Plastics recycling with microbes and worms is further away than we think (2018) | Hacker News Reader

Plastics recycling with microbes and worms is further away than we think (2018)

cen.acs.org

137 pointsEL_Loco77 comments

Two promising technologies:

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

Heat and pressure turn plastic back into oil.

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

Oxidize plastic in a molten salt bath, exothermic reaction, produces synthesis gas. "... destroys all organic materials while simultaneously retaining inorganic and hazardous components in the melt."

Trash incineration with district heating is highly underrated. Not only does it save space and prevent methane emissions from landfills, it also lowers the urban cost of living. Unlike an enzyme, oxygen will destroy almost any kind of plastic.

https://stateofgreen.com/en/sectors/district-energy/district...

Apologies if this is off topic, but I've never read such a well researched science article, citing many primary resources and papers. Well done.

One should hope so, if it’s on ACS website. And their journals are also pretty reputable and have pretty high impact factors. :)

What could possibly go wrong if those microbes inevitably get into the wild? This should recreate the situation with cellulose. At first, trees didn't decompose but nowadays, you have to prepare wood if you want to use it long-term.

Plastic is used because it doesn't decompose. What good would plastics be if they wouldn't be stable anymore?

As the article indicates, the problem is not necessarily technological but economic; trying to find a market-based solution to a notable market failure might be a sign of a pathology of our times.

https://www.penguinrandomhouse.com/books/539747/winners-take...

Great book on this very topic!

The solution to "internalizing the externalities", which is the economic jargon for such, is to tax it.

If you want more of something, subsidize it. If you want less, tax it. Governments are good at taxing things.

Taxing it aligns the economic incentives to produce the desired outcome, rather than banning it which leads to all sorts of distorted outcomes.

More and more countries are banning certain uses of plastics such as plastic bags and one time use plastics. Do you think that’s gonna have a distorted economic outcome? I think we could step out of the economic bubble sometimes and do things that are good for the environment - without which there would be no economic activity possible.

> Do you think that’s gonna have a distorted economic outcome?

Yes. Typically, such laws embed exceptions. But the exception list is always inaccurate.

For an example, when the EPA set fuel economy standards for cars, it exempted trucks. The station wagon disappeared and was replaced with the SUV, which was a "station wagon" configured to pass the EPA definition of a truck.

Instead of banning plastics and having an ever-wrong list of exemptions, raise the price (via taxation) so other materials become cost effective.

This. How about a "plastics management" tax every company must pay based on the amount of plastic each of their products uses, including manufacturing, shipping, etc. That, or ship all plastic waste back to the company who made it to manage.

When I walk into a store these days, I can't help but think almost everything there will end up in a landfill or the bottom of the ocean.

Should we maybe not try to recycle plastics, but just try to contain them in landfills?

Our atmosphere is polluted with CO2, wouldn't recycling or incinerating plastics release even more of that?

Creating microbes for eating plastics seems like a recipe for a lot of goo....turning all our insulation, computer gear, and a billion other things in our homes into microbe food seems to me poorly thought out.

Indeed. Imagine termites, but at a far bigger scale...

Don't forget all the very important medical applications of plastics where their inertness matters --- if organisms exist that can start eating away at those, and proliferate, it could cause even more damage to human life.

There was a recent scifi novel about this, I forgot the title. The plot was some anarchists discovered a virus that ate plastic, and released it all over the world, and caused the collapse of civilization.

I don't see any big problem with burying the plastic in a landfill. Just don't dump it in the ocean.

Burying it doesn’t really solve anything though. And while seemingly unlikely, dumps can be damaged. A recent storm damaged one in the south of New Zealand, spreading plastic down a river and along hundreds of kilometres of coast.

https://www.tvnz.co.nz/one-news/new-zealand/fox-glacier-land...

> Burying it doesn’t really solve anything though.

It solves it better than any of the alternatives.

> And while seemingly unlikely, dumps can be damaged.

Not only does it seem unlikely, it is unlikely. One case doesn't make it likely.

Once buried is it solved, or is it that we can’t see it? Waste plasticn needs a solution, but I don’t think that burning it is the answer. We badly need to reduce the volume created.

That’s an awful comment. I’ll try again.

Once buried is it solved, or is it that we can’t see it? Waste plastic needs a solution, but I don’t think that burying it is the answer. We badly need to reduce the volume created.

It has to go somewhere, we can't launch it into the sun. Burying things is not a long term problem - coal is trees buried for millions of years.

