Analysis of energy efficiency of forest chip supply systems using discrete-event simulation

Abstract

Legislative changes have increased the allowable dimensions and weight for heavy transport vehicles in Finland, and this has been essential for the efficiency of wood chip transportation. In a typical forest, the supply of chips from roadside landings to the end-using facilities, such as combined heat and power plants, the balance of production capacities between chippers and the transportation of the chips by truck-trailer combinations substantially influence the performance of the system. The aim of this study was to investigate how new innovative chipper and vehicle types with increased chip carrying capacity would affect the cost and energy efficiency of the entire supply system. A method involving discrete-event simulation was used to investigate efficient solutions for the forest chip supply chain. By running several case scenarios, the aim was to examine the supply costs and efficiencies of new supply systems, and to investigate the difference at supply level between logging residues and small-diameter trees as raw materials.The study confirmed that new vehicle types with an increased chip load capacity can improve the cost, fuel economy and efficiency of forest chip supply. The results indicate that for most scenarios and transportation distances, the use of larger, 69-tonne truck-trailers with electronic trailer steering systems in combination with a highly productive traditional chipper unit was the set-up with the lowest cost per megawatt hour. However, smaller, 52-tonne semitrailer alternative vehicles also increased their competitiveness in cases where the material being transported had a higher moisture content or higher bulk-weight density.