The blue bin is for paper, the red one for plastic, green for glass, and yellow for metal. Sorting materials should be a simple task, but who has never been in doubt? Does the long-life milk carton go in the blue or yellow bin? And what about the chocolate wrapper, which is plastic on the outside and metallic on the inside? Packaging like these, made from more than one type of material, not only complicate selective collection but are also much harder to recycle. Of course, manufacturers have their reasons. Each material used is responsible for providing different characteristics to the packaging (such as strength, elasticity, impermeability, protection against light and heat), and together they ensure high performance in the primary function of packaging: protecting the products.
On one hand, multi-material packaging is more effective, allowing for reduced losses during product transportation and even extending their shelf life. On the other hand, although their components are technically recyclable, separating the materials is labor-intensive and increases costs. Often, the final result is also not of the best quality, as one material contaminates the other. The good news is that solutions are emerging.
Carton packaging, known as Tetra Brik - better known by the brand, Tetra Pak - is one example. Composed of paper (75%), polyethylene (20%), and aluminum (5%), they revolutionized the food market by allowing food preservation without refrigeration. Although this represents less waste and significant energy savings, around 12 billion packages of this type are produced each year. Their recycling is complicated but feasible. Discarded packaging is agitated with water, which hydrates the paper fibers and allows for their separation. The residual mixture of aluminum and polyethylene can be mechanically recycled (for the production of injected parts), through pyrolysis (which recovers aluminum), or is incinerated to harness the released energy. In 2005, Brazil received its first Tetra Brik recycling facility through plasma technology. Temperatures of 15,000°C are needed to ionize the mixture of plastic and aluminum, resulting in pure metal and paraffin, which can be used in the petrochemical industry.
Packaging made solely from plastic can also pose a significant challenge for recycling. This is because many are composed of parts or layers of different polymers, which require distinct recycling processes, or are incompatible at the molecular level. PET and PVC are a good example of plastics that should not be mixed. PET processing occurs at high temperatures, which would transform PVC into several substances, including hydrochloric acid. Therefore, even small amounts of PVC contaminating PET can make its recycling unfeasible.
To avoid, or at least minimize, contamination of one type of plastic by another, careful separation is necessary. Generally, the first step consists of primary separation, which can be manual or automatic. After that, the material is shredded into smaller pieces. The pellets or flakes undergo a washing process, which consumes around 2 to 3 cubic meters of water per ton of material, but dry washing techniques are already emerging. Then the material goes through a second sorting, being separated based on color, density, and electrostatic properties. The use of lasers for identifying the pellets is a recent technology that has the ability to differentiate various types of polymers. This technology is only used in a few European facilities. The advantage is that the better the separation, the wider the range of applications the material can have, and the more times it can go through the recycling process.
Although recycling mixed plastics is more labor-intensive, it still represents a “savings” in greenhouse gas emissions, estimated at around 0.5 tons of carbon dioxide per ton of recycled material, according to data from the Waste & Resources Action Programme (2008). This information becomes significant when we remember that global plastic production in 2010 reached 265 million tons (according to the Plastics Europe report, 2011), with petroleum as the main raw material. Unfortunately, the recycling of multi-material packaging is still quite limited due to the lack of specific technologies for the proper separation of some components, as well as the high costs involved. But one of the biggest barriers preventing the development of the recycling sector (in general) is selective collection, which is practically non-existent in most Brazilian municipalities.
In 2010, the recycling landscape in Brazil began to take new directions, driven by the implementation of the National Solid Waste Policy. To reduce waste disposal in landfills, the new legislation encourages the reuse and recycling of materials, in addition to making companies co-responsible for the entire lifecycle of their products. This has a significant impact on the packaging sector, whose challenge now is to create options that use less material and are easier to recycle, while remaining attractive to consumers and maintaining practicality in terms of transportation, storage, and distribution.
Today, one of the major bets in the sector is the stand-up pouch laminated packaging. Its design represents a huge material saving compared to rigid packaging. Extremely practical, it can already be found in any supermarket, protecting various types of food and cleaning products. There is just one catch: most recycling companies still do not work with laminated packaging. Although there are already some pioneering alternatives for the reuse and recycling of these packages, further studies are needed to develop technologies for broader applications that allow for their effective reintegration into the recycling chain.
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References
HOPEWELL, J.; DVORAK, R.; KOSIOR, E. 2009. Plastics recycling: challenges and opportunities. Philosophical Transactions of the Royal Society B 364: 2115-2126. doi:10.1098/rstb.2008.0311
MARSH, K.; BUGUSU, B. 2007. Food packaging – roles, materials, and environmental issues. Journal of Food Science 72(3): 39-55. doi: 10.1111/j.1750-3841.2007.00301.x
PLASTICS EUROPE, 2011. Plastics – the Facts 2011. An analysis of European plastics production, demand and recovery for 2011.
PIERCE, L. M. 2011. No. 2 Pouch can be recycled with shopping bags. Packing Digest, August 30, 2011. Available at: http://www.packagingdigest.com/article/519234-No_2_Pouch_can_be_recycled_with_shopping_bags.php
TETRA PAK LTDA. 2011. Sustainability Report 2010-2011. Available at: http://www.tetrapak.com/br/sustentabilidade/relatóriodesustentabilidade/pages/default.aspx
WRAP (2008) LCA of management options for mixed waste plastics. London, UK: Waste & Resources Action Programme, MDP017. Available at: http://www.wrap.org.uk/sites/files/wrap/LCA%20of%20Management%20Options%20for%20Mixed%20Waste%20Plastics.pdf
YANG, Y.; BOOM, R.; IRION, B.; HEERDEN, D.J.; KUIPER, P.; WIT, H. 2011. Recycling of composite material.
Chemical Engineering Processing doi:10.1016/j.cep.2011.09.007
ZORKMAZ, A.; YANIK, J.; BREBU, M.; VASILE, C. 2009. Pyrolyses of the tetra pak. Waste Management 29: 2836-2841. doi:10.1016/j.wasman.2009.07.008
