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Plastic-eating caterpillars: An escape from a shopping bag triggers an idea (economist.com)
139 points by rahulshiv on Nov 9, 2017 | hide | past | favorite | 43 comments



This actually sounds a bit scary, and I hope doesn't become reality, since it might turn out to be like termites --- given how much we rely on plastics, the damage caused by an inadvertent release or application could be severe.

Also, polyethylene is one of the simplest plastics and can be recycled quite effectively; so the real problem is getting people to reuse and recycle, and not disposal. Much of it comes from petroleum sources so a nontrivial amount of energy was already spent in its production too.


I think your second point is the most pertinent. I recall hearing about this subject a while back.

Frankly, I wonder why (besides the loud sound of the Sunchip bags[0]) that cellulose and other bioplastics aren't utilized more—at least for common and commonly-dispensed items like beer-can rings, food wrappers, and other short-term packaging.

---

[0] https://vimeo.com/9664621


and other short-term packaging

The main problem with biodegradable plastics is that they have an inherent "expiry date", the countdown to which begins basically upon manufacturing. Product which could be stored for an unexpectedly long time may start degrading too early and thus become prematurely unusable. Trying to avoid waste myself, I've had a few times where I reused plastic bags which were biodegradable, without being too aware of it, and had some bad surprises when they functioned exactly as designed and disintegrated at the worst of times.

Personally, I'm not a fan of biodegradables --- they seem to be a way for the manufacturers to keep making things which don't last as long, a sort of forced obolescence, under the guise of being "green". Also, overall it probably takes more energy to produce these materials than recycling existing plastics.


> a sort of forced obsolescence,

That's a good point I hadn't considered. I was referring more specifically to really temporary storage. For instance, those baby spinach containers are usually made of bioplastics because the contents expire rapidly no matter your intentions. There are often other vegetable or grocery-shelf products that might not have long shelf-lives or delayed uses that could utilize the plastics.

Surely we could divide the products into long-life and short-life? I'm speaking mainly to food products here. I don't see the immediate need to eradicate all plastics from use! I regularly keep my grocery plastic bags and reuse them time and time again. I should have been more specific!

That said, it looks like the costs required to manufacture bioplastics are reducing[0]. The problem with non-bioplastics being that many of the refuse that people don't properly recycle will be here maybe long after you and me, or we can just punt it on down the generational-line, but as we've been witness to more recently that doesn't seem to be a great strategy.

---

[0] https://phys.org/news/2015-07-biodegradable-plastic-cheaper-...


Also, if the packaging degrades quickly, then by definition it ends up in your food in larger quantities (not sure if that is a problem though).


The food inside has an expiration date too. As long as your container exceeds that, all should be well for most cases, no?

That leaves two necessary improvements:

1. Decreasing the loudness and crunchiness of the sound, and

2. Controlling the biodegradability of the material.

> Also, overall it probably takes more energy to produce these materials than recycling existing plastics.

Are you taking into account the future cost of de-plasticking oceans, rivers, streams, and other contaminated sites? That should be included too. Deferred costs are still costs.


> they seem to be a way for the manufacturers to keep making things which don't last as long, a sort of forced obolescence

If the product is explicitly marketed not to last I see no problem with it. I prefer buying food without excess preservatives, for example.


Reduce comes before reuse and recycle. There are several countries with 0 landfill rates and high recycling rates in Europe, but that doesn’t solve the problem. We actually need to re-evaluate our use of plastic.


https://www.youtube.com/watch?v=nYDQcBQUDpw

For some ideas about how to cut waste. A different approach, with emphasis on recycling:

https://www.youtube.com/watch?v=eym10GGidQU

As much as the internet likes to make fun of people like this, I honestly don't see anything wrong with what they're doing. And they look happy and healthy.


I'm not sure how true that is [0]:

> What the “0” landfill means is that no waste is landfilled without pre-treatment…

In 2014 there was only Germany that claims 0 landfill (subject to the above disclaimer) and there's 6 self reported countries that claim below 10%.

[0]: https://www.zerowasteeurope.eu/2014/04/and-the-best-waste-pe...


"If a single enzyme is responsible for this chemical process, its reproduction on a large scale using biotechnological methods should be achievable." It seems like the intent is to find the mechanism of action and transfer it to a microbe. Could be super useful in oceans and other places that micro plastics are common.


I'd still keep them in a filter rather than releasing those microbes to the ocean. We don't know what other effects this could have on life.


As far as I’m aware, rubbish dumps are lined with a membrane to help control leaching. Having this membrane attacked would be fairly unhelpful.

https://en.m.wikipedia.org/wiki/Composite_liner


> Also, polyethylene is one of the simplest plastics and can be recycled quite effectively

Polyethylene can be recycled, but depending on the price of oil it's often cheaper to make new things than try to recycle them. Planet money did an episode a few years back that talked about this:

https://www.npr.org/sections/money/2015/03/27/395815221/epis...

"One day it's profitable to recycle a bottle. The next day, some number in the global economy changes and that bottle suddenly becomes trash."


