RESEARCH AND ANALYSIS
Figure 2 Global paper flows in 2012 in megatonnes.
Table 5 Material flows and their upper and lower bound
Uncertainty The data sources are sufficiently reliable to allow construc- tion of a complete and consistent material balance. The appar- ent match between parameters and values from independent data sources reinforce the validity of the results. The follow- ing flows cannot be validated using the mass balance principle: non-fibrous input, virgin fibrous inputs, industrial waste genera- tion, residual waste paper treatments, and industrial waste treat- ments. The amount of non-fibrous materials was calculated as a final difference. The non-fibrous content is 15.1% of final paper and cardboard production in 2012. Cross-checking reveals that this value is very close to the amount of non-fibrous materials (14.9%) used in a selection of European countries (CEPI 2012). The uncertainty of the other aforementioned flows is quantified through sensitivity analysis. Sensitivity analysis shows the effect of parameter variation and is frequently applied to assess the robustness of material flow models (Laner et al. 2014). The approach in this article is to calculate a lower and upper bound for a flow based on the range of the relevant parameter. The parameter for the yield ratio of chemical and mechanical pulping affects virgin fibrous inputs and industrial waste generation, the parameter for net additions to stock affects the residual waste paper treatments, and the parameters for industrial waste treatment affect the total quantities going for non-energy recovery and landfill. The fraction of waste that is burned, but remains as ash, is included with non-energy recovery or landfill. All flows are reported to the nearest 1 megatonne.
Value used (mega- tonnes)
Upper bound (mega- tonnes)
Lower bound (megatonnes)
Material flow
Virgin fibrous inputs Net additions to stock Postconsumer waste to energy recovery Postconsumer waste to incineration Postconsumer waste to landfill
307
347
411
24 19
36 20
48 22
13
14
14
116
130
145
Industrial waste to energy recovery Industrial waste to
134
158
178
16
24
48
non-energy recovery
Industrial waste to landfill
16
24
44
(left) to end-of-life (right). The flow width reflects the quantity. Mill wastes indicate waste flows in the industry that are either used in on-site energy recovery, are non-energy recovered, or landfilled. On-site energy recovery by paper producers is dis- played separately from incineration with and without energy recovery of paper in residual MSW. Waste paper from paper- making is visualized as separate fibrous and non-fibrous losses, and they enter the same recycling loop as postconsumer waste paper. The detailed results including equations are given in section SI-2 of the supporting information on the Web. Table 5 shows the upper and lower bounds for several mate- rial flows based on the sensitivity analysis. The relative variation of the lower and upper bounds from the used value is largest for non-energy recovery and landfill of industrial waste. The ranges
Results and Discussion Figure 2 shows the Sankey diagram of global paper flows in 2012. The diagram displays the flow of materials from harvest
Van Ewijk et al. , Global Paper Flows, Recycling, Material Efficiency 5
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