Assessment of two different separation techniques for building wastes

Abstract

It is a well known fact that construction and demolition wastes (C and D wastes) make up 50% of municipal wastes in countries with a high gross domestic product (GDP). Besides questions about the handling of such enormous amounts of waste, problems also occur with the chemical composition of the C and D wastes. The latter problem is the result of the increasing use of synthetic organic materials and heavy metals in construction engineering during the last decades. In this paper two different treatment technologies for C and D wastes are compared, a wet and a dry separation technique. The comparison yielded the following results: both dry and wet technology are not able to select materials according to their chemical composition with the exception of iron, organic carbon and water soluble substances (in the case of wet sorting). Further, it is shown that there are only small differences in the produced fractions of the two plants. Both plants produce a small grain size fraction with the highest content of trace elements, which should be removed prior to reuse. It became obvious that the (chemical) quality of the input is the most important factor in view of the quality of the output fractions. Consequently, this makes separation of C and D wastes at source, a necessity on the way to multiple recycling steps.