Does it matter, from an environmental perspective, whether you choose milk in plastic jugs or cardboard cartons? It's a toss-up. Plastic is lighter, so it takes less energy to ship. And it’s recyclable plastic—though only about one-third of plastic milk containers are actually recycled. Moreover, in a landfill, the plastic is unlikely to decompose anytime soon.
HDPE #2 (high density polyethylene) opaque plastic milk bottles are easily recycled. Standard milk cartons made of plastic-coated paperboard are recyclable in some communities, too, but not everywhere. And manufacturing the paperboard is energy intensive. Milk in recyclable plastic bags, popular in Europe, may soon be common in the U.S.
Here, though, is a reason to consider forgoing milk containers made of plastic—or at least clear plastic: Clear containers let in light, which can destroy nutrients in milk, especially riboflavin and vitamin A. Just three days in a lighted dairy case can lead to a significant reduction in both of these nutrients. It also leads to a faster breakdown of substances that cause milk to spoil, creating off-flavors and that telltale sour smell. If you find your milk is spoiling too fast, switch to cardboard or opaque cartons.