The Andromeda Strain, an early Michael Crichton novel, ended with the virus mutating to consume plastic...causing a jet fighter to crash IIRC.

Imagine that suddenly, plastics can rust.

Plastics already oxidize through UV, thermal, and hydrolysis reactions.

Wood lasts for hundreds of years in the right environments. Similarly most plastic is not in any real risk from this.

You have literally no idea if this is true. Literally used in the literal sense because until such microbes exist you can't predict their behavior.

I literally know it’s true from chemistry.

Polyethylene for example is a long string of hydrogen and carbon. (CH2-) Microbiology requires more than that for replication. It’s the same reason dry sugar does not get consumed by microbes.

It was too broad an assurance to base on quick chemical assessment. We have different kinds of plastics situated in many different environments. Regarding the sugar example and microbes primary need for water, from the article - "In 2016, researchers in Japan tested sludge from a recycling plant and uncovered a microbe that could completely break down films of PET to CO2 and H2O"

And any opening or crack which rainwater or groundwater or seawater or dust can occasionally access will carry nutrients required for microbial life.

On the table in front of me I have several food items that have not spoilt only because of refrigeration. Should I also start to keep my laptop in the fridge to prevent it rotting? Or maybe I should preserve it in vinegar etc. The problem of preservation of food only seems trivial because so many people have worked so hard solving it.

The table in front of me would rot really quickly if I put it in a composter.

How do you know which situation will apply to plastics if we manage to engineer bacteria that metabolise them?

You literally can't. History shows us that introducing new species with novel abilities to an ecosystem has far reaching, unforeseen, often devastating and usually irreversible consequences. Why would we risk this? Plastic digesting bacteria would be utterly novel and completely outside our control.

Edit: oh and the table is almost certainly treated with some chemical agent that helps preserve it. Be that paint or varnish...

There are very few bacteria that strive in dry conditions.

> How do you know which situation will apply to plastics if we manage to engineer bacteria that metabolise them?

Life needs to obey physics and thus chemistry. Many plastics are already consumed by various bacteria in specific environments yet function perfectly well as TV remotes etc.

Further, plastics have a rather wide range of chemistry. Polyvinyl Chloride (PVC) for example includes a lot of chlorine making it much harder for organic chemistry to deal with. Thus making it suitable for wet environments.

PS: Indoor wooden tables are coated in varnish largely to aid in cleaning and protection from ware. Kitchen cutting boards last for years demonstrating the difference between intermittently damp vs long term wet conditions.

It's not behavior it's metabolism.

Downvotes won't change nature.

You literally can't know what the consequences of plastic metabolism would be. History shows us that introducing new species with novel abilities to an ecosystem has far reaching, unforeseen, often devastating and usually irreversible consequences. Why would we risk this? Plastic digesting bacteria would be utterly novel and completely outside our control.

To make confident predictions about species that don't even exist yet is just hubris.

> To make confident predictions about species that don't even exist yet is just hubris.

I am willing to wager rather large sums of money they are not going to violate the conservation of energy. Unknown, does not necessarily mean unknowable.

That said, I said nothing about their impact on ecosystems just the majority of plastics in use by humans.

Wood gets eaten quickly if it's wet (and untreated). This seems to be a limit on microbes turning civilization into mush - most of our artefacts aren't wet when used normally.

Yet it doesn't get eaten at all if it's submerged because the organisms that produce the ligase to break down lignin, the structural component of wood, require oxygen.

Buried plastics may become the oil of future generations.

The total energy buried and density of it isn't interesting compared to oil, coal, and probably even timber.

Hey childrens children: we left you a present, huge piles of plastic garbage, isn't that awesome?

In the same vein : why not produce/use less plastics ?

The long term answer has to be, produce almost no plastic at all, except those cases where it's a genuine necessity such as medical uses.

I don't think so. The raw materials can be literally synthesized from thin air with enough energy input and you can burn plastics to get rid of them again.

What we definitely need to stop completely is letting plastics escape into the environment. Clothes made from plastic fibers for example need to go away.

If you have to keep the stuff under harsh disposal control, that would rather obviate the non essential uses.

Reducing consumption is the most impactful thing we aren’t doing.

That is the plan.

"Reduce, Reuse, Recycle" is the mantra, after all.

There’s even two more R’s now:

refuse

reduce

reuse (+repair)

recycle

rot

What’s the difference between refuse and reduce?

