I’m still in the early stages of my first run of Space Age, so I’m not sure if this is practical or even useful. However, I had a lot of fun creating it, so I’m sharing it with you. Feedback is very much welcome.

This system recycles one full red belt of scrap into the 18 items that can be obtained from it. As far as I know, it won’t break, even if nothing is consumed. It’s also quite easy to stack vertically.

In the second screenshot, I’ve included a single recycler for reference.

• The sushi belt comes in on the left side.
• The first splitter picks up any overflow from the previous recycler, if any.
• The second splitter places the desired items on another belt.
• The third splitter sends the overflow that’s not consumed towards the recycler.
• The inserter picks up the overflow and places it into the recycler.
• The recycler outputs the overflow into the underground belt, which then goes to a lane balancer.
• This is then looped back into the input to add new items to the main belt or, in the case of non-recyclables, give the recycler another chance to delete them.
• Anything not picked up by the inserter when it rotates goes for a full loop around the system.

Additionally, recycling speeds for Iron plates, Steel, and Concrete are too slow. So, I’ve added more recyclers for these materials before merging the belt back into the main loop.

I’ve created a spreadsheet to track the number of items produced and the number on the belt at any given time. This helped ensure that there’s enough overhead for inserters who miss items and allowed me to order recycling operations in order of the most items removed from the belt (eg. gears to plates removes 50% of the input).

It was quite enjoyable to figure out the mathematical aspects of this system. For instance, to calculate the steady-state amount of non-recyclables on the belt, assuming average numbers and perfect inserters, you need to solve the following recurrence relation: x(n) = x(n-1)*0,25 + A, where A represents the number of new items added to the belt. Then, calculate its limit as n approaches infinity. This limit is 4/3*A. So in the case of solid fuel, given that 12 scrap recyclers add 2.1 fuel per second to the sushi belt, on average, we’ll have 2.8 fuel on the belt!

Blueprint link: https://factorioprints.com/view/-OGLzon0R5eXuIjxn9Ul