I've heard a bunch of impractical proposals for ways to sequester carbon: pump CO2 gas into the ground, grow trees for the sole purpose of burying them underground where they won't decompose... and these proposals all seem impractical to me.

By contrast, it seems quite doable to allow people to consume single-use plastics, and dispose of them in well managed landfills. (I wouldn't exactly say we should encourage the practice, not until we have bioplastics in widespread use and green energy powering plastic production). Stringent efforts should be made to ensure the plastic is not burnt and is kept out of the marine environment.

Plastic is very chemically stable, it won't decompose and form methane or anything else, it won't bubble up to the surface, and mixed in with garbage it becomes unattractive for future generations to dig it up.

I'm also making the assumption that any oil not used for plastic production would be used instead in the transport industry or at least somewhere where it'll be put straight into the atmosphere. I think it's naive to think that if I forgo my plastic drinking straw, there'll be one more drop of oil remaining forever in the ground - it won't be left in the ground, instead it'll be made available to the transport industry.

I've tried to get an answer to this question from New Scientist, Australia's Dr Karl and basically every chemist or physicist I encounter and no-one can explain why I'm wrong. So it seems to me governments everywhere who are banning single-use plastics are doing the opposite of what they should be doing.

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    $\begingroup$ Could you edit your question to focus on what would happen long-term, chemically, with (micro)plastics buried in well-managed landfills? That would make it more unambiguously on-topic here. $\endgroup$ – gerrit Jan 28 '20 at 9:02
  • $\begingroup$ I fail to see the greatness, or an attempt to research the effects of plastic on the environment and foodchain, from production to waste. "noone explained why i am wrong" ist a good hint, the idea to encourage even more environmental damage ist almost absurd. nationalgeographic.com/environment/habitats/plastic-pollution $\endgroup$ – user18607 Jan 28 '20 at 9:02
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    $\begingroup$ First principle of sustainability: Don't do stuff. Whatever you not produce/consume doesn't pollute. You could stuff the rest down a mineshaft, but your idea to "sequester carbon" is bollocks - mainly because without the production of the plastics, there's no carbon to sequester. $\endgroup$ – Erik Jan 28 '20 at 10:11
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    $\begingroup$ Very much on-topic IMHO. This is not just a geology stackexchange. $\endgroup$ – Semidiurnal Simon Jan 28 '20 at 13:23
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    $\begingroup$ Well, conventional plastic is produced from fossil carbon deep underground in the first place. At best you can say it is an incomplete fossil carbon cycle that is quite leaky. A "perfect" cycle (which is impossible) is at best carbon neutral to the atmosphere. Carbon sequestration is commonly defined as taking carbon out of the atmosphere. $\endgroup$ – y chung Jan 28 '20 at 21:19

Plastic isn't a good way to sequester carbon the sense that this term is usually meant.

Carbon sequestration is normally assumed to mean

[...] the long-term removal, capture or sequestration of carbon dioxide from the atmosphere to slow or reverse atmospheric CO2 pollution and to mitigate or reverse global warming.

(From Wikipedia, my emphasis.)

This is not how plastic production works: the great majority of plastic is made from petrochemicals. So almost all plastic is made from fossil carbon, not from carbon extracted from the atmosphere recently.

With plausible assumptions about the energy used in making plastic and its source, then turning fossil carbon into plastic which is then not burnt is probably better in terms of carbon emissions than just putting the fossil carbon straight into the atmosphere. But it's worse (again in terms of carbon emissions) than just not making the plastic at all.

Note that there have been plastics made from plant materials, and many early plastics were made like that: Celluloid is a good example. I thought Bakelite was as well, but it turns out it's the first one that wasn't.

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    $\begingroup$ Yeah, the production part is the major contribution to the CO2 footprint of plastic. Consensus is to lower plastic production and raise recycling rates. ciel.org/plasticandclimate. Plastics from plant material iopscience.iop.org/article/10.1088/1748-9326/aa60a7 can be done, but e.g. crop production for biofuels has lead to monoculture with all its downsides. $\endgroup$ – user18607 Jan 28 '20 at 11:11
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    $\begingroup$ +1 for the insight that plastic's carbon was already sequestered before we dug it up! The bit about Bakelite is interesting, I have fond memories... $\endgroup$ – uhoh Jan 29 '20 at 0:44
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    $\begingroup$ @uhoh: the smell of hot phenolic resin / bakelite is something you don't forget! $\endgroup$ – tfb Jan 29 '20 at 11:09
  • $\begingroup$ I've edited my question to make clear my assumption: that all oil will eventually be dug up. (Although I hope this is not also true of coal). In other words, if it's not used for plastics then it'll be used for transport. Dunno if other people share this pessimistic belief. $\endgroup$ – Tim Cooper Jan 30 '20 at 0:35

Plastic waste is a problem already and it is growing quickly. Huge rafts of plastic flood the ocean, they end up in the foodchain, killing huge numbers of animals, even endangering species, and human health. With ocean deoxygenation coming into view and the sheer amount of plastic being produced (as @tfb pointed out by releasing CO2) and little recycling taking place, the suggestion to deliberately use one way products to eventually sequester CO2 must be regarded as not sustainable as long as plastic production is fossil fuel based, little recycling takes place and the disposal poses such huge risks.

IOW: this is not a good idea.

Edit: one can further search man-made soils, effects of landfills from waste disposal, and their impact on fresh water, farming, health, etc. as well as the carbon footprint of plastic production. There is work on these subjects.

  • $\begingroup$ I did say "Stringent efforts should be made to ensure the plastic is not burnt and is kept out of the marine environment." I think banning single-use plastics makes more sense in Indonesia than Australia because Australia can ensure good management of waste and Indonesia can't. $\endgroup$ – Tim Cooper Jan 30 '20 at 0:36

tib is absolutely right in what he says, but damage to the environment and more specifically to wildlife is another reason for greatly reducing our use of plastics made from fossil hydrocarbons. Those made from biological sources are better, but have their disadvantages too. Some biodegradable plastic bags, for instance, biodegrade while the contents are still in them if you don't use them straight away.

The worst damage is done when the plastic gets into the ocean. Turtles and other marine creatures mistake plastic bags for jellyfish and swallow them. Seabirds occasionally feed them to their young or incorporate plastic items in their nests which entangle their young. Other creatures such as dolphins,sharks and turtles become entangled in plastic rope or fishing nets, and die of suffocation.

Plastic bottles are among the worst forms of plastic pollution. The sheer number of them is staggering. Tap water is quite healthy; we don't need to go around all day sipping water from plastic bottles as though we were afraid of drying out like a slug on a hot pavement. Then there is the problem of plastic micro-particles produced by the breakdown of larger items. It has yet to be established exactly how harmful these micro-particles are, but they enter the human food chain when we eat sea food.

The best biodegradable bags are made of paper, so we should return to much greater use of paper bags. I know trees have to be cut down to make paper, but done properly the forest or plantation will eventually regenerate. Packaging of all sorts is usually too lavish, and needs to be reduced.

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    $\begingroup$ This answer seems to have very little to do with the question. $\endgroup$ – Semidiurnal Simon Jan 28 '20 at 13:22
  • $\begingroup$ I did originally say: "Stringent efforts should be made to ensure the plastic is not burnt and is kept out of the marine environment." $\endgroup$ – Tim Cooper Jan 30 '20 at 0:39

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