Methodology questions

Methodology questions

Closed-loop approach

When performing environmental studies such as Life Cycle Inventory Analysis for products made from wood fibres, the whole life cycle of the fibres must be evaluated from the fibre production until the fibre is lost as waste, normally after having been recycled several times.

Recycling may either be characterised as a closed-loop or an open-loop process. Closed-loop recycling returns the material to the original process and open-loop recycling refers to a product or component going from one system to another for use as raw material in the production of a different product.

To analyse an open-loop system, the inputs and outputs from the linked systems have to be studied. This, however, is not practicable in the case of paper recycling, since the linked systems are extremely complex and very difficult to survey.

To simplify the system, recycling of corrugated board may be looked upon as processing of the primary fibre after use in corrugated board or as raw material processing for the secondary product (or recycled products), also used in corrugated board. At present this is a fairly just simplification seeing that the main raw material for the recovered paper mills is used corrugated board, thus flows in and out of the system of other kinds of paper are ignored.

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