Socio-economic assessment and feasibility study on - Ã–ko-Institut eV

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50 A August 2010 B C D <strong>Socio</strong>-<strong>economic</strong> <strong>assessment</strong> <strong>and</strong> <strong>feasibility</strong> <strong>study</strong> on sustainable e-waste management in Ghana A = Steel scrap B = Aluminium scrap C = High grade precious metals fraction D = Copper cables E = Low grade copper fraction F = Plastic fraction Photo 8 Manually dismantled <strong>and</strong> sorted desktop PC (Source: Öko-Institut 2010) Nevertheless, even with deep manual dismantling, some copper <strong>and</strong> precious metals containing components like cables, small motors <strong>and</strong> reading/writing devices of drives need further pre-treatment. Although even these steps could be carried out manually, the <strong>economic</strong> output might not justify the high labour intensity. Therefore, this residual fraction could be passed on to mechanical pre-treatment facilities. Thereby it is of particular importance to identify alternative local treatment options for cables in order to eliminate the common practice of cable burning (see photo 7). Generally, copper cables can either be stripped manually using knives <strong>and</strong> bench vices (to fix the cables), or automatically using a cable shredder or cable granulator. Both options have distinct strengths <strong>and</strong> weaknesses, which can be summarised as follows: - Manual cable stripping is only suitable for thick cables. With thin cables, it is quite difficult to liberate all copper strings from the insulation. E F
<strong>Socio</strong>-<strong>economic</strong> <strong>assessment</strong> <strong>and</strong> <strong>feasibility</strong> <strong>study</strong> on sustainable e-waste management in Ghana August 2010 - Manual stripping is very labour intensive. As scrap yard workers at Agbogbloshie are now used to the practice of burning, it might be difficult to convince them to deploy significantly more labour for comparable copper outputs. - Automatic shredder <strong>and</strong> sorting machinery is capital intensive <strong>and</strong> requires investments costs in a range of US$ 25,000 to 100,000 – depending on size <strong>and</strong> capacity of the installation 30 . Additionally, the machinery needs electricity (usually 400V at 50Hz) as power dem<strong>and</strong>s are in a range of 3 to 100kW. - Unsound operation of shredders can lead to dust emissions <strong>and</strong> dioxin formation. This is especially the case, when the machinery runs hot. - Both, manual cable stripping <strong>and</strong> mechanical shredding lead to copper losses into the plastic fraction. This might require a subsequent sorting of the plastic fraction in a saltwater-bath (plastic floats, while copper sinks). Taking these issues into account, it can be concluded that despite some disadvantages, mechanical cable shredders should be deployed to provide alternatives to the common burning practice. End-processing The output fractions of the manual pre-treatment are passed on to end-processing operations. Ideally, such end-processing operations are able to combine efficient material recovery with high environmental st<strong>and</strong>ards. The steel scrap is processed in electric arc furnaces that produce secondary steel products. There are currently five electric arc furnaces operating in the port city of Tema. The aluminium scrap is passed on to aluminium remelters that produce cast alloys from aluminium scrap. There are several aluminium remelters in the region of Accra <strong>and</strong> Tema. The high grade precious metals fraction can be sold to two major types of end-processing enterprises: Pyrometallurgical refineries <strong>and</strong> hydrometallurgical refineries. Thereby it has to be noted that pyrometallurgical refineries focus on a wide range of metals, while hydrometallurgical refineries exclusively target precious metals. In terms of recovery rates of precious metals, pyrometallurgical refineries are preferable to hydrometallurgical refineries as the melting process affects all input materials, while the hydrometallurgical treatment only affects the surface layer of the feed material. Although the PWBs can be grinded to particle sizes that allow quite comprehensive treatment, these physical size reduction processes are also likely to generate precious metals losses. Additionally, interactions of chemicals also reduce the effectiveness of metal recovery (Schluep et al. 2009). From an environmental perspective, there is an ongoing debate on the sustainability of hydrometallurgical refineries: While some authors argue that they provide a 30 Cable shredders / granulators are usually available with capacities ranging from 50kg/hr to 1000kg/hr. 51
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Socio-economic assessment and feasibility study on - Ã–ko-Institut eV

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