Decomposing the Secrets of Plastic

Transcript:

I’m Olivia Andrusiak. My project, 'Decomposing the Secrets of Plastic,' was inspired by my school’s breakfast program. We had plenty of healthy oranges and bananas, but our community lacked the composting facilities to handle the waste. It made me wonder, could we turn that food waste into something useful before it ever hits the trash?

I developed bioplastics using orange peels, banana peels, and potato starch. I tested their durability and buried them in different soil environments to see how they compared to traditional PET plastic and store bought alternatives.

The results were a breakthrough. While the PET plastic showed zero change, the Potato Starch Bioplastic was the clear winner. It was strong enough for daily use, but it achieved a staggering 96% mass loss in just two weeks. I also discovered that 'dry' soil with air circulation actually breaks down these materials faster than oversaturated, wet soil.

This matters because it shows companies can turn their waste into eco-friendly products. One spoon at a time.

The inspiration for this project came from school breakfast programs that provide oranges and bananas, but the school and community lack composting facilities. This led to a critical question; How can we manage this organic waste effectively? The goal was to determine if food waste bioplastics actually decompose faster than Polyethylene Terephthalate (PET) plastic or other alternatives in different soil environments.

The project investigated how bioplastics (banana and orange peel recipes) would decompose compared to traditional PET plastic when buried in wet and dry soil. Over one month, samples were monitored in various conditions including a frozen climate, and room temperature conditions. Changes in pH, moisture, and physical structure were measured and observed.

The study found that while PET plastic showed no observable changes, banana bioplastic quickly developed fungal growth and microbial activity, especially in warmer environments.

Further research found that potato waste was a significant bio-waste material, with over 2.4 million potatoes being disposed of daily. (Source: Food Hero) This led to further testing using potato starch. Manufacturing potato starch at home proved to be very labour intensive. Phase 2 testing was all done with pre-made potato starch. Potato starch bioplastic emerged as  being the most durable, while also remaining stable.

By proving that bioplastics made from food waste can be both functional and biodegradable, this project shows how companies can turn their waste into eco-friendly products. This shift helps keep oil based plastic out of our oceans and contributes to the global effort to prevent climate change.

Phase 1

Two sheet pans of biodegradable plastic, one made with banana peels and one with orange peels, were each cut into six equal pieces. Six bins containing 48 litres of soil were placed in three locations: the Garage, Basement, and Living Room, with each location having a "Wet" bin and a "Dry" bin. Each bin also contained a piece of PET plastic water bottle, and a birch utensil. The starting mass was recorded for each material.

The Process: Every day at 4:30 PM, the temperature, humidity, pH, light lumens, and moisture were measured for each bin and recorded. Once a week, the samples were dug up and weighed to track mass loss.

Application Phase 1

Thirty-three bioplastic spoons were manufactured with either potato starch, “moldable” orange peels, dried and ground orange peels, or banana peels. The durability of these bioplastics were tested on ceramic tile, laminate and carpet surfaces. After, a bend test was performed where a bioplastic spoon was placed on a protractor and bent to determine the flexibility in degrees.

Phase 2

Seventy-two bioplastic spoons were manufactured with either potato starch, dried orange peel, or banana peels. Twenty-four additional spoons were made using a potato starch/banana peel mixture. Each bin also contained a PET spoon and 3 store-bought biodegradable spoons. The same 6 soil bins from phase one were set up in the same locations with the same conditions.

Application Phase 2

The 96 spoons were also used for 4 physical durability factors. The drop test, the bend test were done in addition to a shear test and tensile strength test. The shear test determined the Newtons (N) of force to cut through the bioplastic and the tensile strength tested how much weight could be applied until the bioplastics snapped.

The investigation into organic alternatives to traditional PET plastic revealed that organic waste can be effectively transformed into functional, biodegradable tools. Through two phases of testing, focusing on decomposition and structural application, the project identified a clear "winner” among the homemade recipes.

