Recycling technology has improved a lot over the last decade, which in a way has made the logistics of what you can and can’t toss in the recycling bin a lot more confusing.

“All garbage goes somewhere; it does not go away. So we must all take more responsibility to sort our discards into the proper bins,” says Robert Reed, a spokesperson for Recology. Recology runs recycling collection programs along the west coast including San Francisco’s highly successful program, which recycles about 80 percent of the city’s waste.

Doing a bit of research before you try to recycle can make all the difference. Recycling rules of course vary from one municipality to another, but here are a few ways to improve your recycling routine.

Don’t put your recyclables in a plastic bag.

It’s not that we don’t have the technology to recycle plastic bags. They just cause a lot of issues in the recycling process. Though the type of plastic (#2 and #4) that’s used to make plastic bags is recyclable, throwing them in with the rest of your recycling has ramifications down the line. “Plastic bags cause problems in all of our operations,” says Reed. “They wrap around and jam recycling equipment. They contaminate paper bales. They cause problems at our compost facilities. They blow off of landfills and wind up in waterways and oceans and seas.”

If you accumulate a lot of plastic bags, your best options might be recycling programs that focus exclusively on them. Many grocery stores collect plastic bags, and some city recycling programs offer plastic bag pick-up or drop-off programs. In some cases, recycling programs may ask users to put items like packing chips or shredded paper in plastic bags.

You can now recycle plastic bottle caps.

Traditionally, plastic bottles with caps on caused problems at recycling sorting facilities. Bottles are made from a #1 plastic plastic, while caps are made from a #5 plastic called polypropylene, which melts at a different temperature during the recycling process and would need to be processed separately. Also, a tightly screwed on cap can stop up a bottle full of air, which takes up more transport space. Caps can even be a hazard to workers: they can shoot off unexpectedly during compression.

But times have changed. Processing equipment has improved—the projectile cap is no longer an issue, and caps and bottles are divided into separate streams in sorting facilities. In some cases, tossing bottles and caps into a bin separately is worse. If an unscrewed cap slips through the mechanical sorting line, it will also likely end up with trash headed for a landfill. They’re also hard for sorters to spot separately.

You probably still can’t recycle styrofoam.

Styrofoam or expanded polystyrene is made of plastic #6. The general rule is the higher the number of plastic, the harder it is to recycle. Yet recycling companies have gotten pretty good at handling higher numbered plastics (you can even throw #12 shampoo bottles in the recycling bin these days). However, just because plastic #6 is recyclable doesn’t mean that your local recycling center accepts expanded polystyrene. In fact, it probably doesn’t.

Expanded polystyrene easily gets contaminated—whether from food or from the dirt and grime it might interact with during transport. Most recycling facilities don’t deep clean materials, and styrofoam can absorb a lot of dirt. There’s also less of a market for styrofoam than other recyclables.

Styrene is petroleum product, meaning it’s flammable and hard to break down. That makes the recycling process more complicated, but not impossible. According to the Expanded Polystyrene Industry Alliance 93 million pounds of styrofoam were recycled in 2012. Some communities have special expanded polystyrene drop off centers, and commercial companies have adopted special programs to recycle their styrofoam.

The styrofoam that does end up in a landfill takes 500 years to break down, so doing your best to reuse packing chips and styrofoam items—or even better, using degradable packing peanuts made out of milk and clay or plant material—would be best for the environment.

Shredded paper is recyclable. However…

Shredding paper reduces the grade of the paper, and thus its quality and value. The grade depends on the length of the fiber, and recycling facilities separate paper into bales based on grades. Shredding paper turns it from high grade (letterhead and printer paper) to mixed grade, which includes telephone books and magazines.

Not all recyclers take mixed grade paper, and most curbside pick up programs determine what they can and can’t take based on the length of the shreds. Some recycling companies will only take long shreds; others won’t accept shreds at all. Many collectors ask that you contain the shreds in plastic bags, so if your curbside collection service doesn’t take plastic bags, they probably don’t take shredded paper. If the paper has been reduced to confetti, your best bet might be composting.

You couldn’t recycle a pizza box even if you wanted to.

Though they often display recycling symbols and cardboard itself is recyclable, pizza boxes are often not accepted in local pick-up programs. Why? It all comes down to the grease. The food and grease that accumulates on the box makes the paper product unrecyclable—that is unless you can remove the pizza remnants from the box. With grease, that’s pretty much impossible.

This problem isn’t unique to pizza boxes, though. Most food containers run into a similar issue, whether it’s a smoothie bottle or a take-out carrier. Recycled items don’t have to be pristinely clean, and food residue can render recycled materials less valuable. More than metal or plastic, paper absorbs oil and residue from food, so it’s harder to get out. Beyond pizza boxes, paper napkins, plates, and towels are all non-recyclable for this reason.

Just because you can’t recycle them, doesn’t mean you can’t compost them. Paper napkins and towels can go in the compost bin. “Soiled paper contains short fibers, which microorganisms in compost love, and soiled paper absorbs moisture in compost collection bins, which helps control odor,” says Reed.

Most juice boxes and milk cartons aren’t recyclable.

These containers are mostly paper, but they have an ultra-thin plastic coating low-density polyethylene or LPDE (a #4 plastic). Some juice boxes also include an aluminum foil lining. Though these items are individually recyclable, it can be quite hard to separate these linings from the carton, hence why many curbside recycling programs don’t accept juice boxes. Some facilities have “hydro-pulping” machines that can achieve this separation seamlessly, but others don’t.

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Will recycling always be this complicated? Perhaps not: Some cities such as Houston are considering plans in which residents use an all-in-one bin—they would dump garbage, recyclables and compost in one container, and the container's contents would be sorted automatically at a waste facility. Houston is currently examining proposals for technology that could accomplish this without increasing greenhouse gas emissions.

But until such automated technologies are developed, the above points will remain general rules of thumb. Before trucking it all the way to the dump or your local recycling plant, always look up your local regulations. It’ll save you the trouble, and the gas.