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Make your own algae bioplastic

by Green Plastics


Our recent news article about algae as a source for bioplastic has received a lot of attention.  But there is something very important that it didn’t tell you:

You can make your own bioplastic from algae.  And we will give you step-by-step instructions on how to do it.

It’s a fun little science project.  You can do it in your kitchen, with stuff you buy at the grocery store.  And you can see what “algae bioplastic” really looks and feels like.

First, a little background. You might not have known this, but when people talk about “seaweed” they are actually talking about a form of algae. That is what we are talking about in the context of bioplastics: red algae, also known as “red seaweed.” The specific chemical that we are interested in is agar, which appears in red seaweed in abundance. When you hear Cereplast and other companies talk about developing bioplastic made from seaweed, they really mean that they will be using the chemical agar, which is extracted from the seaweed.

agarFortunately (or unfortunately?) this project won’t have you traipsing out to the ocean to collect seaweed. Agar is used as a food additive in confectionaries, desserts, beverages, icecream and health foods. It’s also used as a non-food additive in toothpaste, cosmetics, and adhesives. It’s not that difficult to get: if you can’t find it at the grocery store, you can Google “buy agar” and you get plenty of results there.

Before we get to the actual recipe for making your very own “algae plastic”, you should understand what role agar actually plays. Like all other plastics, bioplastics are composed of three basic parts: one or more polymers, one or more plasticizers, plus one or more additives. Roughly speaking: polymers give plastic its strength, plasticizers give it its bendable and mouldable qualities, and additives give it other properties (color, durability, etc). Agar is a biopolymer.

From the Green Plastics book:

Agar, either by itself or in blends with other biopolymers, appears to impart favorable properties to plastic sheets. In plastics containing agar and glycerol (a plasticizer), the effectiveness of the glycerol lasts longer, because the agar seems to slow down the increase in brittleness. Agar also seems to improve resistence to microwave radiation, and it improves clarity in sorbitol formulations. Agar is more expensive than starch, which limits its large-scale use.

Are you ready to try this? You basic procedure for making the bioplastic will be the same as described Brandon’s Remix video. The main difference will be in the actual ingredients and proportions. Here are some suggestions you can try. Each of the following combinations will produce slightly different plastics with different properties.

Agar Only

3.0 g (1 tsp) agar
240 ml (1 cup) of 1% glycerol solution
180 ml (3/4 cup) water

Agar-Starch Blend

1.5 g (1/2 tsp) sorbitol
3.0 g (1 tsp) starch
300 ml (1 1/4 cup) water
0.75 g (1/2 tsp) agar
120 ml (1/2 cup) of 1% glycerol solution

Gelatin-Agar Blend

2.25 g (3/4 cup) sorbitol
2.25 g (3/4 cup) gelatin
2.25 g (3/4 cup) agar
180 ml (3/4 cup) of 1% glycerol solution
240 ml (1 cup) water


The procedure is basically the same in every case. Mix all of the ingredients together in the amounts above, and stir. Keep mixing until there are no clumps and it is as dispersed as it’s gong to get. Then heat the mixture to 95 C or to when it starts to froth (whichever comes first). Stir the mixture while you are heating it, and once it is at the right temperature (or starts to froth), remove the heat and keep stirring. Scoop out excess froth with a spoon, and make sure there are no clumps. Carefully pour the mixture into a drying pan, and make sure to spread it out to let it dry.

How long it takes will depend on the temperature and humidity in the room, and it may take several days (depending on your formulation). You won’t be able to remove the plastic from the drying sheet easily until it is completely dry, so be patient! If your first batch turns out too sticky or slimy, you can try it again with slightly less plasticizer. Remember, the above recipes are just starting points…. have fun trying different proportions and combinations, and see what kinds of plastic it makes!

Happy experimenting.

(For many more recipes like these, and a lot of good information about the background and science of bioplastics, get the Green Plastics book.)

Comments (20)

  1. Hello love your website and was interested in making these but had no idea what 1% Glycerol solution is. Eventually found this in the Appendix of the Green Plastics book:

    “Before you begin, it will be useful to make up a stock solution of diluted glycerol.
    Mix up a solution that has 10ml of glycerol for every litre of water (or 2 tsp of glycerol for every quart). This will give you a solution that is 1% by volume. Everytime a recipe calls for a certain amount of a 1% glycerol solution you can then simply measure from this stock”

  2. Veronika says:


    is there anything wrong with the agar-starch-blend recipe?

    1.5 g (1/2 tsp) sorbitol
    3.0 g (1 tsp) starch
    3.0 g (1 tsp) agar
    240 ml (1 cup) of 1% glycerol solution
    300 ml (1 1/4 cup) water —> water again?
    0.75 g (1/2 tsp) agar —> agar again?
    120 ml (1/2 cup) of 1% glycerol solution —> glycerol again?

    Is it two recipes? Or am I supposed to make two mixtures and blend it afterwards?

  3. Anthony says:

    Find small or large amounts of Agar powder at TheHalloweeners.com , I get stuff all the time there

  4. klvalkyrja63 says:

    I am wondering the same thing: why are are repeat ingredients of different amounts n the recipe for the agar-starch-blend recipe?

    • Green Plastics says:

      Thanks for the comment! You are absolutely right, there is a typo / error in the recipe. I will go correct it immediately.

      Thanks for pointing it out!

  5. Nicola says:

    You can buy agar, usually called agar agar, for next to nothing from Asian grocery stores.

  6. Kerri says:

    What can I substitute for sorbitol? Can’t find it anywhere.

    • Ahalya says:

      Its formula is C6H14O6.It is know by many names.So make sure you check every chemical.For example its also know as Mannitol.

    • Crazyrlt25 says:

      I got sorbitol only on Amazon. It would be very difficult to find it at grocery stores. Sorbitol is a substitute for sugar but I don’t know if you could use sugar in place of sorbitol for the recipe.

  7. Crazyrlt25 says:

    I made the gelatin agar blend and it doesn’t harden. It’s just a jelly. Do you have any suggestions?

    • Green Plastics says:

      If you used the recipe on this page, the most common mistake I see people make is with the glycerol. The amount listed in the recipe is for a 1% glycerol solution, i.e. 1 part glycerol for 99 parts water. If you use a glycerol solution that is too strong, it will make the result gooey like jelly.

  8. Monica says:

    So if I make a box from this and it goes in the ocean…can fish eventually eat it or are any of the mixes toxic?

    • Green Plastics says:

      The main ingredients listed here are all non-toxic. The only way it would be toxic is if you decided to ADD something toxic to it, for example if you wanted to change the color and used a toxic dye. As long as you are careful not to add anything toxic, the basic ingredients listed here are all safe and environmentally-friendly.

  9. Laure Fernandez says:

    Hello, I am a french fashion design student and I am experimenting bioplastics. I would like to know if I am doing it right because the result is not what I expected. When I heat the mixture it stays liquid and it take quite a long time to dry after that. Also once the plastic is dry, it is not strong at all, and if I put it under water it becomes slimy and sticky. Is it supposed to be waterproof ? I am trying to use it in my final year collection so I would be very grateful for your help !

    Thank you

    • Vera says:


      You should contact Ingrid Rautemberg if you are studing fashion. She won an Award last year with Kering group and her collection was entirely made out of bioplastic. Hope this helps.

  10. Lot says:

    is it works by anyone? i bye the green plastics book and try but is not working….

  11. Sarai says:

    How is it in water? Does it return back to its goo state if submerged in water?

  12. michael clark says:

    I was wondering if it was edible. Because if so, it could be fed to livestock and it would never enter the environment at all.