If possible, auxiliary and process materials should be used in closed cycles. Re-use (i.e. without destroying structures) should be preferred to recycling (materials cycles after destruction of structure). If the materials needed for are used up in the process operation (e.g. printer ink, toner...) re-use of containers or other components (ink cartridges, toner cartridges) should be considered.
Type and quantity of waste generated during the use stage of a product may considerably influence the total environmental balance of the product. Strictly speaking, only active (consumption-intensive) products consume energy or materials at their use stage. Considering the whole life cycle of the product, the consumption of these resources usually dominates the overall environmental impact of the product. Therefore, the prevention of waste at use stage is very important with this type of product. The example shows the use of rechargeable accumulators instead of conventional batteries.
Strictly speaking, only active (consumption-intensive) products produce emissions and effluents at their use stage. Considering the whole life cycle of the product, these usually are a dominant factor in the overall environmental impact of the product. The example shows a possible solution of the problem; the method uses a flue gas catalyst to reduce the harmful environmental impact. However, for such approaches an analysis of the total consumption has to be realized in order to prevent that the problem is merely shifted to another area.
Collecting waste arising at use stage is reasonable not only with a view to disposal (used batteries) but also in the context of potential re-use (parts and components) or recycling (materials). The example shows a system for returning empty toner cartridges of a printer. The empty cartridges can be refilled and re-used. Using the cartridges in a closed cycle results in a high value added. Incentives (bonus, exchange campaigns...) can make this system highly attractive for users.
In addition to collecting waste from the use stage for the purpose of re-use, recycling, too, is possible and desirable in compliance with the concept of closed cycles. Either it is possible to recycle waste products on the site (see example candle stumps) or they are collected, recycled elsewhere and fed back to the production process. In plastic processing, for instance, adequate admixtures of new to recycled material yield plastics suitable for the same applications as the original. Plastic parts containing up to 100% are used predominantly for invisible interior parts and components of a product.
Waste material from the use stage that cannot be re-used or recycled must be disposed of in an environmentally acceptable way. This refers to best practice disposal (hazardous substances) or, if possible, to an integration in natural cycles. On the whole, the issue of waste often depends on perspective; for, waste generated in one part of the system may be considered valuable raw material in another part of the system. A sophisticated combination of different systems, organization of process stages in cascades can often result in a total avoidance of waste.
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