How do we know how long some things take to decompose if it’s claimed they take longer than what they’ve existed for? (Example, plastic bags)
In: Chemistry
1) It’s a guess based on what we can determine about how it breaks down extrapolating into the future based on understanding of it’s physical and chemical properties.
2) It doesn’t account for the evolution of things that will treat it as a food source. Depending on what we’re talking about that may be more or less likely.
You accelerate the breakdown. A typical method is to use temperature, although it’s not the only way. You take a substance and figure out how to quantify its breakdown. Then you take multiple samples and expose them to multiple high temperatures (usually at least 3) and measure their breakdown vs time. You usually do one set of samples at temperature T1, another separate set of samples at T2, etc.
After you’ve done this and plotted the results, you can calculate how much breakdown occurs vs. time and temperature. There are some pitfalls you have to avoid, but if you are smart about it you can figure out the degradation rate at any reasonable temperature and time frame.
This same basic technique works in a variety of situations, not just plastic bags. For example, it’s how engineers figure out how long light bulbs are going to last.
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