Just because something is cheaper, or more profitable, doesn't make it the right thing to do. You'd ideally include externalties that are not captured by the price.

To give one related example, just dumping your trash in the street is cheaper than paying people to come and haul it away but no one seems to make the argument all about cost in that case.

Particularly in the US, propaganda campaigns against the entire concept of recycling seem to have been very succesful. Often these are pushed by libertarians and you can trace the funding back to the Koch brothers who (entirely coincidentally of course) are invested in companies that supply the virgin feedstock materials to make new plastic bags or whatever.

They've also spend millions on anti-EV and anti-solar campaigns two other rival industries where their product is only "better" if you totally ignore externalities.


If you are of the belief that we have reached or will soon reach peak oil, then this sounds like a business opportunity for temporal recycling in the form of stockpiling the plastic until recycling it is valuable.


This was in April 2017. A more recent report questions the previous publication:

"Although the biochemical decomposition has not yet been disproven, the sensational report of plastic eating caterpillars at least appears highly doubtful in the light of these results." [1]

[1] https://www.sciencedaily.com/releases/2017/09/170915144156.h...


what about this? "To confirm it wasn't just the chewing mechanism of the caterpillars degrading the plastic, the team mashed up some of the worms and smeared them on polyethylene bags, with similar results.

Read more at: https://phys.org/news/2017-04-caterpillar-bags-biodegradable...


The waxworms in the article eat polyethylene. Common meal worms are capable of eating another plastic, polystyrene -- you can observe this yourself by just grabbing some from a pet store and putting them in a styrofoam container for a few days.

In the case of the mealworms, the digestion is coming from gut bacteria, but it remains unclear how waxworms are able to do it with polyethylene.


>Another question is the composition of their faeces. If these turn out to be toxic, then there will be little point in pursuing the matter.

In other words, we don't even know if they _digest_ the plastic, or just eat it. If they don't digest it, there's no utility....


No, they digest them. Here's another article with more information.

https://phys.org/news/2017-04-caterpillar-bags-biodegradable...

>To confirm it wasn't just the chewing mechanism of the caterpillars degrading the plastic, the team mashed up some of the worms and smeared them on polyethylene bags, with similar results


Thats one hell of a test..


Scientist 1: it may be an enzyme in the caterpillars, how we can we test for that

Scientist 2: well how about we anaestetise the caterpillar and use a microfilament to extract the gut contents, then we can ...

Scientist 1: <splat>


I'm currently sitting next to Paolo Bombelli... He laughed and said that your version of events is fairly accurate, although they used liquid nitrogen as an "anesthetic".


I'd just put them in the centrifuge that they use to liquefy mice.


Oh God. There is a centrifuge to liquify mice?!


Yep. The animals are euthanized with CO2, placed in the device, and reduced to liquid in seconds. Obviously, this is not done when specific organs need to remain intact, but if you can do your measurements from homogenized whole animal, it saves a lot of time on rapid perfusion and dissection.

Specialty devices exist, but a standard high-speed desktop centrifuge can also be used, as a mouse will generally fit into a 50 mL centrifuge tube.

Generally best not to think about it too much if you like animals, but also like biochemical sciences. But if you're after a specific enzyme that would not be destroyed by rupture of the cell wall, whole-animal sacrifice by centrifuge is the cheap and easy way to get at it.


I like the humorous way in which you put it, but oh, can’t help but imagine some higher creature talking about experimenting on us in a similar way /shudder


How is... "homogenization" by centrifuge different than just using a blender or food processor?


I don't understand what this means. Results similar to what?


Similar to letting them eat the bags.


Looks like instead of worms, they should focus on the enzymes that can break down the plastics. Apply gratuitously during waste processing and add them to landfills.


Potential downsides to consider:

1. What happens when we remove the "negative" side of using plastic products? Why use less if the worms can eat it all? I'm guessing production and consumption of single use polyethylene products will increase.

2. What if the worms escape control, (like the possums in New Zealand, the farmed salmon in the pacific etc etc) then what sort of new disaster do we have on our hands?


To your first point, I don't think we currently reduce plastic at all. There are some people who want to reuse and switch to alternatives but in general, plastic usage is not limited by environmental factors currently. So I doubt we'd use more plastics if we can safely recycle it all.


Even if the worms turn out to be good for plastic disposal, I still don't see how that implies your first point. The products with which plastic is made are still a limited resource.



There is also nylonase, or the nylon eating bacteria

https://en.wikipedia.org/wiki/Nylon-eating_bacteria


>Article title: Plastic-eating caterpillars could save the planet

Wait, since when is plastic the main menace to our planet?

>Another question is the composition of their faeces.

Yeah, it would suck if it produced even more CO2 and methane. Even if we can catch the methane to make energy, that's more CO2 that would have been otherwise sequestered.



Non-paywalled article: http://archive.is/0Ja6H


What could possibly go wrong?


This is pointless.

Once you have collected it bury it, burn it or recycle.

If anything this will just release CO2? or Methane?


Harvesting methane in a controlled environment could be used to generate electricity. And even if it's pure CO2 it would be cleaner than current methods.




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