Paper recycling: perspectives and limitations

by Ilaria Braschi, Enrico Buscaroli, Chiara Bisio, Stefano Marchesi, Leonardo Marchese from the Re-Paper project of Università di Bologna.

In the digital era, paperless is the rule. Despite a steep worldwide decline in classic publishing and graphic paper, the global paper market has been growing steadily at 1% of Compound Annual Growth Rate in the last decade. Mostly, thanks to paper packaging [1].

Paper is a cheap and versatile material, ideally recyclable indefinitely and easy to obtain too. Not surprisingly, these properties make paper the most used material within the packaging industry. In Europe, paper accounts for 40.9% of waste generated by packaging material: 31.8 billion tonnes, specifically [2]. To date, 84.6% of this waste is being recycled [3]. For comparison, the global EU paper recycling rate was only 72% in 2019. Therefore, the paper packaging sector is largely anticipating the EU commission global paper recycling rate targets of 85% by 2030.

Nevertheless, recycled paper materials do have some limitations. During the recycling process, paper tends to accumulate consistent amounts of hazardous contaminants, mostly aromatic and aliphatic hydrocarbons (the so-called mineral oil hydrocarbons: MOH) that are used as an ink solvent in offset printing [4]. Benzophenones, diisopropylnaphtalenes, photoinitiators, phthalates and bisphenol A are commonly found in recycled pulp as well. For this reason, recycled paper is not considered a safe material for food and beverage packaging, which is the higher growth rate and most demanding sector. In fact, MOH and the other recycled paper contaminants can migrate into foodstuff, then accumulate into human fat body tissue and may, eventually, produce long-term toxic and carcinogenic effects or endocrine interferences in mammals [5,6].

Safety and efficiency. Is it a trade-off?

The awareness of these contaminants only increased significantly in the last decade, thanks to analytical assessment improvement and many food safety studies. The European Food Safety Authority (EFSA) began to collect data on the topic in 2012. Responding to the EFSA call for data, most of the food and food packaging industry implemented few strategies to mitigate the risk. Most of them simply ceased using recycled paper in favour of virgin white pulp in food-contact paperboard, as a precautionary measure. Other strategies involve the use of multi-layered materials or functional barriers together with recycled paper. In this way, MOH migration into foodstuff is surely prevented, although some criticism may be raised. Although barriers protect food, paper contamination keeps persisting in that it is simply confined or moved elsewhere. Most importantly, these multi-material packaging products have higher costs and are also more difficult (if not impossible) to recycle.

Following a completely different approach, why not simply remove the mineral oil and all the other contaminants from recycled paper? Cellulose fibres have high specific surface and porosity. At a first glance, it may seem that removing organic contaminants from such an intricate matrix would be difficult, to say the least. In fact, commonly used decontamination techniques have limited efficacy or excessive costs.

Re-Paper project: improving recycling process

Re-paper project was born from a 2017 study [7] by researchers from the University of Bologna and the University of Eastern Piedmont “Amedeo Avogadro”. The vision behind the project was clear from the start: using advanced material technologies to obtain safe and superior quality recycled products, producing value for the industry, consumers, and the environment.

Re-Paper has been developing a technology to easily decontaminate recycled paper from MOH and other organic contaminants using specifically designed sorbent materials. These sorbents combine high affinity towards poorly soluble hydrocarbons and organic contaminants with excellent resistance toward high temperature and pulp alkalinity. Its use does not alter pulp quality, nor requires substantial modifications on the production line. In addition, the materials are recoverable, regenerable, and reusable. The technology was patented in 2017. In 2020, about 120k€ were raised as research grants from both public (Italian Ministry of Economic Development, the University of Bologna) and private funds (Venture Factory s.r.l.).

Re-Paper technology would be able to largely improve the quality of recycled paper, saving costs to paper producers and adding value to the paper recycling process in terms of efficiency and safety of recycled paper and paperboard.

At the moment, Re-Paper team is looking for industrial partners for scaling up their research and is keen on collaborating with capital equipment manufacturers serving the paper industry.

References

[1] Berg, P. & Lingqvist, O., 2019. Pulp, paper and packaging in the next decade: Transformational change. McKinsey & Company.

[2] Eurostat, Packaging waste by waste management operations. https://ec.europa.eu/eurostat/databrowser/view/env_waspac/default/table?lang=en

[3] Monitoring report 2019, European Paper Recycling Council

[4] Lorenzini, R., Fiselier, K., Biedermann, M., Barbanera, M., Braschi, I., & Grob, K. (2010). Saturated and aromatic mineral oil hydrocarbons from paperboard food packaging: Estimation of long-term migration from contents in the paperboard and data on boxes from the market. Food Additives and Contaminants — Part A Chemistry, Analysis, Control, Exposure and Risk Assessment, 27(12), 1765–1774. doi: 10.1080/19440049.2010.517568

[5] Ozaki, A., Yamaguchi, Y., Fujita, T., Kuroda, K., & Endo, G. (2004). Chemical analysis and genotoxicological safety assessment of paper and paperboard used for food packaging. Food and Chemical Toxicology, 42(8), 1323–1337. doi: 10.1016/j.fct.2004.03.010

[6] Concin, N., Hofstetter, G., Plattner, B., Tomovski, C., Fiselier, K., Gerritzen, K., . . . Grob, K. (2008). Mineral oil paraffins in human body fat and milk. Food and Chemical Toxicology, 46(2), 544–552. doi: 10.1016/j.fct.2007.08.036

[7] Buscaroli, E., Bussini, D., Bisio, C. et al. Stabilization of mineral oil hydrocarbons in recycled paper pulp by organo-functionalized mesoporous silicas and evaluation of migration to food. Eur Food Res Technol 243, 1471–1484 (2017). https://doi.org/10.1007/s00217-017-2867-5