What material cannot be recycled and does not decompose?

All plastic can be recycled, but it is usually not economical to recycle thin plastics like bags and plastic film. These are often contaminated and cleaning them first is a problem.

So plastic bags and other soft plastics will not be recycled and will not decompose.

All metals, glass and paper can be recycled.

All organic matter like food scraps, wood and leaves will decompose.

Material like rock, cement and concrete cannot be recycled and cannot decompose.