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| Fig. 1: Simplified flow of the European paper-recycling system illustrating two major bottlenecks examined here (highlighted in red). The export route risks losses in recycling gains through waste colonialism, while the domestic route faces unoptimized operations at the drying stage. Both pathways present distinct challenges that limit overall system performance. (Image source: N. Tan) |
Recycling is central to modern energy and emission reduction strategies. Yet repurposing discarded materials is far from simply recovering what was originally used. Paper and board, among the most widely recycled materials, face economic and political pressures to meet ambitious targets. These pressures can distort reporting and undermine the performance goals recycling systems aim to achieve. Meanwhile, genuinely recycled material undergoes mechanical and chemical treatments that hinder the potential energy savings of paper recovery.
This paper examines these institutional and technical bottlenecks in Europe's paper-recycling system to show that sustainable papermaking depends not only on increased, but smarter recycling.
Europe provides an ideal setting for examining the performance of paper recycling because its high reported recycling rates and long-term growth reveal both the strengths and underlying complexities of a large-scale circular system. Paper recycling rate in Europe reached up to 79.3% in 2023, representing 53.7 million tonnes of recovered material, the highest among global regions and well ahead of metal, glass, and plastic. [1] The rise from 40.3% in the 1990s shows how central recycling has become in Europe's sustainability strategies and how the region serves as a global benchmark for circular production.
Because paper dominates material generation and recovery, even slight distortions in reported rates or small efficiency gains carry substantial implications for regional energy use and carbon reductions. Europe thus offers a lens to evaluate the political and technical bottlenecks that constrain paper recycling efficiency. Figure 1 provides an overview of these pathways.
Despite Europe's high reported recycling rates, its paper-recycling system faces structural and economic pressures that undermine the reliability of these figures. In 2021, 12.4% of Europe's collected paper, amounting to 4.4 million tonnes, was exported outside the EU, primarily to India, Indonesia, and Turkey. [2]
This pattern reflects a form of waste colonialism, in which wealthier regions shift environmental and social costs onto countries with weaker regulatory protections. In India, large portions of the recycling chain remain informal, with collection and sorting often handled by unregulated workers and enterprises. [3] These conditions create uncertainty about whether exported paper is recycled safely, efficiently, or at all.
Exported paper bales also are estimated to frequently contain 5-30% contamination, including plastics, food residues, moisture, and chemically coated papers. [4] These contaminants reduce the fraction of recoverable fiber and disrupt key processing steps, contributing to efficiency losses examined in the next section.
Together, these risks can undermine the energy and emission savings attributed to recycling, showing how political and financial incentives obscure the true performance of Europe's system.
For the paper that enters proper recycling channels, a second major bottleneck emerges. Unlike purer materials, paper must be mechanically and chemically rebuilt each cycle.
Each cycle degrades cellulose fiber, shortening them and reducing their ability to form the strong bonds needed for commercial strength and surface properties. Studies done on hardwood kraft pulp show that repeated recycling lowers water retention value (WRV) by up to 25% after 7 cycles due to reduced swelling and flexibility. [5] Although lower WRV suggests less water in the fiber walls, it actually results in poorer drainage during pressing, leaving more water in the web. This water must then be removed through energy-intensive drying.
Drainage inefficiency is compounded by strengthening agents, known as stickies, which accumulate on fiber surfaces, block pores, and worsen drainage. [6] Stickies use increases with each cycle as material deteriorates. This combined effect of mechanical and chemical deterioration forms the principal bottleneck in paper recycling, forcing mills to rely heavily on drying steam.
Since 64% of the energy in paper recycling is consumed in drying, these bottlenecks have major implications on overall mill efficiency. [7] This creates a paradox: as paper is recycled more frequently, the process intended to conserve energy becomes less efficient. This does not mean that recycling is counterproductive but highlights the mechanical and chemical limits that must be addressed to improve results.
Improving the water retaining behavior of these recycled sheets remains one of the clearest opportunities for energy savings. Better drainage in the press section reduces the load on drying equipment, which dominates the energy footprint of paper recycling. Conversely, even small losses in press drainage can increase dryer demand and raise overall energy use. Thus, focusing on the factors that govern water removal efficiency at the fiber level is one of the most direct ways to improve energy performance.
Paper recycling has advanced significantly, but major opportunities remain when political and technical constraints are considered. Europe's system shows how reported recycling rates can mask underlying issues, undermining the environmental benefits recycling is assumed to deliver. Meanwhile, the paper that is reprocessed faces intrinsic limitations. Fiber degradation, declining WRV, and increasing stickies reduce drainage efficiency and force mills to rely heavily on energy-intensive drying. Addressing these dual bottlenecks is essential to realizing the full potential of circular papermaking. Improving fiber-level drainage behavior and understanding how efficiency declines with successive cycles could unlock energy savings, while stronger traceability and lower contamination would help ensure recycling statistics reflect real environmental gains. Given the scale of paper production, even small improvements in process efficiency or system integrity can yield meaningful energy and emissions reductions. Ultimately, progress will depend not only on increasing recycling rates, but on practicing smarter recycling.
© Nathan Tan. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] "Monitoring Report 2024," European Paper Recycling Council, 2024.
[2] M. Stravens, "Disposable Paper-based Packaging for Food," Profundo, September 2023.
[3] L. Sridhar and P. Kumar, "The New Face of Waste Colonialism: A Review of Legal Regulations Governing the Import of Waste into India," National Law School of India University, Bengaluru, Socio-Legal Review 15 101 (2019).
[4] T. Karlsson et al., "Plastic Waste Trade: The Hidden Numbers," International Pollutants Elimination Network, March 2023.
[5] E. Letková. M. Letko and M. Vrška, "Influence of Recycling and Temperature on the Swelling Ability of Paper," Chem. Pap. 65, 822 (2011).
[6] I. Diaconsecu, R. Patrascu, and E. Minciuc, "Energy Efficiency Study of the Paper Making Drying Process," IEEE 8120806, 2017 Intl. Conf. on Energy and Environment (CIEM), Bucharest, 19 Oct 17.
[7] D. Licursi et al., "Monitoring/Characterization of Stickies Contaminants Coming From a Papermaking Plant - Toward an Innovative Exploitation of the Screen Rejects to Levulinic Acid," Waste Manag. 49, 469 (2016).