Methodology for Calculating the Environmental Impacts of Different Classes of Sawn Timber Strength

In the European Union, when sawn timber has a structural use, it must be classified in strength classes according to the standard EN 14081-1. Strength classes classify each sawn timber element according to its strength, stiffness and density properties. The environmental impacts of sawn timber for structural use have been calculated in several life cycle assessment studies, however, these studies use 1 m3 of sawn timber as functional unit, without specifying the strength class. This means that the environmental impacts calculated for one cubic meter of sawn timber do not take into account its structural use. The structural use of sawn timber products should be taken into account when calculating environmental impacts because in the process of design a timber-based structure, the structural class is essential to determine the volume of timber required. Thus, the main goal of this study is to develop and present a methodology to quantify the environmental impacts of various strength classes by using the results of mechanical grading for a sample of sawn timber of a given wood species from a specific region of origin. This methodology consists of two steps: i) data collection (identification and collection of existing data for combinations of wood species and regions of origin – allocation yields), and ii) allocation of environmental impacts to the various strength classes. In this study, the methodology is applied to a case study of Maritime pine wood from Portugal.