Most Eco-Friendly Milk Container? Plastic or Glass, Not the Carton March 19, 2015 Email Glass is often considered the most eco-friendly milk container because it’s the easiest to reuse and it is endlessly recyclable, but its ingredients aren’t renewable and it’s heavy to transport. Plastic is easily recycled (although recovery rates are lower than they should be), but it often winds up being downcycled, which means it’s turned into products that can’t be recycled. Cartons never come out on top, because they’re not easily recyclable and frequently end up in the landfill. Read more on Slate.com.