Q. When recycling HI-5¢ plastic beverage bottles, the recycling center asks us to remove the caps and gave some reason that the caps make the bottles explode when they crush them. As such, everyone removes and discards the caps. It dawned on me, however, that the caps are plastic, and even if they should be removed, why shouldn't they be recycled? I believe the program was to get people to recycle their plastics. Anyway, what is the deal on this? Why shouldn't the caps be recycled? Also, as the caps have weight, are we being cheated on the refunds?

A. There's a couple of issues with keeping the caps on the bottles, and one is that they might explode. Even if they don't, sealed bottles are harder for the machines to crush and break down.

The other issue is more complicated. You might think plastic is plastic, but there are actually seven different types of plastic in common use. You can usually find out what type of plastic something is by looking for the number in the Reduce/Reuse/Recycle triangle usually stamped on or near the bottom of the container.

For example, beverage bottles are made with plastic "No. 1," polyethylene terephthalate, which is the most widely used recycled plastic. That's the type most likely to have a redemption value.

Bottle caps, on the other hand, are usually made from plastic "No. 5," or polypropylene, which is also frequently used to make drinking straws. Recycling those at the same time as the bottles would contaminate the plastic resin being recycled from the bottles.

When recycling becomes more habitual, residents might be be asked to separate the different types of plastic, but city officials say that at this point they're trying to make it as easy as possible to encourage people to make the initial effort.

Q. Is there a way we can renew our passports locally without having to mail all our information? Someone told me to contact the library, but that doesn't sound right.

A. I checked with the post offices and libraries that process passports and they said all renewals are done by mail now. The exceptions would be if your passport is lost, stolen or damaged; if it expired more than 15 years ago; if it expired and was issued before you were 16; or if your name has changed since your passport was issued and you don't have a legal document formally changing it.

If any of those exceptions apply to you, the nearest passport acceptance facilities can be found on the U.S. State Department's Web site at http://iafdb.travel.state.gov/.