Sources of heavy metal contamination in Swedish wood waste used for combustion.

In this paper, wood waste (RWW) recovered for heat production in Sweden was studied. Previous research has concluded that RWW contains elevated amounts of heavy metals, causing environmental problems during waste management. This study extends previous work on RWW by analysing which pollution sources cause this contamination. Using existing data on the metal contents in various materials, and the amounts of these materials in RWW, the share of the elevated amounts of metals in RWW that these materials explain was quantified. Six different materials occurring in RWW were studied and the results show that they explain from 70% to 100% of the amounts of arsenic, chromium, lead, copper and zinc in RWW. The most important materials contributing to contamination of RWW are surface-treated wood, industrial preservative-treated wood, plastic and galvanised fastening systems. These findings enable the development and evaluation of strategies aiming to decrease pollution and resource loss from handling RWW. It is argued that source separation and measures taken further downstream from the generation site, such as treatment, need to be combined to substantially decrease the amount of heavy metals in RWW.