Can you recycle bottle caps?
Usually yes
Yes, and the instruction reversed years ago: screw the plastic cap back onto the bottle rather than taking it off. Metal lids from glass jars are the exception, going in loose. Do not flatten the bottle first, which is the part almost nobody knows.
Follow it down the line
Three different questions hide inside "is this recyclable?", and the answer can change at each step.
The material · Yes
Is the material recyclable?
Caps are generally high density polyethylene or polypropylene, and both have high demand from applications in domestic and export markets, so the material was never the issue. Nor does the cap being a different plastic from the bottle create a problem, which is the assumption behind the old advice. Bottles are ground into flake and washed vigorously, then the cap material separates from the bottle material in a water bath: PET sinks, PP and HDPE float, and both go on to be recycled into new items. That is worth sitting with for a second, because it means the two plastics sort themselves by physics with no human decision involved. The reason you were once told to remove caps is that the industry could not process them then. The trade association's own account is that collection and processing technology improved and demand for the material rose, so the message changed.
The facility · Sometimes
Will a sorting facility recover it?
A cap on a bottle is a passenger. A cap on its own is a problem, and the reason is the one that recurs across this whole site: it is small. Attached, it travels with a container the equipment can see and handle; detached, it is a coin-sized object on a line built for bottles. Keeping the cap on the bottle, in the recyclers' own phrasing, helps both plastics travel together and then be separated efficiently during processing. There is a second instruction that follows from how sorting works and that contradicts what most people do. Do not flatten the bottle. APR's message is empty and replace cap, and it cites a MRF material flow study finding that flattening bottles can lead to improper sortation and that they may end up in the paper stream, while retaining a three-dimensional form helps containers be sorted successfully. This is the same mechanism that governs aluminum cans: sorting lines read shape, and a flattened container reads as flat paper.
Sources: APR: why you need to keep the cap on when recycling plastic bottles, CuyahogaRecycles: glass bottles and jars
Your curbside program · Widely accepted
Will your curbside program take it?
Caps are accepted about as widely as the containers they came from, and the only thing worth learning is that the correct handling differs by material for a reason. Napa says plastic bottle caps are recyclable but can be lost during processing because of their small size, and asks you to put the cap back on the bottle to prevent that. Its answer for metal bottle caps is one line: recyclable. Cuyahoga County draws the contrast that makes the whole picture make sense, on its glass page rather than a caps page: metal lids should go in loose, because metal lids are unique and, loose, will be sorted properly with the metal cans. So a plastic cap rides through attached to its bottle, and a metal lid gets picked out of the stream by a magnet that does not care how big it is. Two opposite instructions, each correct for its own material.
Sources: Napa Recycling: plastic bottle caps, Napa Recycling: metal bottle caps
What you need to do
- Empty the bottle, then screw the plastic cap back on
- Do not flatten or crush the bottle, which can send it into the paper stream
- Put metal lids and caps in loose rather than reattaching them to glass
- Do not collect loose plastic caps in a bag, which sorts as a bag rather than as caps
Where else it can go
Leave it attached, which is the route
There is no separate collection to find here. The cap goes back on the bottle and the bottle goes in the cart. It is the rare case where the best answer is less work than the thing people currently do.
Empty the bottle first. Attached does not mean full.
Metal lids in loose
Jar lids and beer caps go in on their own, where the magnets take them with the steel cans.
Do not screw a metal lid back onto a glass jar. That sends it through the glass stream instead of the metal one.
Common mistakes
- Removing the cap because that is what you were told years ago. The advice reversed once processing could handle it
- Flattening the bottle to save space, which is the same mistake as crushing a can and has the same cause
- Screwing a metal lid back onto a glass jar, which is the one case where reattaching is wrong
- Saving loose caps in a bag or a jar to recycle together, which produces a bag of caps rather than recyclable caps
- Assuming a cap made of different plastic from the bottle must be separated by hand. A water bath does it