Yes, I've come to the conclusion that it's better to bury most plastic waste.

Most plastic comes from oil, which means 'biodegradable' plastic is essentially the same as burning the oil. Actual recycling can work in some cases, but even after all the expense and energy of recycling, the recycled product is usually much lower grade plastic, so it's not sustainable. Better just to bury it (in leak-proof pits), where it will turn back into oil eventually.

The real problem with plastic waste is COLLECTING it, making sure it doesn't wash into the oceans, etc.

At least the recycle logo might help with that, even a fake one.

In a world where fossil fuels are still a thing, how does burying it stack up against just burning it as fuel?

I get that it's sequestered if it's in a landfill, but it seems like it might be more efficient to burn the carbon already extracted and turned into plastic than it would be to dig up new stuff and burn that (i.e. you get to leave more of the already-sequestered oil-carbon in the ground rather than digging it up and sequestering the plastic-carbon).

The scientific consensus is that recycling > burning with energy recovery > well managed landfill > badly managed landfill > open burning. Nations not under the control of fossil fuel groups have been putting this into action for decades.

Landfill seems to be the contrarian's choice but this appears to some anti-regulation propaganda after effect.

Headlines like "Thing you do to save the planet actually hurts the planet" is like catnip for some people, and they dont ask any awkward questions about who is claiming this and why.

Landfill as an imagined route to sequestration is easily seen through with the right thought experiment.

If you incinerate the trash instead of burying it, carbon does indeed get released.

If you burned enough coal/naturalgas/oil to produce the same amount of energy produced by incinerating, you would release a comparable amount of carbon.

Burying it doesn't sequester anything, if you assume it gets burnt to produce energy. If you burn it, you displace burning fossil fuels.

I wish recycling was more realistic, it frustrates me to no end that out of all those cute numbers that indicate you should feel good putting it in the recycling bin, odds are that anything you put in made of 3, 4, 5 (sort of), 6, or 7 is counterproductive. It just contaminates the good stuff.

But tangent aside, if you consider the plastics to be fuel it makes absolutely no sense to sequester them instead of burning them to displace fossil fuel use, reduce land use, and also centralize a major pollution source (plastics and such contaminating groundwater near landfills over centuries vs a centralized emissions filter).

The fly in the ointment of this idea that it’s better to just burn it for energy is that 40% of US electricity is already carbonfree, ie not coal, oil, or gas, plus burning trash tends to be less efficient than high efficiency combined cycle natural gas plants.

I do sure wish it was further along, and agree that it makes more sense to sequester it or convert to syngas for converting it back to useful products with more free energy.

It seems like a lot is simple once most electricity has a low marginal cost (environmentally, of course they'd usually negotiate feed-in tariffs or other guaranteed long term pricing that accounts for the capital costs of construction).

As I understand, I may be wrong, burning it releases the carbon to the atmosphere, but also releases some noxious chemicals unless burned at high temperatures, which often requires energy input. And any ash that's left can be problematic too.

Also I believe landfills will be future mines.

I wonder if it's possible though to turn garbage to charcoal, to sequester the carbon in a more stable form, and at the same time burn the 'wood-gas' for energy. Like bio-char, garbage-char.

> Better just to bury it (in leak-proof pits), where it will turn back into oil eventually.

What's the time scale of turning back into oil? How long those pits are estimated to stay leak-proof?

Given our best sealants are plastics, this is the best question.

I would say vitrification is a better sealant. Or maybe welding shut in a thick stainless steel container.

> Yes, I've come to the conclusion that it's better to bury most plastic waste.

Alright, here is a controversial hot take - we should probably just burn plastics - and most garbage actually - as fuel. Done properly, incineration is a simple way to limit environmental contamination caused by plastics and other waste materials. The extra GHG production would be partially offset by savings from simpler logistics for processing (no more shipping barges of waste plastic going to overseas dumps) , and significantly reduced methane emissions from landfills. And - depending on how cost-effective incineration is - we may be able to take savings from waste processing and double-down on removing emissions from other industries (e.g. Energy, transportation).

Gasification, using it as a fuel makes more sense. Reducing it down to basic carbon constituents. At least in this forum it’s productive and photosynthesis can turn it into organic mater.

If you do incineration right (with pollution controls and energy recovery), simply burning it is more direct.

Gasification is a nice intermediate step if you need to mix it with syngas or natural gas to augment supplies, but if you really just are going to convert to electricity or heat eventually you may as well just do it in one centralized step.

Either way the plastic product is just one stop on the path from hydrocarbon to energy and CO2+H2O, but I do think centralized incineration is more practical (especially since it's already done all over the place) with little real downside.

Just assume as a rough estimate that the gas you'd get from gasification is displacing natural gas production. If you just burn the plastic (and other trash) in a way that prevents serious pollution from getting into the air it's bound to be more efficient to do that and then just burn less natural gas -- versus trying to turn what is essentially already fuel into natural gas substitute.

Wait, does plastic really turn back into oil over time? How much time are we talking about here?

Not our lifetime. I disagree with the original poster. Often times manufacturing fresh polymer, while cheaper, uses many times the carbon content of the polymer in process energy.

Just as an example I know about offhand, isoprene rubber takes five times the carbon content of the product to process from petrochemical feedstocks. That said, recycling isn't very good either, so better would be to just not use it unnecessarily in packaging.

I do think it is better to incinerate than to recycle wrong and contaminate the entire recycling stream though. To me, ruining all the other recycling on top of lying about it being recyclable in the first place is way way worse.

