Hah! Sunk costs.

I just deleted everything but the electric and robot network and rebuilt it from scratch. I was able to keep and simplify my assembler island, since I am no longer filtering on that island - only taking one kind of item from fixed-type cars and sending them to where they used to go after the absurd filtering setup.

Everything is much cleaner now, and I feel better about Fulgora.

I used to do this - recycling into oblivion - but then I discovered that, for me, Fulgora produced floods and droughts. I'd get flooded with low density for a few hours, but then I'd go for a day or two seeing almost none, and finding myself having to actually create a low density pipeline so I could launch rockets.

It's everything. Right now, for the past few days, I've been flooded with gears. Millions of gears. But early on, when I was recycling overflow, I spent a day or two getting almost no gears, and I had to drop steel from a platform and make them. Then it did that with low density; too much, then suddenly none and I had to build plastic production. Most recently, I spent a couple days getting no coil, but at the end of yesterday, it started coming in as a flood.

I'm talking about what the raw recyclers produce. They're always producing a too much of one thing and nothing of something else for hours, then they switch to some other item. Ice was an issue for a while.

The only thing I haven't been swamped with, yet, is holium. Of course.

I think my game just has an RNG seed that's producing pathological behaviors.

The Nilaus Master Class for Fulgora scrap recycling on YouTube explains this idea really well. Technically, I think he uses storage chests instead of buffer chests, just so that he wouldn't have to check "Request from buffer chests" on his requesters. The one exception is that he uses active providers for holmium ore to push it into an "infinite" array of buffer chests instead of relooping it. You never want to recycle holmium ore -- it's the whole reason to be on Fulgora.

My initial design for Fulgora was much less efficient, but "worked" well enough to move on to the other planets. (Fulgora was my first destination.) I was recycling into storage chests and had a big grid of buffer chests for each product. I then set up arrays of recyclers with requester chests for each product that was clogging up the scrap recycling. So, for example, I started with a bunch of gear recyclers. I used circuit conditions on the inserters to only feed those recyclers when the buffer chests were near full (but I wasn't recycling buffered stuff, only from the first stage storage chests, to keep the scrap recycling flowing).

After retooling my solution into the belt-based filtered splitter model, I managed to increase my scrap per minute from about 5k to 17k per minute. So, while the bot-based solution works, it was way more complicated and slower than the belt loop. (Also, after retooling, I think my logistic bot usage dropped from about 1500 at all times to about 180.)

Edit: Oh, another trick that I learned from the Nilaus video is the importance of "compressing" certain high volume and/or slow-to-recycle items on your return belt. Don't loop stone, turn it into landfill and loop that. Feed a couple of iron gear recyclers into an iron chest assembler (directly, no inserter required), then put the iron chests on the belt. Turn concrete into hazard concrete, then immediately recycle that (into 25% of the original concrete). Turn steel into steel chests, since they recycle so much faster. Ice and solid fuel should run through recyclers before going on the return belt since there's so much of both.

Scrap must flow

Yes, this exactly.

Here is an example I made https://hackertalks.com/comment/5590460

This ! I suggest taking a look at the videos from this Youtuber :

https://www.youtube.com/watch?v=NAsBS2JqjEs

It helped me a lot to use this strategy.

Also his special splitter setup is super helpful.

I was recycling directly from the miners, and then dumping everything into trains, shipping them to an island where I'd sort everything onto belts and into a factory complex. So offloading from the trains, I'd get sushi boxes, and for some reason, every inserter pulling from those boxes onto the belt that fed into the filter sorter set-up collectively selects the same item out of the sushi boxes for minutes at a time. So: given 18 sushi boxes off a train, (almost) every inserter would choose to pull (e.g.) blue chips for several minutes. Then they'd all start grabbing iron plate, and do that for several minutes. It's like a really broken RNG for item selection, or else it's not random at all and just works through some sequence - and they nearly all do it in lockstep.

The end result is that my sort filter field would get jammed up with something. Low density plastic. Red chips. Whatever. I'd clear it, and come back and it'd be jammed up on something else. So I sat and babysat it one day and noticed that inserter behavior. They'd start out looking random, but given long enough and they'd sync to the same item, and then stay on that item for long enough that the sushi belt would be all gears. Or fuel, or coils.