When it comes to recycling, not all boxes are the same. This is not only due to the quality of the paper, but also any materials added to optimize the box for consumer use.
Take the example of gable-top cartons and aseptic containers, which you may know as milk/juice cartons and juice boxes, respectively. At first glance, these products seem destined for the paperboard recycling bin, but think about what would happen if you poured orange juice in a cereal box. These aren't your normal paperboard boxes.
A good portion of these containers are manufactured by Tetra Pak, and they are comprised of approximately 85 percent paperboard. The boxes are also lined with low density polyethylene (LDPE, or #4 plastic) to help insulate the liquid inside, and in the case of drink boxes there is also a lining of aluminum foil.
In the case of Tetra Pak, the company used almost 77 percent less LDPE in global manufacturing in 2008 than in 1999, but this plastic lining is still present. It also needs to be removed in order for the paper to be recycled.
This isn't to say that paperboard food boxes require no preparation for recycling. These boxes are usually coated with kaolin clay to improve the printing surface, which must also be removed.
But for milk and juice cartons it is a more difficult separation process, which may be a reason why your local recycling program won't accept milk and juice cartons.
According to Earth911's recycling directory, paperboard is accepted in 22 percent more curbside recycling programs than milk and juice cartons. Tetra Pak claims that 27.1 billion of its packages were recycled worldwide in 2009 (an increase of 1.5 billion over 2008), and the packaging is also compostable because of the large percentage of paper content.
In cities like Vancouver, milk and juice cartons aren't collected at the curb but they are accepted at Return-It centers. However, the Metro Vancouver area also reported 42 million milk cartons were landfilled in 2009 as opposed to 3.5 million plastic containers, although this discrepancy may be related to the fact that consumers receive a refund for recycling beverage containers other than milk cartons.
If your local recycling program does not collect these cartons, it's important to not include them to prevent contamination. You'll also want to remove any straws from drink boxes and rinse/flatten cartons so they don't start the compost process early.