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I found this story regarding ongoing research of using bacteria to turn plastic into protein:

The team demonstrated that once the plastic is broken down by heat and a reactor, it can be fed to the bacteria. The microbes flourish on this meal. They keep growing as long as they have plastic to eat, producing more bacterial cells. Given that these cells are about 55 percent protein, once the plastic has been broken down, they can be dried down as a protein powder for later use.

The team hopes to find a way to make the process completely biological so that the plastic doesn’t need to go through heat and special chemical reactions to be broken down. It is possible that enzymes exist to help break down the plastic
Method That Turns Plastic Into Proteins Wins $1.2 Million Prize - iflscience.com

Do you think this will solve the problem of plastic pollution, at least in the long term? Will it be possible to produce proteins by this way in a large scale?

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  • But first, what's your own view, and what is that based on? Jan 8, 2022 at 22:23
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    What is meant by "plastic"? Feb 4, 2022 at 16:15

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There are two ways this can be done.

Firstly, it's possible to collect the plastic somehow from oceans, and then convert into protein. However, this approach has two problems:

  1. It's only feasible to collect the largest plastic pieces from large garbage areas, as opposed to collecting the most harmful microplastic so you are collecting only the least harmful objects (but there may be some benefit still as "macroplastics" today will be microplastics tomorrow),
  2. If you collect the plastic, why convert it into protein in a bioreactor -- why not burn into energy in a waste-to-energy plant as that surely will be cheaper than a bioreactor?

So, it seems collecting plastic waste from oceans is not a good approach: you can collect only the least harmful waste, and if you do so, you don't need the new microorganism but rather can burn the collected plastic.

Is there some other way? Yes there is -- if the microorganism has been engineered to survive in the oceans, we could release it into the oceans and let it multiply and do its job. However, in this case we would be releasing genetically engineered microorganisms into the wild, which seems like a bad idea. It's uncertain how this would affect the ecosystems around the world.

We can actually note that long time ago, lignin and cellulose in wood couldn't be eaten by microorganisms. Therefore, old forests became coal deposits as there were no organisms that could consume the dead trees. Today, that will no longer happen because microorganisms have evolved the ability to consume the nutrients in dead trees. So it may be that one possible solution for plastic pollution could be if microorganisms developed the ability to eat plastic -- either by genetic engineering or via natural evolution. So certainly having plastic-eating bacteria in oceans is one possible solution.

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    If you release it into the wild, the main positive effect of plastic (doesn't degrade) vanishes, which would simply lead to a new undegradable material which will pose the same problems.
    – DarkTrick
    Jan 1, 2022 at 9:12

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