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A Crushing Experiment: Milk Jugs

A Crushing Experiment: Milk Jugs

Posted by Katie Deska on Mar 13th 2020

Just how much space can you save in the recycling bin by crushing your milk jugs? Our diversion coordinator, Sean Barton, enlisted the help of his kiddos and conducted an experiment to find out. Results indicate that removing the air from a milk jug can reduce its size by well over half, thus more than doubling the available space in your bin and ours.

At MSU's drop-off center, a large container is used to collect these cloudy #2 plastics, made of high-density polyethylene (HDPE). When the container is full we haul it to our material recovery facility, and empty the jugs into the baler. Typically one full container produces a bale that weighs 600-800 lbs., which is on the light side since most jugs are usually left expanded. But, if all the jugs were crushed to a 70% volume reduction, we could fit an additional 560 lbs. of jugs in that same container. Doing so would mean one bale would contain more jugs, which would help hold the bale together better, resulting in a higher quality product. Plus, it would reduce the number of times per week that the container needs to be serviced, thus conserving the fuel and energy used to operate the truck and machinery. 

A note of caution, though! The time to crush a milk jug is as soon as its empty and rinsed! Take our word for it -- the stench of an old milk jug is just not pleasant! 

So remember -- for healthy bones, drink milk, but for strong muscles, please crush those jugs! To see the method behind this study, take a look below, and consider trying it out with your kids.


To determine how much space is saved in the recycling bin by crushing a milk jug rather than leaving it expanded.


For the control test, fill a gallon milk jug with water (food coloring, optional) then, dump the liquid into a measuring device and note the volume. For the experimental test, fill the milk jug again and crush it jug over a bucket, then measure the liquid and note the volume. 

  1. Fill a gallon milk jug with water and add food coloring. 
  2. Rally a kiddo to do their best to squash a milk jug. Pour out the remaining liquid and measure the volume.
  3. Enlist the help of a professional to further crush said milk jug. Pour out the remaining liquid. Measure the volume.
  4. Follow formula to determine results. Compare results from the apprentice versus the professional. Notice how much more space you can save with a little more oomph! 


TestLiquid in expanded jug (cups)    Liquid remaining in crushed jug (cups)
Experimental          163.5

Formula: [(Starting Value – Final Value) / |Starting Value|] x 100 = percent decrease in volume

Results:  [(16-3.5)/16] x 100 = 78.1% decrease in volume when crushed


Results indicate a 60-78% reduction in volume when crushed by hand. Yes, crushing by hand is the professional method.  :-)