Efficient use of materials, process and auxiliary materials by applying adequate technologies (best practice) reduces the overall consumption of raw materials. This, in turn, reduces damage to the environment through waste, on the one hand, and reduces the quantity of raw materials extracted from the environment, on the other. Low emission production technologies reduce the need for downstream purification and filter plants. In addition, the amount of usually toxic residues from purification and filtering will be reduced.
Irrespective of the energy consumption and emissions during normal operation certain technologies constitute a high environmental risk and may cause considerable environmental damage in the case of accidents. This also includes risks through the use of toxic auxiliary and process materials.
The goal of each production process consists in the transformation of raw materials into products. Thus, process waste may be considered an indicator for inefficient use of materials. Apart from the environmental impact caused by the disposal of waste the consumption of raw materials extracted from the environment has to be taken into account. In many cases, the procurement of raw materials that are transformed into waste in inefficient production processes, is a decisive cost factor. Avoiding this type of waste not only reduces the cost of disposal but also purchase costs for raw materials.
An important strategy of waste prevention and cost reduction consists in closing materials cycles in the production process. Recycling waste materials and returning them into the production process reduces consumption of primary raw materials as well as the cost of waste disposal. In addition, there is less transportation than for external recycling or disposal. One of the prerequisites consists in the use of recyclable materials and in collecting and sorting of process waste.
In many cases it will not be possible to avoid process waste altogether or to return these materials in the production process. It should be considered to re-use/recycle them for the manufacture of new products. However, in this context one has to ensure that the manufacture of these new products does not generate waste even more hazardous than the original material, which would counteract the intended beneficial effect to the environment
In spite of all efforts an altogether waste-free production can be realized only in rare cases. This unavoidable waste has to be disposed of in such a way as to ensure that the environmental impact is kept to a minimum. One possible way consists in waste separation and subsequent specific re-use or disposal of materials. In this context, careful handling of hazardous substances is particularly important. Another approach focuses on the input aspect and aims at actively controlling the composition of waste materials by selecting appropriate materials, auxiliary and process materials.
Sorting and separating process waste constitutes an essential prerequisite for, both, in-house or external recycling and re-using of materials as well as for specific treatment of different types of waste. In some cases, separation for classes of waste may be sufficient. In order to achieve this goal it often suffices to rearrange the sequence of individual production stages. For example, cutting to size structural parts consisting of different materials before they are glued together avoids composite material waste, which can be separated only at great expense.
Minimizing the reject rate is an important goal if only with a view to cost reduction, and it is also a key factor in quality management and quality assurance. Rejects could be defined as product without any direct benefit attributable to the input of resources used up in the manufacture of the product; this means that resource efficiency is absolutely zero. If consumption of resources is set off against the other products the overall resource efficiency decreases with the reject rate. A further problem of rejects, especially if they are rejected at a late stage in the production process, consists in the fact that the components have to be disassembled before they can be recycled on the production site.
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