Dear Jenny,They say the recyclables you put in the blue bin should be clean, but honestly, how clean does that pizza box or shampoo bottle really have to be?-Amanda, BostonHow much cheese is too much? And what about the shampoo caps? Do I have to flatten the cardboard? And really, why no broken glass? These are the kinds of questions that freeze well-meaning recyclers in confusion between the blue bin and the trash can.To get to the bottom of these mysteries, I checked in with the head of Los Angeles's Solid Resource Citywide Recycling Division, Neil Guglielmo, who may be one of the few people in America who actually knows how much cheese is too much. Paper and cardboard, Neil says, do in fact need to be clean. "If it had a sandwich on it and you knock off the crumbs, that's OK. If it had stuck-on lasagna, it can't be recovered." Ditto the pizza box." Both will end up in a landfill. As for unflattened cardboard, it will get recycled, but it hogs a lot of unnecessary space in the truck. And broken glass? It shatters into pieces that are impossible to sort.The trouble with that oozing Aveda bottle is that "it all goes into a big truck, and that smushes this nasty stuff" with the nice clean paper. Neil suggests that you rinse out the bottle once or twice and replace the cap. (Yes, to caps!) And yes, a bottle with a small lake of rosemary-mint shampoo in the bottom will still be recycled, but before that happens, the government has to use our taxes to wash it for you.These mysteries alone don't account for all our recycling mistakes, however. Much of the pepperoni in the blue bins owes less to confusion and more to fear. After all, how many times have we heard that if we all just all recycle, we can save the planet? American environmentalists have always ascribed a lot of earth-saving power (maybe too much) to individual virtue, which puts a lot of planet-saving pressure on individual acts-the flip side being that if you don't recycle, you're destroying the planet. And have you seen a landfill lately? It's a two-day hike to the top.Talk about guilt. Really, it's in the space between confusion and guilt–driven by fear of not knowing whether an item is recyclable and wanting intensely to recycle it-that most recycling errors happen. Remember that wanting the box to be recyclable will not make it so. You decided to order the pizza-not a terrible thing to do, in my opinion-and if you put it in the blue bin it will only take the scenic route to the landfill, which will use up a lot of extra energy and take a lot of innocent paper with it.So take a deep breath and throw the box away. Reduce, reuse, and recycle all the things you reasonably can. And be sure to advocate for green laws and the implementation of new technologies-for the large-scale acts that will make us all more virtuous, collectively, as a community.Jenny Price, environmental writer and "Nature Girl Ph.D," would love to hear your questions about how to be environmentally smart in our complicated 21st-century world. She'll pick the best questions, talk to experts, and get back to you on our site. Leave yours in the comments section.