My guess would be to refuse some things, like plastic food wrappers where they can be switched out with paper. Reduce is using the same product material but using less of it in a single package.

That's easy to suggest and hard do. How are you going to change the behavior of entire populations? We are already trying education.

Environmentalists are fighting an uphill battle so long as business, whose packaging decision are practically unilateral, aren't held accountable for their contributions.

The "education" that gets the most funding is simple mis-direction away from supply-side pollution to consumer-blaming "solutions".

Yes, but how do you make businesses accountable? Legislation perhaps? Who's going to vote for those? Perhaps if we could educate people to care, but as I said we're already trying that.

On a individual basis, I guess bringing up the issue more often is the best we can do really, I would definitely appreciate more environmentalism in politics discussions, but it feels very low-impact.

> how do you make businesses accountable?

Well, to whom are businesses accountable currently? Shareholders.

Naive solution: make impacted communities shareholders.

Price it appropriately. For the vast majority of the uses of plastic, it isn't the best solution, just the cheapest. Keep adding tax until something more sustainable is cheaper.

But then people couldn't use 30 disposable water bottles a week.

How do you get the government to add the appropriate taxes? That's also easy to suggest and hard do.

I wonder if people would start drinking tap water or disposable wooden water bottles first.

Milk cartons work perfectly well for water too.

Milk cartons contain plastic.

They don't have to and not all do. There are non-plastic food-safe waterproofing liners for cardboard.

Tap water really is not an option in most of the world.

Make companies responsible for the full life cycle of whatever product and packaging they put into this world.

> Our atmosphere is polluted with CO2

"Polluted" isn't the best word to describe it when CO2 levels are 2x historical (for a very long definition of history) levels. They're likely high enough to cause significant climate change, but "polluted" is a funny way of putting it.

> recycling

If you look at where oil goes, most of it is energy and transportation, not plastics. We're also talking about recycling and not incinerating.

But I vote for incinerating for energy. Plastics are too incredible of a technology to not use, but at least now, too hard to feasibly recycle, so I'd rather we burn them and offset the emissions.

A key part of this has to be reduced usage. There is an awful lot of plastic made and used that isn’t necessary.

Polluted is perfectly fine.

adjective

contaminated with harmful or poisonous substances.

The quantity of the substance is harmful.

I would quibble with the use of "contaminated" for something that's always been there.

In fact, the atmosphere had quite a lot of carbon dioxide a billion years before there was any significant quantity of oxygen.

E. coli, staph and salmonella are everywhere and all over you, but we still call things that have them "contaminated".

We don't, except in some narrow contexts, like "Large quantities of E.c. found in bottled water". Looking at pristine lake far in woods one wouldn't say "Look, such a contaminated water!" just because there are bacteria. We also don't say "My intestines is contaminated with E.Coli" in spite of the fact it's there too.

But if there was too much bacteria it would be contaminated. It's about there being an inappropriately high amount of something.

The risk is microplastic, which can escape cheap containment several ways (wind, water, etc).

Yes, turning every planet-wide scrap of plastic into combustion byproducts would release a lot of CO2. It's likely it would pale in comparison to fuel though, since the most it can release is the oil embodied in the plastic, plus the energy used in reprocessing.

We can burn the waste and capture the carbon. We don't need new technology, it's purely economic - capturing carbon is still relatively expensive and carbon emissions are underpriced.

https://pubs.acs.org/doi/10.1021/acssuschemeng.7b03283

Note that the article only covers PET. Some polymers are much more difficult to decompose, e.g. PTFE.

But their mass is orders of magnitude less than PET. We just don't use that much teflon relatively speaking.

PET is by far the most common plastic, and it's not the most dangerous (to humans or the environment).

what about feeding cows seaweed?

https://foodtank.com/news/2017/06/seaweed-reduce-cow-methane...

Interesting in its own right, but has nothing to do with this article.

Is it really? I've just assumed all along that it won't be during my life time (outside of small scale demonstrations and special plastics).

I think most recycling (outside of obviously simple wins like aluminum and steel cans) is a joke, designed to keep people busy and distracted while real polluters (like aluminum manufacturers who use gigantic amounts of electrical power mainly derived from coal plants and over the road truckers who are still fighting implementing 30 year old emissions standards) go about their business. We train children that recycling paper and yogurt boxes is going to save the planet when in reality consumer recycling is a drop in the bucket and amounts to basically nothing.

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