Adelka Felcarek-Hope
Age 17 | Montréal, Québec
Canada-Wide Science Fair Excellence Award: Intermediate Silver Medal Western University $2,000 Entrance Scholarship
INTRODUCTION
Plastic is, without a doubt, one of the world’s most useful materials. It is used to create common everyday items from coffee cups and bottles to chairs and clothing. However, it is often employed in the production of single-use items with slow decomposition rates, ranging from five hundred to a thousand years (Parker, 2018). Therefore, plastic is one of the largest contributors to pollution.
In eighth grade geography, I learned about fossil fuels, which are natural fuels resulting from the degradation of organic matter over millions of years. An example of this is petroleum. Petroleum is required in the creation of plastic and will soon be entirely exhausted, preventing future production of essential material (Kunzig, 2015). It is therefore critical to reduce our use of petroleum in order to prevent the decreasing supply from being completely depleted. This can be attained by decreasing its use in plastic production and replacing the end product with a functionally similar one which does not require the use of fossil fuel derivatives.
As a resource, algae are abundant across the planet and need to be put to use as they can become harmful to marine ecosystems. Dense algal growth covers bodies of water, blocking sunlight from entering the water. This consequently prevents photosynthesizing plants from providing oxygen to animals that require it for their survival. In addition, when the algae die, they are decomposed by microorganisms which utilize the dissolved oxygen in the water (Chrislock, 2013). This process decreases the amount of oxygen in the water and slowly kills the ecosystem. Using the excess algae to make bioplastic would lessen these negative consequences. Inspired by the previous issues, the project aimed to solve three primary issues: (1) the depletion of fossil fuels, (2) the negative environmental impacts of traditional petroleum-based plastics, and (3) the harmful effects on marine ecosystems due to excess algae.
The project focused on two concrete objectives: (1) to develop a new method to create malleable plastic from Phaeophycean cellulose that is of comparable quality to low density polyethylene (LDPE) and (2) to create plastics that disintegrate faster when submerged in saltwater, such as the ocean. The second objective was aimed toward finding a solution to the fact that around eight million tons of plastic end up in the ocean annually (Parker, 2018).
PROCEDURE
The algae samples used gave negative results when tested for starch, which is a commonly used polysaccharide, or long sugar chain, in bioplastic production. Therefore, I settled on using cellulose, a different polysaccharide that is found in the cell walls of the algae. The cellulose structure needed to be chemically altered in order to make it more soluble. The process began by boiling and dehydrating brown algae. Then, a combination of acetic acid and sulfuric acid was added to the dehydrated Phaeophycean to act as a catalyst, which is a substance used to increase the rate of a chemical process. This opened up the cellulose bonds to facilitate an eventual acetylation process, the addition of an acetyl group, since cellulose glucose units are tightly held together.
Figure 1. Diagram of cellulose.
Ultimately, the cellulose would need to achieve a stage where it would be soluble in common organic solvents. When the hydroxyl groups in the glucose subunits of the cellulose in the catalyzed algae were combined with acetic anhydride acetic acid, acetylation began. After being held at 50°C for multiple hours, the solution was fully acetylated, meaning it had three acetyl branches per glucose subunit. However, to achieve the cellulose diacetate stage, an acetyl branch needed to be converted back to a hydroxyl group.
Figure 2. Diagram of cellulose triacetate.
A combination of 75% acetic acid, along with 0.15 g of sulfuric acid was slowly added to convert an acetyl branch back to a hydroxyl group. Then, pure distilled water was added until a solid white precipitate formed. The precipitate was extracted from solution with a vacuum filter pump, then left to dehydrate in the incubator for two hours. Once the product was dehydrated, it took on a solid powder form and could be dissolved in various organic solvents, such as acetone. Different concentrations of cellulose diacetate were used to create various samples with different physical properties.
Figure 3. Diagram of cellulose diacetate.
Two aqueous solutions were then added to the product to improve its quality. The first one, an agar-based solution composed of agar-agar, triacetin, along with distilled water expanded the plastic and improved its flexibility and malleability, the material’s capacity to be molded and deformed under pressure. The use of triacetin, a hygroscopic substance, also prevented the bonds in the plastic from being too brittle. This is because hygroscopic substances attract moisture from the air.
The second solution contained fully concentrated starch grafted sodium polyacrylate coated in an agar solution made of agar-agar and distilled water. The agar acted as a barrier between the sodium polyacrylate and the acetone so there was no risk of the bonds breaking prematurely. The use of this solution is to allow the volume of the plastic to significantly decrease when placed in salt water. Both aqueous solutions, along with the previously formed cellulose diacetate were combined. The combination of solutions was then poured into several circular dishes that were left until the solvent had evaporated and the solid pieces of bioplastic had formed.
