Leah Mack

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.

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

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.

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...?

K Eilander wrote:
I've heard of/seen those, but how do you diy your own!??  That would be super interesting!  Do you have links?

No links, I'm afraid, but I did make one myself for a greenhouse at my university when I was going to school up in Maine. The campus greenhouse was 50+ years old, all steam-heated and single-pane glass, and used wax motors for the vents. One busted, and I was able to make a jury-rigged replacement.

I bought two copper pipes, where the inside diameter of one was roughly equal to the outside diameter of the other. I crimped and folded over one end on each, so they were both sealed on one end. I then used a mandrel to expand the smaller pipe very slightly while it was inside the larger pipe, so it was an extremely tight fit between the two.

For the interior wax, I used a mixture of parrafin and mineral wax, that liquified about 85*F. That took a little trial and error, but I imagine if you were better at chemistry than I am you could find a way to calculate the right ratio for an arbitrary temperature. I painted a small amount of silicone sealant around the outside of the interior pipe, to act as a kind of 'piston ring' and keep the wax mixture from leaking too badly.

It worked pretty well, but was eventually replaced. I wish I still had it, or had some photos to share, but I do not.

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!

Sensors, motors, and computers sound like overkill, especially considering how limited power can be in tiny-houses if they're not hooked up to mains electricity.

Just use a wax motor
https://en.wikipedia.org/wiki/Wax_motor
They were used extensively in greenhouses, and can be DIY'd pretty easily, allowing you to dial them in for a specific size and temperature range pretty easily with nontoxic ingredients.

Burton, that's exactly the kind of info I was looking for! The Omick site has proved to be incredibly helpful, especially the page about sizing systems and how long things need to age for. Thanks so much for linking that thread!

Hi Matt,

You make a good point about potentially paying for the use of a land-based storage area. Though I did try to touch on all the available options, I was hoping someone might know of a particular method or design for implementing these options more well-suited to a boat. For example, a person trying to compost food scraps indoors might not be aware of bokashi composting or vermicompost, which are both 'composting' but have particular advantages/disadvantages that make them better for some circumstances than others, if that makes sense?

Anyway, thank you for your comment!

Hi All!

Partially as a result of very high housing costs, climate crises, and personal inclination, I'm looking to start living on a sailboat in the near future. Naturally, I want to do this in the most permie way possible. However, legal and practical limitations are giving me some trouble.

If you have some sort of acreage, it's relatively simple to set up a composting toilet of some kind. Maybe it's just a bucket with sawdust to cover, maybe it's a willow feeder, maybe it's even a whole septic system with a vermifilter. On a 20-30ft boat, though, you lose a lot of options. A bucket with sawdust might work, but then as they fill you're stacking up bucket after bucket in your very limited space. And even once it's aged and become more-or-less safe, where do you put it? Dumping it overboard is hardly ideal.

There are 'Marine Sanitation Devices' that use a biological aeration/separation process to treat urine and feces, but aside from power use they also rely on chlorine to sanitize the effluent before it can be pumped out. I understand that 'activated sludge' could hardly be tossed into the ocean by itself, but chlorinating it hardly seems like an ideal solution. The main approach that many people seem to use is simply having a blackwater tank that they regularly pump out at the marina, sending it into the larger sewerage treatment system.

Are there any systems or designs which might work well in this specific context?
I was thinking a little of an 'incinerating' toilet, drying out the solid waste and then burning it in a rocket-y stove with good ventilation. Urine could be treated a little more quickly and easily by a compact microbial filter I think, producing a low-nutrient liquid that could safely be discharged overboard.

All your thoughts, objections, assertions and general ideas are very much appreciated!