Analysis of contaminants in waste wood

IRG/WP 01-50179

J Jermer, A Ekvall, C Tullin

Waste wood is increasingly used as fuel in Sweden. It is of Swedish origin as well as imported, Mainly from Germany and the Netherlands. The major chemical contaminants are surface treatments (paints etc) and wood preservatives. The surface treatments contribute in particular to contaminants of zinc and lead. In some cases zinc has been found to cause severe deposits in the furnaces. Surface treatments also contribute to increased levels of sodium, chlorine, sulphur and nitrogen. Preservative-treated wood is the most important source of increased levels of copper, chromium and arsenic in the waste wood. Waste wood imported from Germany contains less arsenic but the same amount of copper and chromium as Swedish waste wood. The fraction consisting of wood-based panels is comparably free from contaminants but as a result of the high contents of adhesives wood-based panels contribute to a higher proportion of nitrogen in waste wood than in forest residues. A great number of non-wood compounds (such as plastics and metals) do also contaminate waste wood. By careful and selective demolition and various sorting procedures most non-wood compounds will be separated from the waste wood. Metal objects of zinc, brass and aluminium are considered to be particularly troublesome as they may plug primary air openings. PVC residues may cause considerably higher levels of chlorine in waste wood. Chemical analyses indicate that the distribution in levels of impurities varies a lot between deliveries of waste wood. Difficulties to take representative samples probably contribute to this. The study has confirmed previous studies that waste wood contains a substantial proportion of fine fraction. 25-40% of the waste wood passed a sieve with a mesh size of 4 mm at screening trials. Chemical analyses indicated that the fine fraction will be the main contributor to contaminants of potassium, chlorine, sodium, zinc and lead.


Keywords: WOOD; CONTAMINANTS; ANALYSIS

Conference: 01-05-20/25 Nara, Japan


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