How did we make plastic that isn’t biodegradable and is so bad for the planet, out of materials only found on Earth?

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I just wondered how we made these sorts of things when everything on Earth works together and naturally decomposes.

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Everything on Earth doesn’t do that. When was the last time you saw a rock decompose? Or a glass of water? It’s only living things that decompose.

Decomposition is not some inevitable force of nature. It’s a bunch of bacteria eating organic matter. There are many things those bacteria can’t eat, and those things don’t decompose.

“Biodegradable” mean it is degradable by biological mean. In most situation, it just mean that micro organism can eat it and poop it.

Not many organism can eat plastic. So in most cases, we instead have to wait for natural wear (rain, wind, dust, etc…) to damage it enough that it’ll turn into small particles.

Plastics are made from organic materials, oil, which is hydrocarbons that were once plants, so one might expect plastics could decompose as quick as any plants, except they don’t. The reason is that there’s very little life on earth that knows what to do with the molecules that makes up plastic, humans mix other chemicals with the hydrocarbons to make new molecules that never existed in nature before, they’re so new to biology that almost nothing exists that can munch on it and use it to grow. The chemical bonds in plastics are tougher and weirder than anything natural, which is what makes them so useful to us but so awful for nature. There are some bacteria that can break down plastic with enzymes, because ‘life finds a way’ and hopefully research in developing that into a commercially viable process will make plastic recycling something we can actually do at scale.

Things bacteria and fungi don’t know how to break down happen sometimes even without our help. The Carboniferous period, when most of the world’s coal formed, was the time after plants started making lignin and before decomposers learned to break it down (the lignin piled up, got buried, and eventually got compressed into coal).

> How did we make plastic that isn’t biodegradable and is so bad for the planet, out of materials only found on Earth?

Bit of a false premise on that.

Your question has 3 pieces, and piece #1 and #3 are related, so let’s break those out:

> “How did we make plastic that isn’t biodegradable … out of materials only found on Earth?”

“Biodegradable” means that biology breaks it down. I.E. Living things eating it and turning it into… other things. Generally, where the end result is “dirt”. Dirt itself is quite complicated and isn’t a single thing, it’s many things.

The amount of things that **are** biodegradeable is actually quite small. It has to be something that generally insects, fungus, or bacteria can use as food.

Generally, only biological things themselves (plants and animals) are biodegradeable.

A sandwich will rot. Mold will grow on and eat the bread which is made from wheat, bacteria will eat the meat and cheese which are made from animals, the vegetables which are grown from the dirt will fall apart on their own without the rest of their plant to keep them together. Insects might eat part of it, or animals. All kinds of stuff.

A sandwich was from biological stuff, and it degrades from other biological stuff.

… so… how did we make something that bacteria and fungus and insects and stuff can’t eat? Easy. That’s most of the entire planet. Like, 99.99999% of the planet.

You know how plastic is made. Out of oil. Oil is kinda biological, but nothing really eats crude oil. And, nothing yet has evolved to use plastic as an energy source (food). It’s too new. So… plastic isn’t made out of plants and animals (not on an human-appreciable scale), and, it’s not broken down by plants and animals.

But neither are rocks. Neither is a bar of iron. Neither is gold. And so on. So, you could ask the same question about an aluminum wheel as you do about plastic. Why doesn’t it biodegrade? Because nothing biological eats up aluminum.

So the question of how we can make it is pretty simply answered right there.

Next, the middle part of your question:

> and is so bad for the planet,

Well, what is “bad for the planet”?

In truth, plastic isn’t bad for the planet at all. Landfills in general aren’t. “Landfills filling up!” protests are generally about distracting from the bigger problems humans are causing on the planet. It gives people a tiny problem to feel bad about and focus on, so that they don’t focus on the much worse things we need to stop doing.

Landfills fill up. That’s what they do. If landfills were emptying, they’d be called mines.

Landfills filling up is more of an economic problem, as it’s expensive and inconvenient to find new places to seal our garbage away. We used to just dump garbage into lakes and rivers because it was cheapest. Now we use landfills and it’s a bit more expensive. When those landfills fill up, the next thing will be a little more expensive again. We will never run out of space, not even close, all that stuff came out of the ground originally.

We dig things out of the ground in mines, and then we put things back into the ground and cover them up. No one cares that a rock takes 50,000,000 years to break down, so why do we care about a chunk of plastic or styrofoam in a landfill taking 10,000 years? What harm does it do anyone? How is it any different than a random rock, or whatever else was underneath the ground?

Well, first, the problem with plastic isn’t necessarily that it’s not biodegradeable. There are things that do biodegrade that are still “bad for the planet”, or, “bad for the plants and animals we like on the planet”. For example, plain old sea salt is really bad for the planet if you dump lots of it in a forest. Everything will die. But salt biodegrades really easily, it’s an essential nutrient. Still, if you covered the whole planet in salt, it would kill all plants and animals on the land, for thousands of years.

The problem with plastic is… well… we’re still figuring that out. We have mechanical problems with plastic, like when birds and animals eat it and it gets stuck in their bodies. And we have beauty problems with plastic, because it’s ugly to look at pollution in a park or on a beach. But there are things that might be bad about plastic in very tiny pieces in any animal’s body (they’re probably not bad for plants). Our bodies weren’t designed to have plastic in them, and they don’t have much for processes to deal with them. That said, plastics might not do much damage, the whole reason we use them is because they don’t really react with anything.

In summary, there’s nothing that says that just because we made something from chemicals in the Earth, that is has to be beneficial to life on Earth, or, that if it’s not beneficial it has to biodegrade. Those are each different and unrelated things.