This image shows both old pink fiberglass insulation and the new spray foam insulation. The foam expands to many times its original size. When the insulation expands past the 2x4s, they have to shave it back so they can put sheetrock over it. Here you can see how much waste was generated when they went back and trimmed the insulation to fit the 2x4 cavities.
That dumpster is nearly half full with insulation. What good is a green product if it sends that much waste to a landfill? I gotta believe that they can chop that up and spray it in another wall.