As most of the foods we consume today, the product consists not only in the edible part but also in the packaging. In the immense world of packaging, the most used material is plastic, due to its good mechanical properties, flexibility, low weight and cheap cost of production. A recent study shows that the global production of plastics was raised from 2 million tons in the 1950’s to 348 million tones in 2017 and 359 million tons in 2018(1). However, in all stages of plastic’s lifetime, from extraction to recycling, a great amount of greenhouse gases are produced. While these gas emissions aren’t the only problem related to plastics, one of the biggest issues are the micro and nano plastics freed during its degradation in natural environment. These microplastics harden the CO2 absorption from the oceans, promoting an atmospheric CO2 regulation imbalance, ultimately climbing the food chain and potentially affecting the human health.
How can we prevent plastic misuse?
There are three possible destinies for all the waste we deposit in the plastic recycling container:
- Being actually recycled, renewing packages and other useful sub-products;
- Being incinerated for energy reuse;
- Being dumped in a landfill.
Of course, the landfills are the worst possible solution, and thus the most avoided one. A 2017 study(2) shows that in Europe are produced about 25 million tons of plastic, and of those 25 million, 39.5% were incinerated, 30.8% end up in a landfill and just 29.7% are really recycled. A promising method uses Polyethylene (PE) as a carbon source for the production of Carbon Nano Tubes (CNT’s) by a laboratorial technique called Chemical Vapor Deposition (CVD).
What are carbon nanotubes?
CNT’s are emerging as powerful, flexible and resistant semiconductors. Their industrial application will seriously upgrade solar cell’s yield in photovoltaic panels, the production of display devices like TV screens, touch screens, transistors and others, increasing lithium ion battery’s yield and much more(3)(4)(5).
Carbon atom’s bounds are very strong and for that reason the mechanical properties of carbon nanotubes are also very strong, allowing future ropes and cables to be extremely strong, almost unbreakable.
Small fibers of nanotubes could be used as reinforcement agents of composite materials, increasing their resistance to traction or flexible forces.
How are CNT’s produced?
There are several ways to produce carbon nanotubes but the most promising method, in terms of scalability, is the method of Chemical Vapor Deposition (CVD) (6).
On a controlled environment, little fragments of low-density polyethylene (LDPE) are chosen. Then, they are heated to temperatures between 600oC-1000oC (7) and they are mixed with a catalyst that reduces the boiling temperature of LDPE. Once boiling, the vapor is transferred to another chamber where the temperature is lower. This will force the vapor to condensate. In the presence of a catalyst like a sheet of graphene, the rich carbonaceous vapor slowly deposits its carbon atoms onto the graphene surface forming nanotubes.
However, the growth control of this structures is still very limited. It is hard to estimate what is going to be the length, width and direction of these tubes, and that is still a challenge that needs to be surpassed so that the full potential of carbon nanotubes can be put to use.
This method is presently only developed in a laboratorial enviroment, but it is the most likely to be scaled in a near future due to its lower applied temperatures. Other methods, like laser ablation, employ much higher temperatures and demanding conditions.
Other solutions
Recent advances in bio-fabrication technologies have led several startups to grow exponentially over the last decade, some of them focusing in plastic replacement.
A great substitute of Polystyrene (PS) consists on the compaction of a specific species of mushrooms. It is almost equal to polystyrene, but biodegradable. It was developed by the American company Ecovative and early adopted as packaging solutions for Dell’s products, accommodating technologic products such as computers and accessories. It was later adopted by IKEA in 2016.
As replacement of ethylene, small seaweed-based plastic bubbles were developed, and these can be used to encapsulate every kind of sauce or stable liquid, like water or juice. Being an edible and biodegradable packaging solution, created by Notpla, many fast food chains and retail markets have adopted the invention.
There is still a lot to be done, especially regarding consumer education. General population needs to be educated and informed about what is happening around the world, what are the consequences of inaction, what are the conditions where food is produced and with critical thinking decide if the simple act of buying a specific food can be harmful for someone or something, somewhere on the other side of the world.
There’s a great need to fight ignorance and lack of reliable information, not only in poor countries but also in rich and developed ones. Many companies and public entities work daily to provide knowledge and information to the general public and CFER Labs is one of them.
Written by André Azevedo – https://www.linkedin.com/in/andr%C3%A9-azevedo-668064163/
Bibliography
(1) Shen, M., Huang, W., Chen, M., Song, B., Zeng, G., & Zhang, Y. (2020). (Micro)plastic crisis: Un-ignorable contribution to global greenhouse gas emissions and climate change. Journal of Cleaner Production, 254, 120138. https://doi.org/10.1016/J.JCLEPRO.2020.120138
(2) Ragaert, K., Delva, L., & Van Geem, K. (2017). Mechanical and chemical recycling of solid plastic waste. Waste Management, 69, 24–58. https://doi.org/10.1016/J.WASMAN.2017.07.044
(3) Grace, T., Shearer, C., Tune, D., Yu, L., Batmunkh, M., Biggs, M. J., … Shapter, J. G. (2017). Use of Carbon Nanotubes in Third-Generation Solar Cells. Industrial Applications of Carbon Nanotubes, 201–249. https://doi.org/10.1016/B978-0-323- 41481-4.00008-3
(4) Jiang, K. (2017). Carbon Nanotubes for Displaying. Industrial Applications of Carbon Nanotubes, 101–127. https://doi.org/10.1016/B978-0-323-41481-4.00004-6
(5) Fang, S., Shen, L., & Zhang, X. (2017). Application of Carbon Nanotubes in Lithium-Ion Batteries. Industrial Applications of Carbon Nanotubes, 251–276. https://doi.org/10.1016/B978-0-323-41481-4.00009-5
(6) Wu, X., Mu, F., & Zhao, H. (2019). Recent progress in the synthesis of graphene/CNT composites and the energy-related applications. Journal of Materials Science & Technology. https://doi.org/10.1016/J.JMST.2019.05.063
(7) Ahmad, M., & Silva, S. R. P. (2020). Low temperature growth of carbon nanotubes – A review. Carbon, 158, 24–44. https://doi.org/10.1016/J.CARBON.2019.11.061
CFER is the Centre for Food Education and Research, expert in the development of new food and drink products, optimization of recipes for food businesses and companies and also a strong innovation centre in technological foods and drinks.