Environmental product declaration of timber products: The impact of allocation method to the impact categories

Nowadays, several novel standards guide the environmental assessment work in the field of construction products. In this study, allocation methods presented in EN 15804 standard are demonstrated in a comparable manner for sawmilling products. Cradle to gate assessment was done for three European sawmills, where different allocation methods were used in manufacturing phase. Firstly, were used physical allocation (volume based) and economic allocation (value based). Secondly, manufacturing process steps were divided (subdivision) and physical and economic allocation were used for these. In the third option, used as a reference, all environmental impacts of the manufacturing stage were allocated to the main product. This study focuses on indicators for describing environmental impacts and use of primary energy. Results indicate that allocation influences how impacts are distributed to the sawmilling products. As supposed, sawn timber as main product is getting biggest impact in all cases, because of the biggest quantity in production. Physical allocation is looking volumetric distribution of the products, where economic allocation is also considering value of the products. Additional, subdivision will give more holistic approach based on different production steps together with physical or economic quantities. Based on the results, the subdivision with economic allocation or the economic allocation gives more realistic impacts to low value by-products. Subdivision with economic allocation is the most holistic option, because impacts are allocated by processes, volumes and values. Despite of all standardization work, many different assessment methods can and are still used for the environmental assessment of the building products. That has led to a situation where different datasets are not comparable with each other and this causes confusion in users of the environmental datasets. Therefore, transparent datasets are needed to avoid misunderstandings and the reporting system could be developed to be more uniform.