That all plastics are not recyclable really irks me — things like those clear plastic tubs that spinach comes in. I put them in the recycling bin and the guy in the recycling truck tosses it in the trash along with those little plastics bottles holding hotel shampoo. They don't have the recycling number on the bottom so just a little more petrochemical trash gets wasted. Our recycling folks and some stores take back 1s, 2s, 3s and some 4s, but 5s, 6s and 7s get tossed.
Of course, plastics is an alphabet soup of acronyms - PETE, HPDE, V, LPDE, PP, PS and 7 is "other." I am big believer in recycling and feel strongly all plastics containers should be not be made unless there are made from recylable material. I'm sure the bottle and resin makers would scream bloody murder at the prospect of a federal recycling mandate. For instance, New Hampshire - the Live Free of Die state - considers a bottle deposit an imposition of its inalienable rights. In Massachusetts, we've had it for decades. But it's not the nineties anymore.
Maybe our plastics editor and expert Doug Smock who authors the Engineering Plastics blog can explain why not all plastic is recycleable.