Empty plastic bottles are often dumped carelessly without being flattened but the cap on. I assume no human can flatten such a 1.5l bottle (see example image), but can a garbage truck? I want to convince my local community to at least loosen the top (so that others can compact the bottles) because otherwise

  1. garbage containers fill up more quickly so latecomers will dump theirs around;
  2. we pay more as we practically pay the company that collects our garbage to transport air;
  3. -- and I'm not sure about this -- the garbage truck fills up more quickly.

Therefore I want to know whether a garbage truck (such as the one depicted below) can exert pressure or has some other means that can crush an empty but closed plastic bottle.

Secondarily, I want to know how much pressure force is required to crush an empty but closed 1.5l plastic bottle.

  • Are these garbage trucks picking up recycling or are they taking their load to landfills, incinerators, or some other garbage management endpoint? – Jean-Paul Calderone Oct 23 '18 at 14:07
  • @Jean-PaulCalderone I have no idea, but let's assume they go to recycling or to some other management. My question is really about whether closed bottles pose any problem for a garbage truck (besides taking up space) and whether any mechanism is needed/exist inside to crush closed bottles. – István Zachar Oct 23 '18 at 14:41

Quoting from an answer on Quora:

[the force of a garbage truck compactor] is ~16.2 MPa [...], which works out to almost 160 atmospheres of pressure. To give you some context, every 33 feet (10 meter) you travel underwater increases the pressure acting on you by 1 atmosphere. [...] You would need to go almost 1 mile below see level (5247 ft) to reach 160 atmospheres. According to wikipedia Submarine depth ratings, modern nuclear submarines will be crushed at less than half of this depth (~2400 ft, ~73 atm).*

If you Google for garbage truck compactor specifications you find similar numbers: 170 bar, Main system pressure: 2500 psi = 17 MPa.

So, there really is no need to screw the caps from the bottles.

*(The original source is dead).

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  • That is good to know, thanks. Though my points i and ii still apply, hence I do recommend taking caps off. – István Zachar Oct 23 '18 at 14:51
  • No, garbage trucks always compress. Your point 2 does not apply. – user2451 Oct 23 '18 at 14:55
  • Let me explain: We pay by the container and not by the weight. If we send in 2n instead of n containers, regardless what they are filled with (bottles with air or compacted trash), we pay double fee. You are right in that trucks do not transport air, but this only means that implicitly I had 4 points instead of 3. – István Zachar Oct 23 '18 at 15:03
  • It's unclear from this answer if 16.2 MPa is the force of the compactor, or the force needed to crush a bottle. – LShaver Oct 23 '18 at 15:14
  • 1
    @IstvánZachar Then you must edit your question; because now it is about your own containers and not the truck. And instead of making it two questions in one, I suggest you limit everything in the question to the truck only. The other issue (paying per container) is obvious, and you don't need to ask others about that. – user2451 Oct 23 '18 at 15:27

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