In a world where everyone is trying to reduce plastic wastes, Aerogel can be a superb alternative everyone can turn towards. It is a wonder material invented in 1931 by Dr. Samuel Kistler by removing the liquid component from a silica gel with air. This resulted in the creation of the lightest solid in the world about, 1.5 kilograms per cubic meter. To put this number into perspective, this is lighter than a feather from a goose!
The unique properties of aerogel
Aerogel nowadays does not refer to a specific material but rather a whole range of materials with similar properties. The term often refers to materials manufactured using sol-gel chemistry. This rather ominous term is simply the process by which solid materials are created from liquid solutions. As a result, aerogels having a spongy honeycomb-like structure consisting of about 99% of air. This unique composition gives it rather unique characteristics, such as being a very good thermal insulator and withstanding temperatures up to 1000 °C. Aerogels can also be customized into limitless sizes, shapes, and textures as it can be placed into different molds with specific conditions.
Biobased Aerogel: A Greener Alternative
Aerogels were traditionally made with synthetic materials such as silica gels, alumina, polystyrenes, metal oxides, etc. However, scientists are recently developing biobased aerogels from natural materials such as pectin, cellulose or proteins. Pectin and cellulose are complex carbohydrates found in plant cells.
These bio-based aerogels are a more sustainable alternative compared to synthetic aerogels. The processing steps of biobased aerogels are similar to synthetic aerogels. It requires the addition of alcohols such as ethanol before the drying to remove the liquid without damaging the structure.
Aerogels in food packaging
The food industry plays a huge role in the global economy. In 2024, the global food market is expected to be 9.12 trillion. This large supply chain creates large amounts of environmental damage. Plastic packaging and polystyrene packaging are currently the core materials used for food transportation. In the European Union alone, a staggering 84 million tonnes of plastic waste are generated annually. Finding sustainable alternative options is proving to be quite the hassle.
This is daunting problem maybe tackled with biobased aerogels. Compared to traditional packaging, aerogels are lighter while showing incredible durability. For example, a chitin-based aerogel weighing 60 mg can withstand an object weighing 100g. Chitin is a naturally occurring complex carbohydrate which can be easily obtained.
Due to their amazing thermal insulation capabilities, bio-based aerogels can be used to store temperature-sensitive foods. For example, fish or animal meats, which require cold storage, or ready-to-eat meals which need warmer temperatures, can be placed in aerogel containers, which can help maintain their temperature. Additionally, the pores in the aerogel can be filled with natural preservatives such as hexanal to prevent the growth of microbes. This concept has already been tested on blueberries and cherry tomatoes, which remained more firm and had less mould growth when compared with control samples. A biobased package prototype had also been demonstrated at a package design module organized by Aalto University in 2016. The packaging used limonene as the base material, which is a natural compound found in peels of citrus fruits like oranges. The packaging also contained preservatives and avocadoes were stored using the process.
This means less food waste, less electricity required for refrigeration and fewer chemical preservatives – a big win in all departments.
Challenges and the Road Ahead
One of the major problems related to aerogel packaging is the huge manufacturing costs. This is because it requires expensive chemicals and specialized equipment for the drying phase. However, the costs can subside marginally after large-scale production tilts into full gear. The costs can be further reduced by using waste biomasses such as rice, corn bracts, oat husks, spent coffee grounds, etc.
The development of transparent packaging is also required as food packaging is mostly transparent. However, transparent aerogels formed by oxidized cellulose are showing promising signs and it is expected to be quickly developed.
Finally, the recycling of aerogel is also complicated due to the variety of composition in each aerogel. However, those which are biobased can be composted and the rest can be managed responsibly with clear regulations and further research
A Glimpse into the Future
As aerogel is a relatively new material, it shows immense growth potential. Traditional aerogels were usually synthetic and were hard to recycle. However, the development of biobased aerogels can change the landscape forever.
Even though aerogels application in food packaging has been discussed, it can also be used in various industries such as home insulation, thermal jackets etc. If the initial hurdles can be overcome, aerogels may lead us to a better and sustainable future.
REFERENCES
- New Polymer Nanocomposites for Environmental Remediation, 2018, Pages 389-436, Hajar Maleki, Nicola Hüsing
- https://www.chemistryviews.org/largest-pilot-plant-for-bioaerogels-production/
- Aerogels as porous structures for food applications: Smart ingredients and novel packaging materials Lara Manzocco , Kirsi S. Mikkonen , Carlos A. García-González, 2021
- https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202209003#:~:text=The%20resulting%20polyimine%20aerogels%20exhibit,monomer%20recovery%20yields%20and%20purities.
- Hajar Maleki, Luisa Durães, Carlos A. García-González, Pasquale del Gaudio, António Portugal, Morteza Mahmoudi, Synthesis and biomedical applications of aerogels: Possibilities and challenges, Advances in Colloid and Interface Science, Volume 236, 2016, Pages 1-27
- https://blogs.helsinki.fi/aerowood-project/files/2015/09/Pack-Age-course-story-for-AEROWOOD-project.pdf
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