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Comment by philipkglass | Hacker News Reader

There are actually a lot of ways to destroy per- and polyfluoroalkyl substances (PFAS, colloquially called "forever chemicals") before they are released into the environment. Incineration, supercritical water oxidation, Fenton chemistry variants, even aggressive reducing agents can break these chemicals down into low-hazard "mineralized" residue.

The reason they're called "forever" chemicals is because natural processes that break these chemicals down are very slow acting once the chemicals have escaped into the wider environment. Even then, "forever" is a bit of misnomer. Various PFAS have environmental half lives on the order of decades, comparable to the medium lived fission products in spent nuclear fuel. That's not good, but it's not forever; the real "forever" pollutants are stable elements like mercury and arsenic.

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I think of this idea

https://en.wikipedia.org/wiki/Plasma_gasification

where the idea is you throw in all your municipal waste and the organic material is converted to

https://en.wikipedia.org/wiki/Syngas

which can be burnt to make (much) more electricity than it takes to run the torch and heavy metals get immobilized in glassy slag that can then be broken down and incorporated into building materials such as concrete and roads.

I have this vision though of a civilization that does this for 100,000 years and gradually poisons itself the way we did with leaded gas.

I used to work in gasification, and my understanding is that Plasma gasification has not reached net positive. You use up about as much electricity producing the plasma as you gain from burning the syngas in a generator. Normal gasification on the other hand, which uses oxygen to do the pyrolysis is very much net positive. It's sad to me that this technology hasn't taken off, as you can produce a tremendous amount of electricity and hot water from waste streams such as agricultural waste, woody biomass and trash. Not to mention if you bury the biochar it is carbon negative.

Pyrolysis is one of those things that has a huge literature for very little commercial development, a lot like the liquid metal fast breeder reactor. It’s little remembered that people quit burning coal burning power plants in North America around the same time they quit building nuclear power plants for the same reason which is that it is very hard for a steam turbine to compete with a gas turbine.

There is a huge literature on the possibility of gasifying coal and burning the gas in a turbine or maybe doing the same with biomass, maybe capturing the CO2.

For that matter there are numerous pyrolysis projects aimed at converting plastics into liquid fuels, they usually are fought bitterly by environmentalists concerned about air quality and the fuel being carcinogenic, many of the plants have failed to stay in operation because they couldn’t figure out how to get them running reliably.

Here is a list of mostly failed plasma projects

https://en.wikipedia.org/wiki/Plasma_gasification_commercial...

It only takes one successful attempt, and it's worth it

Don’t put heavy metals in roads. Roads are continuously broken down by traffic and freeze/thaw cycles. The dust from this process then gets carried into rivers and streams by rain as stormwater runoff.

People previously had the idea of using ground up post-consumer plastic pellets as filler in roads. Now that stuff is finding its way into the waterways by the above process.

Well. In Florida, they plan to put radioactive waste in the roads. Checkmate.

Wait what? Lol

"Florida is another step closer to paving its roads with phosphogypsum — a radioactive waste material from the fertilizer industry — after Gov. Ron DeSantis signed a controversial bill into law Thursday. ...The [Environmental Protection Agency] regulates phosphogypsum, and any plan to use it in roads would require a review."

https://www.npr.org/2023/06/30/1185280180/florida-roads-radi...

It's bizarre to me that the EPA says (linked in that article) it's permitted to put this in food, but not in roads.

- "Since there are large quantities of phosphogypsum waste, the industry encourages research into potential uses in order to minimize the disposal problem. The greatest use of phosphogypsum is in agricultural applications. Researchers proposing new uses must file an application with EPA."

- "Phosphogypsum has been used in agriculture as a source of calcium and sulfur for soils that are deficient in these elements. When the phosphogypsum is used as a fertilizer, it is simply spread on the top of the soil. When used for pH adjustment or sediment control, it is tilled into the soil."

- "The activity of phosphogypsum used for agricultural purposes may not exceed 0.37 Bq/g (10 pCi/g). An estimated 221,000 MT of phosphogypsum are taken from the phosphogypsum stacks and used in agriculture each year. There is no limitation on the amount of material that can be applied and farmers do not have to maintain certificates or application records."

- "In the past, phosphogypsum was incorporated into a Portland cement mixture for use in road construction. The use of phosphogypsum for such purposes is banned under the EPA final rule issued on June 3, 1992, which amends 40 CFR 61 Subpart R."

https://www.epa.gov/radiation/tenorm-fertilizer-and-fertiliz...

Quite a bit of phosphate ore is naturally contaminated with Uranium which of course winds up in the soil and then food. Uranium is notorious for being radioactive but it is also toxic in the same way as lead and mercury with a toxicity per pound intermediate between the two. Potentially this is an energy resource

https://world-nuclear.org/information-library/nuclear-fuel-c...

Some things are safe enough to eat but not safe to breathe aerosolized.

For example, pure elemental mercury.

https://www.space.com/air-pollution-reentering-space-junk-de... immediately made me think of where all burn up space ‘junk’ goes.

> Sensitive sensors in the nosecones of the planes analyzed the chemical compounds diluted in the thin, pristine stratospheric air, which is out of reach of Earth-based air pollution sources. The researchers found traces of lithium, aluminum, copper and lead in the sampled air. The detected concentrations of these compounds were much higher than what could be caused by natural sources, such as the evaporation of cosmic dust and meteorites upon their encounter with the atmosphere. In fact, the concentrations of these pollutants reflected the ratio of chemical compounds present in alloys used in satellite manufacturing, the researchers said in a statement.

So.. "fight fire with fire".

"It's technically possible to destroy this stuff"

...that doesn't mean it's relevant to how people are exposed to them, that it is economically feasible or practical to do the destruction, etc.

It does nothing to address exposure from things like cookie wrappers, french fry bags, disposable food trays, bottled water (ironically, which some people have to drink because their water is contaminated with PFAS.)

The whole point behind fighting against disposable plastics, for example, is that despite it being possible to recycle it, almost none of it is.

"It has a half-life of up to decades but that's better than mercury and arsenic"

Whataboutism? And PFAS have nothing to do with mercury and arsenic?

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