Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why don't garbage trucks grind garbage?

  1. Aug 13, 2007 #1
    Strange question, i know. I didn't really know where to put it.

    Why don't garbage trucks grind their garbage instead of simply compacting it? There's plenty of shaft power available in the truck to reduce the garbage into a reasonably fine consistency.

    This would allow the trucks to carry much more garbage on a single route and would also facilitate easier handling and landfill logistics. The garbage could be mixed with water to form a slurry and simply pumped into landfill instead of having to be laboriously moved using bobcat-like machinery.

    I imagine the landfill would be much more efficiently utilised in this scenario, as there would be hardly any air and wasted space within the garbage slurry. The garbage may also decay more quickly when thoroughly mixed as a thick slurry.

    There may also be scope for sorting useful materials from the ground garbage (pre slurry) using some mass dependent hydrodynamic or aerodynamic process and appropriate filter membranes. (Perhaps the garbage could be blown around a bend with high velocity air, with different catchment receptacles for flung particles of varying mass)

    Just a random thought.
    Last edited: Aug 13, 2007
  2. jcsd
  3. Aug 13, 2007 #2
    One problem i could see is an increase in the amount of seepage into the water supply.
  4. Aug 13, 2007 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    When your garbage goes to a landfill, it goes through a special machine that separates out food wastes from plastics and metals. Some of the materials are then redirecting into the recycling streams.

    If you ground it all up together in the truck, you'd no longer be able to reclaim any of it at all.

    - Warren
  5. Aug 13, 2007 #4
    Really? I doubt that is common.

    It's kind of an engineering question, right? A fairly average piece of garbage is something like, perhaps, a cardboard milk carton. There's likely to be a lot of empty space inside that kind of thing, and it won't take so much effort to crumple it down. If you first ground it up, then compacted it down, you still wouldn't get the milk carton much smaller still, but you would need far more energy for tearing it apart. Diminishing returns. Also, the mechanics of a compactor can be hardy, regardless of what type of garbage you have. But imagine the difficulty of maintaining a grinder, which doesn't jam or blunt on paper, doesn't get gummed up by banana peel and plastic bags, but can still grind apart glass and metal efficiently? Wouldn't it be made of sharp edges, that quickly wear down and need servicing? I'd say those trucks don't grind for the same reason they don't atomise..
  6. Aug 13, 2007 #5
    You don't necessarily need sharp edges if you have an abundance of power.

    It turns out the idea was toyed with in Germany at some stage. It was unpopular due to the increased fuel consumption of the trucks. I guess the extra fuel that is used is more expensive than the landfill savings and the cost of a bobcat jockey.
  7. Aug 13, 2007 #6

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper

    If you live in an area that has a "transfer station" as opposed to a "landfill" then the separation process that Chroot mentions is going on right there.

    Other than that, plus the fuel consuption, those trucks already make the goddamdest noise! You want them grinding the garbage at 6 in the morning too?
  8. Aug 13, 2007 #7
    My garbage pickup happens late in the afternoon :)
  9. Aug 13, 2007 #8


    User Avatar

    Staff: Mentor

    I would think that there would be a limit to the tonnage a truck would carry.
  10. Aug 13, 2007 #9


    User Avatar
    Gold Member

    you really see the phrase "one man's trash is another man's treasure" in full effect at transfer stations. Very popular in Alaska. I have friends who's assets are practically made up of transfer station scores.
  11. Aug 15, 2007 #10


    User Avatar
    Gold Member

    Not to mention some people throw out hazardous materials, and grinding a hazmat could contaminate the surrounding environment, not to mention medical waste garbage, explosive, flammable liquids, reactive chemicals with other garbage (ammonia + bleach anyone?), sometimes corpses end up in the garbage truck and it becomes a crime scene which you wont want to destroy
  12. Aug 16, 2007 #11

    Chi Meson

    User Avatar
    Science Advisor
    Homework Helper


    Each one of those is reason enough.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook