SUbstance flow analysis of the recycling of small waste electrical ...

80 Substance flow analysis of the recycling of small WEEE
processed in a facility of type ‘mechanical 2’, whereas the remaining 24% is pre-processed
manually. 26% of collection group 5 is pre-processed manually, 25% in facilities of type
‘mechanical 1’ and 49% in facilities of type ‘mechanical 2’. Table 28 presents the assumed
distribution of the sWEEE over the four kinds of pre-processing facilities in 2007, as well as
assumptions on the recovery rates for precious metals achieved by the three types of preprocessing
facilities. The assumptions are based on the results of experimental substance
flow analyses conducted in pre-processing facilities for sWEEE.
Chancerel & Rotter (2008b) investigated a manual dismantling process and estimated that
around 82% of the gold contained in sWEEE of collection group 3 is sent directly to a
precious-metals recovery process. The remaining gold is either sent to further mechanical
pre-processing or sent to plastic recycling and lost. It is assumed that in total, pre-processing
through manual dismantling allows the recovery of 90% of the gold and palladium. The
results have the same order of magnitude as the results of Meskers et al. (2009), who
investigated only personal computers. Van Schaik & Reuter (2009) mentioned recovery rates
of 15% for gold in a shredding facility that can be assumed to be of type ‘mechanical 1’. The
results presented in Paper 2 showed that around 24% of gold and palladium are recovered in
a German facility of type ‘mechanical 2’. Meskers et al. (2009) conducted similar
experimental investigations in another facility using another type of technology, and
considering only personal computers. Much higher recovery rates (70%) were determined by
Meskers et al. (2009) compared to the results of Paper 2, probably due to the use of another
liberation technology and the homogeneity of the input material (only PCs) compared to the
input mix considered in Paper 2.
All these investigations are restricted to a certain facility at a certain time for a certain input
material. The limitations regarding representativeness of the studies cause high uncertainties
by the extrapolation of the data to the whole subsystem ‘pre-processing of sWEEE’ in
Germany. However, these experimental results are the only available data.
Because personal computers are sometimes dismantled manually in ‘mechanical 2’ facilities,
an average recovery rate of 50% was assumed. Regarding CRT monitors, observations
showed that in Germany the printed circuit boards are usually removed manually (Bolland
2009). Afterwards, they are usually treated mechanically to separate the iron and the
aluminium from the precious metals and the copper-rich materials. This mechanical
treatment leads to losses of precious metals that have, so far, not been quantified by
experimental investigations. An overall recovery rate for gold from CRT monitors of 60% was
assumed.