Mean fiber age, i.e. the mean number of production cycles that fibers in a given paper material have undergone so far, can be calculated theoretically based on the mass flows in a given paper recycling loop. The presentation will show how mean fiber age distributions can be calculated in multiple, connected recycling loop systems, which are typical for countries and regions with high recovered paper utilization and recycling rates. The calculation uses a graph theory approach. The same approach shows that there is a second important value which highlights another aspect of the circular economy-the number of future material uses. This value quantifies how often the fibers in a given paper product will be used on the average by the end of life. Put simply, the 'fiber age' describes the past and the 'number of future material uses describes the future of the fibers in a paper or board product. Calculated results for the European region will be presented and compared for both parameters 'fiber age' and 'number of future material uses'. It will be shown that both values add up to a total number of material uses and should be used together. They are suitable for characterizing the resource efficiency of fiber-based material production.
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