Many municipal recycling programs throughout the world still do not accept plastic lids, tops and caps, even though they take the containers that accompany them. The reason is that plastic lids typically are not made from the same kind of plastic as their containers, and therefore should not be mixed together with them.
In fact, just about any plastic can be recycled, but when two types are mixed, one contaminates the other, reducing the value of the material or requiring resources to separate them before processing.
Also, plastic caps and lids can jam processing equipment at recycling facilities, and the plastic container with tops still on them may not compact properly during the recycling process. They can also present a safety risk for recycling workers. For example, most plastic bottles are baled for transport, and if they don’t crack when baled, the ones with tightly fastened lids can explode when the temperature increases.
Some recycling programs do accept plastic caps and lids, but usually only if they are off their containers completely and batched separately. Given the many potential issues, however, most recyclers would rather avoid taking them altogether. Thus, it is hard to believe but true, in most locales, the responsible consumers are the ones who throw their plastic caps and lids into the trash instead of the recycling bin.
As for metal caps and lids, they, too, can jam processing machines, but many municipalities accept them for recycling because they do not cause any batch contamination issues. To deal with the potentially sharp lid of any can you are recycling, such as a tuna, soup or pet food can, carefully sink it down into the can, rinse it all clean, and put it in your recycling bin.
Of course, the best way to reduce all kinds of container and cap recycling is to buy in large rather than single-serving containers. Does the event you’re holding really require dozens and dozens of 8 to 16 ounce soda and water bottles, many of which will get left behind only partly consumed anyway? Why not buy large soda bottles, provide pitchers of (tap) water, and let people pour into reusable cups?
The same kind of approach can be taken with many if not all of the bottled and canned grocery items we buy routinely for our homes. If more people bought in bulk, apportioning out of fewer, larger containers, we could take a huge bite out of what goes into the waste stream.