Contamination in Swedich waste wood : environmental implications, sources and waste management strategies

Abstract: Today, bulk materials, e.g. wood, plastic, steel, and concrete, are contaminated by hazardous substances such as heavy metals, causing environmental and resource problems during waste management. This thesis aims to contribute with knowledge about the relationships between small substance flows and large bulk material flows, thereby enabling the development of strategies that decrease such environmental problems during waste handling. For this purpose, Swedish recovered waste wood (R WW) and its contaminants were studied in detail. Due to their high toxicity, nondegradability, and frequent use in urban areas, the heavy metals zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), arsenic (As), cadmium (Cd), nickel (Ni), and mercury (Hg) were selected for study.This thesis is mainly based on three studies. To start with, elemental fuel analyses of RWW were reviewed to accomplish a broad assessment of the elemental content in the waste and to define the general extent of contamination. Secondly, the sources for this contamination were tracked and identified by analysing the inflow of the studied substances via different products during the middle of the 20th century. Finally, different upstream strategies to handle R WW, here categorised as separation measures taken before the RWW enters the combustion plant, were compared and evaluated, determining how they would influence the environmental impact generated downstream in the current waste management system in Sweden.It is concluded that current RWW has been substantially contaminated by all of the studied heavy metals during its lifetime in the technosphere. Furthermore, RWW of Swedish and European origin (Swedish combustion plants import RWW fuel from Europe) differ in their elemental composition. Swedish RWW contains more arsenic, zinc, chromium, copper, and nickel, whereas European waste displays higher concentrations of lead, cadmium, and mercury. For Swedish RWW, the main origin of this contamination is limited to a few sources, of which surface-treated and industrial preservative-treated wood constitute the most important ones. From a total metal flow perspective, it seems that the metal flows related to RWW are small compared to other metal flows in Sweden, except in the case of arsenic. Arsenic in RWW is of the same magnitude as other substantial flows in Sweden, such as a contaminant in coal.Today, the management of RWW is mainly downstream-oriented, focusing on measures at combustion plants, such as dilution of contaminants and installing gas cleaning. In contrast to this downstream focus, the results from this thesis emphasise the importance of upstream separation strategies, which exhibit several environmental benefits compared to the current management. However, from a long-term perspective, all strategies suggested for improving the handling of RWW more or less shift pollution problems to the future. Hence, to accurately prevent environmental pollution, upstream strategies must be combined with measures taken further downstream in the current waste management system, permanently immobilising the hazardous substances. Again, upstream separation strategies are argued to be important since they decrease the volume problem, thereby enhancing implementation of such downstream immobilising strategies.