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Comment by nomel | Hacker News Reader

> This take seems trivially and obviously wrong.

I don't think this is obviously wrong at all. Dispersing a fine mist of micro plastics into the environment, where it can enter the air and water system, is very very different than sticking a piece of plastic into the ground, where it will comfortably sit for a thousand years with minimal decomposition.

For a good example, here's [1] a study about how car tires, which slowly disappear into the environment, are a major contributor to micro plastics in the ocean.

[1] https://www.nationalgeographic.com/environment/2019/09/tires...

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You’re missing that not all plastics make into a landfill and are around us already leeching microplastics. I’d think that bricking them and covering them with other materials would lock them in better than a bottle floating in a river

I lived in Kenya. Stuff under the road doesn't stay there long. They get incredible abuse and little maintenance. It's hard to think of anything that would generate more microplastics than putting it in a road. Plastic in the ocean, in your garden, in an animal's mouth, anywhere else, just can't compare to the grinding action of thousands of cars daily.

The road? These are footpath pavers.

He obviously didn't read the article.

Footpath state in Nairobi is awful, I haven't spent much time out of the capital.

But if you're able to collect those plastics it would be better to send them to a well managed landfill rather than make them into bricks.

Nobody is recommending that we throw used plastic in the river as an alternative.

> Dispersing a fine mist of micro plastics into the environment

Huh? I don't see anything in the article to suggest this is happening...?

Why would you require the article to suggest this? It’s an uncontroversial consequence of subjecting plastic to a continuous barrage of abrasive forces.

Similarly, if rain is expected, I don’t need the forecast to tell me that rain makes clothes wet.

How does their use in footpaths subject the pavers to a "constant barrage of abrasive forces"?

People will step on the path when they are walking on it. Rubber wears down paths, as does any sort of abrasive sand or rocks between the shoe and the road. There is a significant amount of wear even on stone paths from foot traffic. There are some plastics I would be willing to try, like UHMW, but wear resistant plastics like that are also very slippery and not cheap even in recycled form.

She is essentially making composite decking but in brick form. The sand filler will probably take a lot of the wear. Solid blocks of plastic last a long time so the degradation will be minimal compared to the waste plastic it is being made from.

> with minimal decomposition.

That's the thing - does it actually decompose at the same rate or slower than eg. concrete or brick?

Concrete and brick are a natural, inert, substances that have been present, in some similar form, in nearly all bodies of water, and most natural enviromnents, since the beginning of life. Plastics have been around for 113 years, and they don't quickly remove themselves from the water ways (they're buoyant), as rock dust/sand does.

The rate of decomposition is not the correct metric to look at, in this context.

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