Log sorting in forest harvest areas integrated with transportation planning using backhauling

Abstract

Paper manufacturers are increasingly demanding wood pulp of an even and good quality. Therefore, there is increasing interest in sorting the raw materials (logs) while still in the forest, to obtain raw materials of a more homogeneous or more specific quality. More sorting leads to an increase in sorting costs as well as an increase in transportation costs as the catchment area for more homogeneous raw materials becomes larger. An integrated integer programming model was developed, taking into consideration options for sorting and transportation planning. The latter includes routing in terms of potential backhaulage routes. The solution method is based on column generation combined with branch-and-bound techniques. Results from the forest companies Södra Skogsägarna, Sydved and Holmen show that the model can solve some typical case studies efficiently. One case study showed that the introduction of specific demands on pulpwood from thinnings by two of the region's pulpmills would lead to a 6% increase in total sorting and haulage costs. By optimizing the use of backhaulage the cost increase could, however, be reduced by 25%.