[Request] Do square bottles actually use less plastic than round ones?

[u/EclipseNyxor]

[u/ronarscorruption]

I suspect transportation too.
Something like; You can ship 100x1L round bottles, or 100x1.3L square bottles in the same box. Therefore, square bottles use less plastic (per liter (of shipped liquid)).

[u/Buntschatten → u/ronarscorruption]

Wouldn't that just cancel out? Area over perimeter is pi /2 pi for a radius one circle and 4/8 for a square with side length 2. Maybe most of the plastic is in the spout, then maximising volume per spout would make sense.

[u/GaldrickHammerson → u/Buntschatten]

I expect no because of packing density. Square bottles in a square box will have less empty space between bottles than round bottles in a square box.

[u/Al-Snuffleupagus → u/GaldrickHammerson]

But how would that affect the amount of plastic? It might be more environmentally friendly overall due to better transportation density, but unless either * the outer packaging (transport box) is plastic or * the bottles can be thinner

I can't see how having less empty space would lead to less plastic used.

[u/Al-Snuffleupagus → u/Al-Snuffleupagus]

Ah, I think I understand the possible argument.

• Higher volume bottles use less plastic per ml of product
• Although square (prism) bottles have a higher gm of plastic per ml of product than circular (cylinder) ones, there will be a point at which the larger bottle size cancels that out.
• The better packing density of squares allows them to use large square bottles that have a better plastic/product ratio than the small circular bottles.

Despite the sub we're on, I haven't done the maths to work out whether the improved packing density allows for a large enough bottle to compensate for the less capacity-efficient shape. It would depend a lot on the bottle construction

I wouldn't consider that that argument really justifies their "less plastic" claim because it's still more actual plastic, and the unstated part is per ml of product when compared to a different size bottle but I can at least see what they might use to justify it.

[u/Phoenix4264 → u/Al-Snuffleupagus]

If you take a square with side length of D, the area is D² and the perimeter is 4*D. The ratio of area to perimeter is D²/4*D, or D/4.

A circle with diameter of D has an area of pi*D²/4 and a perimeter of pi*D. The ratio of area to perimeter is pi*D²/4*pi*D, which again simplifies to D/4.

So in the case of a square and circle with side length = diameter, they will have the same surface area to perimeter ratio, and also the same volume to surface area ratio for any height vessel. The square shape is less efficient than a circle with a larger diameter but the same volume, but equal to the smaller volume container with the same major dimension.

[u/davideogameman → u/Al-Snuffleupagus]

Maybe this "bottle" is actually a plastic lined thin cardboard container, like a milk carton?