Questions about compostable bag experiment

[deleted-306673]

I am doing an experiment to answer under what conditions biodegradable/compostable plastic bags degrade the fastest, and whether they degrade as soon as they are advertised to. I originally planned to test in the sun, shade, with a more moist pile, and a drier pile, but I think this is too many variables, because I also think I should put a sample of a normal bag in each compost bin to serve as the control.

I conveniently found this experiment, it's sort of similar to the one I have in mind. https://www.sciencebuddies.org/science- ... #procedure

Do I need 4 compost bins? Should I bother testing sun and shade, and moist and dry? Do I need a control bag in the bins, or can I just assume that a normal plastic bag would undergo no change?

[deleted-291782]

Hi tadpole,

Very interesting research topic! You could certainly do four different variables for your experiment; however, the time-consuming portion of this would be to create that many different compost bins. If you want to test both sun and shade, you can make both a clear plastic bin (to test the effect of sunlight) and a plastic bin either made of white plastic or one coated in a more light-reflective color (not black because it will absorb light and generate more heat!). I will also mention that you may not need four bins if you can find a good way to separate the two halves. You can try gluing a piece of plastic in the center and sealing it with something like caulking. That way, you could test different conditions within the box made to test sun and the one meant to test shade. I think the best would be to have separate boxes for each condition, especially if you test something like moist and non-moist in the same box, since the water evaporation could affect the other half of the bin. But if you want to have two bins total, try to separate the halves as best as possible.

I would certainly include non-compostable bags in the same bins as negative controls. Ideally, what you would like to show is: a non-compostable bag will not degrade in each of your conditions compared to the biodegradable bag, and that a biodegradable bag decomposes under a known condition (positive control). This last control will tell you that your experiment works. You can place a biodegradable bag in one of your conditions that is known to be conducive to biodegradation and should be degraded by the end of your experiment.

Let us know if you have further questions, and we'll be happy to help. Good luck!