from Hacker News

Garbage In, Toxics Out

by schlowmo on 9/28/23, 2:19 PM with 23 comments

• by fuoqi on 9/28/23, 3:15 PM

  The problem is with trying to "recycle" garbage plastic. Plastic is mostly carbon, oxygen, and hydrogen. Properly burning it using high-temperature (900+°C) pyrolysis converts most of plastic into water and carbon dioxide. There are some issues with sulfides and nitrogen oxides, but scrubbing those is a familiar problem for the industry. Remaining ash is relatively inert and can be used as a filler in various applications. Releasing carbon dioxide is not great, but it's much safer biologically than polluting environment and oceans with microplastics and total volume is relatively small compared to other emission sources.

• by coldcode on 9/28/23, 3:03 PM

  I haven't been a chemist in more than 40 years, but even I know that pyrolysis of plastics makes a horrible toxic soup. There is no way to recycle many plastics in this way, the chemistry to reuse this resultant material doesn't exist. All it does is reduce the volume of material, which you then have to put somewhere. Also, the volatiles you generate have to go somewhere, and I highly doubt you want to breath them. You may as well live next to a battery recyling plant that uses coal for energy and raises pigs.

• by CptFribble on 9/28/23, 4:59 PM

  Why are we still not talking about plasma gasification?

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

  As far as I can tell, the only real "disadvantages" if you can call them that, are:

  1. more expensive than throwing the garbage in a big pile somewhere

  2. need to clean it from time to time

  3. not necessarily a profitable business

  Other than that, it can handle just about anything that's not radioactive, can be designed to produce 0 toxic byproducts, and can run at or at least only slightly below energy neutral. Plasma gasifiers can also consume a huge amount of garbage for their size, so much so that the US Navy is starting to put them on the latest generation of aircraft carriers.

  Not building out more gasifiers seems to me a failure of the free market. Because it's hard to make it profitable, no one is doing it - when really we should just be building one or two near every major city and funneling all our garbage there.

  In theory, we could build out enough to start working through all the landfills too.

• by jwx48 on 9/28/23, 2:55 PM

  I've pretty much given up trying to recycle plastic, and instead throw it in the trash. It's toxic to make (I think?), contaminates food and water when you heat it, and--apparently--can not be recycled safely or efficiently. I realize I can't remove it from life entirely, but I'm actively avoiding it where I can and replacing it as opportunity permits.

• by dr_leviathan on 9/28/23, 6:11 PM

  I have been wondering for years why solar powered pyrolysis wasn't being used to recycle plastics. I thought it could reduce ALL plastics to an oil soup kinda like crude, which could then easily be separated by a distillery into various useful hydrocarbon oils for making new plastics/fuels. However now I'm starting to understand: the resulting soup is more toxic than crude and is difficult/expensive to distill, while the volatile byproducts that don't condense are another toxic liability. Bummer.

• by nerdponx on 9/28/23, 2:55 PM

  As suspected by many. But we should be grateful for actual reporting on it.

  Was this not a problem with the older model of separated recycling (glass, plastic, and paper in separate bins), with plastic limited to numbers 1 and 2 only?

  I'm also curious about if plasma gasification is a better option for plastics than whatever this process is.

• by sydbarrett74 on 9/28/23, 7:50 PM

  Since the transition to electric vehicles will take decades (and some, like aircraft, may never fully make the switch), perhaps the synfuel generated from this pyrolysis can substitute for virgin petroleum. It could help make many parts of the world more energy-independent and less obligated to rely on the Middle East for oil.

  The oil to make the original plastics has already been extracted, so it would be a carbon-neutral solution for the most part, especially if some of the plastics are burned to drive the process.

  THe ultimate solution, though, is to lessen our dependence on plastic (Reduce), and completely eliminate single-use (Reuse).

• by flashback2199 on 9/28/23, 3:54 PM

  I wonder how they make money. This sounds like grifters living off of government grants. I wonder how widespread the problem is of grifters taking government grants for fake green projects. Perhaps the country made the right move by not doing a green new deal after all. It looks like paying grifters to do science doesn't work very well.

• by pstuart on 9/28/23, 2:55 PM

  This is so disappointing (but not surprising).

  Many years ago there was a lot of press about a company call Changing World Technologies (https://en.wikipedia.org/wiki/Changing_World_Technologies) that touted how they could use pyrolysis to convert any hydrocarbon feedstock into fuel (garbage, sewage, etc).

  It was going to be cost competitive and clean. Turned out to be not so much when their pilot plant processing turkey remnants stank up the town and shut them down.

  The technology seems to be valuable, but it looks like capturing and containing emmissions is still not cost effective so they just dump it.