RESULTS
Two main samples of the bioplastic were produced, both made with the same substances, but different concentrations. The first sample, sample A1, had a 34 % concentration of cellulose acetate, while sample B1 had a cellulose acetate concentration of 37 %. The variation in the concentration of cellulose diacetate found in each sample affected each sample’s level of rigidness.
Figure 4. Sample ratios in each sample.
Once formed, multiple tests were conducted on the two main samples, A1 and B1: a force test, a decomposition in an ocean simulation, a water resistance test, and a strength test. These tests were performed to determine the quality of my product in comparison to commercial grade low density polyethylene (LDPE), as well as an old sample that I made in 2018, sample 18.
The force test, also doubling as a flexibility test, used a spring scale on which the plastic was attached then pulled horizontally, until it broke. The tool consists of a spring attached to a numbered scale. It can be used to evaluate how much force is being exerted on a given surface. The sample B1 outperformed all the other plastics with a strength of 143N, including the industrial LDPE.
Figure 5. Force/flexibility evaluation data.
The decomposition in an ocean simulation was a process where the samples of plastic were placed in an accelerated ocean simulation. The degradation process was graphed as an exponential decay function and the x-intercepts showed that in the ocean, my plastic would fully degrade in 21-25 days. Comparatively, LDPE would take around 450 years to degrade completely (Parker, 2018).
Figure 6. Ocean simulation test data.
Just like LDPE, my product is water resistant (tested in distilled water). The only sample that degraded in the distilled water was sample 18, plastic from my early 2018 trials.
Figure 7. Water resistance data.
Lastly, the supportable mass, or strength, was calculated by using spring scales with the gram (g) unit. The plastics were attached and then pulled vertically. Once again, sample B1 was the optimal plastic and could support up to 14 kg.
Figure 8. Supportable mass/strength test data.
DISCUSSION
Many samples of cellulose-based biodegradable plastic were made from Phaeophyceaen algae. Algae have a tremendous amount of potential as a resource for bioplastics because of their ability to grow in a range of environments at exponential rates. It also has a low production cost and can be harvested year-round (Choat and Schiel, 2003). The produced plastic could have many practical applications. For instance, it could be used in the production of plastic coffee cups, water bottles, or shopping/grocery bags, amongst other plastic items. In whole, it could replace many polyethylene products and single-use plastics.
CONCLUSIONS
The initial objective in creating brown algae cellulose-based bioplastic was met. The second objective of decreasing the degradation process time in saltwater was also attained. Additionally, the product was comparable to LDPE in terms of the evaluated criteria. The product responds to the previously mentioned issues since it does not use fossil fuels, it degrades quickly, and it could aid in reducing the surplus of algae. In the future, I would like to look into creating a product that is closer to polypropylene or polystyrene. At the moment, the prototype could replace various single-use LDPE products.
Figure 9. Finished product.
BIBLIOGRAPHY
Braun, D., Cherdron, H., Rehahn, M., Ritter, H., & Voit, B. (2013). Polymer Synthesis: Theory and Practice Fundamentals, Methods, Experiments. Berlin, Heidelberg: Springer Berlin Heidelberg.
Choat, J., & Schiel, D. (2003, March 26). Patterns of distribution and abundance of large brown algae and invertebrate herbivores in subtidal regions of northern New Zealand. Retrieved from http://www.sciencedirect.com/science/article/pii/0022098182901551
Chrislock, M. (2013). Eutrophication: Causes, Consequences, and Controls in Aquatic Ecosystems. Retrieved January 11, 2019, from http://www.nature.com
Kunzig, R. (2015, November). Cool It: The Climate Issue. National Geographic, 42-160.
National Library of Medicine, National Center for Biotechnology Information. PubChem Compound Database. US: (2005). Triacetin. Retrieved from https://pubchem.ncbi.nlm.nih.gov/compound/triacetin
Norris, J. N. (2010). Marine algae of the northern Gulf of California Chlorophyta and Phaeophyceae. Washington, D.C.: Smithsonian Institution Scholarly Press.
Parker, L. (2018, June). Planet or Plastic? National Geographic, 40-91.
The Properties of Plastic: What Makes Them Unique? (2018, March 28). Retrieved from http://www.osborneindustries.com/news/plastic-properties/
Torrent-Sucarrat, M. (2012). Sulfuric Acid as Autocatalyst in the Formation of Sulfuric Acid. Retrieved from http://pubs.acs.org/doi/abs/10.1021/ja8077522
Adelka Felcarek-Hope
Adelka Felcarek-Hope is a secondary five student at Royal West Academy. She is a competitive athlete and musician. In 2016, she developed the concept for "The Poly-Phaeophyceae Method", an algae-based bioplastic. She pursued the project at McGill University. Along with Sofia McVetty, she won the gold medal at Royal West Academy's science fair and the Montreal Regional Science and Technology Fair, as well as first place overall. At the Canada-Wide Science Fair, she won a silver medal. In her free time, she participates in her school's debate team and plays soccer & tennis.