Some allegedly "compostable" things take ages to break down. Why is this bad?

So I just saw this:

The linked article discusses a paper, whose claim is that a lot of the allegedly “compostable” things (particularly plastics) take much longer to break down in compost than organic matter.

Assuming this is true. Why is this bad? I mean object A (say a banana peel) releases X grams of methane in a month, and object B (say a “compostable” bag liner) releases X grams of methane over 18 months. Then object B is better, as in causes less global warming. As methane breaks down in a few years anyway, so maths (my maths at least) say the X grams will be in the atmosphere for a shorter time than object A. At the very least (if my maths is wrong) B is no worse than A, its still X grams of methane getting released.

What an I missing here?

The article is terrible writing mixing lots of different issues and jumping around like a spastic Yorkie on uppers.

The thing I see with home compostable plastics is that if I put some food waste & grass clippings in my composter, and a supposedly compostable plastic bag that doesn’t much degrade over the next decade or so, after 6 months I’ll have some nice mulch and a plastic bag. So then I reload my composter with more food waste, more grass clippings, and another plastic bag. 6 months later I’ll have some nice mulch and two nearly intact plastic bags.

See where this is going? Unless the plastic stuff degrades at a similar pace as the fully organic stuff, pretty soon your composter will be full of plastic bags with little room for anything else.

There is an important difference between biodegradable and compostable. You are trying to make compost as @LSLGuy says. Even so, biodegradable ought to mean reducible usable chemicals too often means it breaks down to tiny plastic particles, without actually degrading.

Not exactly - your compost doesn’t evaporate. You will have compost soil for your garden with bags mixed in unless you fish them out. A few years from now you will have shredded bits of plastic bag mixed in with your garden soil as the bags deteriorate.

Another point is conditions - IIRC, wet composting does not accelerate plastic decomposition for “compostable” plastics. It’s the breakdown of the molecules over time. In fact, for some it’s UV that helps, so they are better off not being buried. Whereas paper, being more organic plant material, will decompose with composting - but you’re better off starting with shredding it and distributing it through the soil. A big wad of paper, especially shredded paper, by itself not mixed in becomes a thick chunk of paper mache.

My wife managed a restaurant where the owner’s wife thought nice puffy valences on the window curtains looked nice - so she stuffed them with regular plastic shopping bags, back in the day when they were everywhere. Three years later they decided to change the look, but all those bags in the sunlight (even through a nylon material) has decayed to the point we were pulling out shreds and chips of plastic bag…

(My neighbour uses laid out newspaper as a weed mat under their wood chips - they just poke holes to plant flowers, so there are fewer weeds growing where the paper blocks it.)

My son, who is like a gardening god, uses this technique for a way to pioneer new vegetable beds over existing lawn grass. Layers of newspaper or a corrugated cardboard box flattened out, cut through for transplant seedlings, and topped generously with fresh compost and wood chips.

Grass clippings, wood chips, and kitchen waste amount to a poor recipe for compost. Ideally, you need shredded tree leaves. You can throw in some coffee grounds to speed up the process, but it will make a nitrogen-rich compost.

If you want to feed your garden with garbage, it’s best to enlist worms to process the stuff first. Remember, no fat, no bones.

Many years of making mistakes and correcting them by listening to You Bet Your Garden on NPR have made me a better gardener.

If you want to make compost, go here first. How to Compost | Gardens Alive!

Recently, I changed what brand of potatoes I buy. My grocery store was out of the usual 5 lbs packaged in plastic bags, so I looked around and found some 3 lbs paper bags. The paper bags have a notice on them that they’re compostable.

The town I’m in has a yard waste pickup in addition to the usual trash and recycling. Some time back they said you can put kitchen scraps in with the yard waste for composting. So I thought I could put those bags in with the kitchen scraps, but I’ve never been certain that was the best thing to do. Based on this thread, it sounds like my reservations were correct and I should be putting the bags in with the paper recycling.

If they have a giant mixer-shredder for the yard waste compostables, where they make sure everything is shredded to bits and mixed with existing soil, then they probably shred and mix the bags enough to help them on their way to soil heaven. However, probably not a good idea to dump all of last year’s newspaper into the yard waste bin in one lump.

Maybe not - I am supposed to put my yard waste in either an unlined trash can or a paper lawn and leaf bag.I assume the ratio of bag to leaves and mixing makes it work.

Our secret ingredient for our compost is horse shit. Lots of horseshit.

I started adding sea weed to my compost and it was like magic. The cities rake the beach every morning and will happily give it away. Sea weed, duck poop and lots of grass shavings and leaves, Keep it just dry enough where it will crumble in your hands.