Plastic-agnostic composting? Bio-degradation of petrochemicals

Hi all,

If you look into community compost projects, the same issue raises its head pretty reliably. People throw in anything. Now, I'm a pretty open-minded composter. Oily or greasy foods? Sure! Meat? Toss it in! Even pet waste is no big deal as long as you know you're going to get to safe temps or hold it for a long enough period.

However, plastic waste is usually cited as the big concern, and for good reason. Pretty much any organic material can be safely and effectively composted without having to work too hard, but plastics? Even the "biodegradable" ones are kind of suspect, and can tend to shatter into small pieces without actually undergoing any chemical transformations into less-toxic compounds.

What if that wasn't a concern, though? What if folks could throw in old sandwich baggies, and styrofoam takeout containers, and all manner of godforsaken trash, and it'd all come out in the wash? There's been some research on superworm digesting styrofoam and successfully breaking it down. Some species of Aspergillus fungi have also managed to break down polyethylene.
What if you found the perfect combination of bacteria, fungi, archaea, and arthropods that allowed you to take everybody's food waste and the packaging it came in, and break it down into something healthy enough to grow more food in? How amazing would that be?!

What I'm asking for, is more information (and in my wildest dreams, case studies) about practical setups for taking advantage of some of these amazing organisms' ability to break down petrochemicals. I'll also happily take ideas and objections on the subject. I've been spinning this idea around in my head for a little while, so any outside input is accepted and appreciated.

Thanks!

Thanks for bringing up this important topic Leah!  

My approach to dealing with plastics has been to:

1- avoid using it or buying it

2. When it cant be avoided, I separate it into bins and throw it "away".

Of course, we know there is no 'away".  I am guilty of passing on the problem further down the line, but would love to find some better solutions that are practical in a permaculture full loop system, where we could take this problem and turn it into a solution, and capture this overly abundant resource to turn into something beneficial.

This stuff has become ubiquitous, and from what I have seen so far there is no getting rid of it, as the particles just get smaller and smaller, and as they do break down they actually release toxic gick, which might make us feel better momentarily because we cant see it anymore, but just means it is becoming more bio-available, which puts it deeper into our internal organs, tissues,....brains!  

Hormonal imbalances and Endocrine Disruption, Inflammation and Gastrointestinal lining damage, Oxidative Stress, Reduced Nutrient Absorption, Thyroid Dysfunction, Cancers, Respiratory Issues and Lung Tissue damage (asthma and COPD), Cardiovascular problems, Impaired Cognitive Function,....the list goes on and on.  Its the nanoplastics that worry me, and the unknown synergistic effects, where the plastics combine with other toxins and environmental stressors to create an even worse outcome.

When our bodies are already being bombarded with an increase of various pollutants it becomes more and more difficult for our livers and kidneys to keep up, and from what I understand the micro and nano plastics are especially difficult to remove from the body.  

So, with that said, I have concerns about putting any plastics into composting systems, and eventually into the food chain.  

So far the best solutions I can see are to reduce exposure, and  filter contaminants and isolate.  

By concentrating the plastics, rather than mixing, it might actually make it easier to deal with them. For example the 'Blest Machine". There was once a video I saw of a person who was able to convert plastic waste back into oil/fuel through a pyrolysis process:



This is now, supposedly, being done on a larger scale, however it is energy intensive, is not fully clean with emissions, and has yet to become more economical than using virgin oil.  

My big questions at the moment are...

How to filter the micro/nano plastics out of our environment without having them enter the food chain?
Biochar?

How to detoxify our bodies?  

What I'm asking for, is more information (and in my wildest dreams, case studies) about practical setups for taking advantage of some of these amazing organisms' ability to break down petrochemicals.

Have you ever heard of "Biological Transmutations"?  Maybe there are some answers found in there somewhere. I really hope we can solve this problem sooner than later.  

There isa book written on the topic: https://www.google.pl/books/edition/Biological_Transmutation/Q8zFnA6qScwC?hl=en&gbpv=1&printsec=frontcover

Here on the forum, this has been a concern for some time now.

In case others are interested, meal worms, waxworms and the larva of darkling beetles can do this.  

Here are some threads for you and others that might want to read more about these superworms that eat plastics:

https://permies.com/t/72035/Styrofoam-Composting-Mealworms

https://permies.com/t/50485/composting/Mealworms-Eating-Styrofoam

https://permies.com/t/103412/Superworms-bioremediation-polystyrene-ideas-extending

Thanks for linking the related threads, Anne! Some of the topics discussed and methods people are using there (feed to meal worms, then fungi, then back to worms, then compost, etc.) are very interesting.

I think one of the limiting factors is that meal worms (and super worms) aren't great at breaking down mixed food scraps. My understanding is that they need much drier conditions than you tend to get when you're using kitchen waste. That's kind of the problem that I'm most interested in addressing. Any kind of bioremediation of plastics is awesome, but when I say a "plastic-agnostic" compost, I'm thinking about a system that's mainly yard and kitchen waste, but could also safely decompose plastic that's added in error.

I'm sure lots of people who buy/use municipal compost have noticed little bits of bread ties and blue tarps mixed in, and there are a lot of people who avoid using it for that reason.

I wonder if initially drying/dehydrating scraps might make them more palatable to the mealworms and maintain a better environment for them? If it was solar, some amount of UV might also help to start breaking down plastic so the worms can digest it more readily...?

Leah Mack wrote:I think one of the limiting factors is that meal worms (and super worms) aren't great at breaking down mixed food scraps. My understanding is that they need much drier conditions than you tend to get when you're using kitchen waste. ...?

How much plastic do you have in your food scrapes?

