The Green Lantern

Disoriented in the Dairy Aisle

Should I buy milk in glass, plastic, or cardboard containers?

I’m baffled by all the choices there are when it comes to buying milk. How can the glandular secretions from a single ungulate arrive in so many different types of packaging? Does it matter if I buy it in plastic, cardboard, or glass?

The Lantern wonders whether the first humans to wring milk from a cow’s udder around 9,000 years ago had any idea what kind of environmental consternation they were unleashing. Leaving aside the questions of cow versus goat versus sheep, and whether we’d be better off just getting our milk from beans, we might very well consider which milk containers are easiest on the planet.

First, a quick review of the main choices. Most plastic milk containers are made from high-density polyethylene, also known as HDPE or No. 2 plastic. Plastic milk jugs have a lot going for them. At just 4 ounces per half-gallon container, they’re so light that relatively little energy is required to ship them from the manufacturer to the dairy, and then on to the retailer and finally the consumer’s home.

The jugs are also recyclable, at least in theory. While plastic bottles can be melted down and made into new bottles, none of the milk containers in the United States are actually made from recycled material. That’s because of safety concerns over bacterial and chemical contamination, and strict FDA guidelines for the manufacture of food packaging from such second-hand sources. When it’s reclaimed, plastic from milk bottles is usually turned into toothbrushes, flower pots, and children’s toys, among other things. But according to the EPA, just 28.9 percent of it ends up in the recycling bin. The rest may spend hundreds of years decomposing in a landfill.

A second kind of milk container—the gable-top carton—is made from paperboard and coated with a layer of low-density polyethylene. Like the plastic bottle, gable-top cartons are made from virgin materials. Recycled paper isn’t as strong as the stuff straight from the trees, so a recycled container capable of carrying that much milk would have to be much thicker, heavier, and more expensive.

Paperboard is made of trees, a renewable resource, which is good. And they’re only 1 ounce (25 percent) heavier than plastic bottles. But the environmental positives end there. Making paper is a resource-intensive process, requiring huge amounts of water, fossil fuels, and chemical bleaches. While major manufacturers have launched a campaign (PDF) to get municipalities recycling both the paper and the plastic content of gable-top cartons, most Americans have no choice but to send them off to the landfill.

And then there are the milk containers made of glass. The major ingredients—sand, soda ash, and limestone—aren’t renewable, but they are plentiful. (Sand is, incidentally, one of the main exports of North Korea. Just a bit of trivia.) Producing a milk bottle’s worth of glass takes a substantial amount of energy, since the stuff has to be heated to more than 2,700 degrees Fahrenheit. (It’s still more energy-intensive to make a plastic container from paperboard, however.) Fortunately, if consumers return their bottles, the energy required to sterilize and refill them is far less than what’s required to make a new gable-top carton.

Glass is really heavy, though. If you filled a delivery truck with half-gallon bottles of milk, the glass would constitute about one-third of the total weight of the shipment, compared with 5 percent for plastic and 7 percent for gable-top cartons.

So what’s the bottom line for you, the confused consumer shivering before the massive wall of moo juice? As with many environmental quandaries, the answer depends on whether you care more about climate change or solid waste, chemicals in the ground water or human toxicity, acid rain or smog. But there are a few bigger points.

According to a study released in 2010 by the U.K. environmental organization WRAP (PDF), extraction of raw materials and manufacturing consume, by far, the most energy in the life of a milk container. So choices that can be reused or recycled are preferable. A 1997 EPA study bears this out, as refillable glass was found to use about half as much energy during its life cycle than either plastic or gable-top cartons.

Managing waste also uses up a lot of energy, so recycling is a good second choice to reuse. HDPE is therefore a better option than gable-top cartons, as long as you actually place it in the blue bin rather than tossing it in the trash.

Given its high costs and third-place environmental finish, you might wonder why the gable-top carton is still hanging around the dairy case. It’s probably because ultraviolet light, which can penetrate clear glass bottles (PDF) and HDPE (PDF), degrades vitamins A and D and riboflavin. That’s no small matter, considering between one-third and one-half of American adults are vitamin D deficient.

There are other choices out there. Manufacturers have experimented with refillable HDPE containers on a small scale. Plastic pouches for milk, though neither recyclable nor refillable, require fewer environmental resources than even reusable glass bottles. While the Lantern remembers when his elementary school cafeteria flirted with this approach, American consumers, so far, seem a little uneasy with the amorphous sacks. And maybe we just don’t want another option.

Is there an environmental quandary that’s been keeping you up at night? Send it to, and check this space every Tuesday.

Like Slate on Facebook. Follow us on Twitter.