Plant Power: Creating Bioplastic from Starch

Plastic pollution has become one of the 21st century's largest problems. Every year millions of tons of plastic are thrown onto landfills where they will remain forever as they are not biodegradable. Plastics also end up in the ocean and into the ocean where they pose a threat to marine animals. Furthermore, the production of plastics creates air and water pollution. Therefore, it is important to increase the use of biodegradable alternatives for plastics.

The goals of my project were to: i) create plastics from three different starches (from potato, corn, and rice); ii) evaluate the impact of different proportions of ingredients on the bioplastic properties; iii) test how the bioplastics react in water; iv) evaluate the strength of bioplastics, and v) produce a prototype of a bioplastic spoon.

My hypothesis was that using a mixture of potato starch, agar powder, glycerin, distilled water and vinegar will produce a strong and flexible film with better qualities than rice and corn due to the structure of potato starch allowing for more flexibility.

Biodegradable plastics are increasingly being considered as an alternative to the common non-degradable synthetic plastics. Natural plant starches can be manipulated and turned into plastic by mixing them with distilled water to loosen the starches, glycerin as plasticizer to increase space between the polymer chains and increases the flexibility, vinegar to break down the amylopectin chains into simpler amylose chains, and agar powder as a thickening agent to strengthen the chains.

In my project, I extracted potato and rice starch, and using those starches (along with store bought corn starch) I created bioplastic sheets and coins. I used five different recipes, one taken from an online resource and four in which I determined the quantities of ingredients.

From my first batch of bioplastic I produced sheets for which I used qualitative measurements such for transparency, flexibility, and strength. I conducted water solubility tests to evaluate the biodegradability in a short time. To do this I immersed pieces I had weighed before hand in water for twelve hours, then dried and weighed them again.

From my second batch of bioplastic I solely used potato starch as it had previously created the best results. I produced small round samples and used a spring scale to determine the force required to break the bioplastic. Finally, I created a mold form two-part silicon rubber and produced a bioplastic spoon prototype.

Recipe 1 (Base)

100ml water

15g starch

15g glycerin

10g vinegar

Recipe 2

100ml water

15g starch

15g glycerin

3 tsp agar powder

Recipe 3

100ml water

15 g starch

15g glycerin

10ml vinegar

1 1/2 tsp agar powder

Recipe 4

100ml water

15g starch (potato only)

10g glycerin

10ml vinegar

Recipe 5

60ml water

15g starch (potato only)

10g glycerin

10ml vinegar

Qualitative Assessment

After 1 day a few long cracks could be seen, they were smoothed over and moved to a more temperature consistent environment

After one more day the cracks had spread and multiplied greatly completely breaking the plastic into many pieces

The only plastic that did not fracture was recipe 1 potato starch

The recipe 1 potato starch had the smoothest texture, was most resistant to bending, was the clearest, and seemed to take the most force before breaking while being pulled apart.

Corn starch 2 was by far the weakest.

Description of Bioplastic Coins

Recipe #1 created coins with the fewest cracks and even texture

Recipe #4 created squishy and soft coins that bent and broke easily

Recipe #5 with less water created the hardest coins

Description of Prototype

Spoon had uneven surface and cracks, very flexible, not functional

• The results supported my hypothesis that potato starch would perform best

• Other starches and recipes did not produce usable bioplastics

• Recipe #1 without agar produced the best results

• Reducing the amount of water increased density and strength

• A prototype showed the potential of creating a biodegradable utensil

• However, mixture and procedure must be improved to produce functional bioplastics to be used for products like spoons

In a continuation of my project, I will tackle the following aspects:

● Evaluate further proportions of ingredients and drying processes to create stronger bioplastics

● Improve mold so that spoon better maintains its shape

● Evaluate water from solubility test under microscope and spectrophotometer for micro plastics presence

● Evaluate biodegradability by placing bioplastics in dirt.

Leonor von Baer, my mother, for purchasing the ingredients and letting my occupy the kitchen.

Thomas Tannert, my father, for helping me with the experiments and reviewing the report.

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