3 ms·

I feel like this is fundamentally an energy prices problem. If energy were cheaper we could replace quality with quantity and instead of everything being made

I feel like this is fundamentally an energy prices problem. If energy were cheaper we could replace quality with quantity and instead of everything being made of the thinnest plastic molded in expertly crafted dies that don't put a drop of plastic anywhere it doesn't need to be our world would have more products made from bigger chunks of lower grade plastic.

PaulHoule 2y ago
The number on my mind is that the monomers used to make common plastics cost about 50 cents a pound or $1000 per (short) ton. (Gas costs 50 cents a pound, almost anything that comes out of an oil refinery or a petrochemical plant costs 50 cents a pound) Chemical recycling (never mind mechanical recycling( of plastics runs into the problem that the products are worth 50 cents a pound which isn't much.
pjc50 2y ago
Energy problem on both sides. There's no advantage to larger chunks of lower grade plastic, that just makes the problem of disposal worse. On the one hand, it takes energy to recycle plastic waste, energy to sort it, energy to move it around. On the other .. the feedstock is actually really cheap, because petroleum is still cheap for the tremendous benefits it gives. So it's easy to just make more of it. The pyrolysis process mentioned sounds interesting. I wonder how efficient it is and how much CO2 byproduct there is.
- PaulHoule 2y ago
  Pyrolysis is one of those El Dorado energy technologies like the fast breeder reactor that has thousands if not tens of thousands of technical report for every actual installation. An extreme form is https://en.wikipedia.org/wiki/Plasma_gasification https://en.wikipedia.org/wiki/Plasma_gasification which can turn the combustible parts of waste (what space colonists would call "volatiles") to syngas, extract some metal, and turn the rest to slag. Trouble is if you want to do anything with the syngas (say turn it into fuel with the Fischer-Tropsch process) or even it scrub it for impurities, you need to attach a chemical factory to it and chemical factories expect to get consistent inputs so they can get consistent outputs. For instance a machine like that could process building waste which is mostly chunks of concrete if that waste is mixed with rubber tire scraps or something high energy. In recycling plastics they usually don't run the process so hard and they aren't aiming for syngas but to usually break plastics down to aromatic chemicals similar to the ones that exist in the BTX section of a petrochemical refinery, trouble is you get these along the way https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbo... with some particularly toxic examples such as https://en.wikipedia.org/wiki/Benzo(a)pyrene https://en.wikipedia.org/wiki/Benzo(a)pyrene which is basically a drug that causes cancer. In principle such a factory could be tuned up for a particular sort of plastic and try to be more selective about the chemistry: the 50 cent per pound BTX products are worth more than syngas.
zaptrem 2y ago
Problem is microplastics

PaulHoule 2y ago

The number on my mind is that the monomers used to make common plastics cost about 50 cents a pound or $1000 per (short) ton. (Gas costs 50 cents a pound, almost anything that comes out of an oil refinery or a petrochemical plant costs 50 cents a pound) Chemical recycling (never mind mechanical recycling( of plastics runs into the problem that the products are worth 50 cents a pound which isn't much.

pjc50 2y ago

Energy problem on both sides. There's no advantage to larger chunks of lower grade plastic, that just makes the problem of disposal worse. On the one hand, it takes energy to recycle plastic waste, energy to sort it, energy to move it around. On the other .. the feedstock is actually really cheap, because petroleum is still cheap for the tremendous benefits it gives. So it's easy to just make more of it. The pyrolysis process mentioned sounds interesting. I wonder how efficient it is and how much CO2 byproduct there is.

PaulHoule 2y ago
Pyrolysis is one of those El Dorado energy technologies like the fast breeder reactor that has thousands if not tens of thousands of technical report for every actual installation. An extreme form is https://en.wikipedia.org/wiki/Plasma_gasification https://en.wikipedia.org/wiki/Plasma_gasification which can turn the combustible parts of waste (what space colonists would call "volatiles") to syngas, extract some metal, and turn the rest to slag. Trouble is if you want to do anything with the syngas (say turn it into fuel with the Fischer-Tropsch process) or even it scrub it for impurities, you need to attach a chemical factory to it and chemical factories expect to get consistent inputs so they can get consistent outputs. For instance a machine like that could process building waste which is mostly chunks of concrete if that waste is mixed with rubber tire scraps or something high energy. In recycling plastics they usually don't run the process so hard and they aren't aiming for syngas but to usually break plastics down to aromatic chemicals similar to the ones that exist in the BTX section of a petrochemical refinery, trouble is you get these along the way https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbo... with some particularly toxic examples such as https://en.wikipedia.org/wiki/Benzo(a)pyrene https://en.wikipedia.org/wiki/Benzo(a)pyrene which is basically a drug that causes cancer. In principle such a factory could be tuned up for a particular sort of plastic and try to be more selective about the chemistry: the 50 cent per pound BTX products are worth more than syngas.

zaptrem 2y ago

Problem is microplastics