Not all plastics come from fossil fuels. You can make plastics using biological materials, and you can make them at home! Since you’re using a knife and a lot of heat, you’ll need to get a parent or guardian to help out here. This procedure comes from the Junior Cycle for Teachers.
Here’s what you’ll need to make your bioplastic:
100g of potatoes (approx.2 or 3 medium-sized potatoes)
Pestle and mortar
Three containers that can withstand heat (e.g., two 1L beakers and one 500 cm3 beaker)
Potato starch powder (optional) (note: removes the need to extract the starch from the potato)
White wine vinegar
Food colouring (optional)
Now you’ve got all that, the first thing you’ll need to do will be take the starch out of the potatoes (unless you’ve already got starch powder!). Here’s what you do:
1) Cut up 100g of potatoes into small pieces using a knife
2) Grind the potatoes into a pulp using the pestle and mortar
3) Add the potato pulp to a 1L beaker along with 400mL of water
4) Sieve the mixture into a separate 1L beaker
5) The filtrate (liquid) should be left to settle overnight (a white film of starch will form at the bottom of the beaker)
6) Siphon or decant off the liquid in the beaker to leave behind only the white film
of starch. Allow the starch to dry overnight.
Now you’ve got your starch, you can turn that into bioplastic film:
1) Add 15g of the potato starch (dry) to a 500cm3 beaker
2) Add 100mL of water to the beaker
3) Add 10mL of white wine vinegar (to remove unwanted things that aren’t your bioplastic) to the beaker
4) Add 10mL of glycerin to the beaker. This makes your plastic easier to work with
5) Add 5mL of food colouring to the beaker (optional)
6) Place this mixture on a hot plate (medium heat setting). Stir the mixture with a spatula until a viscous substance (glue-like) forms
7) Add 2.5g of sodium bicarbonate and 30mL of water to the beaker. Stir the mixture until a viscous substance (glue-like) forms again
8) Using a kitchen knife, scrape the substance off the spatula and spread it evenly onto a piece of grease-proof paper (as thin of a layer as possible)
9) Drying the bioplastic: it takes about one day on a radiator or sunny windowsill, or two days at room temperature. Alternatively, use a drying cabinet (90 minutes at 100 °C).
Now you’ve got some bioplastic! What does it feel like? How does it compare to the other plastics around your house? This is a lot like what we’re doing at Grain-4-Lab, just on a much bigger scale!