Phase 1

Initial testing established that environmental conditions, specifically temperature and air circulation, are the primary drivers of decomposition.

The PET Control: Traditional PET plastic showed 0% decomposition across all environments, highlighting its persistence in the environment.

Oxygen vs. Saturation: Samples in "dry" soil (retaining some humidity) decomposed more effectively than those in oversaturated "wet" soil. This is because saturated soil cuts off oxygen, which is essential for the aerobic bacteria and fungi that break down organic matter.

Temperature Stability: The living room proved ideal for decomposition, as it avoided the freezing temperatures of the garage (which reached -3.7°C) that essentially preserved the materials.

Phase 2

While Phase 1 identified Banana Peel as the fastest decomposer initially, the application based testing in Phase 2 challenged this finding.

Functionality: When molded into functional items like spoons, the Potato Starch Bioplastic became the clear leader in decomposition, reaching a staggering 96% mass loss by Week 2.

Decomposition and Structure: While Banana Peel bioplastic was prone to early fungal growth (as early as Day 4 in phase 1), the Potato Starch version maintained better structural integrity even as the decomposition process fully took hold.

Application

To replace traditional plastics, these materials must survive daily use. Physical testing measured tensile strength, drop test, a shear test, and flexibility.

Tensile Strength: Potato Starch bioplastic was the most durable, withstanding an average of 1.25 kg before breaking.

Flexibility: It demonstrated exceptional flexibility with a 180° average degree of bend, matching the Banana Peel version but with a far more stable interior structure.

Manufacturing Impact: In application phase 1, the method of production proved vital. The “Dry” Orange Peel method created a much more durable product than the "Moldable" version, which was prone to surface cracking.

The most significant conclusion of this study is that Potato Starch Bioplastic is the superior homemade alternative to traditional plastics. While initial testing suggested banana peels decomposed fastest, the refined Phase 2 application revealed that Potato Starch spoons achieved a staggering 96% mass loss within just two weeks.

This discovery is vital because it proves that performance does not have to be sacrificed for sustainability. Potato starch provided the highest tensile strength (1.25 kg) and maximum flexibility (180° bend), matching the physical capabilities of traditional PET plastic while returning to the earth in a fraction of the time.

Key Findings:

The method is as important as the matter. The failure of the "Moldable" Orange Peel versus the success of the "Dry" method proves that manufacturing techniques significantly alter the durability of organic polymers. This means that with the right production standards, "heavy-duty" biodegradable tools can be created.

Soil saturation has practical implications for waste management. Bioplastics should not just be buried, instead, they require oxygenated composting conditions to break down efficiently.

PET plastic is a permanent material (0% change), the potato starch prototype achieved decomposition while matching the flexibility of traditional plastic. This suggests that for single-use items like takeout cutlery, the PET plastic, a thousand year material, should not be used for a 20 minute meal.

To extend this investigation, the focus will shift to bioplastic durability during practical use. Future research involves testing material integrity in various liquids, such as hot, salt, and carbonated water, to determine viability for food and beverage products.

Refining recipes, such as increasing starch in potato starch bioplastics, could create heavy-duty utensils. Testing across diverse environments like home compost piles versus forest floors provides practical waste-management data. These steps bridge the gap between laboratory success and real world use, ensuring eco-friendly alternatives are both sustainable and reliable for daily consumer needs.

I would like to thank my parents Claire and Michael Andrusiak for supporting me, giving encouragement, and being my lab assistant in the kitchen, while making your house into a science lab. My brother, James Andrusiak, for eating so many bananas. Catherine and Dave Williams for teaching me, editing, and listening to my project. St. Anthony’s School, for saving your waste for me, and fundraising for some of the cost of my project. Staff at BGCDSB for lending me many appliances so I could share my results with others, including Michelle Downey, Amanda Saxton, and Danah St. Amand. Mme. Boivin for giving me suggestions and critiquing my work. Finally, the Bluewater Science Fair committee and my team for all your support and encouragement while we prepare for Canada Wide.

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Images

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