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Comment by drewcoo | Hacker News Reader

If it were biodegradable, geofoam hills would turn into geofoam-vacant sinkholes.

Many substances are selectively biodegradable i.e. remain shelf-stable forever as long as they are not exposed to oxygen or sunlight or whatnot.

Also, concrete degrades by itself. In decades it crumbles, pulverizes and goes back into being soil.

But, importantly, it does not become toxic particulate like plastic.

[edit: corrected phrasing, thanks zdragnar]

Same for other sustainable materials like compacted soil, gravel, sand...

Isn't that simply weathering?

Biodegradable would seem to imply to me that bacteria and fungi feast on it and convert it to what we consider soil.

The production of concrete is responsible for a ton of pollution in the world and while there's significantly lower environmental impact concrete available, few projects use them because of its higher costs for primarily environmental benefits. The distribution of the lifecycle of the environmental impact matters and if things are pretty bad now I'd strongly consider anything with backloaded environmental costs over ones that have environmental costs incurred up-front.

The bit about petroleum solvents, makes me wonder about sinkholes. "causes it to dissolve and break down into a non-load-bearing sludge", so if some joker tips a bottle of that in the park then a sludgy hole in the ground will start forming?

If there is any reasonable amount of soil above it, I suspect the bacteria and fungi will eat it well before it gets down to the foam.

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