Why would you use a plastic bag for milk? Most of the milk I buy comes in paper cartons.[1] Paper should degrade much faster than a plastic bag, plastic bottle, or glass.

[1]https://www.horizon.com/faqs?f%5B5%5D=field_faq_category%3A9...

The inside of that carton is still lined with plastic tho.

Plastic foil, much more biodegradable and probably compostable to boot, unlike PET.

24% polyethylene is still much better than a near 100% plastic bag or milk container.

It depends. If your county has the right equipment to recycle those mixed paper/plastic cartons then probably so, otherwise the whole thing goes into landfill or is incinerated, and that's more material than a plastic bag. You can check online if your county has the facility (unfortunately mine doesn't).

Tetra is expensive. Great for long term storage and backpack durability, but not worth the added cost (read: resources used in their manufacture) for something that must be consumed within 1-2 weeks of opening.

I do buy cheap wine in tetra boxes. They have a spigot to limit air-intake, so you can take your time to finish it.

I get my milk in sturdy glass bottles, which come with a $2 deposit so you bring them back for a wash and reuse.

In China there actually is milk (and soybean milk) sold in bags: https://static.businessinsider.com/image/4b05d2300000000000d...

In Canada too.

http://canadiandesignresource.ca/graphics/packaging/bags-of-...

We had milk in bags in elementary school in the late eighties in northern FL. You could pop your straw in, place on the table, apply rapid downward pressure: milk cannon! Amazing design, 10/10

Glass bottles?

Used glass is difficult to transport and not very efficient to recycle. It's a great option as long as you re-use the container locally.

I wish Heinekin’s World bottles succeeded: https://worksthatwork.com/artefacts/world-bottles