-05-14 Last updated: 2013-11-07

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