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After all those scary stories about microplastics (I think you don't need references on that one), I was surprised to discover plastic solutions being suggested, even promoted you can say, in environmental publications. Take this, for example. It praises polyethylene mulch! It sounded crazy to me, to apply plastic to soil on purpose. How is it a good idea, with microplastics getting into groundwater and so on (even with the fact that it keeps water from evaporating from soil better than organic alternatives)?

Then we have this thing called tire-derived aggregate, or TDA. I know about the environmental toll of sand extraction (TDA is supposed to be substituted for sand), but it can't be right that shredded tires spread over land is a green, sustainable alternative. Again, I suppose, it will degrade into microplastics and wreak colossal damage if this becomes a widespread practice. California's bluest greenest government doesn't seem to agree, mentioning some studies.

Even reusable plastic bags, if you think about it, will end up, sooner or later, in a landfill (that said, I personally do use reusable plastic bags sometimes). I know plastics emit relatively low quantities of GHG during the production phase (compared to paper bags, for instance), but you should consider the entire life cycle, right? So I wound up wondering, can plastics be sustainable after all (including its application to soil, in one form or another)?

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  • Part of the answer lies in the quality of recycling systems for plastics. Regions with high populations will have better potential for quality recycling systems simply on the basis of scale of throughput will reduce the costs associated with operating the recycling systems.
    – Fred
    Jul 25, 2021 at 4:56
  • It's not difficult to make plastic from strong sugars. The trick is to make plastic from affordable weak sugars like wood chips. But the plan was for the plastic to be easily biodegradable but they changed their mind because the food industry wanted safer shelf life. Now the plastic will be biodegradable but not easily biodegradable. The source for this is the company history of Avantium. Now renewable electricity can be combined with captured carbon-dioxide and with catalysts to make carbon-neutral plastics. The source for this is RenewCo2.
    – S Spring
    Jul 25, 2021 at 13:21
  • You might be interested in this from the BBC, The fungus and bacteria tackling plastic waste.
    – Fred
    Jul 30, 2021 at 5:32
  • 4
    I've had this question open for weeks, as I would really like to provide an answer. I worked with plastics in my master thesis and have become opinionated about it (obviously based on the research I read, but what's objectivity anyway?!). The short answer is: no. Whenever you can use some kind of rock, wood, mineral, glass, or degradable material (for which you don't have to ask whether it is or isn't), use that instead. Don't color it, as there are plastics in colors, or use natural pigments, y'know. If a material has the properties and the durability of a plastic, it's probably just as bad.
    – thymaro
    Jan 11, 2022 at 16:43
  • @thymaro - Oh, please do expand that into a proper answer :)
    – Robotnik
    May 18, 2022 at 11:11

2 Answers 2

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The main sustainability problem of plastic is microplastics. Anything else is a non-problem, for example plastics made from oil -- only few percent of oil is used to make plastics, so if all oil usage apart from making plastics is phased out, making those plastics won't be a climate change problem. Even plastic recycling isn't strictly speaking necessary, as if we create all plastics from oil with absolutely no recycling at all and then burn them to energy, the carbon dioxide emissions will be minimal.

If we want plastic to be 100% sustainable, we have to:

  1. Educate people that leaving plastics into environment is not permissible, as every lightweight plastic object left to environment will be carried by wind or birds into oceans where it becomes microplastics.
  2. Have every public trash can modified so that there's a lid that prevents birds from exploring the contents of that trash can and distributing plastics to environment.
  3. For plastics used in clothing (think about fleece that becomes millions of microplastic particles in a washing machine), we need some way to remove microplastics from wastewater or in washing machines before they even reach wastewater.
  4. Ideally have some way of recycling it. The main problems of current plastic recycling is that even after the first round of recycling, quality is crap. This is evident from the current plastic bags. Years ago, you could buy plastic bags made of new plastics from any grocery store. I have a small amount of plastic bags still that are approximately 5 years old and are still going strong, being used often. Yet if I buy a new plastic bag, I can only buy recycled bags today, and those generally become torn during the first use and reusing them requires careful inspection of tears and is possible only few times until they become too severely torn. The most promising way of recycling plastics is to burn them to carbon dioxide in a waste-to-energy facility, then capture that carbon dioxide from flue gases, combine it with hydrogen produced using electrolysis to create methane, then post-process that methane to create longer chain hydrocarbons and eventually plastics. This recycling via burning creates plastics that are chemically 100% identical to new plastics, so no quality degradation takes place.
  5. Have a way of creating new plastics that doesn't use oil. Today, oil-based production is cheapest way of producing plastic, but once oil is phased out, new plastics can be made from trees. That's bit more expensive today but if plastic producers have to pay for the CO2 problem of oil being used to create plastics, it may become cheaper. Anything that can be created from oil can be created from a tree. We have enough trees to create all the plastic in the world forever in a sustainable manner.

Every problem in this list is solveable with technology, apart from (1) that might require legislation changes and severe fines for those who leave plastics into environment, and even then not every offender will be caught.

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ALL plastic is recycleable, it's quality concerns. The problem with plastic is it's extremely low value. We knew that 50 years ago, that's why plastic became the dominant packaging/container medium because it's sterile, non-biodegradable and very cheap. But re-collecting that plastic that's been distributed is a nightmare. A 20 fl oz plastic bottle empty weighs 23.8 grams An empty glass bottle weighs 8 oz or more. Glass weighs 10x more than plastic.

IN ALL manufacturing there's resources and materials involved. Plastic, even waste plastic has uses. Thermal depolymerization is an industrial process where polymers, even complex ones can be converted to monomers/mixture of. This can be powered by renewables/various clean energy

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  • This doesn't target the main concern of microplastics.
    – Erik
    Jul 26, 2021 at 9:02
  • Recycling Bakelite is particularly challenging.
    – Fred
    Dec 22, 2021 at 16:27

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