Maybe the solution is to separate the food scrapes from the plastic in you kitchen waste then maybe have two bins one  labeled plastic and one label food waste or just give the food waste to the chickens...

Anne Miller wrote:
How much plastic do you have in your food scrapes?

Maybe the solution is to separate the food scrapes from the plastic in you kitchen waste then maybe have two bins one  labeled plastic and one label food waste or just give the food waste to the chickens...

I, personally, have zero plastic in my food scraps. This is not an issue of me, specifically, having plastic in my compost.

I feel like I must have explained this poorly, because everyone's answer is "separate the plastic and food scraps!" when that's exactly the step I'm looking to remove the need for. If you read my original post, I described a common problem with community and municipal compost projects. They often end up with plastic trash being added, potentially contaminating soil and certainly lowering the quality of the compost.

For a community or municipal compost project, it is not possible to have an educated person in everyone's kitchen checking what they add. Depending on scale, it is likely not possible to meticulously check each bucket/bin that gets brought in for pieces of plastic. Due to the overuse of plastics in our society, a large enough composting project is practically guaranteed to be contaminated at some point. It is simply not possible to reliably exclude all plastic from community compost projects.

Ergo, my interest in a "plastic-agnostic composting" system. A method of composting which produces good quality organic matter with no contaminants dangerous to human or soil health, even if some plastic gets mixed in or otherwise added by mistake.

It is easy to forget something that is said in a first post, or at least for me and sine I read that yesterday.

I feel part of the problem with plastic in community recycling projects, it is impossible to get folks to understand how bad plastic is when there is so much in their daily lives.

It might be easier to get industry standards changed to get plastic out of the food business.

Anne Miller wrote: It might be easier to get industry standards changed to get plastic out of the food business.

Most large community compost systems accept yard waste.

Most yard waste involves leaves raked in the fall. Most humans use their environment as their garbage can for their coffee cups, chip bags, and beer cans.

This is a big problem with community compost projects all over. We *need* yard waste composted rather than landfilled. It should be a resource rather than a liability, but I don't see any practical way to ensure that it's plastic free.

If we can find some sort of secondary processing with microbes/insects/fungi either on an individual or community level, that would we a good thing.

More pressure on people to not litter may be helpful, but not all littering is intentional, so we need to assume that plastic is there, and find ways to fix the problem.

Jay Angler wrote:
This is a big problem with community compost projects all over. We *need* yard waste composted rather than landfilled. It should be a resource rather than a liability, but I don't see any practical way to ensure that it's plastic free.

If we can find some sort of secondary processing with microbes/insects/fungi either on an individual or community level, that would be a good thing.

That's also the perspective I'm coming at this from. I've been doing some more research on the topic and I have both good news and bad news.

Consumption and degradation of different consumer plastics by mealworms (Tenebrio molitor): Effects of plastic type, time, and mealworm origin by Pham et al
This study basically fed mealworms five of the most common types of plastic. These were polystyrene aka Styrofoam, high-density polyethylene, low-density polethylene, polyvinylchloride aka PVC, and polypropylene. The mealworms ate and degraded all of them.
However, they didn't degrade them all at the same rate. The graph below shows that while the small colonies of mealworms ate about 170mg of styrofoam over 30 days, they only consumed 10 or 20 mg of most of the other plastics.


This might not be the end of the world--larger colonies of mealworms eating more diverse foods (rather than a pure-plastic diet) and multiple 'cycles' achieved by feeding frass to mushroom colonies and then the spent substrate back to the mealworms, or similar, might be sufficient to achieve zero plastic in the end result.

There's another interesting paper here, Optimizing mealworm rearing conditions and gut microbiome function for enhanced plastics biodegradation
It's honestly worth reading, but the long and the short of it is that mealworms were found to consume polyurethane as well as the above-listed plastics. Generally the older the insects were (the higher their 'instar') the higher their efficiency in degrading these plastics (grams degraded per weight of larvae). Apparently they generally also preferred regular misting, which is surprising considering a lot of info I've seen suggested mealworms do best in drier conditions. Perhaps when exclusively consuming/burrowing in hydrophobic plastic they dry out more easily?
Graph below is a summary of their results

Ah, I forgot to add this paper as well--Cockroach Blaptica dubia biodegrades polystyrene plastics: Insights for superior ability, microbiome and host genes

The authors found that the orange-spotted roach is also capable of degrading polystyrene, and may well be capable of degrading lots of different kinds just like the mealworm. It's possible that they're capable of consuming a greater quantity of plastic relative to their bodyweight than mealworms, and I'm sure we're all familiar with blatticomposting, though if I recall that mainly uses Eublaberus species of roaches. Still, orange-spotted roaches are apparently popular 'feeder' insects for amateur reptile enthusiasts, and aren't too picky about their food. More research required, etc.

Dealing with plastics...

This is a tough subject because there are many types of plastics out there...

From my perspective I believe we can find alternatives for plastic like clay, stopping the problem from the start is a good way to move.

But the reality is plastic is how 95 % of water is transferred to homes today with PVC Pex pipes,  which is a great upgrade from the lead pipes that were used and in some places still exist in plumbing.

We can recycle the plastic our self with heat, and make different items with it.       But one needs to be cautious of the fumes created by heating the plastic....    

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


Others have extracted the oil from plastic to make fuel for engines.      Yet another method used is to burn the plastic directly stopping the micro plastics from polluting the environment  and using the heat...

Myself, I don't trust the science that tells me that worms can eat plastic and then it is all ok to use to feed to my plants...     The Science of times past also told us that DDT is good for you and me....        This might be possible, but not something I trust.        I like the idea of doing a clean burn in an incenerator as the best option I see, much like they do with tires to produce electricity.