“Empty and Replace Cap” is a recycling instruction found on the How2Recycle label, a standardized system used on packaging across North America. It means two things: use up or pour out as much product as possible, then screw the cap back onto the container before tossing it in your recycling bin. The instruction exists because loose caps cause problems at recycling facilities, while caps attached to their bottles get recycled successfully.
What the Label Is Asking You to Do
The How2Recycle program breaks this instruction into two steps. First, empty the container and remove as much product as you can. You don’t need to rinse it spotless, but you should pour, squeeze, or scrape out what’s reasonably possible. A thin film of residue left inside is fine. Second, put the cap back on. That’s it.
You’ll see this label most often on plastic bottles for beverages, condiments, shampoos, and cleaning products. The label sometimes appears alongside a recycling number and a note about whether the packaging is “widely recycled” or only accepted in certain areas.
Why Loose Caps Get Thrown Away
Recycling facilities, known as material recovery facilities or MRFs, use conveyor belts, screens, and optical sorters to separate materials at high speed. Loose bottle caps are small enough to fall through the screens at the front of the sorting line. When that happens, they end up mixed in with non-recyclable debris and get landfilled. As one recycling facility operator put it, the bottle is the carrier that gets the cap through the system. Without the bottle, the cap has almost no chance of making it to a recycler.
This is a relatively recent shift in recycling guidance. For years, consumers were told to remove caps before recycling. The concern was that sealed bottles could trap air, causing problems during processing. Modern facilities now use pressurized systems that pop caps off and flatten bottles mechanically, making this a non-issue. Many municipalities have updated their guidelines accordingly, though the change has rolled out unevenly. Oregon, for example, is formally adding screw-on plastic caps to its accepted recycling list in July 2025.
How Caps and Bottles Get Separated
Even though you put the cap on the bottle together, they don’t stay together forever. Plastic bottles and their caps are typically made from different types of plastic, and recyclers need to sort them apart. The bottle body is usually PET, which has a density of about 1.38 to 1.41 grams per cubic centimeter. Caps are usually made from polypropylene (PP) or high-density polyethylene (HDPE), both of which are significantly lighter, with densities between 0.85 and 0.97.
Recyclers exploit this difference using a simple, elegant method: water tanks. After bottles are shredded into small flakes, the mixed material goes into a sink-float separation tank. PET flakes sink to the bottom. PP and PE cap flakes float to the surface. Each material gets skimmed or collected separately, resulting in high-purity plastic streams that can actually be turned into new products. This is why keeping the cap on doesn’t contaminate the recycling. The system is designed to handle both materials together.
How Empty Is Empty Enough?
You don’t need to obsess over getting every last drop out. The standard practice is to use common-sense methods: pour it out, give it a shake, let it drain. If there’s a thin coating of yogurt on the inside walls or a small amount of salad dressing pooled at the bottom, that’s generally acceptable for curbside recycling. Heavily soiled containers with large amounts of food still inside are a different story, as they can contaminate other recyclables like paper and cardboard on the sorting line.
A quick rinse helps if the container held something sticky or pungent, but it’s not strictly required for most curbside programs. The key threshold is that you’ve made a reasonable effort to get the product out.
When This Rule Doesn’t Apply
The “empty and replace cap” instruction is specific to plastic containers. Glass bottles with metal caps follow different rules. The EPA recommends recycling metal bottle caps separately from glass bottles, not leaving them on. Metal and glass go through completely different sorting and processing streams, and a metal cap left on a glass bottle can cause issues during glass crushing and melting.
Similarly, if your packaging label says something different, like “empty and remove cap,” that means the cap material isn’t recyclable in most programs or needs to be handled separately. Always follow the specific instruction printed on the label you’re looking at, since packaging varies. The How2Recycle label is designed to give you the right answer for that particular container, so you don’t have to guess.
Should You Flatten the Bottle First?
Crushing a bottle before replacing the cap might seem like a space-saving move, but there are a couple of things to consider. Pressurized air trapped inside a sealed, crushed bottle can cause the cap to pop off unexpectedly. More importantly, some optical sorting systems at recycling facilities identify bottles partly by their shape, and a completely flattened bottle can be harder for machines to recognize and sort correctly. If your local program asks you to flatten containers, do so gently and then replace the cap. If they don’t mention flattening, leaving the bottle in its original shape with the cap on is the safest bet.