The biggest problem I see with recycling right now is separation of materials.
The recycling plants aren't very good at breaking things down into separate materials, and some things (like e-waste) are very difficult to break down by design.
You usually sterilize things by heating them a lot, but plastics can't be heated that much before they break down, so plastics generally can't be sterilized. (that's why the hospital sends you home with things like your water pitcher, they CAN'T sterilize it for reuse)
And then diapers have an added problem of being a "medical waste". Not only is the plastic, pulp, elastic, and tapes all glued together, but it's mixed in with urine, feces, and biohazards. Right now Japan is actually incinerating diapers. (they have a huge garbage problem there due to no space for landfills) This gets rid of the diapers, destroys the biohazards, and burns it all for its down fuel. I don't know if they are a net-producer or net-consumer of power in this process, but it has to involve heating a lot of water, (so many wet diapers!!) so it's probably tough to come out ahead on it. Burning plastic does return some of the energy you put into it, but it's nowhere near as good of a recycling method as just plain melting down and reusing. The big problem there is usually the toxic gases that come out. Incineration breaks down even those, but it just required higher temps/more energy/more cost to do. (and that's why incineration is really the only eco-friendly way to recycle e-waste)