Here we have a more expensive disposal system for anything with food residue. Dry goods and wet goods go to different land fills. They encourage us to rinse food containers and discard into the dry waste/construction waste.
In the recycle streams they don't take dirty paper/cardboard or dirty sheet plastic. But they take any kind of plastic pail, even ones that had motor oil in them. Oil is drained out, the plastic chipped, rinsed with solvent, and the chips recycled into things like nursery pots.
Two rubrics occur from these examples:
- Rigid materials are easier to clean. So chipping and cleaning isn't unreasonable.
- Stuff with high surface to mass ratios (foams, thin sheet goods) are more likely to be unaffordable to clean.
- Stuff that is going to be processed with high heat and a runny liquid state can be sorted/filtered in that state.
Paper is dissolved, and sand/dirt difficult to separate.
Steel, aluminum will be smelted, and organics burned off, and dirt trapped in the slag.
Plastic is heated to the gooey stage, then is molded/ turned into garbage bags, etc. Hard to separate dirt.
There are some applications that would make a new market for some types of waste:
E.g. Styrofoam right now is difficult to deal with. Even crushed, the low density makes transport expensive. A possible use could be to wash it, drain it, then mix with an acetone/water/alcohol solution that partially dissolved the surface, then press it into large lego blocks. Sand would actually be a useful addition givening them enough mass to not blow around. A system using these would make for inexpensive emergency shelter. Mould grooves into the exterior surface, and you can plaster them for longer term use. (Styrofoam degrades in sunlight. Mould grooves into the top surface and you have easy to run wiring channels (As long as you wire when erecting walls.
E.g. A while ago you could buy fence posts made from wood chips and plastic bags. Dirt didn't matter, nor the type of plastic. Melt together and extrude under pressure. The material was dense, not very strong, heavy, and incredibly ugly. Never caught on.