Photo credit: Kingdesmond on Flickr

As an Environmental Engineer and Urban Environmental Management in training, I've developed somewhat of a trash obsession over the years. The world of trash is complex and fascinating and I can assure you that anyone with a good understanding of trash is also an expert in human behavior. Even though I am not an expert, I can say that as my obsession matured, I've gained a fair share of understanding of how waste, and recycling, works.

So I thought it was about time that I shared my bottomless pit of trash knowledge with the world, and maybe inform some peeps on all those things "they" don't tell you. If you are still reading this far and think that recycling your cans and bottles is a big sacrifice, read no further. This post will only confuse and demotivate you. But if you want to recycle EVERYTHING you possibly can, this post is for you.

Now, here is what you must know about how recycling systems work: 1) there is a LOT that they don't tell you. The reason is, they don't want to confuse you and demotivate you from recycling. It's for your own good, really 2) recycling materials, most of the times, are sorted by cranky, busy and underpaid employees (think Ten Worst Jobs in America). If something is not up to standard, it is rejected. No one is going to wash the plastic cup you didn't wash. Best case, they will just reject the peanut butter jar. Worst case - they will assume the whole lot is contaminated and landfill it all.

Of course, recycling depends very much on the place you live, so my first recommendation is to check with your local recycling system and see what they do and don't recycle. There is no point in separating all your plastic if it's not accepted.

The Most Important Rule is:

Do NOT recycle anything that is greasy or dirty

This will most likely result in a whole batch of perfectly good recyclables getting sent to landfill because recycling collectors will assume the whole container is contaminated. This WILL happen, for example, if they see a food-soaked item in a cardboard recycling bin [1], like a pizza box. No one is going to go through a container and separate the 'clean' from the 'dirty'. And if it doesn't get rejected right away, it will force a recycling worker to go handle rotting food on the sorting table by HAND.

And here are the general rules for each material:

Glass and metal:

• Remove the caps.
• You don't need to wash these because they are processed at high temperatures, so contamination doesn't affect the recycling [3]. (Some places recommend a quick rinse to prevent odors, but personally I don't think it's necessary)
• Glass bottles from olive oil, for example, are ok too, as well as sardine cans and things like that.
• Only glass bottles and jars can be recycled.
• You CANNOT recycle light bulbs (not CFLs), ceramics, Pyrex, kitchen glassware like glasses and plates, white skin cream jars, broken window glass. These types of glass have different melting temperatures than regular glass and form solid inclusions in the final product [4].

Paper:

• You don't have to remove staples, plastic windows, spirals from notebooks. These get strained out when the paper is turned to pulp [1]
• Remove tape if you can, because it tends to gum up the machines, but it's ok if there is some left. [1]
• No dirty or greasy paper (very important!!). This means no napkins or tissues (even if they are only slightly dirty :))
• Do NOT recycle pizza boxes!!! Even IF the pizza box IS clean, they will still assume it's dirty and toss it just the same, and possibly the whole container as well! Treehuggers, enviro-freaks, you don't want to risk that, do you?
• Waxed, composit or laminated paper is generally not allowed, like milk cartons, fast food wraps, drink boxes. Note: Some places accept drink cartons, but I wouldn't recycle it if it means getting milk all over clean paper and ruining it for recycling. I cannot emphasize enough that if that happens everything will get tossed!
• Thermal paper cannot be recycled - this means fax paper, but I also think it means supermarket receipts, which are increasingly printed on it, are not recyclable either. "Just say no"... or toss it yourself. [2],[3]
• Flatten cardboard boxes - again, if they are not flattened, they can be rejected [1].

Plastic:

• #1 and #2 are the best to recycle, as long as it's clean
• #4, 5 and 6 can be recyclable, even though it's expensive and/or complicated, so avoid buying these if possible.
• #3 almost exclusively indicates PVC, aka "poison plastic". Avoid this one like the plague! It is evil, and trying to recycle it does more harm than good.
• #7 has virtually no recycling potential [3] and is also preferably avoided. And of course, don't bother recycling it.
• Always remove the bottle caps and toss them. They are a different plastic than the bottle and most of the times are not marked.
• Don't even bother washing plastic if it's been in contact with grease. You are wasting water on something that will be rejected anyway. Let me explain, even if you do get that peanut butter jar sparkling clean, because everyone else doesn't, they will assume it's greasy and toss it.
• If it's been in contact with non-grease liquids or food, give it a little rinse. But a little bit of soda residue is fine.

Some cities have recently been changing from having separate material collection to Single Bin Collection , with new optical sorting recycling systems making automated sorting a reality. This system allows lower collection costs, while securing a much higher participation from the public. If your city has recently asked you to put all your recyclables in one bin, keep in mind you should be more careful to avoid contamination. This means you should let jars and bottles dry before you put them in the bin so they don't contaminate the paper and/or plastic, and you should probably avoid recycling greasy glass and metals as well, even though these are otherwise OK to recycle.

And finally, last words of wisdom:

• "When in doubt, throw it out". [2] 'When in doubt, recycle' is a common mistake, and as you've seen in this article, has less than desirable consequences.
• Don't bother recycling small pieces of paper and plastic. Normally, grading is one of the first stages in recycling plants, all the small bits and pieces are sifted out and trashed.

Are you still with me, brave reader? I hope I didn't overwhelm you too much... You must be brave now, and go forth and recycle! Don't hesitate to speak up if you have any questions, doubts or comments!

Sources:

[1] Harvard University Recycling FAQs

[2] The World's Shortest Comprehensive Recycling Guide

[3] The Consumer Recycling Guide: Commonly Recycled Materials

[4] Tchobanoglous "Integrated Solid Waste Management - Engineering Principles and Management Issues"

Further Reading:

• Recycling with KAB Man