By Christopher Thompson

1. Your coffee cup probably isn’t recyclable

Items composed of different kinds of materials present a big challenge for recyclers. The billions of single-use coffee cups discarded each year are a classic example: a thin, plastic coating inside the cup may prevent leakage, but it’s extremely difficult to separate it from the paper cup itself. That means the cups can’t be recycled as paper, nor can they be recycled as plastic. Their ultimate destination is usually the landfill.

Coffee cup lids don’t fare much better – due to the low quality of the plastic, they aren’t particularly attractive to buyers of secondhand plastic, and in any event they tend to fragment into small, unusable pieces. Some curbside programs recommend putting them straight in the trash bin. The best solution is to get your own reusable coffee cup.

2. Toothpaste tubes need special treatment

Clean teeth, yes. Clean planet, questionable. Toothpaste tubes are another troubling composite: while the bulk of the tubes may be made of plastic, they can contain other materials such as a thin coating of aluminum. Tubes and toothbrushes also contain different kinds of plastics mixed together (hard handle, soft bristles), increasing the challenges of separating and processing each type individually.

Most curbside programs don’t accept oral care products but new schemes, such as a partnership between Colgate and Terra Cycle, are encouraging people to send in their old tubes, toothbrushes and floss containers for proper processing. Metal tubes, glass jars and tins of toothpaste are more widely recyclable than their plastic counterparts, and plastic-free, compostable bamboo toothbrushes are becoming increasingly popular.

3. Don’t be fooled by food containers

It’s bad enough that fruit and vegetables, which come pre-packaged in their own nutritious skins, are sold in plastic containers. What’s worse is that the flimsy “clamshells” they often come in are low quality and made of different kinds of plastics – the container must be firm while the hinge must be soft – and thus are poor candidates for recycling in the US. This applies to takeout containers, too.

In general, plastic bottles labeled with the recycling numbers 1 and 2, including items such as soda, water bottles and milk jugs, are accepted across the US, says Mitch Hedlund, the founder of the not-for-profit Recycle Across America. “Any empty plastic bottles with a neck and screw on cap are recyclable,” she said. Beyond that it’s less assured, and you should check with your local recycling facility. She suggests keeping strawberry containers and other flimsy clamshells out of your curbside recycling unless your local provider accepts them.

4. Yes, your recycling needs to be cleaned

If you assume that a magical person at a recycling plant is washing out your jar of crusty tomato sauce or scrubbing last night’s takeout containers, think again. Recycling facilities typically do not clean recycling before processing it, so if you don’t you may be creating an even bigger problem.

Most US recycling programs are “single stream”, meaning all household recycling (paper, cardboard, plastic, glass) goes into the same bin. A plastic container filled with food, soda or leftover shampoo could leak and contaminate an entire batch of perfectly good recyclables, rendering everything junk.

“Food waste is definitely a contaminant that can make other items dirty and attract pests,” says Marissa Begley, of Millennium Recycling, a recycler in Sioux Falls, South Dakota. While recyclers say your items don’t have to be squeaky clean, dirty items will benefit from a quick rinse or removal of excess food and liquids. “This could mean simply scraping out a peanut butter jar with a spatula,” says Begley. “We definitely appreciate it.”

5. Plastic bags are a recycling plant’s nightmare

Despite single-use plastic bag bans in California and New York, and rising awareness of their harm, many still find their way into the recycling system. Hedlund, of Recycle Across America, calls them the worst culprit of wish-cycling because of the damage they cause at the recycling plant.

Flimsy plastic bags quickly degrade and can clog up expensive sorting equipment, causing delays and endangering workers. “Often recycling centers’ multimillion-dollar processing machines have to shut down every half-hour because the plastic bags get jammed into the equipment,” Hedlund says.

Plastic bags should be kept away from curbside recycling unless your local recycler advises otherwise, and definitely don’t use them to bag up your other plastics or line your recycling bin, she says.

6. Those little arrows? They don’t mean anything

Time for a big debunk. Many people believe this instantly recognizable triangle icon indicates that an item is recyclable, or that it is made from recycled materials. Actually, what is known as the “chasing arrows” icon is “essentially clip-art”, explains Hedlund. “There is no oversight for how the recycling icon is used. As a result, it is often misused on packaging to make it look like something is recyclable, when in fact it’s not. This misleads the consumer and causes them to throw that packaging in with the real recyclables.”

The symbol emerged in 1970 to honor the first Earth Day. The Möbius-strip inspired design is now in the public domain, meaning anyone can use it for any purpose. The numbers inside the arrows, from one to seven, were developed by the plastic industry in the late 1980s. Misleadingly, not every number is recyclable.

In fact, hard plastics with the numbers 1 and 2, such as soda, shampoo, and laundry detergent bottles, have the most consistent recycling markets. Numbers three through seven include a lot of the soft plastics mentioned above – clamshell containers, coffee cup lids – and present greater difficulty.

7. Plastic can’t be recycled for ever

Recycling conjures up an image of a closed circle. Yet “one of the biggest misconceptions about plastic is assuming that it can be recycled into the same kind of object”, says Kim De Wolff, a professor of environmental philosophy at the University of North Texas.

Beverage companies tend to use only a small amount of recycled plastic in their new bottles (if any), because unlike virgin plastic, 100% recycled plastic is not translucent. More likely, your plastic bottle is being turned into an item of lesser value, such as plastic lumber, carpets or a fleece sweatshirt.

Plastic degrades in quality when it is recycled, and while it’s tough to know how many times a piece of plastic will get recycled before becoming unusable, experts estimate it may only be once or twice. After that, it is landfilled, incinerated, or ends up in the environment.

There’s only one real solution, these experts say: make and consume less plastic.