Quantitative and qualitative dynamic modelling of secondary raw materials from wood products in Germany

Abstract

Wood is a versatile natural resource widely utilized for material and energy purposes. In recent years, the growth in demand of harvested wood in Germany caused by efforts in substituting non-renewable materials and energy-intensive resources, as well as fluctuation in oil prices, has created challenges in the current harvesting and processing rates of primary and secondary wood raw materials, respectively. The supply of primary raw materials is currently covered by the growing rate of forests; however, no significant reserves for a further increase of harvested wood volumes are available. Even more, an increasing use of secondary raw materials for energetic purposes has been perceived, with a crowding-out in material applications. We can say that current use of wood as primary raw material comes near to sustainable harvesting. Thus, an enhanced use of secondary raw materials shall reduce stress in demand for primary sources and should have positive impacts on the environment. Besides the estimation of total amounts of secondary raw materials, a qualitative classification shows to be useful for a potential optimization of recycling. In this article, we estimate potential waste volumes and qualities using a dynamic stock and flow model of anthropogenic wood products. We take Germany as a case study considering consumer-based patterns of material use for satisfaction of services until 2050. Based on a material flow analysis (MFA) methodology, wood products are classified under a service perspective, in 14 product groups and 23 applications with specific in-use lifetime and average raw material compositions. It was found that secondary raw materials from recycled paper wastes suffer a decrease in the following decades, while wood waste, especially from residential buildings and furniture will increase with a possible stabilization by 2040. In the model a qualitative approach is introduced to provide future quality distribution of recovered wastes. This identifies volumes of secondary raw materials in quality groups which are the basis for improvements in waste processing technologies, management and sorting, to increase high quality waste fractions, and reduce the pressure on primary raw materials.