And no, you cannot generally recycle PLA... I'm not sure where that is coming from. I hate that PLA (often labeled as 7 even though that just means "other") confuses everything even worse when people try to just toss it into typical compost and thus ruin the compost too. Of course it would also ruin the recycling... it would literally be better to just throw it away to be incinerated or else use good old numbers 1 and 2.

You can recycle PLA into recycled PLA filament for 3D printers. You can buy it online; it at one time was cheaper than new.

I don't doubt it, but not in standard curbside recycling bins basically anywhere.

I'd really like to know the answer to this as well. From all the research I've done in the past 10 minutes, you'd think that plastic is simply immutable and indestructible, and that even after millenia has passed it will still be plastic (even if in smaller pieces). But the Google SEO on this is dominated by environmental groups trying to emphasize the short-term life cycle of plastics, and it's hard to find anything with a longer-term perspective.

I think if you wait long enough (billions of years) then the landfills will eventually be under miles of earth and subjected to high enough pressures that they fundamentally change; in the same way sedimentary rock can change into metamorphic.

Your second sentence is false. Almost all of the biodegradable/compostable plastics (those that are marketed as such) are biomass based. PLA comes ultimately from corn

If you make plastic by pulling CO2 out of the air, then it would still be more efficient to recycle that into new plastic. You'd still be storing the carbon, just in things that are in active use.

There's some potential methods when you can just extract the carbon, which in turn you could also bury, but why not use it for something instead?

I feel the "lets put it in a hole" thing has been artifically boosted by fossil fuel interests who just happened to be emptying a hole as they dug it up anyway. If that wasn't the case I'm not sure storing stuff underground would be an obvious solution.

Using it for plastics, concrete or other things we need that contain carbon seems like it'll likely be always be a better choice than burying.

> You'd still be storing the carbon, just in things that are in active use.

The idea is to extract carbon from the air, make something useful out of it, and then bury the plastic when the item reaches the end of its useful life, thus sequestering the carbon. Recycling the plastics would compete with pulling more carbon from the air and reduce the amount being sequestered. The energy-intensive recycling process might also release more CO2 as a side effect, offsetting the amount captured in the plastic.

The goal is to get the carbon into the ground, not to create a closed cycle reprocessing previously captured carbon. Immediate burial would also work, of course, but then there wouldn't be any economic incentive to extract the carbon from the atmosphere in the first place.

There's no logical reason why connecting the three steps of the process make sense, unless you start with the premise that you really want to bury post consumer plastic and work back from there.

It would only possibly make sense if recycling was fundamentally a dirty process but since we've got enough zero carbon energy available to suck carbon out of the air we've got enough to recycle. We can then use that energy saved by recycling to suck carbon out of the air.

Unless there's some weird process or catalyst that makes atmospheric CO2 to consumer grade plastic the absolutely cheapest way to extract CO2 it'll always make sense to save energy and redirect that energy to the most effective method of getting CO2 out of the air whatever that is. I have no reason to believe plastic production will be that and it seems unlikely.

>Unless there's some weird process or catalyst that makes atmospheric CO2 to consumer grade plastic the absolutely cheapest way to extract CO2

Well, given that the way we do that is by growing plants, and most CO2 sequestering strategies involve... growing plants, it doesn't sound as far-fetches as you're trying to make it.

> I hope they don’t get rid of the symbol entirely! It’s useful to know what resin a product is made of.

They should use a different, non-similar symbol for this, since the current batch of recycle symbols have all become synonymous (to the layman) with "put it in the recycle bin".

Sure, use a square instead of a triangle. That’s a good idea. Actually, we should use marks that are easily recognized by machine vision so they can be efficiently sorted.

Would it surprise you to hear that the plastics industry came up with that symbol in order to make it confusing to the layperson to differentiate between recyclables and single-use plastics?

"Source" (not a primary source): https://www.youtube.com/watch?v=PJnJ8mK3Q3g <-- which has some links to further reading/viewing and a few sources.

This seems... not hard. For non-recyclables, just use the same recycling symbol, but put a diagonal bar through it, like on a no-smoking sign. And then provide whatever info you want underneath, same as when it's recyclable.

> If the cost were the same and the processing energy the same, wouldn’t it be better for the climate to bury that plastic (sequestering the carbon) instead of recycling it?

Even if it pollutes more to make virgin material than to recycle it -- and I think that's your problem -- if the non-recycled material goes into a landfill instead of the ocean or biosphere, there's a small consolation in that the carbon in the plastic is sequestered.

I don’t think it’s a small effect. There are something like 300 million tons of plastic waste per year, which is about 1 Gigatonne of CO2, or about 3% of global emissions… more than global aviation!

If we cut down all sources of emissions to zero, that would mean humanity using non-fossil plastic (like PLA or electrolytic syngas derived regular plastics) would be carbon negative.

The cost of PLA is about $2/kg, or equivalent to about $600/tonneCO2. About how much Climeworks currently costs for direct air CO2 capture.

>The cost of PLA is about $2/kg, or equivalent to about $600/tonneCO2. About how much Climeworks currently costs for direct air CO2 capture.

It's probably even better than that, if the PLA cost is for ready-to-use PLA, because presumably dirty/unprocessed PLA costs even less.

The symbol you're talking about was actually revised in 2013 to be a solid triangle around a number instead of the arrows:

https://web.archive.org/web/20160126213345/http://www.plasti...