Here's an idea that would make the landfill a lot more useful: make all manufacturing processes in buildings create waste byproducts. Assemblers would produce a small amount of [Trash] when making anything, and the assembler would have two output slots, one for the product and one for trash. Chemical plants would produce small amounts of [Sludge] which would come out one of the two output slots. You could put the [Trash] or [Sludge] into the landfill to get rid of it, at the cost of generating pollution (pollution is especially strong with sludge), or you can store in chests/storage tanks to avoid pollution.
It would be nice if you could also perform a recycling process in which you turn trash into iron plates, or sludge into heavy oil, although it would be slow and cost a lot of power while producing new pollution. So you could be lazy and throw it in the landfill, or build a complex factory that handles all of its waste. You could also add support for the Air Filtering mod to make the dirty filters produce a large amount of sludge when they get cleaned, thus you could make a very complex factory that costs a lot of power and takes up a lot of space, but produces no waste products and only negligible pollution.
I'm thinking inserters should by default ignore trash. Maybe burner inserters would not ignore it--they should also produce pollution when running. So early on you could use burner inserters to pull trash out of assemblers, or later you can do it with filter inserters. Or alternatively, they do pull trash out along with products, and you filter the trash out along the line or in the chests. Or you can be lazy and leave it in the chests. Perhaps if trash arrives on the intermediate product belt, the inserters will put it into the assembler along with the other intermediate products--for example one assembler is producing trash and copper cables, the next one is taking in trash and copper cables to produce trash and green circuits, and all the trash that gets produced just keeps moving down the line without obstructing the production.
