Snack bags are useful, but they are hard to recycle. They are thin, soft, and often look alike. A food bag can look like other plastic packaging. Sorting machines may not know where each bag should go. (fostplus.be)

A large test in Belgium is trying a new answer. Some snack bags carry a digital watermark. This is a hidden code in the bag’s printed design. People cannot see it, but a special camera can. The mark tells the machine that the bag held food. The machine can then keep it with similar food packages. (fostplus.be)

For example, imagine an empty chip bag on a fast belt. A camera reads the hidden mark. The machine sends the bag into the correct group. The project can then recycle that group into plastic film. That film may become new food packaging. The project is still testing safety and quality. So, it is not a complete answer yet. However, these small hidden marks may give old snack bags new life. (fostplus.be)